The Columbia University High-Beta Tokamak

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HBT-EP Archives 2002 - present.


Wednesday December 18 03 58 36492-36513 External Field

During the run I was working with 'high beta' shots that I usually use in my 3/1 experiments. I was trying to develope a model discharge that would be stable to low frequency 3/1 oscilations with the aluminum shells fully inserted and unstable when they're retracted. Due to certain problems with the CAMAC racks and Crunch cabinet I didn't get much run time. Never the less I got several good shots. The data is being analyzed. Regards, Mikhail

Wednesday December 18 05 32 36514-36542 FB setup shots

Developed a "long lived" saturated RWM target mode that lasts about 2 to (sometimes even) 3 ms near the end of the shot. These plasmas were made with the Al shells inserted to suppress higher m/n=4/1 and 3/1 RWMs and 2/1 tearing type modes also. I was successful in bringing the q=2 surface external with a Ip ramp style shot. These shots have an Ip ramp of 2 MA/sec during the first half of the shot and then Ip rolls over somewhat at ~15kA during the last half of the shot when the kink is excited. The kink is of m/n=2/1 helicity instead of our more typical 3/1 variety. The q=2 surface goes out into the vacuum at ~ 4.5ms. The shots typically disrupted at about 8 to 9ms (see shot#35642 as an example). Feedback next.

Thursday December 19 05 38 36543 ICRH

Disappointingly, the large oscillations on the loop voltage now appear not to be related to the plasma after all. Today, in contrast to last week, the oscillation was there even in the absence of plasma. Last week we had one shot, 36486, without plasma, and the loop voltage oscillation was absent. However, today, we took several non-plasma shots, with and without banks firing, 36562, 36564, 36565, where the loop voltage clearly oscillated during the RF. On the bright side, the RF B probe is now absolutely calibrated. The RF B field at the probe is about 1 Gauss, within expectations for vacuum. No clear coupling was seen today, ie. vacuum B fields were basically the same as those when the plasma was around. The calibration factors have all been worked into the MDSPlus tree, so the f_bprobe tag now directly reflects the RF B-field in Gauss. Cory developed some good discharges that would hang around 92-91 cm for a couple of milliseconds. Nonetheless, Q was only observed to dip during inboard disruptions. We did not make significant progress on the triple probe, for lack of time, mostly.

Thursday December 19 05 43 -36603 ICRH Addendum

Two things to add to the report: We just discovered that by mistake, we ran today with the 10% helium mixture instead of the 20% hydrogen. So no chance of heating today. The other thing: I forgot to put in the last shot number of the day. It was 36603.

Friday December 20 04 20 none

Steve Paul was in today and reinstalled a new fiber optic bundle and optics to carry light from the machine to the screen room, as a consequence of that and some work on TS triggering we did not run today. Steve expects a factor of roughly 4 increase in collected light. He also stated he has made progress on fixing the systematic errors in the measurement through calibration improvements. Since the machine will not be running next week we took the opportunity to pump on and bake the Mach and Biased probe bellows and opened them up to the chamber. They should be ready for experiments when we run again. The bake is on.


Friday January 10 04 25 Rivera null none

The lower 12 turn coil has been installed. The OH has been dismantled to facilitate installing the lower 21 turn coil.

Wednesday January 22 05 26 Maurer 36606-36619 shake-down

Finished getting the machine back in order(insulation, TF cooling oil, etc...) today after installation of majority of VF feeback coils during the past two weeks. Took initial OH and VF vacuum shots going in increments up to typical maximun runtime voltages (e.g. VFEL=200V, OHEL=250V). Observed no problems with new coilsets. Ready for TF and plasma shots tomarrow. Since we are a day behind in getting the machine back together we are planning on moving the run schedule back a day. I will continue tomarrow and check out the TF and get first plasmas and Mikhail will then run on Friday.

Thursday January 23 06 10 Maurer 36620-36656 Clean-up

First plasmas were taken today since prior to Xmas and the new VF coil installation. Plasmas started out short (~2-3ms lifetime) but rather quickly started to last out to ~6ms after about ten shots. Tomarrow we should be able to get some real data. New mounts for the fan array SXR amplifier box were measured out and are being machined. They are needed because of the top middle new VF feedback coil location. The array will hopefully be up and running early next week after the table is installed and an extension is added to the copper bellows (Jim & John). Work on the TS triggering system and the new and repaired u-port adapters also piggy-backed on the run today (Alex & Royce).

Monday January 27 05 26 Mikhail Shilov 36657-36722 External Field

During Fri, Jan 24 and morning of Mon, Jan 27 runs I developed a reproducible discharge type which doesn't have low frequency external kink oscillations in the first phase of the discharge with the aluminum shells all the way in and q*

Monday January 27 05 28 Mikhail Shilov 36657-36722 External Field

During Fri, Jan 24 and morning of Mon, Jan 27 runs I developed a reproducible discharge type which doesn't have low frequency external kink oscillations in the first phase of the discharge with the aluminum shells all the way in and q* less ~ 3. In the afternoon of Mon, Jan 27 I applied external 3/1 corotating, static, static with 180 degree phase flip field to those kind of plasmas. The data is yet to be analyzed. Here is some good natural shots: 36664, 36668, 36671, 36688, 36691, 36703, 36720.

Thursday January 30 06 47 Maurer/Paul 36786-36833 Rotation & TS

Ran some calibrations of the new collection optics to start the day. Working out kinks with new collections optcs (for increased light collection). Ran in 10% and 100% He discharges. Small light levels seen on 100% He discharge cases. Currently not understood why light level is so low. Checking various possibilities. TS triggering progress made. Scope and laser triggered off of jorway pulse stopped pretriggering of scope. Need to AC couple the scope inputs to be able to bump the volts per division to measure TS scattered light. (Alex)

Wednesday February 5 05 31 Cates 36835-36943 Smart Shell RWM Feedback

On Tuesday, several hours were spent testing feedback preamps, and repairing small problems in the system. In the afternoon (shots 36855-65), some target current driven plasmas with 3/1 RWM induced disruptions were tested with and without feedback. Wednesday these current ramp shots were used to do a disruption study with feedback gains changed between full gain, half gain and quarter gain, in order to supplement previous gain studies with only full gain and 0.1 gain. I was also able to test the feedback shots (shots 36878-36891, 36939-43) with these gains against a smaller current ramp which is unstable for a longer period of time, hopefully allowing better observation of mode amplitude growth. As a side note, I have found Mikhail's improved solid_tok code (which now runs every shot automatically) to be a very helpful tool for run time analysis and correlating predicted mode stability with diagnostic signals.

Thursday February 6 05 24 Pedersen 36944-36985 ICRH/triple probe

We exercised the ICRF today and tested the triple probes with some new circuitry. We also took more data with the rf magnetic pickup probe, which was calibrated a while ago. ICRF worked as usual (hardware working fine, but no plasma heating) after a filter replacement. New triple probe circuitry allowed us to take useful data. The ion saturation currents were lower than expected and we changed some resistors to increase the signal levels. We took several good sets of data on the scope; they were stored on floppy and are being analyzed. We can extract a plasma density out of these measurements, and we expect it to be low - how low remains to be seen. Floating potentials were on the order of -40 volts (so Te=10 eV). A higher noise level was observed during the ICRF pulse, but it seems that the signals can still be extracted. RF pickup probe: We noticed small bumps (increases) in the signals when plasmas were inboard limited, but only for those plasmas which were still healthy (the current was still rising and the plasma had not disrupted). Examples: 36978, 83, 84 A typical increase was from 1.1 Gauss to 1.3 Gauss, noticeable but not dramatic.

Thursday February 6 09 33 Maurer 36896-37035 Rotation

... the second shift

Ran plasmas for equilibrium reconstructions for Youhong. Got well centered discharges with essentially constant edge q and major radius over a ~2msec(from about 2 to 4ms during the shot) period with limited MHD that should be good for the VALEN eddy current calculations and Tokamac runs. S. Paul came in for a late night run. We fixed the previous run's problems with signal level and then ran a series of discharges where we systematically varied the puff time to investigate changes in measured intensity levels and effects on the observed rotation rates. More analysis needed, but there were incouraging correlations between mini and major disruptions and the ion velocity being driven to zero. The ions are inferred to rotate in the direction of Ip. Also, TS triggering work was carried out during the ICRH run. There are still some noise issues to sort out with the AC coupled scope inputs. No recognizable scattered light was observed when we did take shots with the plasma. (Alex)

Tuesday February 11 06 08 Pedersen/Maurer etc 37036-45 VF Feedback

The feedback coils are all connected and polarities have been checked. The total series resistance is 32 mOhm, as expected. We pulsed the OH and the VF and looked at the induced voltages in the feedback system. These voltages peak at 2-4 kV. The VF start and the OH breakdown spike each contribute at that level but with opposite polarities. The OH spike induced voltages are roughly in line with expectations, but the VF start was not expected to induce as much voltage as it does. In other words, the coupling between the old VF and the feedback coils must be larger than expected. We consider the voltage level safe for the LANL power supply, which is a 10 kV power supply that will be connected to the FB system through a large transformer.

Thursday February 13 06 16 Maurer/Pedersen none Plasma position feedback

Good news and ...more good news: First, the previously reported induced voltages in the FB systems are off by a factor of 10. The scope probe used was actually a 1:100 divider rather than a 1:1000 divider. Hence the induced voltages were actually on the order of 200 V, which is much more in line with expectations. Nicolai calculated coupling coefficients as follows: Feedback coils - OH coils: c=0.0065 (design value 0.0025) Feedback coils - VF coils: c=0.027 (design value 0.018) No gross discrepancy, in other words. Second, we pulsed the Feedback system with the one LANL power supply. It worked very well with current rise from zero to about 200 A in about 100 microseconds. Data was recorded with the scope for a more precise analysis. The cos theta coil pickup will be recorded on a later run day.

Wednesday February 19 09 07 Nick none

The run-summary page is working again. Upgrading to 10.2.4, rewrote the httpd file without PHP support which is necessary for this script to work.

Wednesday February 19 05 17 Maurer fixing SXRs...

Yesterday and today were spent re-installing the SXR fan array which has been off the machine since the top middle VF feedback coil was installed about two weeks ago. The amplifier box, new table and extended bellows are now setup. The cabling was run differently to help minimize icrh pickup (hopefully) in the future. Initially there were 7 "bad" channels. All appear to be working except for channels 14 and 16 which are open circuit at the vacuum feedthrough. These two channels have been bad for some time. It is not known whether this is due to a bad vacuum side connection or if the diodes are bad (usually diodes fail short when the junction fails). The other channels (1,2,10, 13,15) had either faulty amplifiers or cabling problems that have been fixed except for a small oscillation on 13 and 15. We should be able to get an emissivity centroid out of the array as a check on open loop jog experiments with the new VF feedback coil.

Friday February 21 11 00 Pedersen/Maurer 371??-37206 Radial feedback/triple probe

We did several open loop tests using the LANL into the power supply and operated the triple probe as an ion saturation probe. Open loop tests The open loop test shots were 37190-37206. We found a significant pickup on the cos theta coil when pulsing the FB system. There is a simple proportional pickup but there also seems to be a smaller pick up that looks like it decays exponentially. Not sure about what to do about that one. We have enough data to nail down the calibration factor for the simple linear coupling, and can then proceed to get a believable major radius signal. The LANL worked very well, giving up to 300 A, but the signal generator used to drive the LANL waveforms gave us some problems. It is too early to conclude anything about the efficacy of the new feedback system, since the major radius measurement is contaminated by pickup. The SXR fan array may provide useful independent measurement of the radial position. We can report a preliminary analysis at the Monday meeting.

The triple probe was operated in ion saturation with a 300 V battery to ground, with a 24 Ohm resistor used to measure the ion saturation current. Signals were much better than when operated as a triple probe and the densities are higher too. I suspect that one of the probe leads/connections or the triple probe box is flaky, and I would discard the data taken last week on that basis. One probe tip seemed flaky at first but then started working, the other two were fine. Densities for outboard limited shots start out in the low 10^11 cm^-3 range and gradually increase to about 5*1011 after about 5 ms. These numbers assume a constant 10 eV electron temperature and that other calibration constants are also accurate. They are a factor of 5 larger than the inboard limited plasma densities reported with the triple probe circuit. Signals are bursty but follow the overall evolution of the plasma well. We need to do inboard limited discharges next. At present, a single probe tip is being digitized in the north rack and a calibrated density (assuming Te=10 eV) is in the tree with the tag ne_inboard

Tuesday February 25 05 21 Maurer MC feedback

Reconfigured crunch amp box and input sensors today for mode control feedback using new gap coils. Checking polarity of signals and magnitude of feedback gains. Initial plasma shots with feedback taken. More of the same tomorrow.

Thursday February 27 05 45 Maurer/Pedersen 37265-37266 VF feedback

Todays run objective was to continue VF open loop jog experiments with the new VF feedback coil. Unfortunantly we did not get very far. The LANL charging supply failed at the start of the run day. The day was spent toubleshooting the supply(Nick has ordered the required parts to fix it). To be able to run we have currently swapped in the charging supply for the other LANL amplifier. Its installation is nearly complete (one dump relay is not working). It should be up and ready tomorrow morning. A calibration error was discovered in analyzing triple probe data. The calculated density form isat measurements is now approximately ~2e18 per cc on the inboard high field side edge plasma. This value is much more in line with other previous outboard Langmuir probe measurements. Also, mode control feedback data was taken yesterday. Analysis is underway. The new u-port adapter checked out OK and is currently installed in the icrh rack. Reminder: Tomorrow we going up to Argon to re-align Thomson scattering.

Friday February 28 05 16 Maurer/Klein

HBT-EP was up to ~200 Torr of Argon today in order to align Thomson scattering. We are currently pumped down using one cryo to 2e-6 Torr with the base pressure comprised of Argon and H2O. The bake has been turned on. Both cryos were regen'ed during the up to Argon. The TS align had some problems. The stray light level appears to be enhanced over the previous alignment in November. We can discuss this further at the Monday meeting. The LANL supply is back up and running. All the dump-interlocks are now working on the charging supply.

Monday March 3 05 56 Liu 37267-37300 clean up

1. shots 37271-37275 are vacuum shots. When all Krytrons were on and took OH only shot, there was current pickup (about 100-200A) in VF Rogowski coil. However, when VF Krytrons were off, there was no pickup in VF Rogowski coil. This is consistend with prof. Muael's prediction. 2. shots 37276-37300 are clean up shots. plasma lasts 6ms.

Wednesday March 5 06 46 Maurer/Paul 37308-37355 rotation

Doppler rotation data taken using the Thomson scattering viewport to measure the perpendicular plasma He emission. The measured wavelength shift is constant to within 2/100ths of an Angstrom (equivalent to +/- 1km/sec rotation). This constant value will be used to set the baseline of the measurement. There is a baseline shift due to temperature drift that is in the process of being calibrated out now that other systematic errors have been removed. Analysis underway. In taking off the TS collection optics to mount the rotation optics for todays run, a burn spot on the Nikon collection lens was noticed. This might be effecting the position alignment and calibration. Please stop in tomorrow Alex so we can talk. Lastly, we had problems initializing the crates at the end of the day. An unknown RMA error in the action monitor was a sympton. We were unable to correct the problem. cua900 will be rebooted tonight and we will try again tomorrow. This could delay the start of the VF feedback run Thurs.

Thursday March 6 05 27 Maurer/Pedersen 37363-373425 Radial Feedback open loop

Today we did the open loop tests of the radial position control system. It was a very successful day. With the aluminum shells at 8 cm, the plasma moved 2.5 cm in 1.5 msec when we applied a 4 msec square pulse of 250-300 A to the FB coil system. Positive current made the plasmas move inward, negative currents made the plasma move outward. Inward moving plasmas would disrupt early. With the shells at 4 cm, the plasmas were observed to move approximately the same amount but it took about twice as long to get there. The response looks approximately like an exponential decay, consistent with a resistive decay. The outward movements were confirmed by the soft x-ray centroid, which also moved outward. The inward moving plasmas did not have a clear signature on the soft x-ray centroid, presumably because we have several bad channels on the inboard side. Some problems with the LANL control prevented us from doing more fancy waveforms, and will need to be fixed before closed loop feedback can be attempted.

Wednesday March 12 07 07 Paul/Maurer/Cates 37429-37497 Rotation Diagnostic Comissioning

Run was devoted to gaining confidence in the toroidal rotation measurements. Known from earlier runs that the screenroom temperature slightly affects the diagnostic, even though the diagnostic housing is temperature controlled to within 0.2 degrees C. 37429-37445 optimize shots for duration and minimum MHD

37446-37452 track down noise appearing as isolated spikes in rotation diagostic

37453-37464 align detector to look perpendicular to plasma flow; take reproducible shots and record dependence on screenroom temperature

37465-37497 switched to normal toroidal view to look at rotation:

conclusion: 1. once the helium in the plasma is ionized (after 2 msec), the measured value of toroidal velocity is within 1 km/sec of zero.

2. plasma seen to spin up steadily in the toroidal direction up to 6 km/sec in counter-clockwise (looking from above). Plasma velocity abruptly drops to zero (in < .5 msec) about 1 msec before the end of the shot. Plasma always disrupts subsequent to the locking of the plasma rotation. Sometimes the rotation will drop to near zero, but the plasma recovers and spins up again, only to lock a second time and disrupt fatally.

3. For most shots, plasma rotation increases over the lifetime of the shot, never reaching a steady value, when the locking and disruption occurs. On a few, the rotation appears to saturate. On such shots the SXR signal also saturates and rolls over. On the more common shots, SXR increases steadily and drops suddenly just prior to the disruption.

4. I am fairly confident in the results from the rotation diagnostic once the helium is ionized. The next step is to use various techniques, beginning with the bias probe to alter the plasma rotation and see the effect.

Thursday March 13 04 39 Maurer 37498-37514 Feedback & Setup

Today we ran plasmas in preparation for mode control feedback and started to set up the bias probe and mach probe for future experiments. The capacitor bank for the bais probe was run through a dummy load at the end of the day. It appears to be fine. I had a few problems with the pwr supply and a flakey trigger before it worked. We will re-route cabling tomorrow. We should have both probes in the edge plasma tomorrow(that was the goal for today). As a side note, the LANL unit was tested again on Tuesday with its repaired charging supply. The output is railed at 250A(as it was in last weeks expt) when no input is applied! For the initial VF feedback tests of Feb and early March we ran the unit about once a week for a 6-8 hour period. This output is possibly caused by an offset drift somewhere after the input stage that needs to be tweaked or a bad driver tube on the hot deck. We're flying somewhat blind without schematics for the amplifiers so it may take some time to figure out the actual cause. The output tubes appear to be OK in the sense that they turn on and draw the same filament current. Our attempts at actual position feedback will be stalled until this is fixed.

Tuesday March 25 05 21 Maurer 37588-37627 MC Feedback

Todays run goal was suppression of disruptions induced by 3/1 RWMs using the new mode control coil set in order to compare performance of the new system with smart shell feedback. I had great difficulty getting good RWMs to suppress in making the plasmas. The 3/1 external mode observed today was a short bursty fluctuation (almost delta function like) giving a fast kink that only caused minor disruptions. I am using similar bank settings, etc. that we have used in the past to make good RWMs for the smart shell experiments. Varying the Ip ramp rate and initial q after plasma startup did not have a significant effect. Shilov has agreed to run Friday instead of tomorrow, so I will continue with these experiments on Wednesday!

Thursday March 27 05 15 Pedersen 37640-683 ICRH

We ran the ICRH today. Not much progress to report. Most of the day was spent developing discharges that move inboard without disrupting but the run was cut short because of a water leak that is being fixed now. The ICRF was fired on a small number of shots and appeared to behave as usual.

Thursday April 24 05 42 Maurer 37940-37960 biased probe

Ran plasmas in D2 today. Checked out new triple probe circuitry. The new box is working fine (first actual triple probe operation!). Measured Te~12ev in the high field side edge and densities (a few 10^12 per cc) were similar to those that were measured when the probe was measuring just isat previously. Some minor wiring needs to be done and then we should be able to install the box in the north rack and have it as a day to day diagnostic in the tree (Pedersen). Ran biased probe shots later in the day. Had some problems with the floating potential measurement that need to be fixed. So the run was not too productive. More tomorrow. Ended the day by installing and testing the differential amps in the north rack for real time Ro in the control room for position control. One of the four chs checked out ok, but the other three had clipped square wave outputs with a sine wave input. Not sure why. I will pull the box out and we'll have to test it on the bench to see why. It was working previously. An aside on run summaries... As a group we have been somewhat forgetful as of late in writing up run summaries (myself included). To help in jogging our memories to do so Thomas and I thought it would be useful to remind run operators that writing the summaries is not optional. It is mandatory (similar to the checkout list that must be filled out prior to running hbtep). In the future please submit forgotten run reports the next day or asap. Thanks.

Friday April 25 05 43 Maurer 37961-37967 setup for VF feedback

Progress was made on getting real time Ro in the control room today. (I thought this would take the morning, but it consumed the whole day) Pulled the differential amps for real time Ro in the control room out of the north rack this morning and bench tested them. The dip swtiches for the gain stage must have not been been switching properly. I had set them for unity gain yesterday and I must not have pushed down hard enough to engage the switch on the three that were not working. The clipping observed yesterday was due to them still being set for high gain (G=1000). They work fine now. I changed the input integrator on the board to have an RC time of a hundred microseconds so the west rack signals are not so highly attenuated but still low pass filtered for noise.

Signals from the north rack and then west rack to the control room checked out ok through the whole isolation system. The differential amp gain was adjusted so that the "system" gain was ~1 at 1kHz. Plasmas were then made with the actual Ip and cos1theta signals form the west rack going over to the north rack and then via the iso-network to the control room.

Good news: the data base signals for Ip and Ro look uneffected (recall that the everything looked like a flux loop when previously connected). Not so good news: the observed signals in the control room have features of being correct during the bias and startup phases of plasma operation, but then saturate and are pinned at 4.5V throughout the rest of the discharge. Perhaps there is an extra gain I measured incorrectly.

Tuesday April 29 05 08 Rivera/Maurer none LANL fix

Today we made some progress with fixing the LANLs. The LANL hotdecks were taken apart and tested. It looks like one side of the push-pull output now works. Some history: Previously, problems were fixed in the output stage of the low voltage feedback inputs(input trigger and feedback signal electronics). This had minor effects on the railed LANL output. A bad power supply was then found in one of the hot deck drivers and replaced. After which we were then unable to generate any output at all. Today the trigger and feedback signals were measured at the input to the hot deck and checked out OK. A mosfet that drives the hot deck driver tube on the A-side did not have the same feedback signal superimposed on it as on the B-side (A and B are the push-pull sides). This might still be a culprit in the way it was not working before. We can not say exactly because more than one thing has been fixed prior to being able to measure the output LANL current. We then carefully re-assembled the hot decks and powered the system up. The output is now a half wave rectified version of the input sine wave (with no large offset!). It looks like one side of the push pull configuration is now working. The lack of output after the first hot deck fix was probably due to bad/missed connections or the driver tubes weren't seated properly when it was re-assembled (we think).

Wednesday April 30 04 55 Maurer 37968-37977 biased probe

Ran plasmas in 10% Helium for biased probe rotation studies. Fixed the floating potential measurement box and reinstalled it for the days run. Still could not get a good Vf measurement. The digitizer signal looked essentially like a flux loop. I thought this was due to pickup from my extra long cable runs to the south and then north racks since we've moved the probe 180 degrees around the machine to the microwave interferometer section. Previously when the probe was at the old mach probe stand by the south rack I had no such difficulties with the measurement. After inserting the probe more deeply into the plasma to see some type of plasma potential fluctuation signiture on top of the flux loop pickup on the signal it still looked like a flux loop alone. I then checked continuity to the probe tip mechanically in two different ways. It appears that the feedthrough connections to the probe tip have opened up since it was installed. I believe I'll have to pull it behind the gate valve and check the internal connections out at atmospheric pressure. Too bad. This is now probably a good time to switch the positions of the internal magnetic probe and biased probe stands since I am bringing the bias probe head up to air ( so the new internal magnetic probe is at a chamber section with stainless shells instead of aluminium). We can start this in the background while people run Thurs and Fri.

Thursday May 1 05 05 Cates 37978-38020 RWM Smart Shell Feedback

The Smart Shell Feedback configuration was setup and tested for a RWM run using non disrupting RWM unstable plasmas. shots 37992-38007 were discharges with moderate current ramps which had sizable RWM modes and then large tearing modes later in the shot. Feedback with full gain and coverage was applied to these shots in an attempt to see changes in mode growth rate and rotation frequency. The rest of the shots were an attempt to get a plasma with a mild current ramp which was unstable for a longer period of time, but the plasma was moving around a lot in major radius so I was unable to get a better target plasma to apply feedback to.


I used the 10% He gas mix and Steve Paul's rotation diagnostic was online - there may have been some offset problems due to the screenroom being warm at the start of the run (shots 37981-37985). For a few shots (eg 38007,38015) the trend of the rotation signal was slowing down with time - the opposite of the normal temporal evolution - this may be due to a changing major radius, but is worth checking out because it is the first time we have seen this trend.


Dave was able to get real time signals of the plasma current and Cos Theta rogowski coils to the control room for use with the dsp.

Thursday May 8 10 43 Cates 38045-38064 RWM Traget Plasma Development

In the morning the Ebara cryo pump adsorber was replaced and the pump was regenerated. The pump temperature was cycling from 8K to ~40K before the change - this symptom was resolved with the new adsorber. Afternoon run was an attempt to create fast startup (high beta) discharges with unstable RWM. I had trouble getting a fast startup and could not drive the initial plasma current above 8 kA. Something seems to have changed in the breakdown. I was running in 100% D2 - last week I attributed this breakdown effect to the introduction of Helium, but maybe something else is going on. Thomas tested the recently modified triple probe box, but did not get good diagnostic signals. The connection of the Cos theta coil to the north rack and control room for use by the dsp for real time radius measurements had to be disconnected because it interfered with the normal digitized signal by introducing a large pickup.

Friday May 9 11 24 Shilov 38067-39106 External Field

I continued with 3/1 external field experiments with current ramps. Running in 100% D2, I experienced the same problem of low initial current as reported by C.Cates in the previous run summary. Raising puff time to 1.7 ms seemed to fix the problem. Something may be wrong with the puff system. I'll check it tomorrow. Data from static and rotating external field application on current ramps was gathered in the afternoon. Still needs to be analyzed.

Tuesday May 13 01 49 Rivera none LANL fix

The LANL amplifier is working again. The output looks the same as it did when first turned on ~2 months ago. However, it should be recalled that at that time there had been an offset in the feedback signal due to a failing tube in the ouput stage. A problem that was not addressed with this fix.

Thursday May 15 01 27 Shilov 38107-38158 External Field

(note: Shilov is referring to krytrons when he writes ignitrons -Nick)

As I expected, the recent problems with plasma start up was due to a half-dead battery in the puff unit. After replacing the battery I was able to reduce the puff time 2 times compared to what I had to set it in the previous run. The reproducibility also improved. Some good data with rotating external field was collected. Later in the day I started having problems with VF CB bias ignitrons (both) firing spontaneously. Nick suggested it was due to ignitrons' age and cut the 'keep alive' wires from the ignitrons. It seemed to fix the problem with the spontaneous firing but produced another problem which was that the bank wouldn't fire ~20% of the shots. That was pretty annoying. The end.

Thursday May 15 04 29 Maurer none fixing cryo

Cates' run was postponed today so we could pump and purge the ebara cryo He supply to see if that stops the temperature cycling that started Monday afternoon (Shilov ran with only the cti cryo Wed). The adsorber that we replaced last Wednesday appears to have only temporarily solved the problem we were having. If this does not fix the problem the seals are mostly likely bad in the expander head and will either have to be replaced or a rebuilt pump head purchased.

Monday May 19 04 36 stillits 38163-38174 Ip signals

Ip raw signals from North rack were tested in DSP. Unfortunately, the output signal from the DSP did not give the correct profile for the plasma current because the raw data received from North rack was influenced by noise (similar to a flux loop). We have to check it out tomorrow (Tuesday).

Thursday May 22 10 35 Maurer none cryo repair

Wednesday was spent taking off the ebara cryo to be sent out and rebuilt. It was FedEx'ed by the end of the day. The gate valve on that pump stand has a through leak at atmospheric pressure. This brought the base pressure in the chamber up to a few times 1e-7Torr while we were taking the cryo off. We blanked off the 10" gate valve and pulled a rough vacuum behind it to stop the through leak. The base pressure in the chamber is now back down to what it was prior to taking the cryo off at 1e-8Torr.

Tuesday June 3 04 43 Pedersen/Stillits/Rivera none LANL/Radial feedback

Today's objective was to control the LANL power supply (driving the feedback coils) directly from the DSP in open loop configuration. We were partly successful: We were able to control the LANL with the DSP but the signals were noisy and distorted to the extent that this problem will need to be fixed. We narrowed the problem down to the optical isolation output having trouble driving the input on the LANL when the LANL is gated on. We are investigating why. Otherwise, the LANL was working well (except tripping too often), there were minimal current offsets, when driven directly by a signal generator. Also, the optical isolation network seems to be fully functional except for its inability to drive the LANL input. Signals looked clean when input into a scope at both 1MOhm and 50 Ohm.

Monday June 9 02 54 meeting time

The weekly HBTEP status meeting shall forthwith be held at 9:30am Monday mornings in the control room.

Thursday June 12 10 24 Muarer none intalling cryo

The rebuilt cryo arrived yesterday and was re-installed in the afternoon. It was cooled down late yesterday and was valved open to the chamber this morning. Base pressure is back down to 6.6 e-9Torr with the rebuilt cryo head a 8K. Shilov is making plasmas today.

Friday June 13 10 45 Shilov 38276-38314

Clean up shots. Plasmas OK

Monday June 16 05 19 Pedersen/Stillits/Rivera none LANL/Radial control

We used the afternoon to check out the LANL some more. A reference signal was reconnected following a conversation between Dave Nadle and Nick Rivera. This did not substantially improve the signals, which were rather noisy. We then tried to use a 1.5 V battery to generate an input signal to the LANL certifiably free of ground loops. The LANL basically ignored this signal and put out a current of -5 Amps regardless of the polarity of the battery, and whether it was hooked up at all, and even when it was connected in parallel with a large capacitor. I now suspect that the input on the LANL is malfunctioning. On the bright side, 5 A of offset is 40 times better than it used to be. An arc inside the LANL stopped the run and will be checked out tomorrow.

Wednesday June 18 10 30 Shilov 38315-38384 RWM, External Field

I spent the morning developing reproducible target discharge with q* approaching 3 slowly from below. It was successfully achieved after a while. Later in the day I applied static and phase flip external fields to the plasmas. The results look promising. The data is yet to be analyzed.

Monday June 23 03 04 Cates 38423-38454 RWM - IP Ramp

Friday 6/20 - Discharge development in an attempt to get a plasma with a RWM which grows slow enough to observe growth rates without disrupting the plasma. By the end of the run, I was able to get plasmas which would work well for a systematic feedback study. These shots (38444-38454) had large 3/1 modes which grew and saturated in .25-.75 ms with frequencies of 4-7 kHz - excellent targets for our smart shell feedback system.

Tuesday June 24 05 29 Cates 38455-38490 RWM Smart Shell Feedback

I continued making the mild current ramp discharges which looked promising from last week. After finding a fairly reproducible shot, I applied full gain smart shell feedback to the plasmas. The feedback clearly alters the rotation frequency of the mode, and sometimes reduces the amplitude. I will need to check the mode structure and growth rates more carefully. I am looking at the RWM in the first 4 ms of the shot - but these plasmas do last to 8-9 ms with significant SXR sawteeth and saturated tearing modes in the second half of the shot.

Tuesday June 24 09 03 Shilov 38385-38422 External Field

I continued with 3/1 external field experiments on the target discharge developed previous day ( ex. Shot #38371 ). The naturally growing RWM was observed with a short unstable time window between ~2.3 3 ms. The plasmas lasted for ~ 3-4 ms. I applied static external field with phase flips at 2.5ms and 3 ms. After analyzing the data, it looked like the RWM mode is unstable around q ~ 2.8 and stable above that value which could be related to the error of the edge q measurement. Unfortunately the data collected wasnt sufficient to make any conclusion on the difference between plasma field phase rearrangement time at 2.5 and 3 ms. I will continue with the experiment this week.

Thursday June 26 11 51 Shilov 38492-38542 External field

Continued with 3/1 external field experiments with the previously developed discharge. Took a lot of phase flip shots with different flip times. The data is being analyzed.

Friday June 27 02 01 Alex Klein n.a. T.S. calibration

HBT-EP was filled to 170 Torr nitrogen. The non-laser wavelength channels showed a signal when laser was fired through the chamber, due to Raman scattering. I checked to note absence of breakdown in laser beam at this pressure. Collection optics were carefully aligned to maximize signal, then I proceeded to pump down and to collect sets of 5 data sets (for averaging) on scope at several pressures. The signals appear to depend linearly on fill pressure (good). Complete dissappearance of signals at pressures below 1 Torr show absence of stray light leakage into non-laser wavelength channels. Ease and accuracy of interpreting T.C. gauge for nitrogen is a plus. Ease of aligning collection optics in the absence of stray light is a great plus.

A minus: Chamber appears to be water logged; it remains to be seen how dirty of an ordeal a nitrogen calibration is. Will analyze todays data and write short report on Thomson Scattering system.

Monday June 30 05 04 cates/stillits 38542-38559 cleanup & ip-signal testing

Cleanup runs were performed. Ip-signals from north rack: signals are looking much better (having almost the right profile), but the signals are too constant - looks almost like a step-function (which gives a linearly increasing plasma current). We have to check that tomorrow.

Tuesday July 1 05 56 Cates 38560-38619 Clean Up

Clean Up shots taken to recover from up to nitrogen for Raman scattering calibration. Current Ramp discharges are fairly consistent, although the loop voltage is still around 10 V for a standard 10kA plasma (compared to around 5 V last week). Royce has been testing the triple probe: We tested the triple probe's electronics circuitry box today using the oscilloscope. Channel V1 and V3 performed as expected. V2 which will indicate the temperature is still saturating the scope so we are reducing the floating potential from 1/5 Vo to about 1/10 or 1/20 to get a complete measurement; Overall a successful test. Remi has noticed a large magnetic pickup on the soft xray tomography channels which is present even when diodes are disconnected and amplifiers are off - he is testing the system to see if he can improve the pickup.

Thursday July 3 01 48 Cates 38620-38656 CLean Up

On Wed. I tried to reproduce earlier RWM discharges, but the machine was not quite clean enough to get reproducible results. As a reference the Loop voltage for 10kA current ramp shots was down to 7-8 V. So half way through the day I switched to taking high current, outboard limited plasmas which lasted as long as possible in an attempt to scrape the limiters clean. These shots improved through the day. Several diagnostics were tested during the day: Yuhong discovered that the flux loops have been disconnected for the month of June (shots 38257-38647). Remi was able to improve the magnetic pickup on the soft xray tomography channels by finding and removing a ground loop in the copper box. The triple probe electronics box was tested by Royce and signals were very noisy.

Tuesday July 8 05 18 Cates 38691-38723 RWM Current Ramps

This morning I took about 15 shots with high current and edge q near 2 in order to help clean up the outboard limiters. These shots were also good for testing the SXT channels. In the afternoon I switched back to mild current ramps in order to produce observable RWM growth rates. I was able to get good target plasmas with Ip and minor radius increasing monotonically and q edge slowly dropping below 3 to induce a 3/1 RWM at around 2-3 ms. See shot 38719 as an example. Unfortunately about the same time that I was able to get reproducible plasmas - the South Rack digitizer signals became flaky and I had serial highway errors almost every shot when storing the South rack data (the feedback sensor coil data). The south rack is being cooled properly and I am not sure what is causing the serial highway errors. Royce, Remi and Nicolai were working on the triple probe, sxt and vf feedback diagnostics respectively throughout the day - no big news for any of those systems.

Thursday July 10 09 58 Shilov 38724 - 38777 Ext. Field

I started developing a good discharge for RWM external field experiment in the morning. In the afternoon I started getting reproducible plasmas suitable for the experiment. Around that time the same serial highway error appeared and persisted as it did the day before. After a while it was in every shot. So no signals from the south rack could be digitized. I completed the run.

Friday July 11 05 01 Cates 38823-28870 RWM Smart Shell Feedback

First I examined some shots Mikhail has worked on with edge q going from 2.6 to above 3. After checking to make sure the feedback system was in good shape (one board needed a minor repair - signal 5BS1 was bad) I took full gain feedback shots on these discharges. The best shots are 38848-38859. I then switched back to the more standard current ramp shots I have worked with in the last couple weeks in order to complete a gain scan with feedback. Unfortunately the South rack serial highway problems began around 3:15. I did a few tests trying to eliminate this problem and found out that the problem does not go away after an hour with the south rack crate off, that it is not the crate controller or u-port adapter. It must be a problem with the camac crate itself, it did not occur until the crate had been on for about 6 hours, and did not go away in an hour. The plasmas were well behaved with loop voltages around 5V and the feedback system is working well, so it was a disappointment to quit early due to camac problems.

Tuesday July 15 06 08 Cates 38897-38960 RWM Smart Shell Feedback

I completed a gain scan with relative gain values of 1, .5 and .25 on current ramp plasmas with non-disruptive RWM's.

example shots:

38901 fb off

38902 fb on full gain

38934 fb 0.5 gain

38950 fb 0.25 gain

The plasmas were fairly reproducible and the feedback was working well. -Alex took Thomson scattering data - the laser fired flawlessly - the signal strengths were a little weak - which could be explained by lower density and temperature of plasma during current ramps. -Royce continued testing the triple probe circuitry and Remi tested soft x-ray tomography amplifiers. -Nicolai and Dave tested some buffer amps for getting coil current signals to the control room for use in the radial position feedback system.

Wednesday July 16 12 30 Alex Klein

Hello all: The following is a draft of the Thomson Scattering poster abstract to be submitted to APS. Any comments, suggestions, words of approval, etc. would be greatly appreciated. Thanks very much, Alex

"Thomson Scattering on the HBT-EP Tokamak" A. Klein, D.A. Mauer, M.E. Mauel, G.A. Navratil, C. Cates, M. Shilov,??? Thomson Scattering can provide accurate, non-intrusive measurements of the electron density and temperature in a plasma at a spatially and temporally localized point. Thus, this diagnostic represents one of the most attractive methods for measuring essential plasma parameters. We have revived the existing Thomson Scattering system on HBT-EP and improved the resolution and calibration of the instrument. The system is based on a design in use at DIII-D (Carlstrom, et al, Rev. Sci. Instr. 61, 2858, 1990), and uses a 800 mJ pulsed Nd-YAG laser and a five channel interference filter polychromater. Absolute system calibration is achieved using Raman scattering in nitrogen (Yamada, et al, Rev. Sci. Instr. 74, 1675, 2003), because stray light levels have become excessively high and the Raman technique is more accurate than calibrartion based on Raleigh scattering alone. The scattering system is triggered at key times during the 10 msec tokamak discharge; the obtained measurements are compared with conductivity temperature data for several plasma configurations.

Wednesday July 16 06 15 Cates 38961-39009 RWM Smart Shell Feedback

In the morning I took some more feedback data with reduced feedback gain to complete yesterday's gain scan. In the afternoon I ran the feedback at full gain with only the 10 midplane coils activated. I was able to get several good shots with feedback. examples:

38987 fb on

38986 fb off

Unfortunately I lost about two hours due to yet another camac thermal problem - a crate in the west rack has a bad fan on its power supply, and the power supply would shut off every few minutes due to overheating. The crate was stable the rest of the afternoon after adding an external fan to the power supply case. Nicolai and Dave successfully tested a buffer amp to fan out the vfc and ohc signals to the control room for radial position feedback.

Sunday July 20 11 00 Shilov 39010-39133 Ext. Field

I continued with 3/1 external field experiments on "high beta" plasmas. Collected some good phase flip data on Thursday. On Friday I was struggling to get the same reproducible discharge but the plasma s were really disruptive and I couldn't sustained then for more than 4 ms. After a while I realized that the TF bank setting was changed from 6.1 to 5.7 kV some time from Thursday evening to Friday morning without indicating that in the data base. After raising it to regular value the plasmas got much better but unfortunately the south rack camac error appeared at the same time. So I had to finish the run.

Tuesday July 22 04 58 Alex Klein 39137-39195 T.S. parameter space

Rather than run Thomson scattering shots yesterday afternoon, the entire day today was used for that purpose. Yesterday, the biased probe and the internal magnetic probe were installed instead. Todays runs: D. Maurer spent a good bit of time trying to create low temp. high n plasmas, to see the T.S. signals clearly with those kinds of plasmas (Ch. 2,3,4 should vary greatly in the 1-10 eV range). A few shots appear to show low temps according to T.S. data. Fill pressure does correlate with higher n according to T.S. data. Ch. 4 gives generally very hefty signal (up to 250 mV) and correlates well with density for a range of temperatures. The afternoon was devoted to try to achieve max temp and moderate densities, to try to see a signal on channel 5, which is supposed to be sensitive to higher temperature plasmas. Unfortunately, could not see any signal in Ch. 5. Will analyze all data from today more thoroughly later.

Tuesday July 29 05 38 Maurer 39299-39333 cleanup

Cleanup shots only were taken today. As mentioned at the Monday meeting the base pressure was an order of mangitude too high after the weekend bake out and had a N2/O2 ratio characteristic of air. A blown circuit braker and bad pump on a manifold that has a high pressure leak caused the problem. The pump was replaced yesterday and the pressure came down to 1e-8Torr. The manifold that it was connected to contains the limiter piece that we had difficultly sealing after our last up-to-air. This is most likely the location of the leak although we did not leak check separate sections of the manifold to prove it. The first twenty shots taken today were cold with no SXRs and Vloop around 10V. By the end of the day I was seeing some SXRs and the loop voltage was coming back down to 7V. We probably need another morning of cleanup before we get good discharges.

Thursday July 31 04 40 stillits/shilov 39334-39362 testing of signal

The raw and semi-integrated cos1T-signals were finetuned. The signals match the signals on the HBTEP-Tree. PS. CTX has asked us to shot down their camac crate every evening.

Wednesday August 6 12 15 Shilov/S.Pauel 39377-39422 Rot. Diag/RWM

The objective of the experiments was to reproduce RWM shots I use in my external field experiments running with 10%He 90%D2 so the Princeton rotation diagnostic can be used to measure ion rotation. As I pointed out before the plasmas were more disruptive compared to those with 100% D2 and it was hard to maintain q* between 2 and 3. In several discharges which parameters were close to those of target plasmas rotation diagnostic showed pretty constant ion rotation rate of 2-4 km/s. Also speculation can be made that the ion rotation is slowed down by the plasma magnetic field fluctuations. Good shot to look at are:




Also, as S. Pauel noted, the ion rotation measurement could be affected by the plasma moving inwards, which was necessary to maintain the desired q* profile. Since the view line of the rotation diagnostic is fixed, the He rotation was measured at different plasma minor radial.

On Friday 08/06 I tried reducing the He concentration from 10% to 5% by mixing gases from two bottles in the puff line. After the first attempt of mixing 100%D2 with 10%He and 90%D2. The rotation diagnostic radiation levels stayed the same. After the second attempt the levels went below the level required for rotation measurement. I assumed this technique of mixing wasnt working properly.

Wednesday August 6 04 00 Maurer/James/Klein 39432-39442 Probes/TS

Fixed offsets on the triple probe today. Fixed cabling and setup Mach probe. Should be able to piggy back and get Mach ignals in the tree tomorrow. Bad news: TS laser alignment was bumped. The laser was realigned through the aperatures on the optical table. Thomson signal was seen with plasma shots. Data analysis underway to see how much realigned signal magnitude differs from last weeks shots.

Thursday August 7 04 02 Maurer/James/Klein none setup

No plasmas made today.

Setup the capacitor bank, trigger and cabling for the bias probe. Finished setting up the Mach probe. In the process of installing the internal magnetic probe. Should have new data from all three tomorrow.

Friday August 8 05 28 Mauer/Liu/James 39447-39472 Diagnostic

D. Mauer tested the Bias Probe and data was taken. R. James positioned the Mach probe in the plasma (shot 39469), but the signals were weak. We will investigate more next week to improve the signl strength. Y. Liu hooked up the Hall internal magnetic probe system. The whole system is now operational! But there are some things that need to be checked -- channel two is noisy compared to channels one and three; channel four has some problems with the amplifier.

Monday August 11 04 13 stillits/cates 39475-39483 vfc/R - signals

The VFC-signal was fine tuned.

Output-signals for major radius, R, was obtained. The maximum difference in major radius from the MDS-scope and the output-signal on the scope is 3-4 mm.

Monday August 11 06 24 James/Cates 39484-39486 Triple Probe

Just a few shots taken. C. Cates gave an instructional session on how to affect changes to the plasma by adjusting various parameters. Unfortunately, we ran out of time. These 3 shots are an initial attempt to produce cold/inboard limited plasmas, ideal for testing the triple probe. We will continue to produce these cold plasmas plus hot, sparse, and dense plasmas for more testing in subsequent runs.

Friday August 15 11 52 Cates --- Power Outage

Due to the power outage yesterday the vacuum chamber went up to a maximum pressure of 2.2 mTorr. It quickly pumped down to 8e-8 Torr with the turbo pump, and is mostly water. Both cryo pumps have been regenerated and are now cooling. The ignitron cooling lines burst this morning when power was restored and flooded the basement. The water is mopped up and should be ok by Monday. The servers (cua900, beta, sherwood) are back up and running normally.

Tuesday August 19 04 36 Maurer/Rivera none none

No plasmas today. TF cooling oil system problems. The pump on the TF cooling oil turned on briefly and then tripped its 20A circuit breaker while getting ready to run. In inspecting the unit the pump motor is drawing 33A(the breaker appears OK). The starting and running capacitors both checked out OK. The bearings on the unit also seem OK. The compressor part of the unit turns on OK. The motor/pump unit does sound like its running loud compared to previous operation.

We are not sure if it is the pump itself or the motor that is causing problems at this point. We will remove the motor and pump unit tomorrow and test the motor to sort out what is going on.

Wednesday August 20 10 45 M. Shilov/ S. Paul 39382-39422, 39537-39550 Princeton Rotation

Ion rotation rate in the shots similar to high beta 3/1 shots stayed ~ 3 km/s. Natural mode rotation in these shots with 10%He is somewhat less and stays ~ 3-4 kHz whereas the mode rotation in 100% D2 shots is ~ 5-6 kHz.Also S. Paul noted that due to the plasma major radius shift by ~ 1-1.5 cm the rotation measurement could be taken for different minor radia and could not represent the plasma rotation dynamics. Good shots to look at: 39409 & 39412 & 39422 Ion rotation rate starts building up ( upto 8 ms/ in the shots with higher current ramp at ~ 4 ms when significant increase in SXR signals is observed and sawtoothing starts.Ex. Shot: #39538

Wednesday August 20 01 25 Rivera none

The motor was taken out of the TF cooling unit this morning and tested. It is broken. A new motor has been ordered ($350) and sent next day from a distribuor from NJ. If it gets shipped today we will have it Thursday, otherwise it should arrive Friday for installation. We are unable to run until this problem is fixed.

Thursday August 21 04 20 Maurer 39554-39574 clean up

The new motor for the TF chiller was installed this morning. The TF oil pump is working fine now.

Clean up shots taken in the afternoon. I had about 0.25V of SXRs on the central fan array channels by the end of the run. The machine cleaned up in about 15 shots.

The basement AC is broken. This caused serial highway errors at the start of the run. As a temporary fix until the AC is working, opening the basement rack door and using a fan to cool the rack got rid of the CAMAC errors. Shilov is running tomorrow.

Wednesday August 27 02 14 Maurer 39593-39621 Biased probe

Biased probe experiments were run all day Tues and Wed morning. The probe is up and running. The problems that I had last time with a fraction of the bank voltage appearing on the probe prior to gating the scr appear to be caused by leakage current through the scr itself. I removed a capacitor on the probe side of the scr that was put in place to attenuate high frequency noise on the floating potential measurement. The voltage that now appears on the probe prior to gating only charges the capacitance of the probe shaft which is small and quickly discharges through the plasma during the breakdown phase. I can run this way now, but we'll spec out a new scr for future use.

The shots taken were essentially probe clean-up discharges. With V_probe=175V the probe current was maximum of about 60A and changed significantly during the shot. The probe was inserted 2cm into the plasma edge. The plasmas would typically be pushed in by the VF when the probe was pulsed on, most likely due to impurites coming off of the probe itself. I think I will probably need another 1/2 day of cleanup shots.

Wednesday August 27 07 06 Liu 39622-39649 calibrate hall probe

All channels of internal magnetic probe are currently working well. Thanks Nick! VF only shots were taken to check all the channels. From those VF only shots, it's obvious that the vacuum chamber delays the soaking through of the vertical field a lot. A few TF only shots were taken to calibrate the hall sensors and more analysis will come out later on. Plasma shots show that the hall sensor signals are pretty quiet, which are within the bit error (~1Gauss). However, I couldn't see the magnetic field fluctuation, which is about 5 Gausses seeing from SMPs.

Thursday August 28 03 06 stillits/rivera xxxx Lanl

The lanl is working ! Excellent job, Nick !

We triggered the lanl with pulses (from the dsp) of different polarities and durations, and the lanl did what it was supposed to do.

Tuesday September 2 04 48 stillits 39664-39726 Testing Lanl ouput-signal

Lanl's output-signal is on the Tree (hbtep::top.camac.north:L8210_3:input_2). We pulsed (with a square wave) the lanl by the use of the dsp. We did not get perfect, but ok, output-signals. The spikes on the scope (in the control room), however, are gone ! The maximum difference between the output-signal on the mds-scope and the scope (in the control room) is 20-30 A.

Thursday September 4 04 34 Maurer/Liu/Stillts 39746-39768 Bias probe

Ran more bias probe dischages with the probe tip inserted 4cm into the plasma and biased at 150V into electron stauration. Still cleaning up the tip during the first 10 or so shots. Later in the day I saw the first evidence of driving MHD mode rotation to zero and then in the reverse direction. This phase did not last long, maybe 1/2 to 1msec before the modes would re-accelerate in the opposite (natural rotation) direction. There appear to be amplitude effects while this occurs that can be looked at to see what the correlation is between mode rotation and mode amplitude.

Facilites workmen finally stopped by and looked at the AC in the bank room. They need a part to fix the unit and said they will be back on Monday to finish the repair.

Nicolai worked on radial position control signals during the run and took more shots afterward. They seem to be OK after some problems yesterday with one of the buffer amps.

Yuhong also did some Hall probe shots at the end of the day to see how running more than one detector off of a single battery effects noise levels.

Thursday September 4 04 42 stillits/maurer 39726-39743 Signals. From yesterday:

We had hoped to take some open-loop shots, but we experienced some problems with the cos1T-signal. However, this problem was solved today.

Friday September 5 02 17 Maurer none

No shots today. H20 shutdown in Mudd Bldg for plumbing work. Regen'ed Ebara cryo since the compressor was turned off.

Saturday September 6 02 16 Maurer/Liu 39786-39820 Biased probe

Continued biased probe experiments from Thursday. Fixed a pretriggering problem and then slowly increased the bias probe voltage over the course of the run to V_bprobe=250V. The probe appears to be relatively clean now. I was able to reverse mode rotation from the induced Er. In some cases this did appear to effect the external mode amplitude. Hall probe data taken also.

Monday September 8 05 19 stillits/maurer 39821-39860 testing of signals

The cos1T- and Ip- channels on the diff. ampl. have been fixed and are now working. We are getting slightly better values for the major radius; the max. deviation is 3 mm (compared to the mds-scope).

Tuesday September 9 06 25 pedersen/stillits 39861-39884 open- and closed-loop tests

Open-loop tests (39862-39868) were conducted with success.

Moreover, closed-loop tests (39883-39884) were conducted. The desired position was R = 93 cm. The lanl was triggered after 1.4 ms, and the closed-loop algorithm gave the correct lanl-current. In both closed-loop runs the plasma moved in to R = 93 cm after 2ms before it moved out to R ~ 93.5 cm. So, fine-tuning of the feedback coefficients needs to be conducted to improve the feedback system.

Wednesday September 10 06 34 Maurer/Pedersen/Stillits 39885-39951 Biased probe/VFFB

Plasmas were ran today for closed loop VFFB tests and biased probe rotation experiments.

The biased probe voltage was systematically scanned from 100V up to 400V in a series of current ramp discharges that caused the q=3 surface to go external at about 2ms. The induced rotation appears to stabilize the m=3 mode as it goes out into the vacuum. More data analysis needed though. Also, in monitoring the triple probe density signal there was a systematic density increase with increasing applied bias voltage from 100V to 250V on the probe. Unfortunantly the triple probe stopped working during the run, most likely due to a blown chip, so I was not able to see the increase up to the 400V level. The probe current appears to saturate somewhat once the voltage is up past 150V at 50 to 60A. Tomorrow I will run plasmas with 10% He and the Doppler rotation diagnostic.

We made several closed-loop runs today (39891-39906) with different desired positions of the major radius (91, 92, and 93 cm). Some runs were more successfull than others. The biggest problem with the closed-loop runs seems to be the spikes in the dsp-calculation of the major radius, but we have fixed that by using an interpolation of the major radius. Moreover, we also experienced problems with triggering of the DSP; that also needs to be fixed. We will continue the closed-loop runs tomorrow.

Thursday September 11 05 37 Maurer 39952-39991 Biased probe RWM expts

Discharges were made today in 10% He 90% D2 to study the effects of biased probe driven ExB rotation on m=3 RWMs.

I setup a control shot similar to Shilov's with an initial edge q of about 2.7 slowly moving inward in major radius. The edge q would go through the 3 surface at about 3ms. This gave me a burst of m=3 RWM that lasted from 2 to 3ms of typically 3G max amplitude and frequency around 2 to 5kHz. To try and keep the RWM stability evolution due to the evolving current profile the same on a shot to shot basis I kept the start up bank settings the same and varied the OHEL a little on a shot to shot basis to always keep the q=3 surface entering the plasma edge at 3ms.

I gated the Bprobe on at different times during the wall mode burst with 100V or 200V on the tip. At the lower voltage I was able to torque the RWM frequency to zero and then down to -5 or sometimes -10kHz. The mode was still present at these rotation speeds. There were periods where the RWM amplitude appears modulated and correlated with frequency modulations as the mode rotation changed due to the probe.

The most interesting effects were observed at 200V on the tip. Gating the probe on at 1.5ms just prior to the usual onset of the RWM at 2ms spins the plasma enough to essentially suppress the RWM. What MHD is there before the probe is turned on (start up modes/noise) appear to rotate up -20kHz or so. More data analysis needed. To see this effect look at shots 39986 or 39987. A control shot is 39971 to see the typical RWM burst with no probe voltage. Unfortunantly, the Bprobe had some arcing problems at 200V that I don't understand, so I don't have too many shots like these yet. There also was a systematic change at 200V on the rotation diagnostic (although somewhat small maybe?). I will continue the run tomorrow once I cure the arcing problem.

Monday September 15 04 16 Maurer 39998-4007

Attempted to fix the bias probe by conditioning the tip with 1.5KV at 5mA power supply. The probe tip to ground resistance was 85kOhms before conditioning. After high-potting, the resistance to ground was about 5MOhms measured using the 500V meter. Vacuum shots with the probe tip at 350V had the correct RC decay. Plasma shots with the probe tip inserted 4cm into the plasma with 200V on the tip are still arcing unfortunantly. I will take the probe out tommorrow morning.

Good news: Triple probe electronics were re-installed and are up and running. Royce also finished bench tests of the differential amp for the Mach probe. We should be able to install it tomorrow.

Nicolai re-intalled his differential amp and tested out his signals. Everything is OK.

Tuesday September 16 05 38 stillits/maurer 40008-40030 testing of signals

Biased probe removed this morning. Arcing damage was found from the copper conductor to the stainless steel housing back by the mounting conflate flange. There did not appear to be substantial arcing or tracking on the Alumina itself from the Moly electrode. The probe is already under repair. We are shooting to have it fixed and re-installed by Friday.

The Hall probe saw its first kink mode fluctuations!

The signals were tested and are now working. Moreover, the new interpolated major radius calculation is also working (max. deviation is 1-2 mm) and without any significiant spikes.

Wednesday September 17 05 38 stillits 40031-40066 Testing of algoritm

I spent most of the day eliminating bugs in the feedback program. They were found and eliminated, and we got very nice and smooth output signals for the major radius. However, the output signal for the plasma velocity is not smooth enough, but that will be fixed tomorrow.

Thursday September 18 06 50 stillits 40067-40090 Testing algoritm

The new feedback algoritm with the velocity term added is working. The major radius has a max. deviation of 2-3 mm, and the calculated plasma velocity is close to the velocity in the scope. Thus, we should be ready to make the first closed-loop run tomorrow morning.

Friday September 19 05 18 stillits 40091-40114 cloased-loop runs and testing

40091-40108: testing of feedback algorithm with derivative gain. closed-loop runs:

40109-40110, we tried to stabilize the plasma at R=93 cm. It was partly successfull.

40111-40114 (except 40112, the dsp was not triggered), the desired position was R=92 cm (40111 is awesome !).

In these shots there are small deviations in the actual position, but they are only of a few milimeters. In future runs we will let the lanl be switched on for more than 3 msec because 3 msec is too short, as can be seen in some of the runs.

Monday September 22 06 45 stillits 40123-40146 cloased-loop runs and testing

Today, the lanl was turned on for 6ms (earlier it was 3 ms). Moreover, in all shots the desired major radius was R=93 cm.

We were able to stabilize the plasma at ~ 93 cm for almost 7 ms (shot number 40134). So, the lanl is working for 6ms.

We are experiencing problems shutting off the lanl when cos1T reaches a certain value. That needs to be fixed.

Corey fixed the major radius so that the major radius, which influences q and beta, is automatically recalibrated.

Tuesday September 23 06 36 Liu/Stillits 40147-40202 Feedback + Hall probe

We ran the feedback for R=93 cm (40147-40154), R=92 cm (40155-40165), and R=94 cm (40166-40178). Moreover, the duration of how long the lanl is switched on was increased from 6ms to 9 ms (from shot 40169). Because of that we were able to repeatedly create plasma of 7-8ms duration. However, the shots for R=94 cm are little too volatile, but that can be adjusted by lowering VF (the lanl was not triggered in shot 40170 and 40173). (Stillits)

Hall probe was checked for its low measurements on poloidal field. The reason is supposed to be the influence of the high toroidal field. I am trying to figure out if I can fix this problem. (Liu)

Wednesday September 24 05 21 stillits 40203-40229 feedback

Channel 2 (the Ip-signal) on the diff. ampl. was down today. So, shots 40203-40217 are useless.

In shots 40218-40222 we tried to stabilize the plasma at R=94 cm, and in 40222 we created a hot plasma that lasted for ~ 8.5 ms. In the rest of the shots we tried R=91 cm, but it was not a huge success. We were able to stabilize the plasma at R=91 cm for max. 1.5 ms (40223 and 40226). But it can probably be improved by changing some of the parameters.

Tuesday September 30 04 51 stillits 40285-40287 testing signals

We tested the Ip-signal (ch. 2). We are getting a signal now, but the signal looks like a ground-loop signal.

Wednesday October 1 05 13 Mauer/James 40288 - 40305 ICRH/Bias Probe

ICRH fired successfully today! We are still waiting for another crate power supply from Princeton or to receive one being repaired to get comprehensive data, but we did see the ICRH fire via an oscilloscope. We also saw pickups on the mach probe from ICRH which fires at about .002 sec. It looks like one of the channels is OOC on the Mach probe again so I am going to trouble shoot it tomorrow [James].

The bias probe is up and running again(only tested at low voltage yet). I had some problems with triggering that are fixed now at the start of the run. The SCR does appear to be going bad that is used to switch the bank voltage on to the probe tip. I was getting about 10V leakage on the tip prior to pulsing it with only 50V total on the bank. Probe cleanup shots tomorrow.

Thursday October 2 05 22 Maurer biased probe

Took biased probe cleanup shots today. The run was cut short because of problems with the TF bank. An eyebolt nut came loose and caused the one side of the rope dump to short the bank while it was being charged (the bank was at about 5kV). This boiled the local dump water resistor and blew its top off. The cupper sulfate H20 blown out of the first dump resistor appears to have then allowed a conductive path from the neighboring dump resistor, which was at whatever residual voltage was left on the bank, and then shorted the rest of the TF charge to ground burning an arc path in the wood shelf that the dump resistors sit on. The H20 has been cleaned up. We still need to cut out the carbonized material on the wooden shelf before we run again. This should be finished tomorrow morning.

Friday October 3 06 07 Maurer/James/Klein 40319 - 40350 Bias probe/ICRH

Tf repair was completed this morning(Nick and Jim). The bank was brought up to full voltage before lunch and tested OK. Plasmas were made in the afternoon and more biased probe clean-up shots taken. The probe tip was biased to 200V by the end of the day. It appears to still be a little dirty. More clean-up tomorrow at higher voltage.

The power supply for the ICRH crate was installed and is a permanent member of the serial highway! Took a few shots and worked out some triggering bugs. Now, the signals are in the tree and showing up on the scope but some of the inputs look switched (will diagnose this weekend). The Mach Probe is also installed and the digitizer for one of the channels is the problem and not the electronics; it will be switched to another open channel.[James]

Saturday October 4 01 45 Maurer 40352-40382 biased probe

Continued taking biased probe cleanup shots today. V_probe= 300V with I_probe=30 to 50A. Nothing exciting to report.

Tuesday October 7 05 34 Maurer/Stillits 40383-40422 Biased probe/VFFB

More bias probe clean-up shots and work on the VFFB signal problem today. First hints of a temperature increase on the triple probe were seen in some shots today. Not as dramatic as previously observed but an improvement from Saturdays run. Typical currents with 300V on the probe are about 50A. The probe appears to be clean enough to apply 100 to maybe 200V on the tip without disrupting the plasma. shots taken with 300Vs still cause the plasma to move in and disrupt, probably due to impurity influx. Hopefully the 200V case will be a useful ICRH target for tomorrows run.

The feedback system is up and running. Nick solved the problem we have had with ch. 2 on the dsp.

Wednesday October 8 06 36 Mauer/James/Stillits 40423-40461 ICRH/Feedback

It took about half he day to with the scope and signal generator to put the ICRH system back together again. Once that was figured out, we took a few shots before Shilovs Invited talk dry run. We were unable to perform the high density inboard limited plasmas with the working ICRF because of time restraints, but we were able to get some good baseline ICRF data while tuning the feedback system. If there is time, tomorrow afternoon we will try again with the bias probe (to get high density plasmas).

Subsequently, the feedback system has been fixed and all channels are operating normally. The feedback system (and most of the other diagnostics) was greatly affected by the ICRH discharge. Some sort of filter or shielding will have to be explored now that we are actively trying to couple the plasma.[James]

Monday October 13 05 22 James/Stillits 40557 - 40590 Testing (Triple Probe/Feedback)

Shots 40557-40579 Feedback shots to calibrate system with newly installed filters. ICRH Will fire tomorrow to test filters. [Stillits]

Shots 405780-40590

Tested the triple probe and mach probe electronics and they are working at spec. on the bench. When installed in the rack, density signal (triple probe) is still erratic and the right channel (mach probe) is flat/no signal. Concentrating on the triple probe (for the ICRH run on wed. and thurs.), I tested the cabling from the probe to the electronics with the high voltage meter and they were good. Next I bypassed the t-probe electronics and used the m-probes power supply, rogowski coils, and electronics/o-scope to test the raw t-probe signals. After 10 shots, the probe appears to be working normally, but more testing tomorrow so we hope to lock in a solution. Alex was able to prep Thompson Scattering and get signals into the o-scope. It is ready to go for tomorrows Testing. Thanks to Yuhong for hanging around and babysitting the new plasma shooters! [James]

Tuesday October 14 05 35 Klein/Stillits 40610-40630 Thomson Scattering

The plan was to create very hot plasmas which tend to be outboard limited, then use position control to (rapidly) push the plasma inwards into the field of view of the TS collection optics. In preparation yesterday, I (Klein) crudely aligned the laser. Should have done this more critically.

Today: Very healthy signals on all channels, including #5, which is supposed to come in to play for hot plasmas, was very encouraging. These signals were present for warm plasmas at r = >94 cm, surprising. Then we made hotter plasmas and pushed them inboards, as planned. Timed TS to coincide with r= 92 cm position. Signals looked the same. Finally, TS was fired after plasmas had long died: signals looked the same. Conclusion: laser beam is poorly aligned, scraping some edge or surface, overwhelming stray light is creeping into each channel. Will re-align laser and try again...

Tuesday October 14 05 50 stillits/klein/james 40592-40649 testing of signal + TS + IRCH

The feedback system is up and running again with the new filters installed. The max. deviation is only a few millimeters. That is also the case when ICRH is turned on. The problem we had getting the lanl to give a zero current when the semi-integrated signal for cos1T is less than zero has been fixed. So, we should be able to run the ICRH with feedback tomorrow.

Wednesday October 15 05 27 stillits/james 40652-40667 feedback + ICRH

40652-40655: The signals were tested with IRCH on.
40657-40669: The feedback was turned on and the plasma was positioned at 92cm.

40660-40662: The feedback was turned on and the plasma was positioned at 91.5cm.

40663: The feedback was turned on and the plasma was positioned at 92 cm. The IRCH was turned on at 2ms.

40663: The feedback was turned on and the plasma was positioned at 91.5 cm. The IRCH was turned on at 2ms.

Rough day at the shop for the triple probe. I was unable to diagnose the problem with the density channel. After making some repairs to the electronics and installing protection, the output was not correct. I was also unable to get the third channel to trigger on the scope and ran out of time before I could try the others. I will try those early tomorrow and if I cant get the probe to function as a triple probe, then I will run it as an Isat probe or use the mach probe electronics and use it as a double probe for ICRF testing with the Feedback system. [James]

Friday October 17 09 24 Pedersen/Stillits/James 40680-40733 ICRH

Today's objective was to do plasma-RF antenna coupling experiments using the radial feedback system to move the plasmas inboard in a controlled way, and the triple probe to confirm increased densities. Although we did not observe any clear signs of heating, we did see some antenna loading, so the run was successful overall.

Transient loading of the ICRF antenna was clearly observed on a number of shots, including on the order of 10 shots where the loading was clearly observed before the plasma disrupted (eg. 40692). Towards the end of the run day, a decent target discharge for further studies was developed.

Shots 40720 and 40723 are good examples of this discharge without ICRH. The radial feedback was preprogrammed to move the plasma from outboard limited to inboard limited for 1 msec, then back to being outboard limited. Ion saturation current from the inboard side triple probe (the box is still bad, hence no real density measurement) would increase by 30-80% during these jogs. On a number of shots we hit the plasma with ICRF during this phase. Most of these shots disrupted but a few survived (40728 and 29). These two plasmas were apparently not pushed far enough inboard to couple to the antenna. We will want to continue development of these discharges next week, hopefully with the Bdot probe and the triple probe box up and running.

Monday October 20 07 55 James 40734 - 40749 ICRH-RF Pickup Probe

Ran ICRF this afternoon to prepare for tomorrows run. I first used the o-scope to insure that the probe and transmission lines were operational. They did in fact produce a signal, though it seemed a little askew. I then tested multiple digitizers until I was able to get a signal. Finally I was able to reproduce a signal in the tree that resembled the signal in the scope, but not the typical RF B probe in absences of plasma; see shot #40749 (atypical) and compare to #36547 (typical). Also notice that the loop voltages are very different in these two shots, but I am not sure it could cause such a drastic difference in the RF B probe signal. In the morning I will run with a plasma and the ICRF and diagnose the problem if indeed there is one.

Monday October 20 10 32 Nick None

Since no runs were scheduled at this morning's meeting we used the time to modify the ICRH cabinet. The ICRH should not be run until I have time to inspect the cabinet for run readiness.

Tuesday November 11 04 31 pedersen/stillits 40751-40758 ICRH + feedback

We did not make any plasmas today because of problems with some of the U-port adapters.

Wednesday November 12 05 38 pedersen/stillits 40760-40802 ICRH + feedback.

We tried to create reproducible plasmas that behaved like preprogrammed in feedback:

1.8msec - 2.8msec: R = 93 cm

2.8msec - 3.8msec: R = 91.5 cm

3.8msec - disruption: R = 93 cm

At the end (shot#: 40795-40802), we were finally able to create reproducible plasmas that behaved as preprogrammed in feedback. The ICRH was turned on in shot# 40796, 40798, 40800, and 40802, but turned off in shot# 40795, 40797, 40799, 40801.

However, we did not see any heating of the plasma that could be a consequence of ICRH. Next ime we will try to push the plasma farther inboard (to R ~ 90-91 cm).

Thursday November 13 05 23 pedersen/stillits 40803-40836 ICRH/radial feedback

We continued developing discharges for ICRH coupling using the radial position control system.

The ICRH rack appears to give serial highway problems so it was bypassed. We (Corey+Dave) suspect the power supply is faulty. The rack was bypassed, so no antenna loading measurements today.

On the positive side, the triple probe box works fine, and did so all day yesterday as well, except for some minor offsets on the temperature. Using the triple probe inboard density measurement, we developed discharges that have 3.5-5*10^18 m^-3 density for about 1 msec as the plasma is shoved inboard by the radial control system (used in both closed loop and open loop feedback today). This is a factor of 2 improvement over typical inboard densities (2*10^18), and is close to inboard densities seen during inward disruptions (5 to 8*10^18). The ICRH was pulsed during some of these discharges. No clear effects of heating but we are somewhat limited by several diagnostics being offline (ICRH diagnostics were out due to CAMAC problems and the soft x-rays appear not to be working).

Further discharge development will be done when we have ICRH diagnostics available to confirm loading and coupling.

Friday November 14 04 10 stillits 40837-40877 ICRH + feedback

Shot# 40837-40867:

We tried to creaty discharges (with 20% H2) with and without ICRH. We were able to obtain inboard edge densities around ~ 5e18 m^-3 (shot# 40863, ICRH turned on at 3.5 msec), and we presumably saw an increase in temperature in shot# 40855 (ICRH turned on at 3ms).

Shot# 40868-40877 (Steve):

We tried with He 10% to create discharges that stayed at R = 92 cm for a considerable time. In the last shot we succeed in doing that.

Friday November 21 02 51 steve paul/stillits 40868-40922 rotation + feedback.

Friday December 5 07 37 Rivera/James/Mauer 40923 - 40937 ICRH

We tested the voltage dividers on the ICRF today via the oscilloscope and they performed as expected! Data from the run with voltage and current measurements is being analyzed. We are in the process of setting up the digitizer to make the dividers a permanent diagnostic measurement for the ICRH system. The CAMAC crate and power supply we ordered came in about mid-day and was immediately tested and installed. Preliminary tests show that it is operating normally. Shot # 40936 shows an ICRF only shot through the tree. The B-dot probe is not set up correctly, but the others are performing normally. Soon after this shot, we had some trouble with the dumps not responding to the reset controls in the control room. This problem fixed itself, but we are not sure of the cause or the fix. The air conditioners in the basement also froze causing the CAMAC racks to fail. We shut down in effort to let them cool off with external fans, but they were still over heated by the end of the day. Nick is working on the air conditioner repair, but until that is complete, we may have to revert back to shutting down during lunch and any other periods of extended down time between shots.

Friday December 5 12 24 STILLITS 40939-40941 testing software

Thanks to Mikhail, the software for the feedback system is now up and running.

John (study group) put the feedback current cable in the ceiling, and it is working.

Monday December 8 06 27 Maurer/Stillits/James 40949-40967 A little bit of everything

CAMAC problems from last week caused by ICRH rack, possibly due to the fiber optic cable to the u-port adapter. Everything is working OK now. Worked on circiuitry for capacitive dividers for ICRH. (James)

Shots taken to check out new control panel operation of radial position feedback setup writing text file to dsp, recompiling the program, and initializing the dsp fro an external trigger. So far so good! (Stillits)

Turned up gains for new RWM feedback. Checking out sensor and control coil signals. Real feedback on current ramps tomorrow. (Maurer)

S. Paul called and is planning on coming up Friday.

Tuesday December 9 05 15 Maurer/Stillits 40968-41007 testing feedback and software.

Checking, correcting and figuring out some errors in the RWM feedback wiring. Nothing important to discuss yet. (Maurer)

The software for the radial position feedback control system is up and running. The feedback system was successfully tested with new software and the new feedback-current cable. So, the feedback system is now operational!!! (Stillits)

Thursday December 11 10 33 Maurer 41007-41021 RWM feedback

Yesterdays run was cut short due to the same intermittent bank problem we had last week. The cap bank dumps were not reseting properly from the panic panel. Nick and I went to work on it this morning but the dumps worked fine. Again, the problem "fixed" itself. So we will have to wait until it breaks again(and stays broken long enough that we can diagnosis whats going on). When problems are about to occur the bias bank dump fails first. If you are taking shots the signature of this to look for is the OH bias bank controller not reaching full charge while the rest of the banks do(red light never goes on). The next time the dump button is hit on the panic panel the dumps will not reset. If this happens let Nick and I know so we can fix try and diagnosis whats going on.

Thursday December 11 12 01

Today at 1pm, I'll show how to use the feedback system.


Thursday December 11 03 59 james/pedersen/stillits 41025-41036 ICRH + feedback

We tried to create a discharge that behaved as a square-wave with respect to major radius. We succeeded in doing that when we got problems with the ICRH. The charging power supply in the basement is down.

Monday December 15 06 12 James 41069 - 41099 ICRF

It was slow running today. The CAMAC Serial Highway was down most of the morning and half the afternoon. Apparently there were some access violations that fixed themselves after Cory rebooted the system as the administrator. Some good news, the circuit breaker seems to be holding on between shots.

Had trouble with the B-probe as well. The L_8210 did not seem to be working. I replaced it with another and tested it with an fxn generator. Then tested again with new digitizer and both rectified and un-rectified signals. Neither signal was seen via the digitizer or the scope (turns out that the new L_8210 is not 1 mega-ohm, and a new 1mega-ohm will have to be found and installed, but the scope was set for 1 mega-ohm and it did not see a signal). I tested the resistance of the lead wire form the probe coil in the machine to the ICRH crate and there was none. There may be a problem with the wire, connections or the probe itself. I did just get signals from this probe after APS, so the failure is even more peculiar and recent. I checked the connector, and it was tightly fixed so I will have to probe deeper to find the solution.

I was unable to test the capacitive dividers at high voltage, but further analysis of the low voltage tests performed earlier last week show the frequency to be ~4.505 MHz.

Tuesday December 16 07 01 D. Maurer/S. Paul 41100-41174 bias probe with radial control

We were looking for fluid rotation effects with the bias probe turned on. Typical example without probe is 41124, where the natural rotation is about 5 km/sec in the ion drift direction (toroidally clockwise, when viewed from above HBTEP). Edge MHD measured by the shell probe increases from 5.2 msec onward on that shot, and the mode growth is coincident with the braking of the plasma. The plasma rotation slows to near zero by 5.9 msec, at which time the plasma disrupts.

For the most part, the probe seemed to make the plasma cold and difficult to control. Perhaps the reason is lack of conditioning as the probe was last used some time before the APS meeting. The best example of the bias probe's effect the rotation is 41145, where the ion flow was reversed, however that does not occur often. Shot 41142 had the bias probe turned on, yet the results were very similar to shot 41124, as described above.

The best correlate with high rotation appears to be a strong SXR signal. A good example is 41109 and 41127, where the edge rotation jumps following each sawtooth crash.


Friday January 9 03 42 Alex Klein n.a. TS calibration

Filled chamber with nitrogen and performed Raman type Thomson Scattering system calibration. Laser was stil aligned through the chamber, needed no adjustment, near perfect burn spot on inboard side. Laser energy still 800 mJ. Inspected optics, all clean and good. Collection lens was aligned carefully. Took 5 shots at each pressure (from 150 to 5 Torr), swapped Ch. 3 and Ch. 5 electronics to calibrate Ch. 5 and repeated. Data was saved in spreadsheet form for more precise analysis. Now will have to calculate gain coefficients for each channel.

Water contamination appears to be minimal (RGA says 10^-7 Torr, mostly nitrogen, after 1 hour pump down).

Wednesday January 14 04 06 Maurer 41175-41205 Clean-up

Clean-up shots taken after up to N2 for TS realignment and calibration. Plasmas lasting 5 to 6 msec by the end of the day. SXRs visible after only 10 shots or so. Will continue tomorrow.

Tuesday January 20 06 31 T. Pedersen, R.James, N. Stillits 41242 - 41257 ICRF

We were able to run ICRF (with no B probe) today. We took about 15 shots with the Feedback system on. We did see some signs of loading (comparing shots 41249 vacuum shot to 41256), but were again stopped short by what seems to be more CAMAC problems. This time in the VF current, and it seems to be intermittent. We will look into it more tomorrow. We are planning to try again on next Tuesday. It seems like we are on the right track with the high density plasmas moved into the antenna with the feedback system approach.

Monday January 26 04 16 Maurer 41258-41279 feedback

Took several VF only shots to start the day and check out the VF bank current monitor problems from last week. The digitizer/circuitry behaved correctly the whole run day. I will keep an eye on it this week to see if the problem re-occurs.

The rest of the day was spent taking set-up shots for the weeks feedback runs. I am starting to see some nice m=3 fluctuations as the edge q drops below 3. These are in shots that start with an initially low plasma current, have a rapid Ip ramp and send the q=3 surface into the vacuum anywhere from 2 to 4ms depending upon the bank voltages. I had some difficulty keeping the plasma centered and this would lead to some shot-to-shot variability. I plan to run tomorrow with the radial position control from the start to help keep the major radius from moving out and forcing the edge q too low. Todays run is cut short because I have to go in for my allergy shots at 5pm. I will continue tomorrow.

Tuesday February 17 07 49 Maurer 41477-41506 MC feedback

Todays run goal was to continue the feedback experiments of a week ago using the new mode control coil set with poloidal field sensors.

I had some difficulty during the whole run generating target RWMs to feedback on. Started to see small RWM fluctuations near the end of the day. Also had some difficulty breaking down late in the day. The D2 bottle is nearly empty (has been low for awhile) and I plan on changing it before tomorrows run. This might have lead to some of the problems getting a nice fluctuation to feedback on relative to last week where I was adjusted the puff time to change the RWM onset time with qstar. The feedback was turned on during a few shots to check the loop. Things seem to be OK. I will continue again tomorrow.

Wednesday February 18 05 28 Maurer 41507-41531 Feedback

Spent the day trying to setup plasmas for feedback. Still had problems with the breakdown off and on again. Changing the D2 bottle had small effect on the breakdown problems. As an aside the D2 manifold is showing its age. It has to be maxed out to just barely get the fill line pressure above 20 psig(where we usually run). This was one of the reasons I though the bottle was low and the high pressure side gauge might have been reading incorrectly. I now think think the high pressure gauge is OK. Also checked the puff fill pressure and it seemed reasonable at 2.4 e-5 for 1.5ms puff with the puff battery voltage at 223V (the input circuitry for the puffline says it needs 220V). Checked the egun and its working OK with 9A of filament current and 220V bias.

Later in the day I replaced the puff line battery with a new one (246V) and the breakdown became more consistent. I was able to get the puff time back down to 1ms and still had it breakdown. It looks like the battery was marginal and giving rise to most of the problems breaking down. Not much progress in setting up target plasmas as a result. More tomorrow.

Thursday February 19 05 55 Maurer 41533-41557 Discharge development

Spent the day trying to develop an Ip ramp down case with nice m=3 RWM fluctuations for feedback. Had no breakdown problems today. Discharges exhibited lots of tearing activity with minor or major disruptions before the q=3 surface went external. Some signs of RWMs but nothing as nice as the target plasma fluctuations of last weeks runs. The change in puff valve pulser battery has changed the machine fill pressure for a given puff valve pulse time. I am adjusting for this to effect to try an reproduce the previous runs RWMs with essentially the same bank settings. It hasn't quite worked out yet. I will continue tommorrow.

Friday February 20 05 17 Maurer

No shots taken today. Planning on Saturday feedback run.

Saturday February 21 12 58 Maurer none none

Came in this morning to run and found the base pressure at 5.5e-5Torr and the Ebara cryo head at 268K. The CTI cryo was still pumping, but the head temp was at 15K(a little warm, should less than 10K). After valving off the Ebara the pressure came down to 3e-7Torr and was composed mostly of water on the RGA readout. I spun up the turbo and switched over to it so I could regen the CTI cryo. The base pressure went up slightly to 5.3e-7Torr. I am currently pumping on the CTI head. I have also pumped out the Ebara cryo head. I turned on the bake to help get rid of the water.

The base pressure is now in the low 1e-6 range with the turbo only. I am not sure what happened to the Ebara cryo. After inspecting the compressor it appears to have blown one phase of its 220V, 3phase pwr. I found the cable plug had a blackened pwr pin on it. The circuit breaker appears not to have blown which I find confusing. Hopefully the compressor is not damaged. I will stay until the CTI head has been pumped on fully and turned back on to cool down. This takes 2 to 3 hours to reach final temperature. If someone who lives nearby wants to stop in at 5 or 6PM and switch over pumping to the CTI cryo once it is cold let me know. Otherwise I'll stop in Sunday and do it.

Sunday February 22 03 55 pedersen

I switched over from the turbo to the CTI cryo at ~3:30pm today (Sunday). Pressure was 2.7e-7 before the switchover and started dropping at a good rate when the gate valve was opened to the cryo. It is currently 9.7e-8 and continues to drop.

Monday February 23 03 53 Maurer None

Opened up the Hall probe array bellows to the vacuum chamber after the group meeting. The pressure went up to a few 1e-7 composed mostly of water. Kept the bake on until midafternoon. The base pressure is now in the low 1e-8 range. Nick is currently inspecting the compressor to make sure it has failed. We will try hooking it back up to pwr tomorrow when new plug ends arrive from McMaster. There was no obvious damage inside the compressor housing. Maybe it was just the plug ends that failed.

We have a quotation for an advanced exchange with a 2 day turn-around time (they have a matching compressor in stock) from Genesis Vac Tech if it turns out the compressor is bad. The price is $3950. I did not get a chance to take any cleanup shots today. I plan on starting tomorrow morning. After about ten shots or so if the machine still looks dirty I will glow in He. Also, Yuhong is ready to piggy-back and test the four Hall probe channels that she has installed.

Tuesday February 24 04 19 Liu 41560-41573 test Hall array

There were just two shots were caught in today's run and the rest of the day we experienced serial highway failure. Mikhail tried to bypass CTX and ICRH, but it didn't work out. The Hall array was working except they were more noisy than the old array. More shots need to run to analyze the reason.

Wednesday February 25 06 01 Maurer/Liu 41578-41639 Clean-up shots

Took clean-up shots today. Started to see SXRs and tiny sawteeth by the end of the day. The Ebara compressor is OK. The cable end only was damaged in the weekend failure. This is very good news. It has been re-installed and was opened during the last 1/3 of todays run. This helped quite a bit in pumping out stuff knocked off the walls. I had to raise the puff because I had trouble initially breaking down with both cryos pumping. It was after this that I was able to get some SXR signals on the fan array. Yuhong ran piggy back and worked on her Hall sensor signals.

The noise problem of the Hall sensors comes from the power of the amplifier. When I used a battery, one of which were used for Hall sensor current source, together with a car battery powered the amplifier, the annoying random noise was gone. Also, G=10/100 were tested for vacuum shots and both worked fine. I will monitor the Hall sensor's behavior when Dave runs tomorrow.

Thursday February 26 05 20 Maurer 41640-41682 Clean-up shots

Took more clean-up shots today. By the end of the day things were looking good enough that I was starting to develop a target plasma for feedback. Vloop was less than 10V at plasma start-up evolving down to 5 or 6V at discharge termination compared to greater than 12V yesterday during most of the run. I am switching to the shot type with a RWM generated by the initial qstar less than 3 and slowly evolving up to 3 (similar to shilov's case) that I used for RWM bias probe experiments this fall. This would typically give a burst of m=3 magnetic fluctuations between 2 to 3 ms. Yuhong also worked on her Hall probe sensor signals. There appears to be high frequency noise on the signals at discharge start-up and termination that might require filtering.

Friday February 27 05 16 Maurer 41683-41691

Only a few shots taken today. Tested out the Hall sensor array. The problems with noise are a result of layout and cabling problems. This is good news in that an input filter will not be needed. The actual layout of the 20 channel array will have to be done very carefully.

Monday March 1 04 12 Maurer 41692-41732 target plasma development

Spent the day trying to generate m/n=3/1 RWM fluctuations. Tried dialing in old shot number bank settings that Shilov used as a target shot. Plasmas generated this way were different from the database case, with typically higher loop voltage and different major radial and qstar evolution. The wall-limiter conditioning must still be not quite up to what we need to generate these plasmas. Spent the rest of the day trying to develop a case with the initial qstar at about 2.7 after discharge start-up evolving toward qstar of 3 by 2 to 3ms into the shot. This would traditionally have a RWM fluctuation from 2 to 2.5ms and a few Gauss amplitude in the past. Was somewhat successful at this but the plasmas did not have a good m=3 fluctuation to feedback on perhaps due to profile effects. I will continue tomorrow and turn the feedback on even if I don't have a mode just to check things out. I am out early today to go and get my allergy shots.

Tuesday March 2 07 15 Maurer 41733-41780 Setting up target

Took more shots today trying to develop target for RWM feedback experiments. I had one clear example of an m/n=3/1 RWM on shot 41744. This can be seen on the smps and ssi Br sensors just around 3ms. I took this shot after the machine sat for 1 hr, so the prior shots residual gas was well pumped away. I was unable to reproduce this plasma by lowering the puff (so far at least). Comments and suggestions welcome.

Also, the Ebara cryo head has recently started to make pinging noises most likely due to the seals starting to go bad in the head. It was rebuilt last June so I hope it is under warranty.

Wednesday March 3 05 17 Maurer 41781-41792 target development

Working on target plasmas (still). Trying to adjust puff time and bank settings to generate RWM fluctuation burst as qstart approaches 3. More work to be done tomorrow. Both beta and sherwood had to be restarted this afternoon. I hope this did not disturb peoples work too much. Nick has contacted the company who rebuilt the Ebara cryo head this summer about warranty coverage. Hopefully we'll know by tomorrow or the end of the week what the situation is. As it stands now the head is holding its 8 K temperature. There has been to signs of temperature cycling yet.

Thursday March 4 05 31 Maurer 41781-41826 target development

More of the same. Another day of trying to get a good RWM for feedback studies. I am contemplating going back to the ramp down case. Comments.

Sunday March 7 10 47 Maurer 41728-41778 target development

Took more shots Saturday. After trying to develop target discharges, I switched to a high Ohmic input plasma to generate SXRs and cleanup the limiters and walls.

Tuesday March 9 07 13 Maurer 41881-41891 clean-up

Had a short clean-up run only today. I will try the RWM case tomorrow. In other news the Ebara cryo head has stopped squeaking for at least the last two days (maybe Sunday too). Maybe it will last longer than was first thought after all. I will keep a close watch on it. The FPGA arrived yesterday. Alex is sorting out some software driver issues with NI. The leaking pipe in the bank room is sceduled to be fixed tomorrow morning. The run will commence after that is finished.

Wednesday March 10 05 29 Maurer 41892-41942 Clean Up/Target development

Took 30 clean up shots to start the day. Then switched to target development shots. Started to see a choppy burst of MHD fluctuations as q_star was approaching and going though 3 from below. The fluctuations were of lower frequency than the background MHD nosie. Reproducibility was better than during the last weeks, but still not too robust. These are the first encouraging results in about two weeks! Here's looking forward to tomorrow.

Thursday March 11 12 40 stillits 41953-41960 Testing RPFB

The RPFB is up and running again. Moreover, we have modified the control panel application.

Thursday March 11 04 36 stillits none Modification of Control panel application.

- the control panel application has been modified to use triangles instead of square-wave as input for RPFB.

Monday March 15 06 12 stillits 41962-42017 feedback

Feedback on major radius (with the new application) is now working. Feedback on q* seems to be working, but some more finetuning needs to be done.

Friday March 19 10 11 Maurer 42018-42027

Yesterdays run was cut short by a problem with the TF charging resistor. There was some arcing from the top of the resistor to the water column. The top electrode had broken off from the charging supply lead during the run. A new electode is being manufactured and will be installed asap.

Monday March 22 05 26 stillits 42069-42124 q*-feedback

We tried to perform feedback on q*. The algorithm does the right things, but there are some minor problems with the gains, which need to be finetuned. We'll work on that tomorrow.

Tuesday March 23 04 35 stillits 42125-42154 q*-feedback

We were able to get the feedback on q* up and running today. There are, however, some "small" deviations between q* in the scope and q* we calculate. The max. deviations in q* are approximately 0.2-0.3 and in some cases 0.4. The reason for this is the small value of the minor radius a squared (a^2 ~ q*), which will change q* by 5-10% when the major radius in the scope deviates by, for example, 4 mm compared to the major radius we calculate. When we take into account these deviations, we can still get very nice feedback values on q*:

Shot #42137-42146: We tried to put the plasma at q*=3.5. After having chosen the suitable parameters (which only took a few shots), we were able to get some nice shots #42141 and #42142 (and also #42143).

Shot# 42147-42154: We tried to ramp up the plasma from q*=2.7 at 2.4 msec to q* = 3.1 at 4 msec. Again, it took only at few shots to tune the parameters. The nice shots are #42150, (#42151), and #42154.

Monday March 29 04 12 stillits No shots. Application.

The Control Panel Application has been modified. Control of q* (including q*-ramps) has been included.

Tuesday March 30 07 23 James No Shots Maintenance

At about 9:45 last night I found a large amount of water on the floor in the basement. It was centered on the bias probe electronics and when I looked to find the source I noticed that it was the leak that Jim has been trying to get maintenance to repair. Over the weekend I guess it had filled the drip pan. It was a lot of water and it spread over to the dump, I vacuumed it up with the wet-vac, but before we run today that space (from the wall behind the bias probe to the dump) should be checked again to be sure I didnt miss anything before it is powered up.

Tuesday March 30 07 26 James No Shots Maintenance

At about 9:45 last night I found a large amount of water on the floor in the basement. It was centered on the bias probe electronics and when I looked to find the source I noticed that it was the leak that Jim has been trying to get maintenance to repair. Over the weekend I guess it had filled the drip pan. It was a lot of water and it spread over to the dump, I vacuumed it up with the wet-vac, but before we run today that space (from the wall behind the bias probe to the dump) should be checked again to be sure I didnt miss anything before it is powered up.

Wednesday March 31 05 10 Maurer RWM development

News from Tuesday: the leaking pipe in the bank room was finally fixed by facilities. Todays run was cut short by a minor arc on the TF coil set. A nut on one of the coils for the lug connection to the current feedthru had come loose. When the last shot of the day was taken part of the lug was vaporized giving rise to a big flash when the arc occured. The TF current trace looks just like the previous shot, so the full bank current still flowed through the arc to the coils. Nick and Jim have cleaned up the contacts and re-made the lug connection. All other TF connections have been checked also. I will check the resistiance and inductance of the coil and compare it to others before running tomorrow.

Thursday April 1 03 52 Maurer 42176-42185 checking out TF

We had another TF lug arc at the same spot as yesterday. Started the run today by bringing the TF up a kV at a time until we reached 6.1 kV to check out the new lug end. Everything appeared to be fine. Took one plasma shot with full TF, VF and OH banks. On the second plasma shot the lug arced at the TF current feed just like yesterday, blowing off the end of the lug. Apparently, the threads were damaged enough that the nut loosened up again an caused an another arc. We are discussing various possiblities about how to proceed. Input and any comments are welcome. New lugs have to be ordered and should be in tomorrow.

Monday April 5 05 05 Maurer 42185-42205 TF check-out

Checked out the new TF coil lug attachment today that was arcing last week. So far so good. I brought the TF up in kV steps initially checking the lug nuts between every shot. After reaching 6kV with the TF only I took about 5 shots with full banks making plasmas while still checking the lug nuts every shot. They were nice and tight every time. After that the remainder of the plasma shots were taken checking the lug nuts every 2 shots then 3 shots. They were OK the whole afternoon. I will continue to check them tomorrow gradually increasing the number of shots between inspections. Tomorrow I will be attempting to generate RWMs approaching qstar=3 from below using the Ro-qstar equilibrium feedback to help reproducibility.

Wednesday April 14 10 43 D. Maurer, Alex K. 42248-42270 FPGA tests

Yesterdays run summary...

Inserted FPGA processor into one poloidal set of sensors/control coils (bottom shell, upper set).

Digitized raw sensor signals, filtered signal that reach the FPGA, signals from the FPGA, and current in control coils. Will analyze data to see how it is consistent with mode control algorithm and filters.

We tried several gain settings on the analog boards to see at what point crunch amplifiers are overdriven.

More work needs to be done, including checking polarity of control coils and current shunts, (spatial) phase shifting of output signals.

Wednesday April 21 02 51 Alex Klein 42271-42315 FPGA testing

Yesterday, fixed polarity issues with current shunts. Also took many shots with sine wave driving things instead of sensors (no plasmas), to measure overall system transfer function.

Today, verified control coil polarities and then ran toroidal phase shift scan on bottom-midplane FPGA group with all signals looking very nice. Took shots at 0,45,90,135 and 180 degrees toroidal shift. Will analyze data.

Hope to wire in remaining FPGA groups by end of week.

Thursday April 29 09 53 A. Klein 42326-42434 wiring/repair/configure

The FPGA global mode control system is installed and functioning. All analog boards, FPGA wiring details, control coil current shunt polarities, crunch amplifiers, control coil polarities, sensor coil polarities, coil integrities, etc are fixed, configured, functioning, verified. Now ready to apply feedback to RWM plasmas at various spatial phase angles using 20 sensors/coils configured in 4 groups of 5.

Thursday April 29 05 07 D. Maurer, Alex K. 42438-42457 mode control testing

Applied DFT FPGA mode control with all available coils. Only covered 2 spatial phase angles for feedback: 0 and -85 degrees. Will require much analysis to see actual effects on the plasma, and much analysis to see what effects should be acting on the plasma.

Friday April 30 04 33 Maurer none

Bias probe reinstalled and bellows assembly leak checked this week. Opened gate valve to chamber this afternoon. Pressure rise was maximum of about 6e-7 Torr and composed mostly of H2O. The bake has been on for over an hour and the base pressure is already down to 2.8e-8 Torr. We will continue baking over the weekend.

Thursday May 6 04 54 stillits 42464-42519 clean-up shots.

Clean-up shots were taken with RPFB and biased probe turned on.

Friday May 7 04 53 stillits 42520-42591 clean-up shots.

Clean-up shots were taken with the biased probe and RPFB (R=94 cm and R=93 cm) turned on.

Monday May 10 03 43 stillits 42592-42605 H-modes (Biased probe + RPFB)

In our attempt to create H-modes, we ran the biased probe with RPFB. However, after a few shots, the biased probe arched. We measured a high-voltage short between the tip of the probe and ground. The probe has been pulled out, and the gate valve has been closed.

Tuesday May 11 05 39 Alex Klein 42607-42630 Global Mode Control

Initially, trouble with basement digitizer. Ch 2 on 8210#2 in basement appears to be out, switched VF bank signal to Ch3. Then, developed discharges to yield q* < 3 at start, then slowly ramp through q*=3.
Ran several shots with FPGA mode control ON at t=2 msec, off at t=3.5 msec for 0 and 180 degree spatial phase shifts.
Did not run radial position control, will do so tomorrow.

Wednesday May 12 05 18 Alex K 42631-42668 FPGA mode control

Performed gain scan on FPGA system: It had been slightly overdriven previously (increasing gain caused no increase in crunch amp current). Reduced FPGA gain setting and found gain setting which causes max crunch amp output (5-7 amperes)for typical plasmas.

Ran with radial position control, with goal of keeping plasmas alive as long as possible while slowly ramping through edge q =3 from below. Found m =2 tearing modes to dominate everything at 4 msec, resulting in disruptions. While FPGA feedback was on at various times for many shots, these may not be too meaningful...

Plans now have changed: perhaps run through edge =3 quickly and from above, to look for RWM before tearing modes dominate ? Did some discharge development in this direction.

Friday May 14 10 15 Alex Klein 42669-42722 FPGA model control

Spent a while developing discharge with aggressive OH ramp, such that edge q runs through 3 from the outside early on in the shot. Got to the point where RWM consistently observed between t=2 and t= 3 msec as edge q dipped below 3.

With this type of shot, then ran with FPGA mode control. Control output gated on between t=1.5 and 3.5 msec. Took data at 45 degree spatial phase shift increments for FPGA output. Have at least two shots at each angle with RWM.

Will have to look at data carefully to be able to say reasonable things about mode control. The RC filters and digital integration, as well as control coil inductances are causing control coil output to be dominated by low frequencies, and phase between sensors and controls highly susceptible to frequency as well.

Puff valve: For unknown reason, puff valve required to be open for 2.2 msec to get comparable gas levels as existed earlier in the day with valve opening only for 1.2 msec. Battery on valve checked out fine (235V), gas lines were all open with adequate pressure.There may be something wrong with the puff valve.

Friday May 21 03 49 Alex Klein 42723-42747 Mode Control

Again used discharges where plasma current ramp = agressive, edge q comes from the outside and rapidly dips below '3', giving rise to RWM early on in the shot. Very clear and reproducible RWM's.

With FPGA mode control algorithm now using much reduced integration time (~15 micro-secs), determined what spatial angle to dial into DFT to have 90 degree spatial phase shift between N=1 sensor mode and N=1 control mode. Took many shots at this setting with and without FPGA running. Consistently had 90 degree phase relationship.

Saw evidence that at "+" 90 degrees, feedback system excites N=1 mode. Fairly reproducible increase in sensor mode amplitude and lower mode rotation rates when FPGA is on, vs. when it is off.

Then, adjusted DFT angle by 180 degrees, to attempt "-" 90 degree feedback, should be suppression of RWM. No clear results. Mode amplitude looks always similar, regardless of wether FPGA is on or not.

Why? -> Consistenly had NO fixed phase relationship between control and sensor coils, i.e. phase is all over the place. Mode rotation rates seem high.

Will now do more rigourous analysis, with some objective method for quantifying data.

Thursday June 3 04 46 Alex K. 42748-42792 FPGA mode control

Picked up where we left off 2 weeks ago. Plasma behaved exactly the same, without any tweaking required (edge q comes to 3 quickly, from the outside). Took many shots with spatial phase angle close to 0 degrees, and many shots with phase angle near 180. Cursory glance: RWM looks about the same for the two types. Will require more analysis to say anything meaningful.

Then drove control coils with function generator going into analog boards, to explore gain and saturation limits in crunch amplifiers.

Then with p[lasmas: began gain scan (at spatial phase angle ~90 degrees), will continue tomorrow and perform gain scan at phase angle ~ -90 degrees.

Friday June 4 04 43 Alex K. 42793-42817 FPGA mode control

Hose for ignitron cooling burst, flooded basement. Fixed and cleaned up in the morning.

Then continued gain scan from yesterday, at approx. +90 degree spatial phase shift and -90 degree target phase shift. Nearly finished, cua900 computer acting up... Gain scan should be complete after about 20 more shots (to be done next week).,

Monday June 7 02 34 Maurer/Rivera

The OHEL bank is back up and running...

The fpga is being programed for this weeks latency tests. The run will start tomorrow.

Wednesday June 9 03 56 Alex K. 42829-42871 FPGA mode control

Yesterday, ignitron cooling water hose had burst and flooded basement (again), therefor no runs.

Today: With the usual discharge (see past several run reports): Finished gain scan at spatial phase angle which causes mode suppression.

Then: Implemented FPGA program which has select-able latency in multiples of 10.2 microseconds, while keeping looprate/sample-rate the same. Took shots at 10, 50, 100, 200 microsecond latencies. It will require lengthy analysis to expose small effect, judging by quick look at the data

Monday June 21 05 29 stillits 42873-42894 clean-up shots + biased probe

In the first 13 shots the biased probe was not turned on. In these shots the plasma was cold, lasted between 3-4ms, and the plasma current reached 10 kA. The loop voltage was fairly constant ~ 12 in each of these shots. From shot#42887 the biased probe was turned on. The biased probe voltage was increased from 0V to 350 V in 50V-steps. Saturation was reached at 300-350 V in which I_sat = 100-150 A. We saw a few more spikes in the loop voltage (~ 12), and from SXR the plasma was a bit hotter (but not much). However, there is a lot of noice in SXR, for example, so it is not easy to say anything about spikes in SXR.

The RPFB was not turned on in any of the shots because of problems with the hot decks on the LANL.

Tomorrow we will continue taking clean-up shots with the biased probe on.

Tuesday June 22 05 24 stillits 42895-42931 clean-up shots + biased probe

Clean-up shots were taken. The biased probe (BP) was slowly ramped up to 300V (it looks more like 200 V on the scope), and at 300 V the BP-current was 100 A. The plasmas created lasted for 3-4ms, and the plasma currents were ~10 kA. The signals are very noisy, so it is not very easy - by looking at the SXR-signals - to say anything about how hot the plasmas were, but the spikes in the loop-voltage seem to be absent in some of the last shots.

The RPFB was not on because of problems with the LANL, but Nick is working on it.

We will continue taking clean-up shots tomorrow.

Wednesday June 23 05 21 stillits 42966-43011 clean-up shots + biased probe

Clean-up shots were taken. The biased probe (BP) was slowly ramped up from 100 V to about 300V, and at 300V the BP-current was ~100 A. The plasmas lasted for ~ 4 ms and plasma current ~ 10kA. There are no spikes in the loop-voltage indicating the BP is clean. Furthermore, as soon as the BP is turned on (at 2ms), the loop-voltage remains constant (~ 10) or decreases indicating the plasma is getting heated (the plasma current ramp is 2.5 MA/s). SXR indicates a hot plasma but it is difficult to say because of noice.

The RPFB was not turned on, but Nick is working on the LANL.

Thursday June 24 05 00 Alex K. 43012-43076 FPGA open loop runs

Coerced the machine to produce the types of discharges I have been using for a while now, with agressive current ramp, edgq q approaching 3 from above early in the shot...

Spent the day running "open loop" experiments: All 20 control coils were energized with a set of signals that were out of phase with each other such as to drive a m=3, n=1 helical pertubation around the tokamak. At a certain time during the pulse, the polarity of the signals was reversed. (Phase Flip Experiments)

Initially (in the morning), I had the pertubation propagate downwards poloidally as the toroidal angle was advanced (along plasma current). Saw little or no mode locking at several frequencies (between 4 and 8 kHz). Then I switched helicity, and found mode locking (between sensor coils and control coils) for a range of frequencies. This means presumably that perturbations are tied to the electron fluid. Can now analyze data to measure plasma response to phase flip of magnetic perturbation, also looks like I can measure plasma amplification of resonant perturbations.

Friday June 25 04 21 Alex K. 43078-43107 open loop, closed loop

The transfer functions of a feedback system seem to be surprisingly important.

Tuesday June 29 04 02 stillits/maurer 4343108-43124 Biased probe

The biased probe (BP) was tested. With BP inserted 3 cm into the plasma, an IV-characteristic was obtained with I_sat = 45-50 A at V = 250 V (the BP voltage was increased to 350 V with no sign of increased BP current). There was no sign of impurities by looking at the loop-voltage (too much noice on SXR). Tomorrow we will perform an IV-scan by obtaining IV-characteristics at different positions of BP in the plasma.

Wednesday June 30 04 50 stillits/maurer 43153-43174 Biased probe

We had BP positioned at 1 cm and 5 cm from the edge of the plasma (it was positioned at 3 cm yesterday) to obtain IV-characteristics. The voltage was increased from 100V to 350 V in 50V-steps. For 1 cm, I_sat was 30 A, and for 5 cm it was 55 A. In the 5 cm case I_sat was reached at 100V-150 V, and in the 1 cm case I_sat was reached at 200V - 250V.

Thursday July 1 04 41 Alex K. 43175-43202 Mode control debugging

Was going to run latency experiments, spent the day chasing down bugs and problems instead. Output signals from the crunch amps on bottom poloidal group are not what they should be. Input signals as seen by digitizer are what they should be. Verified that FPGA module works as it should, and analogboard output stage performs properly as well.

Took some plasma shots as part of the bug-chasing work, no good data. Hope to fugure this out tomorrow.

Thursday July 8 05 05 Alex K. 43242-43249 Mode control debugging

The analog boards/rack seem to be fixed after Nick R. worked on it on the bench. All channels are working except for one output signal on one of the bottom control lines (Channel 3B C3). It is a very bizzarre problem that can't easily be diagnosed/explained. Just as I was getting to the bottom this, the CAMAC data aqcuisition failed, presumably because the basement rack is overheating - the air conditioner in the basement is down, Jim A. is on the job of getting it repaired.

Tuesday July 13 05 50 A. Klein 43262-43288 Mode control debugging

Still had problems with one group of output signals - but I think I finally figured out the problem. Will test tomorrow and hopefully everything will be working.

Developed discharges also: while the typical type of shot used previously for mode control studies appeared once in a while, it was not as reproducible and robust today as before. Will continue tomorrow, and hopefully run latency experiments.

Wednesday July 14 05 16 A. Klein 43288-43319 latency in mode control

All signals behave properly now. It took a while to get the target plasma, but then the old mode control shot (aggressive current ramp, edge q comes in to 3 and hovers there for a while, slow freq 3-1 oscillations visible) appeared. Ran feedback with 10, 60,110,160,210 microsecond latency in system. Data looks interesting. Every shot from 43302 to 43319 is relevant, no dud shots (which is nice for the operator).

Will now have to analyze the data more thoroughly.

Thursday July 15 05 01 stillits 43320-43349 biased probe + RPFB

The LANL and the triple probe are working again.

We inserted the biased probe (BP) 5 cm into the plasma, and slowly increased the BP-voltage from 100 V to 300 V. The max. BP-current was 50A-100A. We used RPFB to position the plasma at 94 cm (from 3 to 10 msec), which was fairly successfull.

In a couple of shots, for example shot# 43346, we saw huge inboard edge densities up to 6-8*10^18 m^-3. However, we have to smooth the signals before we come to any conclusion.

In shot# 43332 we see some interesting stuff. At 4.1 msec to 5.1 msec we see a drop (from 60A to 10-20 A) in BP-current, an increase in SXR from 0 to about 0.1 (the loop-voltage decreases from 12 to 9), and a slowly increasing inboard edge temperature from 5-10eV to 20eV.

The inboard edge density seems to be fairly constant. All this could indicate an H-mode.

Friday July 16 08 35 Stillits 43356-43388 Bias Probe +RPFB

Today we ran the biased probe (BP) and RPFB. The BP-voltage was slowly increased from 100V to 250V, and BP was kept at 5cm from the outer limiter. We tried to position the plasma at 93cm and 94cm, but R=93cm seems to be the preferable choise because at R=94 cm we saw huge BP-currents (up to 150A), which could potentially destroy the probe. Beside the noice, we did not really see anything of interest. However, we are getting better at running BP; we were able to create long lasting (8-9 ms) and faily hot plasmas (SXR ~ 0.2-0.3) with BP inserted.

Monday July 19 04 48 stillits 43392-43406 No plasma shots.

We didn't take any shots today. There was water in the basement this morning, and after the basement was dry the OH kryon pulser broke down and some parts had to be replaced. However, everything is working now and as soon we get the D_alpha-meter installed tomorrow we will start taking shots.

Tuesday July 20 05 26 stillits 43407-43447 Bias probe + RPFB

We ran the bias probe (BP) with RPFB on. The plasma was kept at 94cm from 2.5 msec, and BP was inserted 5 cm into the plasma from the outer limiter and voltage was 200 V.

In shots# 43411 and 43421 the RPFB and BP were turned off (however, BP was inserted 5 cm, but no voltage on it).

We had several very good shots (shot# 43418,43420, 43426, 43428, 43430, 43433, 43438, 43439, 43441, and 43442) in which the BP-current almost dropped to 0 A, SXR increased, loop-voltage decreased, inboard temperature slowly increased, and inboard edge density decreased or stayed constant. Several of these shots (especially shot# 43428, 43433 and 43441) experience an increase in SXR (and a drop in loop-voltage) so soon as the BP current drops to (almost) 0 A, and a decrease in SXR when the BP current increases. These shots could indicate an H-mode.

The D_alpha-meter needs to be installed before we can come to a final conclusion about creation of an H-mode. We had expected to install it today but because of APS abstracts we didn't have the time to do it.

Thursday July 22 08 09 James/Stillits 43450 43480 ICRF

Spent the morning putting the ICRF back together. There were some minor problems with filling the cooling system reservoir on Monday that were rectified but put us a little behind schedule. ICRF was revived almost without incident. We have a problem with the Jorway trigger and had to run a cable to the one in the west rack so we could run. We were able to take only a few shots bug free (mostly operator error).

Shots 43467-43480; our vacuum shot (base line) for comparison with the antenna q ratio for loading investigation was #43478. Most of the shots were not high density, but #43477 looks like a good loading candidate at first glance. The feedback system was not on for this shot (43477) but it was for the others. We hope to spend more time next week with in developing more ideal plasmas and using the bias probe.

Friday July 23 04 32 A. Klein 43481-43532 Mode control phase scan

Ran detailed phase angle scan for FPGA mode control using the 2nd order digital filter, lowest latency, moderate (fixed) gain. I adjusted the toroidal phase of the control field, covered 46 different angles. Found phase of maximum feedback, observed mode frequency increase (substantial) to the "left" of that, and frequency decrease to the "right", implying torques on the modes as expected. It was quite a good day: out of 51 shots, only one is not useful.

Wednesday July 28 08 20 James/Stillits 43533 43580 ICRF

Spent the morning developing target plasmas, and fired ICRF in the afternoon. Had to stop running due to difficulty the Jorway timing in the west rack, but fortunately, we were able to get some data and even the data that was time eschewed (baseline vacuum shots) may be salvageable. The bias probe did show increases in the density of close a factor of two, the radial positioning worked like a charm. Thursday we will start with testing the ICRH tree and developing H-mode like plasmas and position them near the ICRF antenna for loading and heating.

Friday July 30 06 14 James/Stillits 43616-43658 ICRF

We fixed the tree problem we were having with the trigger. We were able to basically dial up the plasmas that gave us possible H-modes in the past. We did see some good H-mode candidates during the run (43654-43656), but most were not. However, almost all the plasmas we did develop were ideal for loading studies. We observed loading not just in the initial launch of the ICRF, but also through the shot as well. See the comparison of antenna_q value for shots 43631, 32, 38, 39 (loaded plasma) and 43629, 33, 41 (vacuum) - the vacuum shots are in such good agreement that any of them can be used. I will try to have some print outs available for Monday.

More data analysis to come, but we dont expect to find much evidence of heating. I hope to take more shots like these with the bias probe / RPFB system combination. The densities were close to two orders of magnitude higher than those typically seen without them. So finally we have verified that our theories about positioning densities near the antenna for loading. Next we want to take more shots like these to determine the best density regimes and attempt to heat the plasma!

Tuesday August 3 05 28 stillits 43694-4375 ICRH + BP + RPFB

Today we had the ICRH, BP, and RPFB on. In most of the shots, the RPFB kept the plasma at 94 cm from 2.5msec to 10 msec. BP was kept at 200V in all the shots. With RPFB and BP on, we took shots with and without ICRH. We saw several plasmas that had an "H-mode"-structure (for example shot# 43729). However, there is a problem with the ICRH measurements; the loading is not as high as previously thought, and there is not loading during the whole ICRH shot, as previously claimed.

Monday August 9 04 12 stillits/james 43778-43820 IRCH+RPFB+BP

The LANL is working again, and the D_alpha-meter is installed and working. ICRH: (We ran with Deuterium) The source of the pick-up was found and repaired and the triggering problem was fixed too. We tried all day long to create high inboard densities, but the plasma was pretty "stubborn" today; we never reached above 4*10^19.

"H-mode": The D_alpha-meter started working in shot #43815 (to 43820). In shot #43820, we see something that could resemble an "H-mode" while we see a (slow) decrease in the D_alpha signal. However, this should probably be taken with a grain of salt since we just got the meter to work.

Wednesday August 11 04 46 Maurer

summary for Tues and Wed...

Building power was shut down on Monday night to fix problems with a faulty phase. The cryos where valved off in case they lost power during the shutdown. The base pressure was 1e-4 Torr on Tues morning after not pumping over night and was composed of H20 and some air. After pumping the machine down the base prressure hung at 3e-8 Torr and was mostly H20. We baked in the afternoon and after cooling down the pressure is back down to 3e-9 Torr.

Today getting ready to run we had some CAMAC problems that took the afternoon to fix. Yuhong took some VF shots later in the day to test out the Hall amplifier box.

We have also been experiencing some problems charging the TF bank recently(last week or so). Nick has checked it out and suspects the charging resistor needs to be cleaned out of Cu debris that fills the bottom of the resistor as the top electrode corrodes. We will take care of this before tomorrows run in the morning.

Scheduled runs are still: Thurs ICRH and Fri Biased probe.

Thursday August 12 04 01 Maurer/James/Stillits

More problems today.

There was a small flood to start the day off in the bank room. The TF resistor was cleaned out and put back into service. In getting ready to take a shot the TF bank appeared not to charge. Upon going back down into the bank room we found the water leak had opened up again. After fixing this and cleaning up the floor we had more problems charging the TF. After inspecting the bank with Nick and charging it to low voltage locally we found no obvious problems. The problem appears to be intermittant. Several shots in a row at the end of the day were OK. Hopefully the power supply is OK. We are going to see if we can monitor the bank charging current meter on the camera system to actually see what happens when the bank does not reach full charge. No ICRH run as a result.

Friday August 13 05 18 stillits 43853-43908 "H-mode"

We had BP on = 200 V at 5 cm, RPFB = 94 cm from 2.5 msec, and we ran with 20% H_2, 80% D_2. We saw several shot that could indicate an H-mode: for example shot #43877, 43893, 43895, 43904, and 43906. In shot #43906, we see a very clear signal of an H-mode: BP-current goes to zero, a drop in the D_alpha-signal, an increase in the floating T-probe potential, and increasing SXR's. The major radius was kept at ~ 94 cm during the whole shot. The T-probe batteries were dead. After we changed the batteries we saw much larger inboard edge densities.That could probably be reason why were not able to make large inboard edge densities last week.

Tuesday August 17 04 52 stillits/james 43917-43972 "H-mode" + ICRH Shot #43917-43959:

We were able to lower the puff time from 2.0 msec to 0.9 - 1.0 msec and create some hot plasmas; in almost all the shots the loop-voltage started at ~ 9 and decreased to about 5-6 (we saw a lot of SXR's). With these settings we tried to create "H-modes"; in almost all the shots we saw weak and clear signs of an "H-mode" structure. Shot# 43960-43972: In these shots we ran with ICRH turned on. We increased the puff time from 1.0 msec to 2.0 msec to get high-density plasmas. The inboard density reached ~ 8*10^18 m^-3, and the ICRH was triggered at 25 kV - 30 kV. However, we can not say anything about loading; some more analysis is required.

Wednesday August 18 04 54 stillits 43973-44007 "H-mode"

We ran with RPFB (93.5 - 94 cm from 2.5msec to 10 msec) and BP (200 V, 5 cm) on. We saw several signs of an H-mode (especially shot #43977), but in most of the shots the D_alpha-meter was down because of high temperatures in the screenroom (83 degrees F). We tried to use a fan but it didn't help a lot. By the way, in some of the shots we were able to create very long lasting and hot plasmas: in shot #43985 the plasma lasted for 9.3 msec, and SXR reached almost 2.0 at 8 msec.

Friday August 20 05 39 stillits/pedersen 44017-44074 ICRH + "H-mode"

"H-mode": We ran with BP = 200 V at 5cm, and RPFB at 93.5 cm from 2.5 msec to 10 msec. We saw several cases with an H-mode structure and a few cases with a "Multi H-mode" structure (2 - 3 "H-modes" (of short duration) in same shot). We also tried to perform density-scans (push the plasma inboard towards the Triple probe during an "H-mode") but it was not a huge success. This was tried in shot #44050-44074 (the "interesting" shots are 44060, 44061, 44063, and 44065). ICRH: In some of the shots we saw some loading but it requires some more analysis.

Monday August 23 08 08 Y. Liu 44075-44094 VF only vacuum shot

These shots were used to figure out the noise problem of Hall probe array. As prof. Navratil predicted, it is amplifier cross-talk. After keeping on fixing problems, there are two worst channels left now - I can get clean signal by leaving them off. Further analysis needs to be done to have all channels work well. There was water leak in the basement. It was from the old wound of the tube close to TF banks. The ground under TF banks are wet. I mopped the open ground and left the fan on. Hope it will be fine by tomorrow.

Tuesday August 24 05 02 Stillits/Klein 44095-44131 "H-mode" + FPGA

We ran with 20% H_2 + 80% D_2. The RPFB was on and BP =200 V at 5 cm. First we tried to see if we could generate any H-mode structure. When that was achieved we tried to push the plasma inboard towards the triple probe in order to perform a density scan. It was not huge success, but in shot #44119, 44121, and 44122 we were able push the plasma inboard while the plasma was in some kind of an H-mode. However, we don't see any huge increase in inboard density as we would have expected We tried to do "feedback", i.e. turned on the mode control system to see what effect might be produced by control coils when plasma drops into/out of H-mode and very strong, high freq. MHD modes are present. FPGA algorithm is not at presently designed to deal with 30 kHz modes however, the data is difficult to interpret.

Wednesday August 25 10 25 klein 44132-44137 gain limit scan

Fired vertical field only and ran mode control feedback with various gain settings on analog board to explore limits. Had been running with G=10 for good feedback with plasmas. Now, found strong (saturated) self-oscillations at ~16 kHz for gain settings above 100. (G=100 still OK). Analysis shows oscillations are produced largely as n=1 mode, indicating feedback loop is self oscillating (as opposed to circuitry after FPGA).

Wednesday August 25 04 41 A. Klein 44138-44159 Mode control phase scan

Began filling in more data points for fine phase angle scan, will have data at 5 degree increments (71 shots) by tomorrow. Will then also try to nail down phase angle for positive feedback...

Thursday August 26 11 14 A. Klein 44160-44178 Mode control phase scan

Finished phase angle scan, have data at 5 degree increments for entire torus. Also took some shots around angle where negative feedback is maximized, to try to nail down 90 degree measured phase between control and sensor coil fields. TF charging supply quit for a while, messing with rheostat miraculously fixed the problem.

Friday August 27 02 56 Liu/Maurer 44179-44184

Just very few shots were taken. The amplifer box for Hall sensor has problems. I added filter caps for all the channels, but it didn't get things work better. Instead, some of the chips got hot when the power was turned on for a while. And couldn't see amp outputs even on bench test. Hope to continue to investigate the problem when Nick is back next Monday.

Tuesday August 31 05 08 Liu/Mauer/Nick 44179-44205 Test Hall probe

Both VF only and plasma shots were taken on Monday and Tuesday. We current have 19 out of total 20 channels working fine. There is one noisy channel left. We will continue work on it.

Wednesday September 1 04 38 Liu 44207-44241(84-117) Hall array

With 19 channels, we took both vacuum shots and plasma shots. VF only shots with TF sweep were taken to check TF effect; TF only shots with bank voltage from 170V to 320V were taken for calibration purpose. Shots 44234-44242 were plasma shots. All available hall sensor channels detect clear fluctuations. Hall sensor data is currently located on Langmuir with tree name 'my_tree'.

Friday September 10 04 12 Maurer

Due to building power being turned off to fix the main breaker for floors 1 and 2 of the Mudd Bldg the HBT cryos will be valved off and shutdown overnight and also cua900, beta, sherwood and langmuir will be shutdown overnight at 5PM today, Friday Sept. 10. cua900 and the linux machines will be back on tomorrow afternoon.

Tuesday September 14 05 08 A. Klein 44249-44302 Mode control phase scan

With new (and improved) digital filter, which should give flatter phase response for frequency band 1-20 kHz, began detailed phase angle scan... Will cover toroidal angle in 5 degree increments, expect to fibish tomorrow. Plasma type is as always, agressive current ramp bringing the edge q to 3 early in the shot. Good reproducibility, and data looks good at first glance.

Wednesday September 15 03 40 A. Klein 44315-44359 Mode control phase scan

Finished taking data for detailed phase angle scan using the new and improved digital filter. Had to replace puff valve battery midway through. CUA900 is full, Dave Maurer is working on backing up data to tapes, until he is finished no more runs are possible.

Tuesday September 21 05 35 Liu 44373-44412(149-185)

Plasma shots with SMP shell at both 0cm and 4cm out were taken. In each case, SS feedback was turned on to exciting and suppressing modes. So far, it doesn't look it makes a big difference with one pair of Al shells in(0cm) or out(4cm): phase shift to excite/suppress mode stays same; the regular plasma shots with same bank setup look same also. Hall sensor array was recalibrated by moving to different locations (R). Plan to have another run-day this week by moving Al shells in and out. P.S. ICRH crate seemed have some problem (fan made a big noise) when we tried to turn it on. Therefore, we had to bypass it.

Wednesday September 22 05 26 Liu 44413-44442

m=3 mode was investigated by moving Al shells with different combinations. There is no conclusion so far.

Thursday September 23 04 51 Andrello/Stillits installation

We installed and pumped out the new multiprobe. Tomorrow we will leak check it and hopefully open it to the chamber to bake over the weekend.

Friday September 24 04 40 Andrello/Maurer/Stillits installation The multiprobe vacuum installation is complete. The pressure jumped to 10^-7 torr and quickly came back down to 10^-8 torr. Bake is on for the weekend.

Tuesday September 28 04 38 Liu/Maurer Hall probe

Hall probe shroud developed a leak during todays run while it was inserted into the edge plasma bringing the vacuum chamber up to ~50 Torr. Cryos have been regened, the bake is on, and the base pressure is 2 e -6 Torr comprised predominantly of H20 pumping with the Ebara cryo only so far. Glow discharge cleaning planned for tomorrow and continued baking. The Hall probe tubing has been taken off the machine and melting at the tip is clearly seen. We are currently investigating ways to surround it with a refractory material like alumina.

Wednesday September 29 10 23 Liu CPCI digitizer

CPCI digitizer is now integrated into hbtep main tree. I already tested it - working well. If anybody finds any complain please let me know. Joshua Stillerman gave us a lot of help during the whole process.

Friday October 1 04 51 Maurer/Andrello

summary of cleanup details... Tues. up to 50 Torr of air in the machine. Wed. glowed in D2. Prior to glowing machine base pressure was dominated by water. Miniturbo would not turn on and will be sent back for repair quote. Glowed using a static fill of D2 and pumping out with horizontal turbo every half hour. Ebara cryo warmed up spontaneously during the afternoon(cause not understood might be due to incomplete regen on Tues or something more serious). Thurs glowed in He. Fixed roughing pump line accident on regen line for the ebara cryo and started regen. Machined new new alumina tip for Hall probe array and mounted on shaft. Fri finished cryo regen and installed Hall probe tube and bellows and pumped it out and baked it. Opened it to the chamber after the afternoon talk. Base pressure was 7 e-8 Torr composed mostly of He after yesterdays glow. It is not 1 e-7 Torr and mostly water after opening the Hall probe gate valve. The bake willl continue over the weekend.

Tuesday October 5 06 07 maurer/liu

Tried taking cleanup shots today but had problems with the tree and mdsplus when initializing the shot cycle that took the whole afternoon to figure out. Partial fix has been implemented so we should be able to run tomorrow. Not sure what exactly happened to the hbt tree to cause these problems.

Wednesday October 13 07 29 Liu 44523-44558 vacuum shots

Calibration shots for both old and new Hall arrays were taken. I accidently turned off chamber ion guage. Jimmy came back to the lab from home to check the vacuum system to make sure everything is all right.

Friday October 15 02 15 Maurer/Stillits 44559-44570 TP-array

We tested the triple probe array (TPA). The test was conducted by moving the TPA 1cm into the plasma after each shot. Thus, the TPA is now 4 cm into the plasma. All tips, except for one - the third tip on the third TP, are working. The amps need to be checked. Nick did some work on the TF-charger, but we are experiencing some problems with the TF-charger still.

Tuesday October 19 04 46 liu/stillits 44573-44623 clean-up shots

We took clean-up shots all day long. We started with a puff time at 2.2 msec, but when the puff time reached 1.6-1.7 mesec the plasma had problems breaking down. Beside that, we were able to produce up to 4-5 msec plasmas, loop voltage ~12, and major radius at 94 cm. We had problems with the TF-power supply. The power supply was monitored; when the TF bank got stocked at a certain level, the amps on the power supply dropped down to zero. Thus, there seems to be a problem with the power supply.

Wednesday October 20 04 46 liu/stillits 44624-44688 clean-up shots + TPAWe

Took clean-up shots all day long. The plasma stayed around 94 cm, loop voltage ~11-12, and lasted up to 6 msec. We tried to lower the puff time, but we had problems breaking down the plasma when the puff time was lower than 1.8 msec. We tested the triple probe array (TPA). Thanks to Nick, all 4 triple probes are now working. We will hook up the TPA to the CPCI digitizer tomorrow. The batteries for the triple probe were dead and were replaced. We will continue taking clean-up shots tomorrow.

Thursday October 21 04 23 liu/stillits 44689-44738 clean-up

We continued clean-up shots today. Although we had to increase pufftime instead of decreasing it to breakdown the plasma, the plasma got better comparing with the shots we took yesterday. With VFFB on, plasma typically lasts 5-6ms. Also we saw sawteeth from SXR signal.

. problems: (1) TF bank power supply is getting worse. It failed to charge for most of the afternoon. It's a very high priority for it to get fixed before we could productively run the machine. (2) The first channel of triple probe array still has a problem with the chip - it keeps getting blown - but Nick is looking into it.

Monday October 25 03 11 liu/stillits 44739-44756 clean-up shots

We were only able to take a few shots today before the TF went dead. However, we were able to produce some nice plasmas: loop voltage ~ 8-10, duration ~ 5-6 msec,SXR ~ 0.1 (sawtooth). All four TP's are now working, but we are having problems with blown chips on TP no. 1.

Tuesday October 26 05 03 Stillits/Liu 44757-44785 clean-up

We took clean-up shots all day long. We are beginning to see some very nice plasmas: loop voltage ~ 10, duration ~ 5-6 msec, SXR ~ 0.1-0.2, however, we were not able to lower the puff time below 2.0 msec. The RPFB was on: 94 cm from 2.5 msen till disruption. We checked the puff-battery and it showed 240 V, which should be ok. The triple probe array (TPA) was working well till we blew the board. The second board was installed, and we will continue to test TPA tomorrow. The Hall sensor array is working well and we are expecting to get some useful data if the plasma behaves repeatable tomorrow.

Wednesday October 27 03 54 liu/stillits 44786-44808 hall-probe + TPA

We are beginning to produce plasmas that are behaving very nice: duration more than 6 msec, loop voltage starting at 10-11 and decreasing to ~ 8, SXR ~ 0.1-0.2 and in some cases ~ 0.3-0.4. We ran the triple probe array (TPA) with the new board, and it seems to be working: we are getting very nice signal (one I_sat and two voltage measurements) for TP no. 1. Furthermore, we are not seeing any huge spikes in the signals. We will keep testing TPA tomorrow. The Hall probe array is working normally. We were trying to get some target shots for natural m=3 MHD mode study. The plasmas were quite repeatable. However, we couldn't take enough shots since TF power supply was working part-time. Nick has been working on it - in trying to pin down the problem, he has put light bulbs in parallel at different locations.

Monday November 1 07 14 Liu/Stillits 44809-44850 Mode structure

Good news: Nick has TF power supply fixed! So as we were able to run experiments smoothly today. Although the base pressure is a little bit high (~9*10^(-9)) comparing with the old days, plasmas are quite repeatable. Shots were taken by pulling all the Al shells out. Also, m=3 mode structures were investigated by partially turned on FPGA feedback control (Thanks Alex for adding new fuction on labview control pannel of this purpose). We are looking forward to collecting more data tomorrow.

Tuesday November 2 02 26 Liu/Stillits 44851-44877 Mode structure

We collected most needed data for mode study by investigating m=3 mode with different FPGA feedback scan. However, we had a hard time breaking down the plasma since late morning. PGA showed water and N2 are dominant effect to vacuum at current point. The base pressure is 1.7*10^(-8). TPA has been tested also. Data from the 1st channel is promising.

Monday November 22 02 59 stillits 44924-44939 clean-up shots

We had hoped to take some clean-up shots today, but we were not able to break down the plasma. The pressure was 1.1e-8 and we ran as high as 3.0 msec in puff time, 275 on OH elect, 6.5 on OH start. The e-gun is working and there is gas in the system (a signeficant jump in pressure during a shot). There seems to be a lot of water in the system, which probably stems from a leak.

Wednesday November 24 04 18 stillits 44940-44959 clean-up shots + TPA

The e-gun battery was dead. After having replaced the battery, we were able to break the plasma down. However, we have to run with at a very high puff time = 2.8 msec; if we try to lower the puff time below 2.8 msec, the plasma can't break down. Anyway, with a puff time of 2.8 msec, we were able to create some fairly hot and long-lasting plasmas: SXR ~ 0.3-0.4, duration of 7 msec, loop-voltage ~ 11 down to about 8. The start pressure was 1.2*10^-8. Furthermore, we were able to lower OH_start and OH_elect to 5.5 and 265, respectively. We can probably lower the OH values even further and still get nice plasmas. We will check the puff valve battery on Monday. After Nick fixed the problems we have had with the cable (from the TPA to the digitizer), the TPA signals seem to be working very well (we hooked the cables up to the function generator). On Monday we'll try to insert the TPA into the plasma and get some data. The RGA seems to be indicating that there's some H20/D20 and Nitrogen in the system: 2.5-3*10^-9 for both water and Nitrogen.

Wednesday December 1 07 12 Liu 44968-45040

First, CPCI communication problem has been fixed. The problem probably was caused by network frozen. Today's plasma is repeatable and controllable. With the Hall probe inserteded into plasma 2.5cm (1st channel of the probe at R=1.047), we took shots with current ramps from 4MA/s to 0A/s, et. al. Triple probe array is ready to capture data tomorrow.

Thursday December 2 04 19 stillits 45041-45058 Testing TPA (triple probe array)

We tested the TPA today. There semms to be some problems with the electronic; we are getting saturated signals on all except for one channel - even when we pull the TPA out of the plasma. We will look into the problems tomorrow.

Friday December 3 03 58 stillits 45059-45072 TPA-testing

We tested the TPA today. However, we are still experiencing problems with the TPA-electronic.

Thursday December 16 04 48 David Maurer 45147-45180 Discharge development, bias probe

We've been trying to develop the same shots as used for mode control experiments late in the summer. The puff valve is deteriorating, fresh battery still requires very long puff times to achieve reasonable gas fills. We also experienced a few computer problems, which have been corrected. The discharges now look almost like the target discharge, it may still be a matter of adjusting the gas puff in small increments. Current puff time is 8.5 msec (compared with 2 msec in August to achieve similar densities). We expect to have the traget plasmas by tomorrow morning and turn on the niased probe to affect rotation...

Tuesday December 21 05 26 Maurer/Klein 45198-45235 low kink rotation

By adjusting the fill pressure we were able to generate a plasma similar to those used for the recent feedback studies (see shot 45217 for example, the target shot was 43481). The puff valve response is changing on a daily basis. Current settings are Tpuff=1.15ms gives 3.1 e-5Torr fill pressure. Friday it was Tpuff=4ms for the same fill. In the future, people would be well advised to take static fills of the chamber with the pumps valved off to know their operating point. The biased electrode was inserted approximately 3cm into the edge plasma. Bias voltages of 50, 100, and 300V were applied to the probe tip. The higher settings (100 and 300V) were tried because it was difficult to see any rotational effects at 50V on the MHD. The reason for this is not clear. I plan on trying 5 cm insertion tomorrow and will keep the voltage high until I see an effect on the MHD such as reversal of the rotation direction and then back off the voltage and aim for only slowing the mode down to zero.


Monday January 10 04 46 A. Klein 45292-45337 Gain scan feedback

Performed gain scan with full coverage feedback. Used only two toroidal phase angles (max and min supression). Found feedback effect visible in Rogowski coil signals even at gain 14 times lower than that used previously (although greatly reduced effect). Max gain used was 1.4 times greater than previous setting (distortion of control waveform out of crunch amps limits gain). Pulser for puff valve failed, switched to spare. Nick is repairing the unit. Will continue partial coverage feedback experiments throughout the week.

Tuesday January 11 05 23 A. Klein 45338-45426 gain and partial coverage mode control

Performed gain scan for partial coverage scenarios: midplane only coils activated, and midplane coils de-activated (top and bottom coil sets active). Did detailed gain scan for toroidal phase angle set to max ecxitation and max suppression. Data looks very good (3 shots at each setting) and interesting. Maximum gain (1.4 time greater than previously used) does NOT result in maximum suppression due to distortion of waveforms, high freq. modes excited. Best supression seen when gain is a bit lower than setting used for phase angle scan this summer. Extreme low gains of course diminish feedback effectiveness, and at gains 14 times lower than previously used the kink modes seem unaffected. Puff valve behavior drifted and might require that I re-do the data set for mid-plane only coil sets active, because base shot was a bit different and more varied than usual. The data set for midplane coils turned off case looks very nice though, after I adjusted gas puff time. Problems with the new digitizer (for triple and hall probe arrays) resulted in errors and restarts of cua900, after some time YuHong was able to make the system work. Will continue these types of experiments in the next few days.

Wednesday January 12 03 54 A. Klein 45431-45497 partial coverage mode control gain scan

Todays partial coverage scenarios: Toroidal positions de-activated, did gain scan with shells 1,3,4 on but 2 and 5 off, then did gain scan with shells 1,3 on but 2,4,5 off. Cursory glance indicates that such feedback does not work very well. Minor differences between feedback on and no feedback shots, even at high gain, both for exciting and suppressing phase angle setting. Scan was detailed (three shots each setting, 6 gains, both exciting and supressing phase angle). Puff valve drifted again compared with yesterday but periodic checking of puff time on fill pressure made this not an issue. Will continue these types of experiments in the next few days.

Thursday January 13 04 38 A. Klein 45501-45599 gain scan partial coverage mode control

Ran more gain scans for various partial coverage scenarios: 1) One toroidal location disabled (pretty successful feedback) 2) Redid midplane only coils active (plasma is much better and cleaner data) 3) Every other coil disabled (fairly successful) As before, 2 phase angles (max suppression and excitation) were used at 6 gain settings, three shots each. In general, plasmas are very reproduceable. The machine has cleaned up considerably since Monday. Exception: When the triple probe array was inserted 6 cm into the plasma, very different discharges were observed. These were very quiescent except for intense sawtoothing on the x-ray, very long lived, very hot, edge q went down to between 1 and 2 and stayed there. All other parameters were the same (intense current ramp). These shots were reproducible (5 times in a row), but then probe was withdrawn and I continued with gain scans on the "old" shot types.

Tuesday January 18 05 31 A. Klein 600-627 gain scan partial coverage mode control

Finished taking data for partial coil coverage gain scan. Had some problems with ignitron cooling flowmeter interlocks, but they were resolved. Puff valve was very unpredicteable for the first few shots (50% variability) but then stabilized. Will now analyze the ~400 good shots taken last week.

Wednesday January 19 07 49 Yuhong Liu 45628-45699

It's a long run-day. Current ramp scan was done with all Al shells pulled back.The plasma shot length was not affected by withdrawing Al shells. The puff valve was wavy at the beginning of the run, but it was adjusted from time to time and stayed stable for most of the shots we took taday. Machine behaves well.

Thursday January 20 04 35 stillits 45700-45732 TPA testing

We tested the TPA today. We tried to rotate the TPA 180 degrees (at different positions: 2, 3.5, 5, and 6.5 cm) to see if the results (temperature and density) would be the same. There does not seem to be any change in the values. However, we began to experience some problems with the signals from the TPA after we had rotated it, which seem to be related to some of the connectors. We'll look into that tomorrow.

Friday January 21 03 38 stillits 45733

Friday January 21 03 40 stillits 45733-45744 TPA testing

We ran the TPA today. However, we are experiencing problems with the electronic (connectors) still. We'll look into that next week.

Monday January 24 04 38 Maurer ICRH

Fixed CTS and traverser problems with the ICRH crate Jorway. The trigger is now working fine(several shots at least!). FYI the L8210 does give NOX storage errors in the action monitor and serial crate controller (SSC) errors if the crate cooling is not on and the door is not well closed. The ICRH was turned on and a couple shots taken at 15kV and 25kV to check triggering, etc. The bank fired but the plate currents do not appear in the data base properly yet. I assume this is a cabling and rectifier hookup problem since the digitzers come up with no signals and appear to be storing properly in the data base. I will try to piggy-back and check this out tomorrow or Wed.

Tuesday January 25 04 07 Stillits/Maurer triple probe

Started to diagnosis problems with the triple probe array. Did not get too far along due to CAMAC serial highway sync problems and communication problems between cua900 and the CPCI crate that appears to freeze MDSplus during initialization of the serial highway. It was discovered that the basement u-port adaptor is causing the no-sync problem presumably due to over-heating. CTX has been temporarily jumpered out of the highway during trouble-shooting of the system. Will continue tomorrow.

Wednesday January 26 03 23 A. Klein 45760-45802 partial coverage mode control gain scan

Had intended to run two more partial coverage scenarios with mode control. Instead, experienced and worked on problems all day: U-port adapter in basement failed, needs repair or replacement. Took adapter from CTX experiment and installed in basement. Fiber optic link to ICRF rack appears to have failed, intermittant link took a while to diagnose. Had to bypass that crate. Experienced CAMAC and initialization problems, needed to back up, but back up disc was full. Yuhang deleted shots, then archived data on cua900. Finally, puff valve was extremely irratic, esp. at first. Sometimes no gas at all was admitted to chamber (perhaps CAMAC failure to trigger), when it did open, the amount of gas varied wildly. This appeared to have stabilized towards the end of the day. However, I was unable to achieve target shot, seems as though OH start is much lower than previously despite match in bank settings. Upped OH start considerably, which improved things, then they became worse and worse again (low initial plasma current). Will try again at later date.

Tuesday February 1 04 46 A. Klein 45815-45860 diagnose problems

Had intended to finish partial coverage gain scan for mode control feedback. Instead, dealt with problems. OH Start bank was not providing the voltage one would expect, one of the Klystrons had failed and was replaced by Nick. After that, the OH bank was still not up to par, and produced inconsistent results even for fixed settings. Then determined the OH Start bank is leaking off charge fairly rapidly. Took much of the day to realize this. Played with voltage settings, "refreshing" the charge, adjusting the charge rate so that bank finishes close to when the TF bank is finished charging. This may be moderately succesfull. There must be a capacitor in the bank that is bad. Higher voltage settings result in lower start voltages, it is a mystery and is not explained by leaking capacitors (is it?). Also, had trouble breaking down to form plasma. This may be related to the OH start bank problems, or perhaps not. Checked out e-gun, seems to be working fine. Gas puff also works fine (although long pufftimes are required to get target fil pressure). Formed plasma only 3 times today, which is a bit inexpliceable. The North Rack contiunues to have problems with digitizers for the SMP's.

Wednesday February 2 04 02 Maurer/Rivera

Fixed problems with the Ohmic heating circiut today. The OHST bank dump had failed. The ST bank dump oil was almost black in color. The reduced standoff voltage was enough that the bank was continually discharging through it leading to yesterdays problems. The dump oil was changed and some tracking on the dump structure was cleaned up. The dump was then reinstalled. The bank was the checked and is working properly now. FYI: the CTX crate is back in the camac loop and will have to be turned on before running tomorrow. In addition, the ICRH crate is also back and will need to be turned on. Alex will resume Tuesdays incomplete feedback run starting tomorrow. Lets hope the breakdown problems from earlier this week do not occur.

Thursday February 3 04 09 A. Klein 45867-45951 partial coverage mode control gain scan

More partial coverage gain scans: Today, had no problems with the banks. Plasmas were good (very first shot was target plasma). SMP's still not being digitized properly. Puff valve failry stable, it drifted a little during the day but I compensated with the puff time. I ran 2 scenarios: top two poloidal groups only, and uppermost (single) poloidal group only. The data is very surprising. Recall that the previous data suggested midplane coils only were not as effective for feedback as top and bottom only, and that perhaps this had to do with not having enough poloidal coverage to grab onto the modes. Well, todays data says:Top group is very effective at suppressing/exciting 3-1 mode, with top-midplane group or even without ! At medium gain, the one lone top poloidal group (which is furthest from the plasma surface since the plasma is shifted down somewhat) is as able to suppress the kink as the entire system (all groups on) is. All the data so far suggests that a) midplane coilsets do not couple as effectively to the external kink mode, or b) what we think is the midpalne is the top, and vice versa. I spoke with M. Shilov, he seemed to be sure of what is what, confirming that what I think is the top/midplane is in fact the top/midplane. Perhaps he has it wrong? Thus far I have the coils numbered 1 assigned to the midplane, and the ones numbered 3 assigned to the top (or bottom). Does anyone have documentation to confirm/refute this? Will analyze the data more formally, we can then decide what it might mean or what other experiments should be run.

Monday February 7 04 43 A. Klein 45973-46015 partial coverage mode control gain scan

Investigated partial coverage gain scan for one poloidal group (bottom midplane) only active scenario. Doesn't look like it performed too well. Will keep running these types of experiments tomorrow. ad some trouble due to CPCI data acquisition system, ended up restarting cua900 and disabling the CPCI stuff.

Tuesday February 8 02 30 A. Klein 46015-46100 partial coverage mode control gain scan

Completed partial coverage gain scans for top poloidal group only active and top-midplane poloidal group active only. The data conforms to previous data and trends. The puffvalve now requires 35 msec pulse times to give required fill pressure... I think this may conclude the partial coverage gain scan experiments (I hope). Will analyze the data in the coming days...

Monday February 21 05 07 Maurer 46241-46260 Ran initial tests with new vertical poistion bucking coil.

The coil was run at 50, 100, 200, 400 and 600A of current. No breakdown problems were experienced even when running at the highest 600A level. Plasmas typically had about 350 to 450A of plasma current in the OH transformer bias phase indicating a medium gas fill level. Initial observations showed the global plasma parameters were not changed significantly until 200 to 400A were run in the new coil. Plasmas were actually pushed in major radius at the 400A level. Perhaps indicating that we are pushing it too high. There is preliminary evidence that the poloidal sensor arrays top-bottom asymmetry is less at the 200 to 400A level. No major jumps in SXRs, loop voltage or other parameters were noticed during the expts. We are still having camac problems with the shell mounted coils. I found what appears to be sin(theta) coil cabling in the west rack. Have not yet been able to check out if it is ok yet due to some afternoon camac-vax problems. Nicolai continued to check out ion saturation current measurements on the triple probe array and will also piggy back tomorrow.

Wednesday February 23 04 31 Maurer 46257-46307 Vertical position

Moved top and bottom limiters out yesterday 2cm to allow some wiggle room for the plasma as the vertical position bucking coil experiments continue. Today was a day of problems... shorting stick left on the OHST bank caused some localized arcing and damage to the stainless steel resistor but nothing serious. This was cleaned up in the morning, the bank is OK, and a new shorting stick built and installed. The CPCI crate was taken out of the loop due to a fan failure on the digitizer side of the rack which was extremely noisy and discovered during the mornings run. The company has been contacted about a replacement and the problem fan was removed temporarially and the crate re-installed for tests tomorrow. The polarity of the leads for the vertical bucking coil were reversed (to move the plasma down) as a check on Mondays initial results before proceeding with a more detailed position-current scan. I tried to set up a target plasma but had great difficulty with the puff valve and intial fill pressures. They were widely varying the whole day. So much so that the plasmas were ranging in lifetime from 1.5ms to 6ms. The initial bias phase currents went from about 0 to 1000A. The puff valve pulser was found to be putting out about 100V instead of the 235V battery value when measured on a scope. The input trigger appears solid. The backup pulser was installed but did not give out a pulse when triggered. Nick is checking out the two units. Perhaps the transistors are failing because of the factor of ten to twenty larger puff times that we now require to attain the same fill pressures used in the past (due to puff valve aging?). I would suggest that we take time tomorrow to recalibrate the SMPs, flux loops, etc which has still not been done until the puff pulser is fixed. There is only Mondays data to discuss for Thurs meeting.

Thursday February 24 05 06 maurer

Figured out north rack problem with the smps and triple probe diagnostics in the afternoon. The local serial ribbon cable input on the fiber optic uport adapter is failing. This causes information on the store part of the shot cycle in crates 7 and 9 to be lost (or mostly lost). This appears to be the cause of the recent smp and triple probe problems in the database. The ctx uport adapter was borrowed to trouble shoot the problem.

Tuesday March 1 04 32 A. Klein 46369-46433 vertical position shift

Collected ample data on vertical shift coils and their effect on one type of discharge. Will analyze in detail. Only with extreme currents in the correcting coils does the plasma behave grossly differently/badly. Hottest plasmas near 200 Amps driving plasma upwards. Tried to digitize Sin-theta Rogowski coil, the coil is not functioning (probable short circuit, 0 Volts).

Wednesday March 2 04 51 Maurer/Liu Calibrations

Started calibration checks today on the flux loops, smps, bank currents, etc... work still in progress. Tomorrows run is with the biased probe and triple probes (Stillits). FYI: Dmitry and I will be at PPPL going over VALEN again and in particular learning how to do the partial coverage runs to help in understanding Alex's recent data presented at the last physics meeting.

Sunday March 6 07 11 Maurer 46524-46551 Calibrations

Sunday run... tested HFS triple probe. Even with the north rack camac problems fixed the isat measurement is still not working on the triple probe. The digitizer checks out OK with a sine wave input. Pulled the amp out of the north rack and checked the battery is OK. Must be the opamp or other circuit problem. Will have Nick check it tomorrow. Spent rest of the evening running sine and square waves through the shell mounted probe electronics to check for any AC response differences that might give rise to measurement errors. All the working channels looked OK with a 1kHz square wave input. Also checked the flux loop in a similar manner on Wed with Yuhong. All the flux loop channels were OK also. Still have to go over the bank current rogowskis. Did not get the bucking vertical position coil on today due to the calibration checks.

Wednesday March 9 02 46 Jmaes/Stillits 46560 -46603 Beta Enhancement

Spent the morning checking equipment, ICRH, Triple Probe, RPFS, & Bias Probe. We were able to get ICRH signals in the tree on Monday. Replaced an op-amp in the triple probe, but signals still seemed strange in the tree; still debugging. In the meantime, we will use a t-probe tip to make an Isat probe for a direct relationship to the inboard density. This will allow us to continue the ICRF studies this Thursday and Friday. We were able to develop plasmas that resemble h-modes with the ICRF and bias probe on and the plasma positioned at ~94 cm. We had some problems with the RPFS, Nicolai and Nick are investigating. Dave Mauer has offered us assistance in rerouting the screen room out of the serial highway for tomorrow and Friday. I am not sure if that affects the RPFS or not but we are confident that we can work it out. We needed the extra u-port adapter to replace the one removed form ICRF a few weeks ago. We borrowed CTXs U-port, but returned it yesterday afternoon so they can run this week.

Thursday March 10 10 54 Maurer 46607-46638 vertical position shift

Yesterdays run... HFS triple probe isat measurement is now working. Found bad opamp chip. Hooked up shell probes and had flux loops, hall array, LFS triple probe, poloidal feedback sensors on for todays vertical shift expt. Ran the vertical shift coil in 50A increments to scan position. Target plasma was outboard limited with Ro = 94 to 95 cm. Took three shoots at each current up to 350A. Coarsened scan to 1 shoot per 50A increment from 350 up to 600A due to limited space on cua900 at the end of the day. Data analysis underway. CTX uport returned. Screen rm jumpered out of camac loop to allow for ICRH run today.

Thursday March 10 06 56 James/Stillits 46643 - 46695 ICRH

We bypassed the screen room first thing this morning. We used the bias probe, to increase inboard plasma densities all day, but each time we tried to move the plasma inboard with the RPFS, the densities seemed to fall. We weed to investigate this further, but today, we were just trying to get target ICRH plasmas by whichever tools were available. We left the plasma edge at ~.94 m and found that when the radial current is at 200 A, the edge densities increased noticeably and relatively remained so throughout the plasma lifetime. We then fired the ICRF at lower energy at first (~18 kV) and then up to 28 kV for the final 5 or so shots. I am analyzing the data now, and plans to begin a more systematic sweep tomorrow of edge densities to lock in the ideal parameters for FMSW Coupling.

Tuesday March 15 05 54 Maurer 46765-46829 HFS density optimization

Ran plasmas today to otimize the HFS density measurement on the triple probe. Was able to develop target plasma with edge density of around 4 e-12 per cc as measured on the HFS triple probe. This was done by a combination gas puff, vertical shift coil current, and OH bank adjustments. I was able to make a relatively long lived plasma with Ro at 92cm and another target with Ro at 91cm for a 2.5 ms period. This was done so far without the biased probe or radial position control. Late in the day I turned on the baised probe at 250V and expected the density to increase even further, but this was not experimentally seen. The probe current and voltage signals were very noisy. The major radial evolution changes slightly with the probe on. As as a reference case we usually get a factor of two or so increase in edge density with the biased probe (this gives values of about 5 e-12 per cc). So we are getting close to that edge density without the probe just by todays discharge programming with increase gas puffing, but it is not clear why the probe is not enhancing the density even more. There were some Lanl problems during mondays run that hopefully will not impede tomorrows work. I plan to run from the start with the probe in the morning to see if I can increase the density even further. If this shows no promise I'll switch on the ICRH and use the target I have currently going in the afternoon. In todays run I was using 200 to 250A in the vertical shifting coil.

Wednesday March 16 08 32 James 46738 - 46763 Radial Field Scans

This from Mondays runs: We were unable to use the Lanal, seems to be a repeat of a problem experienced last year see Nick, Dave or Nicolai for more information. The bias probe was on for all shots. Nicolai, help me to set the plasma between 93 and 92 cm with lifetimes from 3-5 ms. Once we were able to have a suitably long lifetime, I began a sweep of the vertical positions starting at 175 A radial current and ending at 225 A, at 25 A increments with about five shots for each step. Looking at the 2.3ms-4.1ms window density averages, the largest were shots 46752 (4.18E+18) and 46760 (4.01E+18). From the sweep, it looks like the 225 A current produced the highest densities in that window. I also turned on the ICRH for shots 46761 63 and 46764 (vacuum shot) to continue to look for some loading and any other signs of coupling while I everything is still working. I ran out of time before I could try 250 A radial field currents, so it may produce an even higher density measurement.

Thursday March 17 10 32 Maurer 46830-46880 High density plasmas with ICRH

Forgot yesterdays run report... I continued making high density plasmas and using the vertical shift coil at 225A. The two target plasmas developed yesterday for ICRH studies are: (1) Ro= 92 cm plasma with edge density of 4 e-12 per cc and (2) Ro= 91 cm inboard limited (on the RF antenna limiter) plasma also with edge density of approximately 4 e-12 per cc. Ran ICRH pulses at 28kV into both of these target plasmas. The SXR fan array has enoungh pickup that it is not useful in diagnosing any temperature rise. I will try to play with cabling to see if it can be reduced. No easily seen signature of loading or heating seen just looking at the data initially during the run. Looking at the Q measurements for subtle loading effects today.

Thursday March 17 04 54 Stillits/Maurer 46881-46948 H-mode + TPA

We had problems with the LANL, which we have had for some time now; each time we took a shot the banks got dumped. We were, however, able to create long-lasting (~ 6-7 msec) plasmas without the RPFB. Furthermore, we couldn't get the D_alpha meter to work; we'll look into that tomorrow. The BP (Biased probe) was on at 250 V and 5 cm into the plasma, and the TPA (triple probe array) was inserted 3.5 cm into the plasma. We saw several cases of "H-modes."

Monday March 21 05 08 stillits 46982-47063 H-mode + TPA

We ran with BP on at 250 V and inserted 5 cm. The TPA was inserted 3 cm into the plasma. We saw some cases of H-modes, some more interesting than others. Among the interesting shots are shot# 47003, 47026, 47043, and 47044. We'll continue with these kinds of shots tomorrow and perform the BP-TPA test. By the way, the high-field TP is not working.

Tuesday March 22 04 21 stillits 47064-47100 H-mode + TPA

We ran with TPA inserted 3.5 cm into the plasma, and BP on at 250 V and inserted 5 cm into the plasma. We saw several cases of H-modes, but the run day was cut short when the TPA stopped working.

Tuesday March 29 04 16 A. Klein 47103-47126 Mode control coverage

Ran to tie up loose ends with partial coverage mode control experiments. Previously, Dr. Mauel had suggested two control coils were always highly correlated with feedback effect (magic coils). There is something to this, judging by todays experiments. Toroidal position #3 apparently is close to Rogowski coil used for analysis, and activating coils at that location strongly affects feedback analysis when based on Rogowski coil measurements. Will have to re-evaluate lots of data, using 2nd Rogowski coil, poloidal sensors, and shell mounted probes.

Wednesday March 30 04 38 A. Klein 47126-47182 discharge development

Developed discharge with R ~ 93 cm, current ramp, external kink when edge q goes below 3 while vertical shift coil was powered with 260 Amperes. Shot 47182 is the target, I think. Will use such shots to do some mode control feedback experiments.

Friday April 1 04 52 stillits 47184-47201 TPA

Thanks to Nick, the TPA is working again. We tried to test how close to the BP we could move the TPA before experiencing any major problems. The BP was on at 150 V and 5 cm into the plasma, and the initial position of the TPA was 3 cm. After having experienced problems with the CPCI digitizer this morning (we couldn't initialize), we got as far as inserting the TPA 4.2 cm into the plasma - 8 mm from the BP - before we again started having problems with the CPCI. Up to that point we didn't have any problems with the TPA getting to close to the BP. Next week we will try to address the problem with the CPCI. On the positive side, the high-field TP is working again and the digitizer for the D_alpha-meter is working again (we will run with the D_alpha-meter next week).

Wednesday April 13 05 15 stillits 47221-47308 H-mode

This is run report for Monday, Tuesday, and Wednesday this week. We experienced problems with the CPCI this Monday; we were not able to initialize the TPA channels. However, Yuhong seems to have been able to fix this problem by creating a completely new publicly - for the HBTEP group - accessible CPCI-tree, which will be tested tomorrow. Furthermore, we are having troubles with the D_alpha-meter. The digitizer is working, and we have tested all the cables (which are also working), but we are not able to get any signals from the spectrometer. We will try to fix this problem tomorrow. Since we have had problems with the CPCI, we have no been able to perform the BP-TPA scan. Instead, we tried to create "H-modes" in which we had the BP inserted 2 cm into the plasma with 300 V. It seems that we are able to create "H-mode" structures with this "BP- setting" too; for example shots #47279 and #47305 are interesting.

Monday April 18 05 06 James 47320 - 47355 ICRF

I used the scope to measure the period of the ICRF oscillations T=2.28x10^-6 s so f= 4.38 MHz (should be 4.5 MHz). I put this into Prof. Mauls program, but we are still unsure of the toroidal B-field, so it is not clear how significant this change is. We were able to develop some fairly high densities (centered around ~5x10^18 [+- 1.5x10^18]). ICRH was fired at full strength, ~31 kV, and a few shots showed significant loading. After looking at some previous shoots, it seems that the inboard density can be double what I got when the biased probe is inserted 5 cm. Combine this with clearing the toroidal B-field uncertainty so we can adjust the frequency, and we should be able to determine weather or not more drastic measures should be taken.

Monday April 18 02 33 Liu CPCI digitizer status - works well

Want to clear that both hardware and software of the cpci digitizer are working well. I spent time last week created a new mdsplus tree on langmuire /home/hbtep, which is accessible for the whole group. The tree's name is 'subtree_cpci'. Anybody who wants to retrieve data from the tree, please just use the standard mdsplus/idl commands/programs. If you want to get data from terminals that are not langmuir, please use "mdsconnect, '' ". The commands "mdsopen, 'subtree_cpci', shot#", "a=mdsvalue('top...')", etc still work the same way as you get data from 'hbtep' tree. Please be sure the correct node name to get data - you can check it using traverser. One thing needs to be mentioned: the problem that cpci digitizer sometimes stops working is quite possibly because the CPU usage on langmuir is more than 99%. If anybody has the idea of limiting user's usage of CPU, it will solve the problem.

Friday April 22 05 18 stillits 47435-47450 BP-TPA scan

Thanks to Yuhong - we were able to run the CPCI/TPA today. The BP was position 5 cm into the plasma, and the voltage was 150 V. The initial position of the TPA was 4.2 cm (= the center of the deepest inserted TP was 4.2 cm into the plasma). we then slowly moved - in step of 2 mm - the TPA into the plasma. We stopped taking shots when the deepest inserted TP was inserted 5.8 cm into the plasma. We did not see any spikes - neither on the I_sat or voltage (float or +) for each of the TP - at all at any position.

Monday May 2 04 00 Alex Klein 46504-47538 mode control compass scan

Began detailed compass-scan of mode control system and tokamak configured exactly as during August 2004, but with toroidal position #3 control coils de-activated. This is the position near an m = 3 Rogowski coil which otherwise is subject to direct pick up. The plasmas look good, data looks good at first glance, will finish tomorrow (am trying to cover 72 different angles).

Tuesday May 3 02 41 Alex Klein 47539-47589 Mode control compass scan

Finished compass scan with mode control system configured as in August 2004, but toroidal position 3 control coils deactivated. Will now analyze data to see how rogowski is affected when nearest control coils are far away.

Tuesday May 10 05 15 stillits 47605-47653 TPA + BP

Thanks to Yuhong, we are now able to take data with the TPA. After we had kicked Bialek of langmuir and changed OS to the old version, we were able to take shots without any major problems, except for a few shots in which the CPCI was not able to store data. we ran with BP at 2 cm & +300V and TPA at 3.8 cm (position of the deepest inserted TP). We saw some cases of spikes in SXR while the BP-current was ~ 0A; at the same time we saw drop in I_sat/density on the deepest inserted TP's, so the "barrier" seems to appear deeper inside the plasma than 3.8cm. But some more analysis is required. Next time we'll try to insert the TPA deeper than 3.8 cm.

Wednesday May 11 04 02 Alex Klein 47657-47699 mode control compass scan

Performed full coverage mode control control coverage scan, to confirm that the feedback system actually still works as before (there had been a question, as plasmas appear to have slightly faster natural rotation rates compared to previously). At first glance: Mode control works, dramatic exitation/suppression on Rogowski coils as before. Tomorrow, will do phase angle scan with toroidal position #7 (far from either Rogowski) control coils muted.

Thursday May 12 03 05 Alex Klein 47699-47778 partial coverage mode control gain scan

Ran detailed compass scan study with mode control coils at toroidal position #1 muted. This is the set of coils near Rogowski m eq 3 coil number two, and also the set mounted on the shells which are partially withdrawn due to Hall probe access. At first glance, it looks like feedback is working, as the Rogowski coil #2 mimicks Rogowski coil #1. Will do analysis to quantify feedback effect.

Friday May 13 02 34 Liu/stillits 47779-47822 Hall probe calibration

Yuhong tried to calibrate the Hall probe today.

However, during these shots we had to reboot the CPCI and langmuir several times. We don't know what makes the system so unstable - but we have emailed Josh and Peter about the problems.

Friday May 20 02 08 stillits 47889-47900 TPA calibration

12 shots were taken today (three for each TP). Data was stored on floppy disk, and further analysis will be done in IDL.

Monday May 23 09 56 James 47901 - 47921 B-dot Probe

Tested the B-dot probe today, ensured the cable was indeed attached and checked it for shorts. Initially took an ICRH only shot to compare with B-dot readings in the past (see shot #36547), with the rectified probe raw signal in the raw bottom antenna current digitized channel. The signal seemed to just be pickup in the wire (see shot #47902). Then bench tested the Ge rectifier, but sig. gen. only went to 1MHz and at this frequency it was hard to tell if the signal was truly rectified. Went back to the ICRH crate and used the o-scope while firing the ICRH to see both the un-rectified and rectified signals over the lifetime of the ICRH pulse. Seems like the rectified signal oscillates with the carrier as it drops, pointing to a possible capacitor failure, but I ran out of time before I could replace them will do so next time and start the toroidal B-field scans with ICRH.

Tuesday June 14 03 50 stillits/liu 47952-47982 cpci

The CPCI seems to be working now. We took about 30 shots, and in each shot all the data was stored; this even happened while Bialek was running (using more than 99% of CPU).

Thursday June 23 02 46 Stillits_Nick 47987 OH test

Tested the OH bank to see if there was any damage from the water leak. It worked fine. Will test triple probe tomorrow.

Friday July 8 05 25 stillits 48192-48218 TPA

The TPA is now working. After Nick had cleaned the pins, allocated new channels on the CPCI (we are now using ch. 49-54 for TPA1 and TPA2) and after we had recalibrated - by means of the effective areas - we were able to get the temperature profile we had anticipated. The temperatures were underestimated by: TPA1 (outermost): 3%, TPA2: 11%, TPA3: 13%, TPA4 (innermost): 5% However, we have not taken into account the ~25% - related to the electronic - we are overestimating the temperature on each TP, but it will not change the profile structure. All this will be added in the tree. Furthermore, after we put a fan in front of the CPCI, the CPCI has become more reliable. There are, however, instances in which data is not stored, but the solution to that problem seems to be to turn the CPCI off and on - without rebooting langmuir. We have also changed the sampling rate on the CPCI from 200K to 250K and (almost) gotten rid of the time delay ~200e-6 sec, but there are still some a few minor problems that need to be solved. I'll try to look into these problems and put it all on the tree this weekend.

Tuesday August 2 04 43 Maurer Fixing broken quartz section

Summary of Monday 8/1 and Tuesday 8/2. Found the HBT vacuum chamber up to air prior to Mondays group meeting. The quartz piece between the Hall probe and SMP chamber pieces had cracked around the circumference sometime over the weekend. The exact cause of the break is unknown. The failure mode is however similar to the quartz piece that cracked next to the ICRH section about 5 years ago when a cinder block wall was taken down in another part of the lab. It was thought then that floor vibrations due to taking the wall down caused enough of an impulse to start a crack propagating in the quarz. In checking with facilites, there was no scheduled heavy construction on our or ajoining floors so I am not sure what caused it (if that is the cause).

The quartz piece was taken out this morning. It took a bit of time to pull the bolts, move the Hall probe stand, pop off its flange and dismantle the connections to the control and sensor coils mounted off of those stainless shells so they could be moved over inside the chamber to allow the quartz piece to be removed (since the gap coils extend over underneath the quartz piece). I broke one wire of the smart shell coils in dismantling them that will have to fixed. Upon inspecting the broken quartz we found a part of the crack that does go over to the edge of the piece and might have been caused by contact with the next door chamber flange. If anyone wants to do more post mortem analysis the pieces are on the table by the door to the control room. We currently intend to install an old single-convolution stainless steel piece in place of the broken quartz. This is being done for ease and quickness of installation. Also, there were no diaganostics at that location that were in use. There is a m/n=2/1 saddle coil that we are planning on not re-installing. The quartz was also jumpered out and not acting as an insulating break either.

Using the convolution piece we have a good chance of installing it tomorrow and perhaps even doing an initial pump down and with baking we might be able to run at the end of next week perhaps. If people think this is not the way to go and they want one of the new thick, machined quartz pieces installed (Mike or Thomas?) please email Jerry and I and we will discuss matters since everyone is gone. Right now we are cleaning the spool piece and orings, making new mylar covers to hold the orings in place, and preparing to install the section tomorrow. We have checked the gap between the chambers and the convolution spool piece should fit with its orings and mylar cover, There is a gap of a little less than 0.1 in. flange to flange. We also checked to make sure the bolt circles match alright. In addition to the above, we pulled off the top microwave feedthru that has been broken for some time so that it can be fixed in anticipation of having the interferometer up and running in the future. I will either blank it off or if i can find it install a window and shutter than S. Paul loaned to us in the past. This could perhaps be used for the new Dalpha array temporarily since the microwaves will not be workijng for sometime. I have tried to inspect the SXR Be filter to see if it was damaged by the pressure wave when the quartz cracked by looking through the bottom window opposite the array. I frankly cannot see it well enough to say if it has minor damage or not. It does not appear that there is major cracks or flaking of the Be.

If there are other up-to-air tasks that people would like to see done now is the time!

Wednesday August 17 05 32 Hanson/Stillits 48559-48632 clean-up

Yesterday there were problems relating to the TF-CB circuit. We chose a new trigger channel and amplifier, and got the circuit to work. This mornining, we still had problems with the TF bank firing for low charging voltages ( < 6.1 kV ). It would seem that the one of the TF ingitrons is no longer good. After achieving solid TF pulses, a clinking noise was heard from inside the machine area. Two loose bolts were found resting on the concrete pad underneath the hbtep near where the quartz piece had been replaced, and were removed. Subsequently, clinking noise was no longer heard. We plan to check again for loose tools and hardware before running tomorrow. Intitial shots (48569-48578) showed little or no ionization. Gas puff time was gradually increased to 3.0 ms, and OHST was gradually increased to 6.5kV. Breakdown was achieved at shot 48580. For the rest of the day, pulse length gradually improved, and was just shy of 3 ms by the end of the day.

Thursday August 18 05 54 Hanson/Stillits 48633-48678 Clean Up

Started the day with a second missing tool search as promised in yesterday's run report. Jim Andrello found a small section of hex stock (that was used in losening the socket head cap screws holding the broken quartz piece) on the machine area floor beneath the concrete base pad. Jim still believes that an allen wrench is missing, but no clinking sounds were heard when firing the TF bank. Runs today showed spotty improvements in discharge time. Typical shots lasted 3-4ms, but we had a lovely 8ms shot towards the end of the day (48677). In order to get breakdown, we needed to keep the gas puff time around 3.0ms. In the afternoon, it was increased to 3.5 ms. We plan to continue making clean-up plasmas tomorrow with the hope of making 8.0+ ms discharges consistently. Ideally, we would test ICRH early next week.

Friday August 19 01 30 Hanson/Stillits 48680-48701 Clean Up

Before running this morning, we installed a new puff valve pusler box. We did at one point swap the old box back in again, but it did not seem to fire. Then we promptly reinstalled the new box. All shots taken today failed to break down. We tried to explore various settings: increased OHB to 03, increased OHEC and OHST to 280 and 6.5, respectively. VFEC was already at 40 from yesterday. We verified visually that the E-gun lights up, and that gas puffs consistently bring the system to order 10^-4 pressures. We ended up increasing the gas puff time to 20.0 ms. Also tried to adjust the tree setting TOP:CAMAC:TIMING:PUFF_VALVE2 a little bit, but I am not sure about the units, and whether it is the length of time or start time for the puff. We've been using nothing but D2 gas all week. Perhaps the missing quartz piece really does make a difference?? On several occassions yesterday, I noticed strings of shots that had progressively longer discharges. However after building to a 6-8 ms discharge, the following shot would fail to break down at all. I'd say this happened about 3 times yesterday.

Monday August 22 05 34 Hanson/Stillits 48704-48708 Clean Up

After poor plasma performance last Friday, the idea for today's shots was to asses the effect of fill pressure on our ability to achieve breakdown. To this end, we scanned gas puff times from 1.0 ms to 10.0 ms with little success. Around mid afternoon, Nic remembered the following: a) there was a small leak in the vacuum chamber which now seems to be fixed. Thus breakdown problems might be due to the chamber being too clean. b) the e-gun has a bias power supply that runs on a battery. We checked the battery on the e-gun bias supply and found that it had about 200 V out of 250. A fresh battery was then inserted. Subsequently, breakdown was achieved when the puff time was set at 20.0 ms. After achieving breakdown and some ~8 ms discharges, the puff time was slowly decreased to 16 ms with no negative result (see shots 48740-48748). Plan tomorrow to keep attempting to lower the puff time and make reproducibly good plasmas.

Tuesday August 23 05 35 Hanson/Stillits/Maurer 48749-48805 Clean-up

Smooth progress today. There were some questions about whether the gass lines were clear of He this morning, so they were pumped out. SXR emissions are slowly creeping up, and loop voltage is decreasing. Discharge times are in the neighborhood of 6ms.

Wednesday August 24 05 05 stillits/hanson/maurer 48806-48859 clean-up

The plasma is slowly getting cleaner. At the end ot the day we were able to create plasmas with puff time = 1.3-1.4 msec, loop-voltage starting at 12-14 and dropped to ~ 6. The duration of plasmas was on average 8 msec, initial plasma current 5 kA and max. current 7-8 kA (OH elect. = 260 and Oh start = 5.8). By the way, there were signs of increasing SXR's.

Thursday August 25 02 54 maurer none baking

After running the past few days with clean up discharges base pressure remains at 2 e -8 Torr. The dominant partial pressure is H20 on the RGA. The ratio of O2 to N2 as about 5 so if there is a leak it is small. I think the easiest way to get rid of the H20 is by baking rather than making plasmas, which is not very efficent at getting rid of the water. The bake is back on and I will see what it pumps down to on Fri morning. I think the fact that some bake controllers are not working appears to have limited our ability to get rid of the H20. The pressure with the bake on is 7 e-8 Torr.

Monday August 29 05 11 Maurer/Hanson 48860-48883 clean-up

Dave turned off and removed the bake system this morning, and we started running at about 1:45. Discharge times today seemed to fall pretty consistently in the 6.0-8.0 ms range. Soft x-ray signals are still small or non-existent. Loop voltage seemed to average about 11-13V. Most notably, the major radius seemed pretty bouncy on a 1-2ms time scale.

Wednesday August 31 04 34 A._Klein 48884-48929 Clean Up

Took many clean up shots. Plasma still prone to multiple minor disruptions, ended up running shots similar to past several days: large R and repeated "crashes" into outboard side, with hopes of cleaning machine that way. Did NOT adjust TF settings as reproducibility is still sorely lacking. Vertical Field only shot revealed poloidal sensor T1 position had its polarity reversed during the recent repairs.

Tuesday September 6 05 27 Hanson/Stillits 48931-48965 clean-up

Took more clean up shots today. Loop voltages averaged 10-15 V; Discharge times, 4-8 ms. Soft x-ray signals were very small. Major radius seemed quite chaotic. Planning to continue clean-up shots tomorrow, and maybe scan the TF a bit in the afternoon.

Wednesday September 7 05 31 Hanson/Maurer 48966-49022 cleanup/tf scan

<p>Spent the morning & early afternoon doing cleanup shots, and switched to coarse TF scan later in the afternoon.</p> <p> Regarding cleanup, discharge length seemed to average about 8 ms, loop voltage~13, no soft x-rays to speak of, major radius still quite chaotic. Nearly all of the shots shared some interesting characteristics: plasma current seemed to ramp up for about a 3rd of the flat-top, hit 7-8 kA, and then ramp back down to ~5 kA by the end of the discharge. During this ramp down period, loop voltage decreased to less than 10 and conductivity temp increased to maybe 10-20 eV. See shot 49001, for example.</p> <p> The results of the tf scan (49006-49022) seem encouraging. Scanned the tf voltage from 4.9 kV to 6.3 kV, in steps of 0.2 kV, with a 3 ms puff time. Was able to reproducibly achieve breakdown even at 4.9 kV, but discharge times here were very short since the vf was not adjusted to compensate. Shots taken at between 5.7-6.3 kV all looked quite similar.

Tuesday September 13 04 55 maurer

Glowed in D2 on Monday. Ratio of N2 to O2 was about 10 with the bake on this morning. Did a initial D2 glow in the morning and switched to He in the afternoon. Current base pressure is 5.0 e-7 Torr after turning off the glow. Mostly He and H20 products (DHO, D2O). Will take shots starting tomorrow morning.

Thursday September 15 04 57 Maurer

Only a few shots taken today. The OH coil started making a louder than usual noise when I was making plasmas. The sound resembles a dull thud. It does not appear to be an arc. It happened quite distinctly on one shot. We are in the process of trying to find out what is loose, moving around and making the noise. It is probably the bottom OH winding that has caused problems in the past. After inspection it does not look like the clamps have broken anywhere. So it is at least not a large scale clamp failure. It is possible that the bolts holding them together are a little loose from pulsing the machine. The clamps we have been able to check so far we finger tight. We will check the rest of the bolts before testing the circiut again. It is somewhat harder than before to access the bolt clamps due to the bottom-middle radial position control coil that is now installed.

Friday September 16 02 12 maurer

Friday September 16 02 21 Maurer

We were able to tighten the clamps on the bottom OH coil enough to reduce any noise back to similar levels as before yesterday. In the process of localizing where the coil was loose an arc flash was observed for a few OH only bank shots. This arc is intermitant in occurance. It was not observed with shots taken later in the day. The chamber sections where we believe the arc was localized were inspected as much as possible given the limited access to examine the clamps and cabling. There was no visible damage to either the clamps or cable that i could see or feel with my hand. Currently the VF winding, turnbuckles and other items that where taken off the machine to be able to inspect those clamps are being reinstalled.

Tuesday September 20 09 56 Alex_Klein

Dear All, I'm doing a dry run for a talk I am scheduled to give at MIT next week. The talk is an overview of the mode control experiments on HBT in the past 2 years + present status. You're invited. If interested, it will be in the control room on Thursday 9/22/05, 9:30 am. Thanks Alex K.

Wednesday September 21 05 13 stillits 49058-49095 clean-up shots

After having installed the Hall probe array this morning, we started to take clean-up shots. The plasma is slowly getting better with small signs of SXR's. The flashes we have been seeing lately were due to a trigger cable from an unused puff valve that was arcing where its connecter was touching the pump stand. It has since been insulated and the probelm has been fixed.

Friday September 23 04 39 stillits 49152-49190 clean-up shots

We spent the day taking clean-up shots. Small improvements of the plasma are seen but we probably have to spend at least one more day taking cleaup shots. We had problems charging the OH bias bank; fortunately it was only a water-resistor that needed to be refilled.

Monday September 26 04 29 stillits 49191-49247 clean-up shots

No major improvements of the plasma. We ran with OH-start ~ 6.9 and OH-elect ~ 290 but the plasma did not last more than ~ 4-5 msec, loop-voltage ~ 12 and only small values of SXR ~ 0.05.

Tuesday September 27 05 18 hanson 49248-49289 clean-up shots

Clean up shots today looked more or less like they did last week. Little or no SXRs, plasma current peaking at 10 kA, loop voltage ~10-15 V, discharge times 4-7 ms. Major radius still seems quite chaotic.

Wednesday September 28 03 14 A._Klein 49291-49359 Clean up/phase flip

Tried to reproduce Shilov-type shot with edge q evolving from below 3. Played around in bank settings but as unable to achieve the shot. Generally, plasmas appear to be fairly clean, some discharges had long duration (9 msec) with some soft x-rays and relatively smooth equilibrium evolution. Only, Shilov target shot is difficult to achieve....

Thursday September 29 03 41 stillits 49360-49417 clean up

No major progress today. The plasma is still fairly lousy. We ran with puff time ~ 1.7 msec, OH_elect ~280, OH_start ~ 6.8, VF_elect ~ 50-100, and VF_start ~ 2.9-3.8. The major radius is very volatile and loop-voltage ~12. Duration of plasma was ~3-4 msec, and plasma current stayed below 10 KA (~8-9 kA).

Friday September 30 04 39 stillits 49418-49454 Clean-up + Biased Probe

No major progress today. We are still faced with a lousy plasma. Max. duration ~ 4-5 msec, no SXR's, loop-voltage ~ 12 even with OH_elect. ~ 280, OH-start ~ 7.0. We tried to insert the biased probe to 3.5 cm with +200 V (biased current ~ 75-80 A) to see if we could see any changes in the plasma. But that was not a success either.

Monday October 3 04 43 stillits 49458-49522 clean up

After Dave had removed the straps/jumpers, we were able to get higher initial plasma current (~7 kA) at a lower OH_start: it is now OH_start = 5.2 compared with OH_start = 7.2 earlier. However, the plasma does not really seem to heat up: SXR's very small < 0.05, loop-voltage ~12-13, duration 4-5 msec, and max. plasma current ~ 10 kA. We will (probably) keep taking clean-up shots tomorrow.

Thursday October 6 12 13 A._Klein 49618-49625 test

Unable to break down plasma. Checked electron source, filament and bias. Confirmed gas fill. Confirmed bank currents. Unable to breakdown, will try again later after consulting w D. Maurer

Tuesday October 11 05 05 stillits/hanson 49626-49810 clean-up

Plasmas seemed very unwilling to breakdown. Nicolai increased the puff time throughout the afternoon to get results. When I took over, puff time was at 15.0 ms, corresponding to a fill pressure of ~2.3E-4 Torr. Shots with 10 ms puff times failed to breakdown. Dave noticed that even with the high fill pressures, plasma current during the bias phase of the shot is more or less zero. Bank traces, however, looked normal.

Monday October 17 03 23 Maurer none

Checked out e-gun circuitry. Bias voltage and heating current tested OK. Initially had a hard time measuring the emission current. After testing various parts of the circuit we were able to measure about 30mA of emission current (lots!). Not sure if we bumped a bad or intermittent conection or not that led to the earlier zero emsision current results. Decided not to pull the e-gun and inspect it since it appears OK. Opened up Hall probe gate value to main chamber and turned on bake. Will insert alumia coated probe shaft tomorrow and take shots. Plans in progress for up-to-air installation of quartz piece.

Tuesday October 18 04 16 Maurer

Took shots today to make sure breakdown is working well enough to make plasmas for testing the Hall probe shaft coating. Will test shaft tomorrow morning witharound 50 shots.

Friday October 28 03 55 Jim_Andrello Quartz installation

The quartz section is installed and sealed. The seals roughed down to 10^-3 Torr. Monday I will leak test it with Helium. The ICRF 10" flange has also been taken off for access to the Faraday shield.

Thursday November 3 05 58 Jeremy_Hanson ICRF hardware work

I completed removal of the Faraday screen from the ICRF antenna as planned on Monday. I then replaced the antenna limiters in their original positions. It turns out that it's possible to remove the Faraday shield/antenna limiter assembly without perturbing the antenna straps themselves. Once this assembly is removed, the Faraday screen straps are easily unbolted. I haven't had a chance to really look closely at the B-dot probe yet. It's covered in a little Faraday screen of its own that will be difficult to remove. My current understanding is that the probe circuit is open. I'll check that tomorrow and then see what else can be done.

Wednesday November 16 02 02 Hanson 49716-49732 ICRF testing

Yesterday, Nick and I removed all but one of the stages from the ICRF delay line in order to be able to test the ICRF with a short pulse. Today, I took vacuum ICRF shots with increasing voltages. I also added one more stage to the delay line and took more vacuum shots. The current traces in the antenna straps seem to track well with the top tank current (bottom tank ws not digitized). All traces exhibit an exponential RC decay, so I don't suspect any arcing. However, a snapping sound is heard when the antenna fires at higher voltages. The delay line was left in its truncated state because I intend to repeat this experiment with plasmas whenever they are available.

Wednesday November 16 02 52 Pedersen none FYI

Just a reminder of the HBT-EP physics meeting tomorrow morning at 9.30 am. I will be talking about our research on bias induced edge transport barriers.

Thursday November 17 01 45 Hanson 49733-49734 icrf testing

Today, Nick and I took a couple more ICRF shots to see if we could determine the source of the snapping sound heard yesterday. However, the sound could not be reproduced today.

Tuesday December 13 04 14 hanson/klein 49735 feedback test

Alex and I did a vacuum test of the feedback system. We put a sine wave on the control coils using the fpgas and then checked to make sure the sensors picked it up. They did. The feedback system seems to be in working order.

Thursday December 15 05 57 hanson/maurer 49738-49794 clean-up

First day of plasma shots since the re-installation of the quartz piece. Plasma currents were ~5 kA, pulse lengths 1-2 ms. Breakdown and the character of the shots seemed quite consistent; much better than the intial clean-up shots taken towards the end of last summer.

Friday December 16 01 03 hanson 49795-49812 clean-up

Friday December 16 01 14 hanson 49795-49812 clean-up

Plasma shots today looked more or less like yesterday. Low plasma current: ~6 kA, and short lifetime ~ 2ms. Discharges are quite consistent and there haven't been any big problems breaking down. The vacuum base pressure has been somewhat problematic; I've been waiting 10-15 min for the pressure to return to the 10^-8 range between shots. Fill pressures are ~3E-5 Torr. Around 11:30 this morning, the base pressure began to climb a little while after a shot. The temperature on the cryo head was about 10K, and a look at the RGA showed Dt and H20 to be dominant; ratio of N2 to 02 was about 10. After climbing slowly to 4.5E-7 Torr, the base pressure began to recede. It's now at 1.0E-7, a little more than an hour after the incident.


Monday January 9 04 22 hanson 49813-49822 icrf test

Made the first tests of the ICRF system with plasma since the removal of the Faraday shield. The ICRF delay line was trimmed to two sections, as with the previous vacuum tests, making the ICRF pulse about .5 ms. Due to the long pump-down time between shots (30 min - 1 hr), I was not able to complete a scan of ICRF voltage settings. Preliminary results don't show any signs of arcing or misbehavior. The plasmas themselves look much the same as they did two weeks ago: plasma current peaking around 7 kA, ~2 ms pulse lengths. Turning on the ICRF doesn't seem to impact plasma parameters. I plan to resume the voltage scan on Wednesday, and eventually add more sections to the delay line.

Wednesday January 11 04 42 hanson 49823-49862 icrf test

Today, I resumed scanning the ICRF bank voltages and added two sections to the delay line. For the most part, the ICRF traces looked normal, and I did not see any big changes in plasma behavior. Evidence of an arc was observed in the ICRF traces for the highest bank setting (20) and 4 sections in the delay line, in the presence of a plasma (49861). No arcing was seen for a vacuum test of the ICRF with an identical configuration. I plan to explore the arcing issue further, with Nick's help.

Tuesday January 17 05 18 hanson 49863-49888 clean-up/icrf test

Took clean-up shots and continued testing the ICRF system. I kept the ICRF bank voltage lower (~20) and did not see any signs of arcing. On one shot (49883) the having the ICRF on seemed to correlate with slightly higher conductivity temperature and plasma current. Most shots showed little or no effect. It turned out that the cause of the bottom tank circuit not being digitized was that the digitizer was not connected to the coil. I'll get that fixed up tomorrow.

Wednesday January 18 04 55 hanson 49889-49917 icrf test/clean up

Today, I digitized light from the ICRF tests using a photo diode pointed through the quartz window towards the antenna straps. Firing the ICRF introduced noise into the photo diode signal, but didn't cause any DC jumps. There was another arc in the ICRF system (49907), when the charging voltage was set at 30 kV. After this, I went downstairs and noticed that the ICRF cooling water purity light had turned red -- indicating impure water. The light did not turn green afterwards, so the ICRF was not fired again.

Thursday January 19 05 11 hanson 49918-49946 clean-up

Took clean-up shots today, without firing the ICRF.

Friday January 20 05 00 hanson 49947-49976 clean-up

More clean up shots today. Plasmas seem to slowly be improving. Average loop voltage has been about 11 V; soft x-rays still negligible; pulse lengths are averaging 5 ms. Replacement ICRF cooling water pump has arrived; plan to replace it on Monday morning.

Monday January 23 05 06 stillits 49977-50044 clean-up shots

Clean-up shots were taken. Outboard limited plasmas were created R~94-98cm. Loop-voltage ~ 14-6, plasma current ~ 5-8 kA, duration ~ 8 msec, and only weak SXR signals. Puff time ~ 2.0-2.5 msec. Will continue to take clean-up shots tomorrow.

Tuesday January 24 04 57 stillits 50045-50131 clean-up shots

Again, clean-up shots were taken. Outboard limited plasmas were created R~94-99cm. Loop-voltage ~ 15-6, plasma current ~ 5-7 kA, duration ~ 7-8 msec, and only weak - but improving - SXR signals. Puff time ~ 2.1-2.5 msec; no break down of plasma when puff time < 2.1 msec.

Wednesday January 25 03 22 maurer/hanson Took about 20 shots and tried to diagnosis why there is no plasma current in the bias phase of the OH transformer. Typical fill pressures to have the plasma breakdown are 1e-4 Torr. Thats about 3 to maybe 5 times what we normally would require. After chasing down a few possibilites iI think its the egun again. Nick and I will check it out.

Friday January 27 05 27 hanson 50153-50222 clean-up/icrf test

Took clean-up shots and attempted further testing of the ICRF system. The good news is that we now seem to be seeing some plasma current in the bias phase of the shot (so the e-gun seems to be functioning after yesterday's repairs). However, large fill pressures (~1E-4 Torr) are still required for breakdown. The plasmas seem to be cleaning up slowly but surely: SXRs are becoming more noticable, loop voltage is decreasing, etc. The ICRF system is still suffering water purity problems in spite of the new pump. The indicator light seems to go red after an ICRF shot, and then turn green again later. Firing 3 ICRF shots in close succession resulted in an arc.

Monday January 30 03 44 hanson 50223-50250 clean-up

More clean-up shots taken today. Attempted to do current-ramp shots as discussed at this morning's meeting. I was able to ramp up to 9.5 kA plasma current, maximum.

Tuesday January 31 05 05 hanson 50251-50313 clean-up

More clean-up shots taken today. I'm now able to get plasma currents up to 10 kA using an agressive ramp. Plan to test run the feedback system tomorrow or Thurs.

Thursday February 2 05 45 hanson 50354-50445 clean-up/feedback tests

Made clean-up discharges and fired up the feedback system today, using an FGPA routine written by Alex. The feedback system seems to work inasmuch as nontrivial voltages appear across the control coils. It's hard to say if any modes were suppressed. I did a scan over the toroidal phase-angle input to the FPGA routine.

Friday February 3 05 02 hanson 50446-50502 clean-up/feedback tests

Took more clean-up and feedback phase-scan shots today.

Tuesday February 7 05 44 hanson 50503-50586 clean-up/feedback tests

Took clean-up shots and attempted to generate magnetic perturbations with the FPGAs in open loop. I had some difficulties getting the FPGAs to generate waveforms on the coils; plan to try again tomorrow.

Wednesday February 8 05 43 hanson 50593-50613 clean-up/phase-flip

Took more clean up shots today, and managed to put some 3:1 modes on the control coils. Also, I had a look at the loop voltage voltage divider. It appears to be in working condition, and the gain settings in the tree give accurate results to within 2-4%.

Thursday February 9 05 39 hanson 50614-50696 clean-up/phase-flip

Took more clean-up shots and did phase-flip experiments.

Wednesday February 15 05 59 hanson 50726-50777 clean-up

Took more clean-up shots. After clearing out the puff-valve lines an switching to pure deuterium, plasma bias current seems to have improved.

Monday February 20 05 12 stillits 50830-50855 New Biased Probe

We tested the new biased probe (BP) today. We took a few regular shots in which we had BP inserted 1cm, 2cm, and 4 cm into the the plasma and no voltage. Thereafter, we inserted BP 1 cm into the plasma and at +50 V we measured BP-current ~50 A, +100 V => BP-current ~100-120 A, and +150 V => BP-current ~ 150 A. Tomorrow we'll try to insert BP 2cm - 5cm and V_BP = 50 - 150 V (it will depend on the current drawn). Clean-up shots were taken too. We are able to create plasma with puff time ~1.2-1.3 msec.

Tuesday February 21 05 05 stillits 50856-50896 Biased Probe

We finished getting I-V characteristics for the new biased probe (BP). We had BP inserted 1cm to 4-4.25cm (max. insertion) into the plasma and slowly ramped the voltage up from +50V to +150V at each position. The BP current is ~1 A/V and fairly independent of the position. Furthermore, we also took clean-up shots. Small improvements are seen: duration of plasma ~ 6msec, puff time ~ 1.3 msec, max. plasma current ~ 10 kA, weak SXR < 0.1, q* ~ 1.5.

Thursday February 23 05 29 hanson 50897-50938 clean-up

Took clean-up shots and experimented with moving the aluminum shells. Putting in the Al shells does not seem to impact breakdown greatly, but does lead to more quiescent discharges. Also, the Ebara cryo-pump has been misbehaving again, oscillating in temperature and causing temporary increases in base pressure.

Friday February 24 05 00 hanson 50939-50981 phase-flip

Attempted to drive 3:1 modes rotating at 5 kHz using the control coils in an open-loop configuration on discharges with little ambient 3:1 activity. I didn't see much correlation on the SMPs. Plan to analyze runs and do a frequency scan next week.

Tuesday February 28 03 58 stillits 50982-50988 TPA + BP

Most of the day was spent on getting the CPCI to work. Afterwards, we took a few plasma shots with the old TPA, but the cpci is still having some problems storing data. On Thursday we will try to get a few plasma shots with the new BP and old TPA to see what floating potentials and electric fields we are generating with the new BP.

Wednesday March 1 05 09 hanson 50989-50139 clean-up/open loop fpga

Took clean-up shots and conducted open-loop fpga tests. I attempted to impose a rotating 3:1 mode on plasmas that had some ambient 3:1 activity. Rotation frequencies varied from 1-8 kHz. Plan to continue frequency scan on Friday. Also, the Ebara cryo pump continues to misbehave, warming up and discharging into the chamber every hour or two.

Friday March 3 05 03 hanson 51069-51110 open-loop fpga

Completed a frequency scan of rotating 3:1 magnetic perturbations using the fpgas. Plasma discharges continue to improve, but the Ebara cryo pump still has temperature cycling issues. Bake is on.

Tuesday March 7 04 41 hanson 51111-51156 open-loop fpga

Applied more rotating 3:1 perturbations with control coils, at various frequencies. Hopefully, these results will guide phase-flip experiments to be done tomorrow and later in the week. Also, the Ebara cyro pump continues to misbehave.

Wednesday March 8 01 43 hanson 51156-51176 discharge shaping

Attempted to create "Shilov style" discharges in which the edqe safety factor slowly crosses 3 from below. These shots seem to be more quiescent than shots with agressive current ramps and may be more suitable for open-loop phase-flip experiments.

Wednesday August 30 01 54 maurer/hanson 51528-51545 systems test

Test fired all banks and the puff valves. Monitored the TF coils with the new flux loop sets, and the traces looked fine. We achieved plasma breakdown on shots 51544 and 51545. Plasmas showed low plasma current (max 5 kA). Pumping has been a bit slow and the RGA still shows lots of water. Plan to bake, glow in Dt this afternoon, and maybe regen a cryo or two.

Wednesday October 11 04 27 hanson/maurer/james 51555-51590 clean-up/neutrals

This was the first real HBT-EP run day since spring. Plasma currents peaked consistently around 10kA, loop voltages were around 10-13 V, pulse lengths grew as the day went on, reaching about 3 ms. Plasma behavior seemed quite consistent from shot to shot with most discharges experiencing a noticable disruption about halfway through the shot. Used the caemra housing, small filter, and single channels on the PDA to test the amp. Signals without the filter were about 1V on average peaking at about 2V and negative (as expected). the H-alpha filter signals were somewhat more reduced, so it was difficut to seperate them from the noise. This could be a result of the plasmas being cold so we will continue tomorrow. If results are unchaged tomorrow, I will revisit the amp.

Thursday October 12 08 59 James_Hansen 51590 - 51627 Cleanup & Neutrals

Cleanup shots continued today, we reached longer lifetimes (about 5.5 -5.75 milliseconds) than yesterday, but we were around 7 kA Ip for most of the day close to yesterdays. We did notice that we had to raise the fill pressure throughout the day after long breaks between shots as expected after a long pump down. We were able to continue testing the PDA to day as well. Filtered signals with a single channel from the array were still too small to distinguish from the noise. All these shots can be viewed in the tree with the PDA.jscp in the HBTEP directory; shot #51579 is a good example to see this. We then replaced the array with the single diode and same filter. The single diode with an area 4 times that of the arrays single channel showed a clear and smooth twin peaked signal as predicted. Next we put two and finally three adjacent elements from the array in parallel to increase the surface area and finally got a noisy but clearly discernable signal, shot #51627. We will be able to test more channels in this fashion once the larger filter comes in on Monday.

Tuesday November 14 05 42 hanson 51636-51668 clean-up

Made clean-up plasmas. Plasma parameters are slowly improving, loop voltage averages around 14 V, plasma current around 10 kA, pulse-length 3-4ms. No soft x-rays yet. Some initial tests were done of the Hall probe hardware and D-alpha amplifier.

Friday November 17 02 56 hanson 51669-51678 clean-up

Friday November 17 02 58 hanson 51669-51678 clean-up

More clean-up shots today. Plasma parameters continue to improve. Most notably, loop voltage now stays below 10V for a msec or two on most shots. Pulse lengths are in the neighborhood of 3-4ms.

Monday November 20 04 23 hanson 51690-51716 clean-up

More clean-up shots today. Loop voltage averages around 10V, and SXRs are still quite small.

Tuesday November 21 06 04 hanson 51717-51757 clean-up

More clean-up shots today. Plasmas are behaving fairly consistently, with loop-voltages a little below 10 V (on the good shots), but no soft x-rays yet.

Wednesday November 22 06 20 _hanson 51758-51796 clean-up

More clean-up shots today. Loop voltage seems to be coming down. Plan to bake over the long weekend and resume clean-up shots on Monday.

Tuesday November 28 06 04 hanson 51797-51828 clean-up

More clean-up shots today. Attempted to make hot plasmas with lots of ohmic heating input. This was somewhat successful: core soft x-rays in the neighborhood of .15 V were observed, and some shots even had some small saw-teeth.

Wednesday November 29 05 14 James/Hansen 51833 - 51873 Clean-Up/D-alpha

More of the same today, clean-up shots mostly, with a mixed with Hall probe and D-alpha testing. The Hall probe seems to be functioning well, calibrations to follow. The D-alpha detector single channel is operating nicely with little gain (about a factor of 2 M-ohms), so the Thompson Scattering port is a good place for collecting light from the plasma. We are still working out bugs in the array amplifier.

Thursday November 30 04 21 hanson 51894-51897 clean-up

More clean-up shots today. We continue to see small improvements in the soft x-rays.

Thursday November 30 04 25 hanson 51894-51917 clean-up

More clean-up shots today. We continue to see small improvements in the soft x-rays.

Tuesday December 5 06 44 hanson 51919-51983 clean-up

More clean-up shots today. Plasmas look a lot like they did last week. Also, the sensor coil digitizers were tested using a function generator, and found to all work. Additionally, OH only and VF only shots (51955,51956) were taken to try to assess whether these effects are corrected for properly in the major radius calculation routine.

Wednesday December 6 05 14 James,_Hansen 51983 - 52030 Clean-Up

More clean-up shots today. The cooling oil fixes seem to be holding up well.

Thursday December 7 04 32 hanson 52031-52070 clean-up

More clean-up shots today. Plasmas continue to improve, but do not behave consistently from shot to shot.

Monday December 11 05 03 hanson 52071-52109 clean-up

More clean-up shots today. The battery in the puff-valve circuit was slightly low, so we replaced it this morning. I did repeated static fills throughout the day to determine if the puff-valve was working consistently -- it is. The minimum fill pressure required for plasma breakdown was about 1.0E-4 T. Plasmas behaved similarly to how they did last week, but did seem a bit more consistent shot-to-shot.

Tuesday December 12 04 04 hanson/james 52115-52123 clean-up

A few clean-up shots were taken this afternoon; during the morning, additional hardware related to the D-alpha experiment was installed on HBT-EP. Also, did some troubleshooting on one of the m=2 rogoski coils (which hadn't worked in recent memory). The coil was installed and in good shape; the problem turned out to be a misconfigured AM502 amplifier.

Wednesday December 13 05 09 hanson 52123-52160 clean-up

More clean-up shots today. Some testing of the D-alpha hardware (with a tangential view of the plasma) was done as well.

Thursday December 14 05 52 hanson 52161-52205 clean-up

More clean-up shots today. There have been problems getting the CPCI to initialize after a restart of langmuir.ap a couple days ago. I've requested help from Yuhong and am waiting to hear back.


Friday January 26 04 26 hanson/maurer 52218-52250 testing

Tested all of the banks, looked for tools dropped near the machine, and sorted out some small kinks that had worked their way into the system since the last run (back in Dec). The TF coils were tested with care, and traces from the diamagnetic loops mounted on the coils looked normal. Also, one plasma shot was taken. Plan to take clean-up shots all next week, as everything now seems to be in good working order.

Tuesday January 30 05 17 hanson 52251-52284 clean-up

Took clean-up shots today. Plasmas are behaving fairly consistently shot to shot, with loop voltages around 8-10V. The sensor coils were tested and found to work, with the exception of two whose analog boards have not been fixed yet. We looked into getting the optical rotation diagnostic connected to a digitizer, but some of the configuration settings for the 6810 were not transparent. Steve Paul has been contacted for advice. Plan to take clean up shots for the rest of the week and work on getting data from the hall and rotation diagnostics.

Thursday February 1 04 33 hanson/james/maurer clean-up

Took more clean up shots. By the end of the day we had nice sawteeth and loop voltages down to about 6 Volts by the end of the shot. The longest lived plasmas lasted about 8 msec. Had problems with the vacuum controller interlocks again (similar problems occured with the main ion gauge last week and caused the vacuum system controller to trip over the MLK day weekend at the start of the semester). It appears that many of the connections on the backside of the gauge controller are starting to fail due to age and fatigue. There might be some problems with the gauge controller itself as well.

Friday February 2 12 07 hanson 52382-52399 clean-up

More clean-up shots today. Saw some nice plasmas with lots of soft x-ray/mhd activity and loop voltages descending to around 6V. We're ending early today to fix oil leaks, bake relays, the ion-gauge connection, and the remaining analog feedback boards.

Wednesday February 7 05 19 hanson 52400-52425 clean-up

Made more clean-up plasmas today. Plasmas continued to look good, but the RGA showed high water levels after the run. The crunch amplifiers and control coils were tested and seem to be working. The new Kalman filtering routine was run and it seems to produce coil signals similar to those made by Alex's routines. Plan to continue with the clean-up shots with some focus on creating discharges with (m,n)=(3,1) activity.

Thursday February 8 05 06 hanson 52425-52490 clean-up

More clean-up shots today. Plasmas continue to look good. Pulses typically last longer than 6 ms and have loop voltages that descend from 10-5 V over the shot.

Monday February 12 04 27 hanson 52491-52528 clean-up

More clean-up shots today. Plasmas continue to look good with loop voltages that approach 5V towards the end of the shot and plenty of MHD activity.

Tuesday February 13 02 58 hanson 52528-52556 clean-up

More clean-up plasmas today. Plasmas continue to look good. As there seems to now be plenty of mhd activity, the plan for tomorrow is to do some initial testing of the Kalman filter feedback algorithm and a compass scan.

Thursday February 15 04 50 hanson 52557-52622 feedback system testing

Did some testing of filter gain and feedback phase settings using both new (Kalman filter with lead-lag compensator) and old (lead-lag compensator only) FPGA routines. Also, more Hall probe calibration data was taken. Plan to do some further FPGA tests tomorrow and think about the results over the weekend. I should be in shape to do some more formal phase scan experiments next week.

Wednesday February 21 05 59 hanson 52654-52672 feedback testing

Did some more tests of the feedback system with a slightly re-designed Kalman filter. (An oversight in the program was discovered earlier this week.) Some D-alpha hardware tests were done and some more Hall probe calibration data was taken.

Friday February 23 02 43 hanson 52691-52710 Rotation Diagnostic/Feedback

We recorded data for the first time using the rotation diagnostic. 90% He, 10% D2 plasmas were made and signals were seen on both channels. Unfortunately, the gas received for these experiments was mixed incorrectly. It should have been 10% He, 90% D2. The gas supplier has been contacted. Throughout the week, I've been trying to pin down the source of some large DC offsets seen in the control coil traces when the feedback system is on. Tests done today seem indicate that at least some of these are due to hardware problems, not bugs in the FPGA routines (as originally suspected).

Tuesday February 27 04 15 hanson/james 52711-52729 feedback/d-alpha

Did more tests of the feedback system today. Some potential problems in the FPGA algorithm were eliminated. I hope to have the rest of the bugs worked out by the end of the week. D-alpha array is working (minus the slit). It turns out that the negative lead to the PDA was borken and has been repaired. I will test with the slit tomorrrow.

Wednesday February 28 04 04 James/Hansen 52730 - 52740 D-alpha Tests

I did initial tests on the Photodiode array today. The tests show that we did remove most of the noise from the system and that there is plenty of white light available. We were unable to get specific levels of D-alpha for a single element of the arrray due to problems with the VF-Start control panel. It is unclear if it is just a problem in the Control Panel or in the basement bank system. Nick is investigating. We plan to complete ths D-alpha tests tomorrow whern VF problem is corected. No feedback work was done due to problems with the analog boards. They don't seem to be getting the correct voltages from the power supply anymore. Work to fix this issue is underway.

Friday March 2 04 46 hanson 52772-52796 feedback testing

After bench-testing all of the analog boards yesterday (all were in good, working order), the feedback system was reassembled for online testing. (It was suspected at one point that one or more boards might have shorts or bad op-amps.) Replacing the +/- 12 V DC power supply for the analog boards with two large 12 V batteries fixed some of the problems we were seeing during the previous two weeks. These were: DC offsets appearing inconsistently in the control coil signals and incorrect power supply voltages appearing across the boards. In any case, eliminating the power supply seemed to do the trick. A replacement has been ordered.

Wednesday March 7 02 40 James 52827 - 52840 D-alpha

Installed a moving mirror setup for the D-alpha array. I used a laser to confirm the angle range to sweep the solid angle from major radius about R=107 inward. The Levels of white light increased as the view was moved in to the center of the plasma, but they were substantially lower than the levels seen with out the mirror, compare shot number 52831 with mirror and 52724 no mirror. When the filter was added the levels drastically dropped to almost zero without the slit even being added yet, compare 52838 with mirror and 52729 no mirror and both no slit. I will print these out for Monday morning meeting. To see the data mentioned look in ICRH_L8210_1:Input_2 in the tree and the signal is negative so it must be multiplied by -1.

Thursday March 8 04 39 hanson 52854-52891 feedback testing

Today, a working Kalman filter was tested on plasmas for the first time. However, the filter did not work as expected on all of the FPGAs. One FPGA/poloidal group seemd to work flawlessly, but the others performed strangely. I'm still pondering this. (Other programs have either worked correctly or not on all of the FPGAs.) Also, plasmas looked quite good; I was able to create discharges with lots of m=3 activity.

Friday March 9 02 33 hanson 52892-52905 feedback testing

I got the Kalman filter working on all four FPGAs today. (There had been a bug in the software preventing matrix data from being loaded correctly onto some of the FPGAs.) I did a few shots with the filter turned on at a constant feedback phase angle and a few reference shots. The plasmas showed lots of m=3 activity, but it was difficult to tell from the raw signals whether I was driving or suppressing anything. I plan to compare the filter output with my model over the weekend and undertake more elaborate experiments next week.

Tuesday March 13 05 46 hanson 52906-52950 feedback

More Kalman filter tests today. I played around with some different proportional gain and phase angle settings. By looking at the time delay in gating on the feedback, I got an estimate for the FPGAs' loop rate. Updating the matrices with this parameter produced control coil currents that were in good agreement with my model for what should happen. Setting the phase angle at 180 degrees (for positive feedback on the kink mode) causes the Kalman filter to blow up. I can even make the FPGAs ring on line noise (with no plasma) at this setting. I Plan to attempt a fine phase scan tomorrow, hardware permitting.

Wednesday March 14 05 50 hanson 52951-53045 feedback phase scan

Did the greater part of a feedback phase angle scan today. I took two feedback on and two control (feedback off) shots for each 10 degree step. Plan to finish up the scan tomorrow and start analyzing the retsults.

Thursday March 15 05 45 hanson 53047-53092 feedback phase scan

The Kalman filter feedback phase angle scan continued today and is nearly finished. The run day was cut short by a failure in the charging power supply for the OH electrolytic bank. The failure point was a splice connector at the 3-phase power input to the supply. The connector had become loose and was arcing and melting. A substitute connector was made in the shop this afternoon, so we should be ready to run again in the morning.

Friday March 16 12 47 hanson 53093-53127 feedback phase scan

Completed the Kalman filter phase angle scan today. The OHEC charging supply was reassembled this morning and appears to be working fine.

Thursday March 22 05 05 hanson/debono 53150-53163 rotation diagnostic tests

We tested the Doppler rotation diagnotic using 10% He 90% D2 plasmas. Signals coming from the optics looked like they were in qualitative agreement with earlier results.

Tuesday March 27 05 13 hanson 53176-53132 feedback

More feedback tests today. After a numerical error was found in the alorithm last week, the first plasma tests of the corrected filter were done today. The control coil currents seem to track quite well with expectations, but it is difficult to tell yet what the impact of the feedback is on kink modes. Further testing and analysis to come.

Wednesday March 28 04 44 hanson 53233-53298 feedback

More feedback testing today. Some time was spent developing a reference discharge with a strong current ramp and lots of m=3 activity. I have not seen any very obvious evidence of suppression yet, but a frequency analysis of the shots has yet to be done. Also, one poloidal group seems to be performing poorly; I hope to be able to address this issue tomorrow.

Friday March 30 04 42 hanson 53299-53310 feedback

More feedback testing. Frequency analysis from shots taken earlier this week showed that the filter algorithm drives the control coils at frequenies that are somewhat smaller than the mode. The filter matrices were recalculated for slightly higher frequencies and tested again today. Also some more data was taken using the rotation diagnostic.

Tuesday April 3 06 11 James 53317 - 53325 D-alpha

Success! I was able to repeat last Friday's tests in Deuterium (vs the 10 percent He mix). The white light and D-alpha output concurrently increased. I then masked the single diode to 1mm and added the filter and lens and was able to sweep the mirror to find the highest D-alpha levels. Outputs were around the 2.5V level through the shot, after the start-up spike. I also documented the rise and fall of the signal around this peak mirror angle. After these initial tests, I replaced the masked single diode with the array and after some quick repair work on the input connector, D-alpha signals between .7V and 1.3V were achieved! Tomorrow I will vary the PDA elements and mirror angle to try and get a framework to begin mapping the chords.

Wednesday April 4 05 06 hanson 53327-53376 feedback testing

I made some changes to the way that the Lead-Lag filter is implemented in the feedback algorithm and tested them piecewise this morning. Initial analysis shows (both in theory and practice) that the lag filter does a good job of flattening the transfer function going into the FPGAs, so that the signal seen by the Kalman filter stage is proportional to B (and not, say, dB/dt). In the afternoon, the algorithm was tested as a whole. Anecdotal evidence of some m=3 suppression and excitation was seen for different feedback phase angles.

Thursday April 5 04 38 hanson 53377-53430 feedback

I did a coarse feedback phase angle scan using the algorithm as described yesterday. Analysis is pending.

Friday April 6 01 13 hanson/debono 53431-53442 rotation diagnostic testing

Took some data using Steve Paul's rotation diagnostic that will hopefully lead to a better calibration.

Tuesday April 24 04 59 hanson 53468-53501 feedback

Two sensor coils that exhibitted signal saturation problems were disconnected from the feedback loop. The analog boards had been eliminated as possible sources of the saturation; there is some suspicion that the shielding on the coils themselves may be damaged. (Recall that the poloidal sensors are mounted on the plasma facing side of the stainless steel shells.) Eliminiting these inputs left the xT_S1 group with only two inputs (a third sensor coil in this set is open-loop). Control coil signals for the xT_S1 group were subsequently much more well behaved, and looked similar to those on other groups. However, I am not yet sure if the spatial DFT coefficients for this group should be modified to compensate for the unevenly sampled data. Plasmas were repeatable, with one or two shots showing signs of possible feedback suppresssion of m=3 modes. I plan to think about the DFT coefficients tonight and continue with feedback experiements tomorrow.

Thursday April 26 05 09 hanson 53524-53566 feedback testing

I attempted to make plasmas in the style of M. Shilov for feedback studies. These plasmas break down between edge-q=2 and 3 on the outboard edge and move inwards, pulling in the q=3 surface as they expand. This type of shot seems to be m=3 unstable without perturbing the two "bad" sensor coils as much. I was able to keep these coils plugged in and have the Kalman filter work reasonably well on the xT_S1 set. I found it more difficult to reproduce the Shilov plasmas exactly, shot to shot. However, I believe that I've seen some anecdotal evidence of m=3 suppression. I plan to continue in this vein tomorrow.

Friday April 27 05 01 hanson 53569-53640 feedback

More feedback shots today, using the "Shilov shot" described in the run report yesterday. I adjusted the banks a little and was able to achieve better repeatablility. I covered a few feedback phase angles; the rest will be done next week.

Tuesday May 1 05 30 hanson 53672-53750 discharge shaping

I've been trying to cultivate a shot with large, low frequency (~5 kHz) m=3 activity. As a model, I'm using shot 43102, from Alex Klein's work. Some important characteristics of this shot are subtle and difficult to reproduce, but I'm making progress. I hope to get back to doing feedback studies tomorrow.

Thursday May 3 04 59 hanson 53823-53875 feedback

I've been able to develop a plasma with a more slowly oscillating m=3 mode--in the neighborhood of 5-7 kHz. Initial experiments with the Kalman filter appear to indicate that I can both suppress and drive it.

Friday May 11 04 41 hanson 54163-54213 feedback

I spent the week developing a discharge with a robust, current driven m=3 instability. I am not able to exactly reproduce the discharge used by Alex Klein, but I have found one that behaves similarly. I seem to be able to both supress and excite the mode using the feedback system.

Tuesday June 5 05 04 James 54326 - 54385 D-alpha

Finally tested the D-alpha prototype amplifier with three signals. The designed board worked perfectly. One of the output connector channels between the CPCI connector and the amp is a little flaky but the amp itself works great. I was able to take a white light shot and get signals that were clipped into the 5 volt region. D-alpha light ranged between .2 V for an inboard view to 1 V in the edge region. These views are not exact but in the general vicinity. The noise was in the .0012 V region and frequency response seems good. Nick and I are working up drawings to submit for a quote on a multi-channel amplifier board made on the economy. Tomorrow morning I will take a few shots with the power supply to check noise levels and hopefully a repaired connector to get rid of the one flaky channel between the CPCI and the amp.

Tuesday June 19 03 01 James 54412 - 54417 D-alpha

I was able to conclusively show that the amplifier boards work. I will verify their freq. response on later this week. I was also able to take a picture of the plasma that I will send out or post after I put it in a better format. I will also attempt to create better pictures of the plasma and hopefully use the d-alpha filter in a few shots!

Monday June 25 04 32 James 54437 - 54440 D-alpha

Theses were short lived plasmas, ~3.5 ms. The pictures were taken through the ICRH port to get a fairly unobstructed view. Able to see D-alpha Light - the center of the plasma does not seem to be emitting much, but the edge of the plasma and not the chamber wall seems to be the source as would be expected when not looking at a limiter. I have e-mailed out a pdf with pictures in it.

Friday July 6 05 02 Hanson/DeBono 54517-54532 Rotation Diagnostic

Tested rotation diagnostic using 10%He, 90%De mix.

Tuesday July 10 06 06 James 54563-54587 D-alpha

Did some calculations with Dave Maurer and determined that the transfer fxn roll-off was mostly due to the 15pF cap in the amplifier circuit. I replaced the caps in each of the channels with a 1pF, 3.6pF, and 6.6pF capacitors and did some signal to noise tests on the bench. I then put the PDA on the machine and tested the cabling and CPCI digitizer. I spent the rest of the afternoon attempting to align the lens & PDA with the mirror - with no success. I will continue tomorrow with this process and then determine noise levels and frequency response for each channel.

Thursday July 12 09 57 James 54588 - 54624 D-alpha

I was able to calibrate the detector and get D-alpha signals into the 1V range through the shoot lifetime. There are still noise problems from the PDA connector, but they will be rectified in constructing the final unit. There was noticeable smoothing in the 6.6pF and minor smoothing on the 3.6pF channels. The 1pF had some extra wiggles but it was on a channel with an obscured view, so it was hard to compare side by side. Yet the freq response test confirm a 31KHz - 35KHz corner freq for the 1pF channel with 30.6KHz calculated. I didn't test the others yet, but the 3.6pF has a calculated corner freq. of about 10.5KHz which seems a bit low. For now we are going with the 1pF and I will do the freq. response for the other two channels to make a decision on Monday for the final design to be processed.

Thursday July 12 03 37 hanson 54633-54647 kalman filter testing

Tested a newly written version of the Kalman filter algorithm today, with actual plasmas. The new algorithm has been optimized for a significantly improved latency: 10-15 microsec, down from 30-40 microsec. Qualitatively, the algorithm performed more or less as expected. Control coil currents seemed to be a bit attenuated on some toroidal sections--this may be due to a numerical error (possibly an underflow) in the algorithm. I plan to check the new algorithm carefully and to work on making plasmas with robust m=3 modes.

Friday July 13 04 23 hanson 54648-54697 discharge development

Spent the day trying to fine tune m=3 kink-mode discharges. I plan to pick up where I left off on Monday and spend the rest of next week doing Kalman filter experiments.

Monday July 16 03 19 hanson 54698-54729 kalman filter

More discharge development and Kalman filter testing today. I've been able to create a fairly repeatable kink mode. There's a small bug in the Kalman filter algorithm that seems to track with the adjustable phase angle. I think I know what's wrong and will fix it tonight and recompile. I hope to be ready to start compass scan experiments tomorrow.

Tuesday July 17 05 41 hanson 54730-54790 kalman filter

This morning, I found and fixed the bug in the Kalman filter (there was some incorrect memory addressing in the inverse DFT step) and was able to start experiments. I completed about a quarter of a feedback phase angle scan. This afternoon, there was some trouble with the TF bank charging electrode: a piece had broken off. With Nick's help, I filled the resistor high enough to submerge what was left of the electrode. Eventually, it will need some attention.

Wednesday July 18 05 39 hanson 54791-54850 kalman filter

The feedback phase angle scan continued today. It's nearly halfway finished.

Thursday July 19 07 35 hanson 54851-54930 kalman filter

More of the Kalman filter feedback phase angle scan today. I am nearly done; plan to finish up tomorrow morning.

Friday July 20 03 51 hanson 54931-54965 kalman filter

The Kalman filter feedback phase scan was completed today. I plan to do initial analysis of the results over the weekend, so we can talk about what to do next on Monday. Also, I managed to overheat the TF charging resistor again: the electrode is now almost gone and needs attention. I'll repair it with guidance from Nick and Dave on Monday.

Tuesday July 24 05 01 hanson 54966-55005 discharge development

This morning, I inserted the aluminum shells fully and re-created the shot used for feedback experiments last week. The Al shells were able to suppress the mode about as well as optimally phased feedback (last week), but this suppression was not spectacular. Perhaps the mode I used behaved too ideally. I am now working on developing a more resistive mode.

Thursday July 26 03 39 hanson 55006-55106 discharge development

I've spent the last couple days fine tuning my kink mode discharge. I hope to get back to taking feedback data tomorrow.

Friday July 27 04 29 hanson 55107-55151 kalman filter

Took some feedback phase scan data today. Much more of the same planned for next week.

Monday July 30 05 05 hanson 55152-55195 discharge shaping

Did some work trying to make a better, stronger external kink mode. Plan to continue in this vein tomorrow.

Tuesday July 31 05 12 hanson 55196-55258 discharge development

Work on making a better external kink discharge continues. I have a candidate that I'll test with feedback tomorrow.

Wednesday August 1 06 10 hanson 55260-55304 discharge development

More discharge development today.

Thursday August 2 05 22 hanson 55308-55379 kalman filter

I started a feedback phase scan with a new, stronger kink mode today.

Friday August 3 06 05 hanson 55381-55447 kalman filter

More feedback phase scan shots today. Initial results show some promise, but the going is slow.

Monday August 6 04 28 hanson 55448-55506 kalman filter

More feedback phase scan data taken today.

Tuesday August 7 04 54 hanson 55507-55579 kalman filter

More feedback phase scan shots today. I'm now done with over half of the compass points.

Wednesday August 8 06 09 hanson 55580-55659 kalman filter

More feedback phase scan data taken today.

Thursday August 9 05 49 hanson/shiraki 55660-55738 kalman filter/hall probe

Finished up the feedback phase scan today. Initial analysis of the data points to some suppression over a decently broad range of phase angles. I'll have some plots for discussion on Monday. aisuke got some hall probe data as well.

Friday August 10 05 00 shiraki/hanson 55739-55781 Hall probe

Took some hall probe data, attempting to recreate Yuhong's shots.

Monday August 13 05 09 hanson/shiraki 55782-55834

In the morning, we pulled the Al shells all the way out to try to replicate a shot from Yuhong Liu's thesis. In the afternoon, the shells were fully inserted to see what effect they had on the mode used for feedback experiments last week. Some suppression was seen, but I'd like to take a few more of these shots.

Tuesday August 14 04 37 hanson 55835-55861 discharge development

First, the mode from last week's phase scan was re-created with the aluminum shells pushed all the way in. Little suppression was seen. Next, the Al shells were pulled back 4 cm from the plasma surface and an attempt at making a shot similar to the one used in Liu's thesis (45645) was made. The behavior in this shot seems to be a little easier to reproduce than seen in Klein's discharges. I plan to fine tune my reproduction tomorrow.

Wednesday August 15 05 47 hanson 55862-55915 discharge development

Attempts to make a better kink mode continue.

Friday August 17 04 50 hanson 55916-55960 discharge development

The search for a better kink/RWM continues. Today, I spent a some time attempting to make shots similar to those used by M Shilov (e.g. 38318). One thing that's nice about this shot is that the mode appears much later in the discharge compared to the shots that Klein used--usually around 5 ms. By this time, the plasma has had a chance to heat up more and there is sometimes a good, solid SXR signal. In any case, I feel like I've been having difficulty achieving good soft x-rays, especially early on in a discharge. Loop voltages are usually below 10 V for "usual" plasma currents of 10-20 kA, but I've been finding that I usually need to grow the plasma in major radius to see much of anything in the SXRs. I've played with the fill pressure a little bit, but perhaps some more systematic studies are warranted.

Monday August 20 05 08 hanson 55961-55997 discharge development

Friday and today, there were some problems getting the banks to fire. The issue has been intermittent, so I haven't been able to pinpoint the cause yet. Also, the screenroom digitizer did not want to power on this morning. It's bypassed for now. I did have time to make a few plasmas. The idea now is to see if I can get them to heat up better by breaking down a little further out (R~=95cm) and then pulling the plasma in. This does seem to be helpful. I will not run tomorrow in order to allow for Thompson scattering and D-alpha hardware work to be done in the machine area. I'll pick back up again on Wednesday.

Wednesday August 22 05 57 hanson 56003-56069 discharge development

Today I made some progress in creating external kink modes in scenarios where edge-q is ramped down through q=3 and where it is ramped up. Mike suggested that I adjust the start time of the VFST bank to coincide with the start time of the OHST bank. This seemed to create a more smoothly evolving discharge in the ramp-up case. I plan to continue tuning both kinds of shots and reproduce them with the Al shells in. Perhaps feedback experiments can begin next week.

Thursday August 23 05 09 hanson 56070-56120 discharge development

I have completed fine-tuning my q ramp up and ramp down discharges. I am now trying to reproduce them with the Al shells fully inserted to see how the modes behave. I hope to have this done by the end of tomorrow.

Friday August 24 04 21 hanson 56122-56165 discharge development

I attempted to re-create my ramp-down and ramp-up modes with the Al shells all the way in, today. The ramp-down evolution was a little easier to get right and showed more mode suppression.

Tuesday August 28 05 02 DeBono/Hanson 56166-56169 rotation

Ran 10%He & 90% Deuterium for rotation diagnostic testing. Had problems with new screenroom digitizer rack initializing.

Wednesday August 29 06 17 B.DeBono/_J.Hanson 56170-56198 Velocitometer

Ran shots 56170-56198 for rotation diagnostic calibration.

Thursday August 30 06 03 DeBono/Hansen 56199-56223 Rotation Diagnostic

Ran shots 56199-56223 for rotation diagnostic calibration

Wednesday September 5 05 12 hanson 56224-56269 discharge development

I studied the effect of the start time of the vertical field on the dynamics of my external kink modes. I made some interesting plasmas, but did not see any modes stronger than what I've made already.

Friday September 14 03 41 DeBono/Maurer 56399-56431 Velocitometer

Ran Cleanup/Rotation calibration shots today with 90%Du/10%He mix.

Wednesday September 19 06 22 DeBono/Hansen/Maurer 56432-56500 Rotation Diagnostic

HBTEP was run with 10%He, 90%Du for rotation diagnostic calibration: Tests were conducted with velocitometer detector mounted to view the plasma perpendicular to its flow (on the ICRH port).

Thursday September 20 06 12 hanson/shiraki 56501-56582 clean-up

In the morning, I tried to re-create the modes discussed at the physics meeting last week. I was able to get very close, but I feel like there might be a little cleaning up that needs to be done yet. However, the plasmas look pretty good. In the afternoon, Daisuke got some hall probe data for edge-q ramp-up style shots.

Monday September 24 04 28 hanson 56583-56606 kalman filter

I was able to get a few shots in this afternoon. Previously, the FPGA driving the top-middle control coil set was using inputs from the bottom-middle sensor coils. After discovering that the phase-shift between top-middle and bottom-middle in the sensor coil data is almost exactly 180 deg (for the m=3 mode), I added a correction to the FPGA algorithm. Data taken today confirmed that the correction works as it should. I plan now to redo my Kalman fitler phase scan, since the correction was quite drastic.

Tuesday September 25 04 57 hanson 56607-56677 kalman filter

I began my Kalman filter phase scan today. Plasmas seem to be a little less reproducible; perhaps we are still cleaning up a little. I had some trouble this morning with a control coil not energizing. After swapping analog boards around and testing one on the bench, I concluded that there was simply a loose connection somewhere. Getting the analog board plugged in "just right" by trial and error seemed to fix the problem.

Wednesday September 26 02 58 hanson 56678-56724 kalman filter

More Kalman filter phase scan data taken today. Plasmas looked just fine.

Thursday September 27 05 50 hanson 56746-56813 kalman filter

More Kalman filter phase scan data taken today. Shot to shot reproducibility seems to be somewhat poorer than in past months; this experiment will likely continue through most of next week.

Friday September 28 02 26 hanson 56814-56834 kalman filter

More Kalman filter phase scan data was taken today. We ended the run day early to get the bake turned on for the weekend. Brian and I had hoped to get some optical rotation data this afternoon, but a shortage of liquid nitrogen prevented us from being able to pump out the puff line to switch gases.

Tuesday October 2 05 37 Hanson/DeBono ?-56927 Kalman Filter/Rotation Diagnostic

Shots were taken by Hanson and by DeBono Shots with 90%Du, 10% He were taken for shots 56905-56927 with the detector looking perpendicular to the direction of plasma flow. The purpose of this run was to assume the rotation velocity of the plasma was 0 (as viewed from the detector) with the data used for detector re-calibration.

Wednesday October 3 05 56 hanson 56928-56990 kalman filter

More Kalman filter feedback shots taken today. Reproducibility is still somewhat poor, although there's no other evidence of the vacuum vessel being unclean. (Base pressure this morning was 1.0E-8 T.)

Thursday October 4 05 10 hanson 56992-57039 kalman filter

More Kalman fitler phase scan shots taken today.

Friday October 5 05 08 hanson 57040-57093 kalman filter

More feedback phase scan data taken today. I'm nearing the end of this experiment; hopefully another day or two will be all I need to finish.

Monday October 8 06 31 hanson/debono 57094- kalman filter/rotation diagnostic

The morning was spent fixing a problem in the cos 1 theta Rogowski diagnostic. The L8210 used for this signal appears to have gone bad, so the signal was moved to a different L8210. In particular, the cos1 signal was moved from crate 5, slot 13, input 1 to crate 5, slot 21, input 4, and the tree was updated accordingly. In afternoon, rotation diagnostic shots 57101-57118 were taken. The detector was moved from its perpendicular viewpoint to a view looking along the torus (i.e, the detector was moved to see plasma rotation). The signals taken were relatively weak and characterized by nonexistant termination shock profiles. I will attempt to correct for this by increasing the light level output from the plasma by increasing the current and/or the pressure fill density.

Tuesday October 9 07 16 hanson 57120-57172 kalman filter

More Kalman filter phase scan data taken today. Yesterday's fix for the cos1 digitizer appears to be working fine.

Wednesday October 10 06 01 hanson 57173-57228 kalman filter

More Kalman filter feedback phase scan data taken today.

Thursday October 11 06 19 hanson/debono 57229-57321 kalman filter/rotation diagnostic

In the morning, Hanson continued the Kalman filter feedback phase scan; in the afternoon, DeBono got some rotation data from 10% He plasmas. The phase scan is nearly finished and preliminary analysis of the m=3 Rogowski signal shows a trend that looks a lot like that of Klein's experiments, but with no excitation above 5 kHz. 3 more shots are needed to complete the dataset; these will be taken tomorrow. Rotation diagnostic was taken with the detector setup to observe plamsa rotation. The tokamak was operated with high OHST and OHEL values in order. These parameters were chosen to gain as much signal as possible from the plasma. Data showed rotation velocities within the acceptable error (+-1km/sec) and with low velocity values (0.3 km/s < velocity < 3km/sec).

Friday October 12 05 10 hanson 57322-57358 feedback

A variety of things was done today. The last data points in the Kalman filter phase scan were recorded; Hall probe data was taken for feedback phasings of clear suppression and clear excitation; an open-loop, static (ie non-rotating), (m,n)=(3,1) field phase-flip FGPA algorithm was tested on the both edge-q ramp-down and ramp-up plasmas. There were problems communicating with the North rack throughout the day. Since this didn't directly impact any data taking, the issue was not fully resolved. Plan to let the crates cool off and see how things are next week.

Monday October 15 06 25 DeBono/Hanson 57360-57397 Rotation Diagnostic

Today I revisited the perpendicular 0-velocity shot after obtaining a wide spread in rotation velocities for a given non-perpendicular shot last week. The detector was moved to a perpendicular view; results showed inconsistent velocities obtained by the diagnostic. More shots need to be obtained for this.

Tuesday October 16 10 23 hanson 57398-57453 mode rigidity study

I'm working on doing Kalman filter feedback runs with one toroidal group of control coils muted. Rogowski coil and Hall probe data will then be analyzed as a function of the muted coil set. The scan is nearly finished; I plan to have it done with by the end of the day tomorrow.

Wednesday October 17 01 15 hanson 57454-57488 mode rigidity investigation

A preliminary mode rigidity experiment was completed today. The Kalman filter feedback algorithm was used with a phasing of 60 deg (for suppression) and a single toroidal group of control coils muted. Four shots were taken for each toroidal location.

Wednesday October 17 07 39 DeBono/Hanson 57489-57559 Rotation Diagnostic

Rotation Diagnostic data was taken with the detector oriented perpendicular to the plasma flow. Tokamak was run with 10%He,90%Du. Shots 57489-57559 were taken. Data seems encouraging with several excellent shots taken.

Thursday October 18 05 19 Jeff_Levesque 57566-57579 Thomson Scattering

Testing the Thomson scattering triggering and data acquisition. Observed scattered light in all channels of the polychromator.

Friday October 19 05 50 hanson 57581-57622 partial coverage

More partial coverage Kalman filter feedback data was taken today. Feedback was performed with different toroidal sections muted, one section at a time. Additionally, vacuum shots were taken to investigate the pick-up from the feedback coils in various diagnostics. These shots were done with the TF, VF, and OH fields present as normal, and a single toroidal section of feedback coils ringing at ~5 kHz.

Tuesday October 23 05 47 Levesque 57633-57691 Thomson Scattering

More tests of the Thomson scattering system. Attempted to increase scattered light collected by adjusting the collection lens. Signal levels stayed approximately the same over a small range of adjustment. Shots taken with laser firing at 3 ms and 5 ms into the plasmas. Verified that only channels 1 and 2 of the polychromator receive stray light.

Wednesday October 24 06 02 hanson 57696-57736 feedback testing

After analyzing SMP data from the last phase scan and not seeing much of a trend, I decided to move the SMPs up close to the plasma and do some feedback excitation and suppression shots. I also spent a little time doing feedback with Alex's old routine to get some data for comparisons between the algorithms. Additionally, Royce plugged his photodiode array into the CPCI and saw signals due to (unfiltered) light on most of the channels.

Thursday October 25 03 03 hanson 57737-57767 feedback

I finished up my run of feedback shots with the SMPs fully inserted today. Several phasings of Alex's old filter were tested in addition the Kalman filter.

Wednesday October 31 09 44 James 57697 - 87854 D-Alpha

Piggy-backed Jeremy's feedback runs. I was able to get all 20 channels working properly, showing both unfiltered and d-alpha. Unfiltered light was in the .15 V range, and the d-alpha .075 V. I was able to work out the channel errors I had. It turns out that I had the channel order on the board backwards. I was able to confirm this with the filament when I was aligning the PDA and mount. The chordal signals track the plasma nicely showing more visible light in the center channels where the most plasma is intercepted and less on the edges. Conversely d-alpha signals are highest on the (outboard) edge and fairly constant in the center channels. Data analysis is the name of the game for the next few days to get ready for the poster.

Friday November 9 11 02 Jeff_Levesque TS Calibration

Performed Rayleigh and Raman calibrations with nitrogen (on November 7 & 8) in order to calibrate Thomson scattering density measurements from 10/31/07.

Friday November 9 12 04 J._Andrello,_N._Rivera

We pumped the chamber back down. The pressure quickly dropped to high 10^-8 Torr. The bake is on and the pressure is presently 2.4x10^-7 Torr

Thursday December 6 05 40 DeBono 58006-58065 Rotation

Shots were taken at the perpendicular viewing port to test anti-aliasing amplifiers on rotation diagnostic.

Thursday December 13 03 35 hanson 58065-58094 clean-up

I am attempting to reproduce the (m,n)=(3,1) kink mode used for Kalman filter feedback experiments in the summer and fall. It is quite possible to match the evolutions of the plasma current, major radius, and edge-q

Thursday December 13 03 48 hanson 58065-58094 clean-up

I am attempting to reproduce the (m,n)=(3,1) kink mode used for Kalman filter feedback experiments in the summer and fall. It is quite possible to match the evolutions of the plasma current, major radius, and edge-q with previous shots, but the mode does not always appear. Possibly, impurity levels are a bit higher (after the Thompson scattering calibration), making it harder to sustain a current density gradient at the edge. The mode did seem to get stronger as the day went on. I plan to turn on the RGA tonight and continue with these shots as time allows, eventually starting phase-flip experiments when plasmas improve.


Monday January 14 05 14 hanson 58235-58264 clean-up

Clean-up shots were taken today, with the eventual goal of producing stable resistive wall modes for use in phase-flip experiments. The plasmas currently exhibit large disruptions before modes have a chance to grow. Loop voltages are around 8V for plasma currents in the neighborhood of 10 kA. Plan to continue running these kinds of shots all week.

Tuesday January 15 05 03 hanson 58265-58312 clean-up

More clean-up shots taken today with the intention of producing a good model discharge for phase-flip experiments. Plasmas are still plagued by large disruptions in mid-shot, but these seem to be getting smaller. Plan to continue this campaign tomorrow.

Wednesday January 16 07 13 Levesque_+_Hanson 58313-58396 Clean up

Clean up shots. Testing automatic recording of Thomson Scattering data. Raw data from TS oscilloscope traces is being added to the HBTEP tree. Royce was able to see a difference in D-alpha emission with changing fill pressure.

Thursday January 17 05 24 Hansen/DeBono 58415-58444 Cleanup shots

Cleanup shots taken today. Plasma seems to be improving.

Friday January 18 03 47 hanson 58446-58470 clean-up

More clean-up shots taken today, with the goal of developing a good model shot for phase-flip experiments. This discharge has been improving over the week, with discharge lifetimes increasing slowly, loop-voltage decreasing to < 8V, and soft x-ray signals starting to come up. We ended early today to insert the filament probe for d-alpha array spatial calibration. Plan to continue these shots next week.

Friday February 8 05 43 hanson 58610-58626 clean-up

We were finally able to get back to running HBT-EP this afternoon. (There were delays due to pumping on the bias probe bellows and air-conditioner maintenance.) There is definitely some more clean-up work to be done, but the plasmas do not look that bad, all things considered. Loop voltages were reaching 8 V towards the end of some shots, for plasma currents around 12-15 kA. On the side, there was some progress made in getting the CPCI to function more consistently. A firmware upgrade to the box fixed some internal triggering problems, so the CPCI now appears to record data at the correct time for every shot. There have been some new troubles getting the time values for the data, but this is less serious.

Saturday February 9 02 02 hanson/maurer 58631-58681 clean-up

More clean up shots taken today. Plasmas continue to improve, with loop voltages that drop below 8 V towards the end of the discharge. Plan to start mode development early next week.

Monday February 11 04 55 hanson 58682-58721 mode development

I am now trying to develop plasmas with external kink modes in which the edqe safety factor slowly ascends from about 2.7 to above 3.0. Currently, plasmas made in this style suffer large disruptions, indicating that there is still some clean-up work to be done. Past experience has been that the disruptions will become less frequent as we clean up.

Tuesday February 12 04 36 hanson/debono 58722-58762 discharge development

Continued working on creating a good q-ramp-up discharge to day. Plasmas continue to improve, but large disruptions are still observed occasionally. Some testing of the optical rotation diagnostic was done as well.

Wednesday February 13 03 41 hanson 58774-58810 discharge development

Attempts to create a Shilov-style kink mode continue. The modes seem to be improving slowly, but these shots are difficult to make. Shot 58808 looked good, but it was not reproduced.

Thursday February 14 04 45 hanson 58821-58862 discharge development

The q* ramp up discharges I've been working on this week are slowly improving in that they last longer and the rise through q*=3 is less dramatic. We are seeing large external modes on some shots, and lots of internal modes, too.

Friday February 15 06 11 DeBono/Hanson 58899-58949 Velocitometer Scan

Shots were taken with 90% De and 10% He this afternoon. Problems involving the Ch1 connector box appear to have been repaired. A shot with a constant major radius profile @ ~94cm for ~4msec was used as the observed chord was scanned across the plasma.

Monday February 25 07 18 DeBono 59023-59063 velocitometer

Shots taken on 59023-59063 with 90%De & 10% He to obtain the HeII emission profile of HBTEP plasmas. After 59063, a loud noise was heard in the basement after the start panel resets were punched. Banks were not charged. No initial sign of damage in the capacitor room.

Tuesday February 26 09 52 DeBono 59064-59094 velocitometer

Ran shot numbers 59064-59094 after refilling OHEL water resistors with CuSO4 solution. No problems, no abnormal occurances.

Thursday February 28 10 53 DeBono 59096-59140 velocitometer

Shots 59096-59140 were taken with 10%He, 90%De gas to finish velocitometer chord sweep of unaccelerated (i.e. no bias probe) plasmas.

Wednesday March 5 06 32 R._James 59164 - 59224 D-alpha

Attempted to understand discrepancies in calibration measurements made from the filament and data taken from the plasmas. Made several variations of inboard limited and outboard limited plasmas to try and determine if I was indeed only seeing part of the plasma as the calibration measurements suggested or the entire plasma which would point to a mishap in the calibration results. Unfortunately, the results are inconclusive. As I lock down constraints (i.e. camera angle, mirror angle, and camera tangential position), things are beginning to get clearer. To do this, I have been switching back and forth between plasma shots and filament scans to investigate the outer and inner channels respectively. I did discover what seems to be either a bad diode channel or a broken connection inside the 'camera' before the amp box in the lower channels (#33) or in the input to the amplifier, it would need to be repaired before the calibration was complete as well. I will need a day or two more to systematically confirm the chord spacing and chordal view next week.

Tuesday March 11 03 02 James 59225 - 59251 D-Alpha

Calibration complete! Channel 33, repaired, Bias probe to be installed this afternoon. Details on calibration to come as white paper.

Friday March 14 05 21 hanson 59252-59273 clean-up

The bias-probe bellows was opened to the vacuum chamber yesterday night, and the first clean-up shots were taken this afternoon. In order to get an idea of what the vacuum conditions were like, I tried to reproduce my kink mode model shot from last fall's experiments: 56079. I was able to get close on a couple shots, indicating perhaps that there is not much clean-up work to do. The bake will be turned on over the weekend and clean-up efforts will continue on Monday.

Monday March 17 05 06 hanson 59281-59301 clean-up

More clean-up shots taken this afternoon. Strangely, shots today did not look quite as good as on Friday. Perhaps the weekend bake re-deposited impurities onto the limiting surfaces. Also, I'm shaking out a couple bugs in the feedback system, but it is more or less working.

Tuesday March 18 03 58 hanson 59302-59353 clean-up

More clean-up shots taken today. We are starting to see more mhd activity, but plasmas are not yet behaving very consistently.

Also, the feedback system is now in working condition. (A D-connector in the south rack was unplugged, disconnecting half of the control coil circuits).

Wednesday March 19 07 21 James/Hanson 59354 -59429 clean-up

Lots of clean-up shots today under the guise of mode development. Shiraki took more triple probe data, Hanson concentrated on Kalman filtering (59369 - 59386), while I did Shilov style RWM development (59387 - 59429). Hanson was able to recreate modes from last fall, yet it seems like the vacuum is still to dirty for RWM's. I plugged in the RGA so we can compare it to Mondays readings. More of the same tomorow.

Thursday March 20 05 27 hanson/james 59432-59493 clean-up

More clean-up shots were taken today. Royce has been attempting to create a reliable q* ramp-up shot for phase-flip experiments, but this has not yet been successful. The q* ramp-down shots are looking pretty good.

Friday March 21 05 03 hanson 59494-59556 clean-up More clean-up shots taken today.

Monday March 24 05 03 hanson 59557-59583 kalman filter

Experiments in adding adjustable amounts of noise to closed-loop feedback algorithms continued today.

Tuesday March 25 10 17 James 59584 - 59659 d-alpha

More clean-up and RWM mode development. The loop voltage has come down to about 8.5 V from 12V last week and Shilov's shots were at about 6V so still a fair amount to do. More of the same tomorrow.

Wednesday March 26 05 14 James 59641 - 59700 Clean-up/ RWM

More clean-up today. A bit of a late start after some CPCI com. issues that Jeremy and I resolved. Base pressure began to creep between shots. From 1.8 e-8 to 4.1 e-9 by the end of the day - I put on the RGA. Did a couple of phase flips, just to get familiar with the system, shot#'s:59700 (3.3 msec) and 59681 (2.5 msec).

Monday March 31 08 24 debono 59733-59790 Velocitometer

Rotation Diagnostic data was taken with bias probe inserted into plasma. Bias probe voltage was varied from 0V to 275V at 25V increments. Data shows sharply reduced plasma lifetime at higher voltages, as well a tendency of the plasma to crash into the inner wall at higher bias probe voltages.

Wednesday April 2 05 58 hanson 59834-59860 kalman filter

The newly reworked Kalman filter algorithm was tested on plasmas today after modeling in IDL indicated that it would behave reasonably. (The accuracy of the IDL model was checked against the actual FPGA algorithm at 10 frequency points and found to be in very good agreement.) Several phase angles and gain settings were tested today. A more formal phase scan will begin tomorrow.

Thursday April 3 06 01 hanson 59861-59921 kalman filter phase scan

I scanned a good number of Kalman filter feedback phase angles today. I plan to continue this experiment into next week.

Monday April 7 07 21 R._James 59993 - 60022 RWM Development

Initiated fill pressure scan today. Plan to complete tomorrow and start phase flip experiments.

Tuesday April 8 04 55 james/hanson 60023-60067 d-alpha/kalman filter

Royce did some fill pressure scan experiments this morning, and I did a few more points in my phase angle scan this afternoon.

Wednesday April 9 05 59 hanson 60068-60102 kalman filter

The first set of phase angles in the Kalman filter phase scan was completed today. I will probably try to do a couple more sets for averaging. The initial results are about the same as those from last fall, but with shifted regions of suppression and excitation. Now that the optimum phase angle for supressive feedback is known, I'm taking a few shots to see if the proportional gain setting can be further optimized. This should be finished by tomorrow.

Thursday April 10 07 40 James/Hanson 60103 - 60141 RWM - Feedback

Hanson continued yesterdays tests following up on the phase scan completed yesterday. More pressure scans, pressure seems to cap at 5.5e-5 no matter how long the puff valve is open and bottom out at ~ 4.4e-5 to still achieve breakdown. More analysis over the weekend will help to determine if is a large enough window to appreciably alter D-alpha emissions and eventually RWM stability. It would be nice to get a factor of 10 and at least a factor of 2 difference. We will investigate the puff electronics and pressure to see if we can improve it next week.

Thursday April 10 09 46 James/Hanson 60103 - 60141 RWM - Feedback

Hanson continued yesterdays tests following up on the phase scan completed yesterday. More pressure scans, pressure seems to cap at 5.5e-5 no matter how long the puff valve is open and bottom out at ~ 4.4e-5 to still achieve breakdown. More analysis over the weekend will help to determine if is a large enough window to appreciably alter D-alpha emissions and eventually RWM stability. It would be nice to get a factor of 10 and at least a factor of 2 difference. We will investigate the puff electronics and pressure to see if we can improve it next week.

Friday April 11 04 18 hanson 60142-60185 kalman filter

More Kalman filter gain scan shots were taken today. I plan to analyze the results of this and the phase scan over the weekend, and we can discuss what experiments to do next on Monday.

Wednesday April 16 05 19 hanson 60191-60255 discharge development

I attempted to make a stronger kink mode discharge for feedback studies. Some progress was made, but I will probably need another day or so to continue developing the shot. In other news, Royce and I added a second puff of gas during the middle of some discharges. This had a dramatic effect, temporarily damping mode activity, and causing some very large disruptions later on. We imagine that higher fill pressures could be obtained by moving this second puff to a time before the plasma breaks down, but this has not yet been tested.

Monday April 21 10 44 James 60343 - 60379 RWM / D=Alpha

Investigated variations in puffed gas during shots to see how the plasma reacts. Used 3.75 ms as a base puff time and initiated a second puff of 1/8, 1/12, and 1/36 of that time at 2.5 ms. It generally takes approx. 1.5 ms after the puff is initiated to see an increase in D-alpha. Emissions were about equal to breakdown peak, half breakdown peak, and 1/5 breakdown peak respectively. The later was still about twice the emissions before and after its flow and ebb - except when theres a disruption immediately following. As expected, 1/36 puff time seems to be the least disruptive to the plasma. The lifetime of the plasma is shorter with a major disruption usually just after the ebb of the d-alpha increase and sometimes during that ebb. Plasma current ramps always leveled off with 1/36 puff having a significant effect just like the 1/8 and 1/12 puff times. However the q seemed to behave much in the same manner as usual as long as the major radius fell off fast enough. I also attempted to increase the pressure before the shot with multiple puffs since I have had better luck with developing the mode for plasma lifetimes between 5 ms to 7 ms. With an increased puff time of 5 ms, I used 3 pre-breakdown puffs, at -95 ms, -35 ms, and -.5 ms to get a slightly higher fill pressure than with 2 puffs, up to approx. 7.6 e -5 torr from 7.0 e-5 torr seen with only 2 puffs. Later I added the 1/36 puff time at 2.5 ms as before totaling 4 puffs. See shot #60379 use scope hbtep_da_review.jscp in my home directory Jscope configurations under. D-alpha emissions are higher at the higher pressures yet the neutrals appear to burn out as the shot continues and the increase between breakdown and final disruption is subtle.

Tuesday April 22 05 25 hanson 60380-60409 discharge development

By examining the effects of small changes to the bank settings previously used for feedback studies, I have been successful in making a mode that is both stronger and more reproducible than the old one. With the new settings, the current ramp is kept about the same, but the edge-q is kept closer to (but just below) 3. This seems to result in a robust 5 kHz mode. The mode also seems to respond to feedback: I've been able to reduce amplitudes in the sensor coils by 40-50% in a couple shots. One shot done at a positive feedback setting showed excitation of the mode. I also did a shot in which the FPGAs were not gated on until 2.5 msec (in the middle of the mode). This appeared to have a near-immediate on the mode amplitude, but more shots are needed to confirm this result. I am planning next to do a scan of the growth rate parameter in the Kalman filter model, as run time allows.

Wednesday April 23 06 00 hanson 60410-60467 kalman filter

I began a scan of the Kalman filter's real growth rate parameter today, using the mode developed yesterday. I'm about halfway finished with the scan; it should take another day to finish up.

Friday April 25 06 10 DeBono 60565-60586 rotation diagnostic

Shots 60565-60578 taken with 90% Du 10% He, and shots 60579-60586 taken with 100% He. Bias bank appears to be working well; probe voltage holds well with bias probe driven currents well exceeding 50 amperes in plasma. Very low signal levels observed with the rotation diagnostic while using 90% Du 10% He mix, obeserved signals became usable with use of 100% He plasmas.

Tuesday April 29 06 11 hanson 60617-60640 diagnostics testing

The RC filtering for the SSI sensor coils was added to the signal path this morning and tested with plasmas. The plasmas themselves were cold and did not display much MHD activity, but the filtered sensor signals were observed to have a quasi-dc component that I believe should come from the Ohmic and vertical fields. One filter was also bench tested to make sure the frequency roll-off was as expected. With regards to the SMPs, the L8100 amplifiers have a gain and a multiplier setting. Originally the these were set to G=100 and M=.5, giving an effective voltage step of dV=.0002 V in the signal. The gain cannot be set above 100, but the multiplier was turned up to 1.0, for an effective voltage step of dV=.0001 V, improving resolution by a factor of 2. In order to achieve plasma break-down, I had to use the double puffing technique to inject extra gas. I was then able to reduce the amount of gas puffed in over the afternoon, but I could not get breakdowns with normal puff times. The plasmas had loop-voltages above 12 V and showed chaotic behaviour and little MHD activity. It also seemed to take a long time to pump out after a shot. An inspection on the RGA showed levels of He/D2 at the same order of magnitude as the base pressure. I've been told that He pumps out slowly, so I've turned on the bake to see if this will accelerate things. I will consult with Jim and Dave about regening the cryos in the morning.

Wednesday April 30 06 03 hanson 60642-60705 kalman filter

More Kalman filter gain scan was done today. The hope is that the modifications to the magnetic diagnostics and the new SVD analysis will reveal a clearer pattern in the scan. After this, I plan to start a phase scan at the optimal gain. (The previous phase scan was done at a rather low gain.) Plasmas looked good today. Poor plasma performance yesterday was likely due to some confusion over what gas was in the puff lines from last week; I may have been puffing in a large amount of He.

Thursday May 1 05 45 hanson 60706-60785 kalman filter

The Kalman filter proportional gain scan begun yesterday was finished today, giving a fairly clear indication of what the optimal gain is for negative feedback. A phase scan was then begun at this gain and is a little over half finished. I plan to finish at least one run of the phase scan tomorrow and possibly move on to scanning the real growth rate parameter.

Friday May 2 04 22 hanson 60786-60838 kalman filter

A first round of the Kalman filter phase scan was completed today.

Monday May 5 05 33 hanson 60862-60899 phase scan

More Kalman filter phase scan shots were taken today. Progress was slowed by repeated CAMAC problems. We were getting NoX errors on large numbers of digitizers during the afternoon. After turning off the Jorway serial highway driver and crates for approximately half an hour, we were able to get 4 shots in before the errors came back. This makes me think the root causes of the problems was thermal -- perhaps related to our air conditioning outage in the server room.

Tuesday May 6 10 24 hanson 60905-90987 kalman fitler

More Kalman filter phase-scan data taken today. There were CAMAC problems again due to the AC outage in the control room. However, CU facilities came by with a temporary unit that is now cooling the server room, and we were able to further eliminate CAMAC errors by setting the screenroom crate's u-port to bypass. The hypothesis is that the screenroom crate was overheating, triggering NoX errors in everything else downstream. In any case, the second round of the phase scan should be complete by tomorrow morning, if there are no further hardware problems.

Wednesday May 7 06 18 Hanson 60995-61063

Jeremy continued with his phase scan, and some Mach probe tests were also done.

Thursday May 8 05 54 hanson 61064-61118 kalman filter

More Kalman filter phase scan data taken today. I am just a couple shots shy of being done with the 3rd round of the scan. The trends in the data are becoming clearer with more points to average over, so I think I will try to do some added noise experiments tomorrow.

Friday May 9 05 38 hanson 61119-61165 kalman filter

More Kalman filter shots today. I finished the third round of the phase scan and started investigating the effects of added noise.

Monday May 12 04 32 hanson 61166-61192 kalman filter

More noise scan data was taken today.

Tuesday May 13 04 32 Hanson/Shiraki 61193-61210 kalman filter/mach probe

The Kalman filter algorithm was tested with external noise inputs today. The Mach probe was tested also.

Wednesday May 14 05 39 hanson 61211-61269 kalman filter

More Kalman filter experiments with added noise today. Initial analysis (on just a few shots) revealed differences between the efficacy of the Kalman filter and proportional gain only filter in both exciting and suppressing the kink mode. I hope to finish getting data by tomorrow and to start writing things up on Friday.

Thursday May 15 05 50 hanson 61270-61329 kalman filter

More added noise experiments today with the Kalman filter and proportional gain only filter. Discharge repeatability has been poorer these past couple days, slowing progress. I'll probably try to run most of tomorrow, and maybe will regen a cryo on Saturday.

Friday May 16 05 39 hanson 61330-61389 kalman filter

More added noise experiments today. The krytron for the VFEC bank failed and we replaced it with a spare. However, this was the last spare; we have no more spare krytrons. Aside from that interruption, the runs went well.

Tuesday May 20 05 05 James 61391 - 61414 RWM Stability

Did some mode development shots today. We decided to regen the other cryo so it was slow going. Was able to get a decent mode relatively quickly plus test the Hall probe channels I will be able to use at the same time as D-alpha. Phase flips will start tomorrow.

Wednesday May 21 10 06 James 61415 - 61458 RWM Stability

Opened up the 2nd cryo today after a few shot and it seems to be doing well. I did a series of static phase flip experiments and a few dynamic ones at the end (61456-58),at 2.5 and 2 ms respectively (before the q*=3 surface was broken. The hall probe, triple probe D-alpha can all be run simultaneously. We should be ale to continue testing tomorrow and include gas puffs.

Thursday May 22 08 34 R._James 61459 - 61521 RWM Stability

Perfected low fill pressure stable RWM and performed static phase flip tests at 2 ms, 61492 - 495. Developed a 3 puff pre-breakdown stable mode which gave an increase from 4.4e-5 to 5.9e-5 and repeated the static flips at 2 ms, 61511 - 61519. These plasmas were a little harder to reproduce from shot to shot, but I was able to get some stable RWM's to experiment with. I will do one more static phase flip experiments tomorrow with a puff early in the shot to complete the static phase flip method. If time allows I will initiate the dynamic phase flip experiments as well.

Friday May 23 03 02 R._James 61523 - 61555 RWM Stability

I completed the Phase flip experiments today. If time allows I will do the resonant response test around the end of next week. Preliminary results are promising, it looks like the realignment times after the flip for a stable mode with normal fill pressures around 4.4e-5 torr are around the same time as those Shilov reported about .25 ms. I increased the fill pressure in two ways. With 3 pre-fill puffs 61510 - 519 and with 2 pre-fill and one puff early in the shot 61541-555. The realignment times for these were subsequently longer indicating a probable decrease in stability with more neutrals!

Tuesday May 27 06 21 DeBono 61556-61590 Velocitometer Scan

Shots were taken with 10%He 90%Du. Measured velocities are inconsistent shot-to-shot with the bias probe inserted (but not with the probe removed), perhaps additional shots are needed to remove impurities from the surface of the bias probe.

Wednesday May 28 06 26 DeBono 61592-616-24 Velocitometer w/ Bias Probe Shots

Plasmas were run from 10% He, 90% Du. The bias probe was energized to voltages of 50V, 150V, 300V to see measured affect on plasma rotation (Probes outer edge inserted to 105.5cm with the velocitometer looking at 99.53cm). The diagnostic detects increasing toroidal rotation as the bias bank is fired, and it appears that increasing bias probe voltages result in higher rotation speeds. Unfortunately, the bias bank pre-fired ~50% of the shots taken (possibly due to craytron noise).

Thursday May 29 06 08 DeBono 61625-61657 Velocitometer scan

Plasmas were run with 10% He 90 % Du. Bias bank pretriggered for nearly every shot taken, upon examination it appears that this is likely due to craytron noise from the VFST and VFEL banks, and possibly also the OHST and OHEL banks.

Friday May 30 06 14 Shiraki 61658-61688

Took hall probe and triple probe data. Results to be analyzed over the weekend.

Wednesday June 4 10 46 R._James 61733 - 61779 RWM

Shot development today, experiments to follow tomorrow.

Thursday June 5 01 47 DeBono 61780-61792 Bias Bank Prefiring Tests

Tests were run in 100% He to test an attempted fix to the bias bank prefiring problem. The tests proved to be successful mostly: the bank did prefire for most shots taken at high voltage (>300 volts) but no pretriggering occured for shots taken at 50 or 150 volts. The fix to the problem is described below.

bias bank power supply was rerouted to a plug outside the capacitor room, as earlier it was plugged into the same power outlet as the crytrons. The power supply connects to an isolation transformer, which has cheaters plugged into both its power outlets to provide power to the avionics trigger and to the power supply for the bias bank as well as potentially avoiding any ground loops. The lid to the bias bank was closed (previously it was left open) as well to minimize EM interference with the triggering circuit.

Friday June 6 04 45 debono 61793-61817 velocitometer scan

Plasma were run with 90% Du 10% He. The repairs to the bias probe triggering appear to work well for voltages <=200V, however, at higher voltages the bank still suffers from pretriggering. A sweep was conducted between 50V and 250V to attempt to characterize the increase in He ion velocity with temperature. Data to be analyzed over weekend.

A loud noise in the capacitor room was heard during the last shot of the day; one of the relays in the TF bank appears to have been the culprit.

Wednesday June 11 12 28 R.W._James 61819 - 61843 RWM

Regend Cryo again today the air conditioner in the room with the Tokamak was repaired just after lunch so we got a late start. When I left, the temp was pegged at 20K and had been for the last 2 hours. It was slow running with the single cyro and mode development was all that I was really able to accomplish. Phase-Flip experiments in the morning. There is leaking in Mo's area from the wall above next to the reactor. The engineering students downstairs came up to let us know and they also called facilities. The water is localized to the floor just under the wall and damage looks minimal to Mo's space, but there is about 3-5 gallons of water on the floor.

Thursday June 12 02 33 James 61819 - 61968 RWM Stability

I was able to get a plasma response from the Phase Flips after a lot of wrestling with the tokamak. I did phase flips at 2ms, 2.5ms, and 3ms which also corresponded to different D-alpha emissions. Plasmas were not very reproducible so it took a long time. I will attempt tocomplete this experiment on Monday after the meeting.

Thursday June 12 06 01 debono 61977-61992 Bias Probe

Shot development with bias probe inserted and 10%He 90% Du plasmas. Slow going due to only one cryopump operational. DeBono

Friday June 13 06 23 debono 61993-62023 Bias Probe

Shots taken in 90% Du 10% He. Shots were taken with bias probe was run at voltages from 0-200V in 25V increments. Pace was slowed considerably due to lack of a second cryopump.

Tuesday June 17 03 04 hanson 62028-62043 discharge development

I've started creating a mode for experiments that will scan the Kalman filter parameters. This will be very close to the mode used in previous experiments, but some small adjustments need to be made, probably due to differences in the vacuum conditions.

Thursday June 19 05 06 hanson 62056-62110 discharge development

More discharge development for Kalman filter studies today. I've had some good shots, but reproducibility has been poor. Hopefully this will improve as I continue to run.

Friday June 20 05 39 hanson 62111-62163 kalman filter growth rate studies

I started an experiment today to scan the real growth rate parameter in the Kalman filter equations for negative feedback. Plan to continue and hopefully finish this scan by mid next week.

Monday June 23 04 42 hanson 62164-62192 kalman filter

The scan of the Kalman filter's real growth rate parameter continued today. Unfortunately, there were problems with the in the output on several control coils: either the output was null or had a large dc offset. It appears that the analog boards may be part of the problem, but investigations are still underway.

Wednesday June 25 02 40 James 62193 - 62231 RWM stability

Completed aditional stability / phase-flip experiments at 2.0, 2.5, and 3.0 ms. Shot to shot variability was better than in the past, but still not the best. these shots will give more statistical might to the results I got two weeks ago.

Thursday June 26 05 31 hanson 62232-62296 kalman filter

More Kalman fitler growth rate scan today. The analog boards seemed to be working normally again. I hope to be finished with this scan tomorrow.

Friday June 27 04 52 hanson 62297-62335 kalman filter

I finished the scan of the real growth rate parameter in the Kalman filter today. Plan to begin a scan of the imaginary part next week.

Monday July 7 07 00 James 62341 -62372 RWM More shot development with additional puff. More tomorrow with Phase-Flip experiments too.

Wednesday July 9 12 16 James 62441 = 62405 RWM

Was able to create shots with 2nd puff during the shot. Plasma parameters seem unaffected for a few ms after the affects of the puff are seen in d-alpha. This is promising. However, our back of the envelope calculation puts the perturbation delivered by the new control coils onto the plasma at about 1/6 of the old coils. Tomorrow I will attempt to get a more stable mode so the response will have some hope of being measured.

Wednesday July 9 11 41 James 62407 - 62501 RWM

Attempted to squelch the MHD noise in the magnetic probes by altering the VFS timing and subsequent mode development. This was not too successful. At times, the MHD noise was much worse that shots I took two weeks ago.

Tuesday July 15 08 35 James,_Levesque 62518 - 62539 Density/Temp Scan

Used Thompson Scattering to investigate density and temperature levels before, during, and after affects of the 2nd puff are seen in d-alpha. Initial inspection shows temp and density to be fairly inversely proportional. I will compare TS data to triple probe data and hall probe data to see how the increase in neutrals changes the plasma. The triple probe had all three tips inserted and one hall probe from the array was inside the plasma.

Wednesday July 16 05 27 hanson 62537-62569 Kalman filter

I started a scan of the Kalman filter's rotation rate parameter today. I'm pleased to report that I was able to reproduce my target plasma relatively quickly. Hopefully the scan will be nearing completion by the end of this week.

Thursday July 17 04 15 hanson 62570-62591 kalman filter

More Kalman filter phase scan data taken today. The run was cut short by a dump relay failure on the TF bank. Work is currently underway to repair the damage.

Tuesday July 22 03 44 shiraki 62602-62604 TF Test

Tested TF bank, up to the usual 6.1 kV. Normal running will resume tomorrow.

Wednesday July 23 04 47 hanson 62605-62634 kalman filter

I attempted to continue my scan of the Kalman filter's rotation rate parameter today, but there was a small vacuum mishap. Sometime between yesterday and this morning, the gate valve for the horizontal turbo pump was opened. Fortunately, the mini turbo was turned on, backing the larger one. However, the RGA showed higher partial pressures of N2 and O2 after this problem was noticed. The behavior of plasmas after the incident was somewhat different from last week, but strong external kink modes were still achievable. We plan to continue running and will start regenning the cryo pump on the large pump stand tomorrow. The base pressure at the moment is down to 1.3E-8 Torr (with one cryo pump valved off).

Thursday July 24 06 34 hanson 62634-62685 discharge development

I attempted to recreate external kink unstable discharges used in earlier Kalman filtering experiments. Plasma behavior seemed to change throughout the day, and I was getting close to my old shots by late afternoon. Base pressure this morning was 6.6E-9. The cyro on the large pump stand was allowed to warm up last night, and the cold head was pumped on today. Pressure in the line was about 10 mTorr at the end of the day, so the regenning will continue tomorrow.

Friday July 25 04 51 hanson 62688-62746 kalman filter

A Kalman filter rotation rate parameter scan was started today. Plasmas and modes looked good. Regen of the cryo pump is still ongoing.

Monday July 28 04 23 hanson 62747-62775 kalman filter

More Kalman filter rotation rate scan today. Plasma behavior was good. Regenning of the cryo at the large pump stand continued.

Tuesday July 29 05 19 hanson 62776-62818 kalman filter

More Kalman filter rotation rate scan today. Regen of the cryo continued as well.

Wednesday July 30 02 15 hanson 62819-62826 kalman filter

The scan of the Kalman filter's rotation rate parameter was finished up today. Regening of the cryo pump is still ongoing.

Thursday July 31 05 07 Levesque 62827-62838 SXR tomography

Tested several amplifier boards in soft x-ray tomography system. Banks off, no plasma -- just amplified test signals.

Friday August 1 06 16 debono 62841-62859 Bias Probe Radial Electric Field Scan

The objective of todays run was to characterize the radial electric field generated by the bias probe using the triple probe array, and to simultaneously measure rotation using the doppler shift diagnostic. Plasmas were run in 10% He 90% Du plasmas. Plasmas appeared cold (<30eV core temp as measured by thomson scattering) but good radial profiles were easily obtained. Bias probe voltages were scanned from 0-150V in 50V increments. Triple probe data seems anomalous, more to follow on this.

Monday August 4 06 33 DeBono 62861-62882 Triple Probe/ Mode Development

More work was done today to characterize the radial electric field generated by the inserted bias probe. The error in the triple probe was confirmed today; the first channel and third channel of the triple probe failed to produce the same signal when inserted into the exact same position in the plasma (done by inserting/withdrawing the probe by 1cm). For some reason the signal from ch1 seems to be inverted compared to the signals obtained from channels 2 and 3, not sure why. This inconsistency problem in the triple probe does not seem to depend on the bias probe being inserted into the plasma, although inserting the bias probe did significantly alter the signal we obtained from the triple probe.

On a positive note, mode development proved highly productive today. Thomson scattering shows core temperatures ~100eV (compared to ~30ev on friday) with a peak plasma current of 17kA with a very strong current ramp, plasma lifetime~7msec, and a very clean major radial profile. Rotation diagnostic signals are very clean, although perhaps some additional signal would be desirable. Plasmas were run with 10%Du 90% He.

Tuesday August 5 05 09 debono 62883-62906 Mode Development

Additional mode development was done today, following experiments from yesterday. Shots developed on 8/4/2008 appear to be favorable for rotation diagnostic studies, however, the presentation of a very low edge q (1.5<q<2.5) results in high MHD activity as well as making it more difficult to potentially use Jeremy's feedback stabilization. Accordingly, efforts today were dedicated to obtaining shots of similar profile to those on 8/4/2008 but with a higher edge q and hopefully also lower MHD activity. Shots were conducted 10% He 90% Du.

Thursday August 7 05 19 hanson 62924-62970 kalman filter

I wanted to get a few more points in the scan of the Kalman filter's rotation rate parameter today, because the optimal phasing for the different parameter settings is not clear from looking at the transfer functions. This work will continue tomorrow.

Saturday August 9 11 38 Hanson/Levesque 62971-63022 Kalman filter + TS

Jeremy continued Kalman filter scan. Took Thomson scattering and SXR tomography data during the scan. TS data show a significant drop in central density at 3ms for shots lasting >~4ms. Temperature shows a linear rise throughout shot, though major radius is also changing. Drops in SXR emissivity around 3ms corroborate TS data.

Tuesday August 12 05 14 hanson 63023-63039 kalman filter

More Kalman filter rotation rate scan data taken today.

Much time was spent troubleshooting a CAMAC problem. The FO line connecting the north and basement racks had become pinched in the door of the basement rack and failed. Jeff and I removed the line and installed a new one. Various racks then had problems initializing properly. Powering off the crates, letting them cool for an hour, and restarting matterhorn fixed this problem. So things are back in working order.

Wednesday August 13 06 13 hanson 63040-63084 Kalman filter

More Kalman filter rotation rate scan data taken today.

Thursday August 14 08 28 debono 63090-63117 Radial Eelctric field

Work was conducted today to observe the radial electric field generated by the bias probe.

Wednesday August 20 05 46 hanson 63143-63183 discharge development

I had intended to begin a scan of the Kalman filter's rotation rate parameter at the different value of the q0 parameter, but I had difficulties reproducing the modes I was seeing last week. It seems the plasmas might be heating up a little more and rotationally stabilizing the mode. I intend to continue my efforts to bring the mode back tomorrow.

Thursday August 21 05 43 hanson 63185-63232 kalman filter

Some Kalman filter data taken today, for a scan of the rotation rate parameter.

Monday August 25 04 40 hanson 63282-63299 clean-up

Clean up shots taken this afternoon following a weekend bake and glow discharge experiments on Friday. With some small adjustments to the banks settings, I am able to come close to reproducing shots from last week, but mode amplitudes are lower. Plasmas improved over the afternoon.

Monday August 25 05 38 Shiraki/Levesque 63233-63281 He glow discharge

(Run report for Friday August 22)

Ran helium glow discharge to attempt a relative calibration of probe areas in the triple probe array using a uniform density plasma. Tried to measure emission using the rotation diagnostic for a zero-rotation calibration. The resulting plasma density was too low to measure with the existing triple probe circuitry, and there was not enough emission appropriate for the rotation diagnostic due to low ion temperature and density.

After the glow, took digitizers-only shots (63241-63281) as part of testing the SXR tomography system.

Tuesday August 26 05 07 hanson 63302-63348 clean-up

More clean-up shots taken today. The kink mode activity continues to improve, getting closer to what was observed last week.

Wednesday August 27 06 17 hanson 63349-63372 kalman filter

External kink modes improved today and some Kalman filter parameter scan data was taken. We had trouble this afternoon with the dump relay on the OH Bias bank. The relay did not fail completely, but was arcing enough that we could smell it in the control room. A couple hours were spent finding, replacing, and testing the relay.

Thursday August 28 04 50 hanson 63373-63420 kalman filter

More Kalman filter rotation parameter scan data taken today.

Friday August 29 05 50 hanson 63420-63483 kalman filter

More Kalman filter rotation rate parameter scan data taken today.

Tuesday September 2 04 41 hanson 63484=63510 kalman filter

More Kalman filter rotation rate parameter scan data taken this afternoon.

Wednesday September 3 11 23 hanson 63511-63587 kalman filter

More Kalman filter rotation rate parameter scan data taken today.

This evening there were problems with low-amplitude signals on a couple of the control coils. Some inspection of the crunch amp cabinet revealed some poorly made connections in the power bus for the amps. The connections were either improperly soldered or not soldered at all, and covered with electrical tape. A dozen or so of these were fixed, but some problems with the amps remain. Debugging of the system will continue in the morning. <

Thursday September 4 05 39 hanson 63589-63608 feedback system debugging

Further attempts were made to get to the bottom of the feedback signal problems mentioned yesterday. Connections at the inputs to the crunch amps were examined and redone, and some testing of the analog boards was done. The problems still have not been resolved, so work on this front will continue tomorrow.

Friday September 5 04 55 hanson 63609-63641 feedback system test

More debugging of the feedback system today. The crunch amps and analog boards have been eliminated as causes of the smaller signal amplitudes observed on several coils. Connections in and out of the crunch amps are now being investigated.

Monday September 8 05 13 shiraki 63645-63649

A glow was created this afternoon for calibration of the triple/mach probe, but was unsuccessful because the transimpedance amplifiers were not designed for dc currents. The bake was turned on at the end of the day.

Friday September 12 07 02 Levesque+Shiraki 63664-63704

Cleanup Cleanup shots following Monday's deuterium glow. Broken krytron in the VF electrolytic bank was replaced using one from the ICRH bank. Had problems seeing light with the Thomson scattering system, but found that the problem occurred because the TS viewport shutter was still closed from the glow (ooops).

Monday September 15 06 11 Shiraki/Levesque/Hanson 63705-63746 Cleanup Cleanup shots.

Jeremy was able to get the feedback system working again by swapping analog boards.

Tuesday September 16 05 26 hanson 63747-63801 clean up

More clean up shots taken today. MHD activity is approaching reasonable levels.

Wednesday September 17 05 52 hanson 63803-63836 clean up

More clean up shots taken today. Hopefully, ELM noise experiments can begin tomorrow.

Thursday September 18 05 31 hanson 63837-63902 Kalman filter

I attempted to take some data for Kalman filter experiments with added ELM-like noise. However, MHD activity in the plasmas was very inconsistent from shot to shot, indicating that perhaps the vacuum is not quite clean yet.

Friday September 19 07 00 DeBono/Hansen 63919-63966 Feedback & Bias Probe

Shots 63919-63966 were taken with the bias probe inserted into the plasma. The objective of the experiment is to apply bias voltage in order to slow down the rotation velocity of the n=1 mode to 0hz (or as close to 0 as possible) and subsequently to apply Jeremy's feedback algorithm. Mode development was conducted today, more results next week.

Monday September 22 07 35 hanson 63967-64019 feedback

Feedback algorithms were tested in vacuum with both elm-like and white-noise inputs. While the algorithm without the Kalman filter appears to be more or less transparent to both types of noise, the Kalman filter reacts to both noise varieties at frequencies near the programmed mode rotation frequency. The vacuum response of the Kalman filter was greater than I expected for both types of noise, given the results of previous experiments with plasma.

Plasma-mode development continued, but there was not much time left for it this evening.

Tuesday September 23 04 45 hanson 64020-64057 kalman filter

Experiments with adding ELM-like noise to feedback algorithms started today, but the run was cut short by problems firing the VF crowbar in mid afternoon. Subsequent investigation pin-pointed the trigger box for the ignitron, probably the krytron tube. Nick is still working on the circuit to eliminate other possibilities. We are now out of krytron tubes.

Wednesday September 24 06 16 hanson 64060-64102 kalman filter

Nick was able to substitute a circuit with a thyrotron for the one with the broken krytron this morning, and runs resumed in the afternoon. More elm-noise experimental data was taken.

Thursday September 25 04 56 hanson 64103-64158 kalman filter

More elm-like noise experiments today. I have enough data to start analyzing, and I will decide tonight if I need to get more tomorrow or if I want to pick up where I left off with the rotation-rate parameter scan.

Friday September 26 2008 7:31 pm hanson/shiraki 64159-64247

More ELM-noise experiments today. Also, a radial scan of basic plasma parameters was taken with the triple probe.

Monday September 29 2008 4:46 pm hanson 64248-64269 Kalman filter

More Kalman filter rotation rate parameter scan data taken today. jmh

Tuesday September 30 2008 4:59 pm hanson 64270-64320 kalman filter

More Kalman filter rotation rate parameter scan data taken today. jmh

Wednesday October 1 2008 5:49 pm Hanson 64321-64358 Kalman filter

More Kalman filter rotation rate parameter scan data taken by Jeremy today. -JPL

Thursday October 2 2008 8:22 pm hansen/debono 64388-64399 Feedback & Bias Probe

Plasmas were run with 100% Du. Bias probe was inserted and effects on plasma rotation were measured. The effect of the edge biasing is to reverse direction on the n=1 mode, however, unfortunatly the amplitude of the observed m=2 modes are rather weak. More work to be done tommorow.

Friday October 3 2008 6:40 pm DeBono/Hansen 64400-64444 Bias Probe/Kalman Feedback

More work was done today on utilizing the bias edge probe to slow down the rotation frequency of the n=1 mode. Mode development work done today, feedback studies to be done next week. DeBono

Monday October 6 2008 8:21 pm debono 64446-64494 bias edge probe

Bias probe inserted from 104.1cm-106cm in 100% Du plasmas. More work was done today on using the probe to generate a shot with ~0velocity for the n=1 mode, with the goal of then conducting feedback studies. It proved difficult to obtain a desired mode unfortunatly, with the two main difficulties being 1. obtaining sufficient signal from the SSI's and 2. flattening out the n=1 mode velocity profile around 0 km/sec. DeBono

Tuesday October 7 2008 4:57 pm hanson 64495-64529 kalman filter

More scan of the Kalman filter's rotation rate parameter today. (The biased probe was turned off and retracted outside the plasma.) jmh

Thursday October 9 2008 1:05 am Hanson/Levesque/Shiraki 64530-64579 Kalman filter

More scanning of the Kalman filter's rotation rate parameter today. Brief testing of the mach/triple probe array and SXR tomography.

One of the two power supplies (PS) in the SXR tomography amplifier box was found to be the source of an overwheming amount of noise in data from this week. Powering all amplifier boards from the other PS alone reduced the noise significantly. Problems with the PS or its connections will be investigated further tomorrow. -JPL

Thursday October 9 2008 8:32 pm debono 64602-64638 bias probe induced n=1 mode braking

More work done today on the n=1 mode breaking done today. Bias bank pretriggering ended up costing about half the runday, however this cleared up evenutally allowing a few hours of productive plasmas. Will try a modification to the bias bank soon in order to try to eliminate the pretriggering.

Friday October 10 2008 2:26 pm hanson 64648-64682 kalman filter

More Kalman filter rotation rate parameter scan data taken today. Scan of the plant noise covariance parameter to begin next week.

Monday October 13 2008 10:13 pm DeBono 64683-64715 Bias Probe

More mode development work done today with the bias probe inserted. The edge q was kept slightly below 3.0 throught the shot duration in attempt to provoke an m=3 mode from the plasma. Biorthogonal decomposition revealed this to lead to a short (~0.75 msec) and relatively weak m=3 mode followed by a much stronger (~4x) m=2 tearing mode which terminates the plasma. More work to follow tommorow. DeBono

Tuesday October 14 2008 11:10 pm debono/shiraki 64716-64791

More mode development today.

Wednesday October 15 2008 11:09 am debono 64722-64782 Bias Probe

More work done today regarding mode development with the bias probe inserted into the plasma. The goal of the days run was to develop a strong RWM with the bias probe inserted in the plamsma for future feedback studies. Biorthogonal decomposition showed that the shots we developed today had an acceptable (but not incredibly strong) n=1 mode between 2-3 msec followed by a tearing mode which eventually disrupts the plasma. After developing the mode the bias probe was initialized at 2msec at a voltages ranging from 0-125 volts to spin the n=1 mode. As expected, the n=1 mode reversed direction, and did so more rapidly as the voltage on the probe was increased.

Wednesday October 15 2008 9:52 pm hanson/levesque 64792-64847 Kalman filter

Jeremey continued Kalman filter studies. Observed internal m=2 mode activity in recent SXR tomography data.

Thursday October 16 2008 10:37 pm hanson/shiraki 64848-64939

More Kalman filter data taken. More shots were taken for the triple probe profile scan.

Friday October 17 2008 4:38 pm hanson 64940-64988 More Kalman filter and Triple probe data taken today.

Tuesday October 21 2008 10:26 am DeBono 65004-65044 Bias Probe & External Mode Feedback

The purpose of these experiments is to spin a sufficiently large n=1 mode using the bias probe, and then to use the feedback system to reduce the size of this mode. We obtained a n=1 external mode with sufficiently usable amplitude last week and showed that the bias probe can be used to drive its rotation frequency negative. Todays experiments was to determine the repeatability of this n=1 mode created so that we can accuratly determine the effect that feedback will have on the mode.

Half the runday was hampered by pathological prefiring of the bias bank, however, the problem seems to have been fixed by moving the bias' banks digital delay generator outside the cap room.

10 shots were taken with the bias probe at a set voltage (voltage dialed on the power supply, not the actual voltage of the probe in the plasma) of ~1.5V, and 10 shots with the probe at a set voltage of 75V. Care was taken to make sure that the plasma parameters of each of the shots was similar. More analysis is needed to determine the shot-to-shot deviation of the n=1 mode amplitude, however, by eye it seems to vary considerably. More work to be done tommorow.

Tuesday October 21 2008 10:04 pm hanson/shiraki 65054-65119

More Kalman filter and Triple Probe data taken. Also, quick test showed that several tomography chords are blocked by the existing stainless shells in the hall probe section.

Wednesday October 22 2008 7:56 pm debono 65145-65206 Feedback & Bias Probe

Feedback experiments conducted on shots with the n=1 mode spun negative by the bias probe. Feedback shots were taken with the Kalman filter both on and off. The start panel was behaving a little erratically towards the end of the runday. Analaysis and more work to follow.

Thursday October 23 2008 5:06 pm hanson 65207-65263 kalman filter

More Kalman filter scan data taken today. There was a small problem with the OHB charging resistor. It had run out of water and was arcing. It was cleaned out and refilled, and then it functioned ok.

Monday October 27 2008 3:18 pm Shiraki/DeBono 65264-65337 Bias Probe / Triple Probe

Tests were done with the triple probe while the bias probe was inserted into the plasma edge (104.1 - 106 cm) and energized.

Tuesday October 28 2008 6:27 pm hanson 65340-65393 Kalman filter

A phase scan with an optimized Kalman filter was started today, following a quick gain scan to determine a satisfactory gain for suppressive feedback. There was some trouble with the serial highway driver. This was fixed by restarting both the serial highway driver and matterhorn.

Wednesday October 29 2008 6:04 pm hanson 65394-65462 kalman filter

More Kalman filter phase scan data taken today.

Thursday October 30 2008 9:36 pm hanson 65463-65543

More Kalman filter data taken today.

Friday October 31 2008 6:05 pm hanson 65544-65605 kalman filter More Kalman filter phase scan data taken today.

Saturday November 1 2008 6:07 pm hanson 65606-65680 kalman filter

A third round of the Kalman filter phase scan was completed today. This will probably be a sufficient amount of data for comparison with earlier results.

Tuesday December 2 2008 3:56 pm shiraki 65749-65753

Tested the OH bias bank for the first time since the pipe burst. Everything seems to be working fine.

Tuesday December 9 2008 6:28 pm DeBono 65754-65781

I worked to reproduce shilov-style shots today as an attempt to increase the length of time the bias probe is able to perturb the plasma rotation (from the current pulse time of ~1msec). Most of the runday was spent doing cleanup shots from the last glow discharge.

Wednesday December 10 2008 7:17 pm DeBono 65782-65823 Bias Probe

More work done today on extending the length of time the bias probe is able to drive n=1 toroidal mode rotation.

Friday December 12 2008 5:59 pm DeBono 65824-65854 Bias Probe

More work was done today on improving the length of time that the bias probe can influence the n=1 plasma mode rotation. It was found that the depth of bias probe insertion into the plasma has a significant effect on this time length. By inserting the bias probe into the plasma to the maximum permitted by the bellows setup (outer edge 104.4, inner edge 102.5 cm) it was seen that the bias probe was able to influence the n=1 mode rotation for ~ 3msec. This is an improvement over previous runs, where the bias probe was only able to influence the plasma for ~1msec. Bryan DeBono s

Tuesday December 16 2008 6:02 pm debono 65862-65881 Bias Probe

More bias probe work done today. A crate error occured at the end of the runday while taking a shot; this prevented the firing of the banks, which were then dumped. DeBono

Wednesday December 17 2008 6:56 pm DeBono 65883-65924 Bias Probe

More bias probe work done. The CTX Uport was giving problems, but we were able to run using the Uport's bypass switch. It proved difficult to obtain repeatable shots at the beginning of the runday, but this cleared up somewhat by the afternoon. n=1 mode amplitude was lower today than in previous runs. DeBono

Thursday December 18 2008 8:39 pm shiraki 65925-65956

The Hall probe was inserted 2.5cm into the plasma. After 17 shots, the probe appears fine. This data has not yet been analyzed. Instead, the majority of the day was spent repairing the SMP's... Channels 13, 15, and 16 were repaired by swapping waveform analyzers and 8100 modules in the North rack. However, Channel 3 went out at the end of the day; the reason is still unknown

Friday December 19 2008 5:49 pm Levesque 65957-65974 Repairing SMPs

Repaired SMP channels 2 and 3 by swapping amplifiers, waveform digitizers, and memory modules in the North rack. Now it appears that the only non-working SMP is channel 14.


Thursday January 8 2009 7:12 pm DeBono 65975-66020 Bias Probe

More Bias Probe work done today. Probe was inserted to 102.5-104.4cm and activated to voltages between 75 volts and 200, in 25V increments, in order to characterize the effect of biased voltage on the probe.

Friday January 23 2009 5:58 pm DeBono 66049-66074 Bias Probe

More work was done with the intention of creating a strong (3,1) external kink with the bias probe fully inserted into the plasma.

Plasmas were created with a current rise of ~6 MA/sec by using a combination of strong OH and a very short (1.35 msec) Deuterium puff time. This plasmas proved to be quite unstable, subject to sudden minor disruptions.

Monday January 26 2009 5:42 pm DeBono 66075-66094 Bias Probe

More mode development work done today.

Wednesday January 28 2009 7:13 pm DeBono 66095-66131 Bias probe

Plasmas were biased at 100V and 200V with the probe fully inserted (inner edge 102.5cm, outer edge 104.4cm). More mode development work done.

Thursday January 29 2009 8:28 pm Debono 66132-66159 Bias Probe

I had been advised by Daisuke and Jeff that the SMPs had been withdrawn in the bias probe shots taken 2/28/2009. Therefore more biased shots were taken today with the SMPs re-inserted for use in mode analysis.

Thursday February 5 2009 3:17 pm DeBono 66160-66190 Bias Probe

CAMAC and matterhorn proved rather testy today, which slowed down the runday. Bias Probe shots taken at 250 Volts.

Upon consultation with Jim we will begin regening the cryos tommorow. Minimum base pressure is ~1.0E-08, a factor of 10 higher than what was obtainable a couple of months ago.

Wednesday February 11 2009 7:04 pm DeBono 66191-66221 Bias Probe

The goal of the run was to examine the current profile of the strong, bias-probe induced (3,1) external modes we have been obtaining. The Hall probe was inserted into the plasma edge (innermost channel @104.5cm). The bias probe was at (102.5,104.4cm) for all shots. Shots were taken with the bias probe @0V and @250V.

Friday February 13 2009 1:02 am DeBono 62222

One shot was taken today to prepare the tokamak for a deuterium light show for some truant NY times reporter.

Upon consultation with Daisuke yesterdays run will have to be repeated due to the Hall Probe not being calibrated. The second cryo should also be regened, will try to accomplish this tommorow. More crate problems today...

Wednesday February 18 2009 12:16 am shiraki 66243-66259

Hall Probe was recalibrated. Shots were taken before and after to confirm results of calibration.

Wednesday February 18 2009 5:29 pm DeBono 66265-66273 Bias Probe / Hall Probe

Shots taken with Hall probe inserted into outer edge of plasma.

Wednesday February 18 2009 5:29 pm DeBono 66265-66273 Bias Probe / Hall Probe

Shots taken with Hall probe inserted into outer edge of plasma. More to follow.

Friday February 20 2009 5:57 pm DeBono 66287-66318 Bias Probe/ Hall Probe/ Mach Probe

Biased edge shots taken with the hall probe and the mach probe inserted to 104.5cm (bias probe at 102.5-104.4). Their was a problem with the D gas puff towards the end of the runday, perhaps the D bottle is empty.

Monday February 23 2009 6:17 pm Levesque/DeBono 66319-66354 Puff Valve

We fixed the problem with the gas puff valve today. The problem was a loose wire.

Wednesday February 25 2009 7:52 pm shiraki 66356-66372

The puff valve circuit failed again today. The problem turned out to be a combination of a blown transistor and a loose ground. The circuit was repaired and seems to be working again.

Friday February 27 2009 2:58 pm shiraki 66373-66391

Tried to find a good shot for n=2 feedback experiments, similar to the ones from the Kalman filter experiments. Also, a problem with the analog boards was fixed, by replacing a broken op-amp dating back to December '08.

Tuesday March 3 2009 6:26 pm shiraki 66465-66538

Continued the n=2 phase scan. Results so far don't show any significant trends, so the plan now is to do more tests with the FPGA emulator.

Wednesday March 4 2009 5:08 pm DeBono 66538-66572 Bias Probe

The days run was severly hampered by crate errors from the west rack. At first I thought the error was due to a defective J222 channel, however the J222 channel tests out fine and the problem ended up resolving itself by late afternoon.

Tuesday March 10 2009 10:45 pm DeBono 66611-66638 Bias Probe

Q scan done, with 3 <= edge q <= 4. Shots were taken with both the bias probe activated to 250V and to 0V.

Significant (tearing?) mode activity was observed with edge q>3, limiting plasma duration.

Wednesday March 11 2009 6:28 pm shiraki 66639-66645

Verified that the corrected n=2 feedback algorithm works properly. The Kalman filter with increased rotation rate has yet to be implemented.

Monday March 30 2009 7:04 pm shiraki 66646-66684

At the beginning of the runday, the oil on the machine was extremely low. There was one leak at the entrance to one of the TF coils, which was tightened and cleaned up... Experiments to measure the effect of mismatched sensor coil sensitivities were performed. VF only shots at the end of the day suggest there may be significant miscalibration or other source of error.

Thursday April 2 2009 5:48 pm DeBono 666688-66710 Bias Probe

More bias probe q scan work done today.

Tuesday April 7 2009 6:31 pm shiraki 66722-66762

Made plasmas with 3/1 mode activity with and without static perturbations. At first I tried to create a base case with the bias probe inserted but turned off, but was unable to see a good mode. I then took shots with the probe retracted, but the mode doesn't appear to differ in an obvious way between having or not having the static perturbation. The sample size is small though (less than 10 shots each) so more data will be added tomorrow, included biased shots.

Wednesday April 8 2009 8:01 pm shiraki 66762-66802

Took more shots with naturally rotating modes, with and without the static perturbations. While yesterday's pessimistic analysis was based mostly on the rogowski signals, analysis of the partially integrated SMP's (B-dot) looked more promising. SMP signals when the perturbation was present seemed to have more "spiky" delta function like fluctuations. At the end of the run day, I blindly sorted through all of the available data (38 shots) and correctly predicted whether the static perturbation was there or not in 26/38 cases (68%). On shots I felt fairly confident on, I was 5/6.

Friday April 10 2009 4:43 pm shiraki 66802-66814

Applied some static perturbations to biased plasmas. Not too many shots taken today, but I'll continue next week.

Monday April 13 2009 5:24 pm shiraki 66815-66829

Applied static perturbations to more biased plasmas at full amplitude (before clipping). We now have data from about 20 biased plasmas (with and without perturbations), and analysis is underway.


Thursday October 7 2010 4:45 pm shiraki 67411-67436 Copper Plasma

Completed the last of the copper plasma experiments, with the last of the Rogowski data taken. Disassembly will begin tomorrow. -DS

Tuesday November 30 2010 5:14 pm shiraki 67604-67610 TF test

We fired the TF today, beginning at 1kV and increasing 1kV at a time up to 6kV. The banks and magnets seem to be working well. A few small (~1mm) air bubbles were seen coming out of the tops of the magnets above 4kV, and a few turnbuckles worked themselves loose from the vibrations. These will be re-tightened before taking any further shots.

Wednesday December 1 2010 6:46 pm shiraki 67611-67654 OH test shots

A good portion of the day was spent resolving a problem with the OH coil, which turned out to be due to overheating of an amplifier in the basement. The remainder of the day was spent firing the OH to find tools below the machine. A few still remain, but we should be able to finish this tomorrow.

Thursday December 2 2010 4:26 pm shiraki 67655-67684 First Plasma!

We achieved our first plasma since the upgrade today. The plasma broke down with fill pressures of between 2.3 and 4.2E-5 Torr. Plasma currents were between 4 and 8kA, lasting up to 5ms. Loop voltages were between 10 and 15V. Currently we have no major radial information, but this data will be post-processed.

Friday December 3 2010 7:04 pm shiraki 67685-67717

We now have major radius data based on copper plasma and vacuum shot calibrations. The plasma usually breaks down around 93-94cm on these shots. Ip is typically 8-10kA, lasting for about 4ms. Loop voltages have come down to 8-9V. The plan next week is to continue taking shots while continuing to add more diagnostics to the machine.

Monday December 6 2010 8:33 pm shiraki 67718-67762

Plasma currents as high as 15kA were reached today. The major radial force balance seems to respond well to the bank settings, and is fairly stable. The first set of feedback sensors (4 poloidal and 4 radial at one toroidal location) were digitized today, and the signals look good despite temporary cabling and improper shielding. Some of the soft X-ray tomography channels appear to be working as well. Additional Fourier Rogowskis will be connected tomorrow, followed by optical diagnostics (fast camera and spectrometer).

Tuesday December 7 2010 7:06 pm Levesque 67763-67827 Shot development

Attempted to make long-lived plasmas with edge q between 2 and 3. Reached plasma currents as high as 18kA. Spectrometer has been implemented, looking at D_alpha light. Lots of D_alpha light is seen during the breakdown and disruption, with the disruption light peak being up to 4 times as intense as the breakdown. The rises in D_alpha light during disruptions correlate well with drops in SXR emission. Mode activity is seen in the feedback sensors and sin3T Rogowski coils when edge q is near rational numbers.

Wednesday December 8 2010 7:33 pm shiraki 67828-67882

Today's shots consistently reached 18kA of plasma current, with loop voltages coming down to 5 or 6V as the plasma heats up. Half (40 total) of the feedback sensors were digitized, including two complete toroidal groups. Biorthogonal decomposition of this data shows a rotating n=2 mode with about 15% of the mode energy. However some grounding problems still need to be worked out for the feedback sensor preamplifiers.

Thursday December 9 2010 7:45 pm Levesque/Angelini/Shiraki 67885-67920 Fast camera testing

Tested fast camera by viewing light through a midplane window port. High light levels were seen during breakdown and disruption. The highest tested frame rate was 24000 frames per second. No obvious current filament was observed during breakdown, but a higher frame rate may help.

Friday December 10 2010 7:45 pm Levesque 67921-67973 Shot development

Attempted to make long lived plasmas with higher edge q values. No significant improvements in plasma duration -- good plasmas still last ~5-6ms at the longest. Having the edge q between 2 and 3 has reproducibly given the longest lasting plasmas so far.

Monday December 13 2010 8:08 pm Levesque 67974-68024 Long shot, spectrometer tests

Attempted to make long-lived, low-current plasmas. Longest plasma durations were 11.5ms, though the plasma currents and major radii were very erratic. Currents for long plasmas peaked at 7.5kA and dropped to ~2kA during the shots. Spikes in d_alpha light were seen during minor disruptions for these long shots. Several spectrometer wavelengths were tested in order to verify the d_alpha wavelength setting and to look for an oxygen line.

Tuesday December 14 2010 7:23 pm Levesque 68025-68065

Long-lived, low-current plasmas. Record duration so far is 15ms with a peak current of 8kA. Long-duration shots achieved so far have produced little or no x-ray emission.

Wednesday December 15 2010 8:31 pm shiraki 68066-68135

More shot development. The longest pulse today was 20ms, with a slow ramp-down of Ip after a peak of 17kA. Bank timing was adjusted slightly, but has not yet produced any obvious effects.

Monday December 20 2010 10:52 pm Levesque 68136-68165 Bank timimg tests

Made large changes to timimg of OH and VF bank firing to investigate different operating regimes. Was able to make several plasmas without firing the OH start or OH electrolytic banks, where the plasma was formed using the OH bias bank and maintained for 5ms using the two VF banks. Was further able to drive this type of plasma by firing the OH start and OH electrolytic banks at 1.5ms into the plasma shot to raise the plasma current to ~13kA. Interesting mode activity was seen throughout these shots.


Wednesday January 26 2011 5:15 pm shiraki 68177-68186

The full set of feedback sensors was tested with the new breakout board. There are still some cabling/grounding issues, which we will begin to resolve tomorrow.

Tuesday February 1 2011 5:45 pm shiraki 68187-68200

Continued debugging of the x10 feedback preamps. Grounding the boards to the rack helps, but the problems remain when more than 3 boxes are connected.

Wednesday February 2 2011 5:28 pm shiraki 68201-68214

All 10 feedback preamp boxes are now working properly, after moving the power supply to minimize the loop voltage on the DC power lines.

Friday February 18 2011 4:58 pm shiraki 68217-68248

The first half of the high density arrays was tested successfully. A few amplifier channels need repair, but signals look good on both poloidal and toroidal arrays. Biorthogonal decomposition of poloidal arrays show mode numbers ranging from m=2 to 7.

Monday February 21 2011 5:25 pm shiraki 68249-68280

Continued testing of the high density array. One issue so far is low signal levels on high-field side sensors on outboard limited plasmas, particularly for high m numbers.

Thursday February 24 2011 7:07 pm Levesque 68309-68331 Feedback sensor tests

Developed low breakdown current shots to prevent feedback sensor clipping during breakdown. Low initial current shots can be used to test equilibrium reconstructions before FB sensor amp boards are modified to prevent clipping during normal shots. Three FB amp boards have been modified so far, and do not clip during the breakdown or disruption for typical shots. The remaining 7 FB boards can be modified in the next few days.

Monday March 14 2011 5:41 pm Levesque 68488-68498 Testing high-resolution sensors

Tested second high-resolution sensor amplifier set. All poloidal sensors and amplifiers are currently working, except for 1 in the toroidal array. Radial sensor data was taken, but has not yet been checked.

Wednesday March 16 2011 6:45 pm Levesque 68521-68535 Fast camera

Tested fast camera mounted 2-3 feet above the Thomson scattering viewport. The camera was able to withstand the high fields without movement or noticeable video distortion. Frame rates were ~47000 fps. Videos generally show if the plasma is far outboard or inboard limited, but there is no obvious emission centroid or clearly defined edge. Fluctuations in light can be seen, but have not yet been compared to magnetic fluctuations. A D_alpha filter was mounted in front of the camera lens for a few shots. Upon first inspection, little difference was seen between the visible light and D_alpha-only videos, other than a large reduction in light intensity due to the small diameter of the filter.

Several magnetic sensor amps are currently not working; trouble-shooting is in progress.

Monday April 4 2011 6:35 pm Levesque/Shiraki 68536-68549 Vacuum field pickup shots

Ran vacuum shots to measure pickup on toroidal array sensors. Various combinations of VF and OH bank settings were used. There are discrepancies (toroidal asymmetries) in vacuum fields as seen by toroidal array sensors. We haven't yet come up with an appropriate explanation for this, but are working on it.

Tuesday April 5 2011 7:07 pm shiraki 68550-68576 Control coil force test

We energized a set of control coils in the presence of the toroidal field, while viewing the coil with the fast camera through the Thomson scattering collection port. Currents were gradually increased from 2A to 36A. Unfortunately, the fast camera view is in the radial direction, as is the jxB motion of the control coil wires. However, motion of the wires is easy to detect when the TF is on, while being almost undetectable when there is no TF, even at full current. There may also be slight flexing of the control coil side of the shell, which may be because of reduced rigidity of the shell due to the Thomson cutout.

Repeating these tests with the fast camera at the bifurcating port should show radial motion of the wires more clearly.

Thursday April 7 2011 11:43 pm Levesque 68600-68612 Vacuum shots

Ran vacuum shots to measure pickup on toroidal array sensors. Tried to isolate possible problems with amplifier boards or sensor mapping. No problems have been found so far.

Friday April 8 2011 4:52 pm Rath 68613-68621 Equilibrium Test

Made some plasma shots with a new tree model that includes magnetic sensor position information. Attempted to do automatic equilibrium reconstruction, but weren't able to do so because of missing polarity information.

Also had trouble getting plasma breakdown at normal puff times, but longer puff times didn't show any problems. We may have problems with the puff circuit or the gas may be running out.

Monday April 11 2011 5:30 pm Levesque 68624-68630 Vacuum shots

Ran vacuum OH-Bias-only shots to measure pickup on toroidal array sensors. Discrepancies in vacuum fields as seen by the high-resolution sensors appear to be mostly caused by pickup along the ribbon cables in the copper bellows between the tokamak and the amplifier boxes. Individual sensor polarities together with the ribbon cable groupings are consistent with anomalies in all toroidal array data taken so far. The fields and pickup areas along the ribbon cables are comparable to the fields and areas of the high-resolution sensors.

Tested this idea by twisting one set of 3 ribbon cables within the bellows (Bottom West set) without disconnecting the bellows. This changed the vacuum pickup by a significant amount. Pickup was reproducible in subsequent shots. Then twisted the same ribbon cables within the bellows further, as much as reasonable without disconnecting the bellows. Again pickup changed, then was reproducible in subsequent shots.

The resolution for this problem will be to replace these standard ribbon cables with twisted-pair ribbon cables.

Monday April 18 2011 6:42 pm Levesque 68673-68686 Vacuum shots

Ran OH and VF vacuum shots to measure pickup on toroidal array sensors. Took shots before and after replacing one of the ribbon cables running from the tokamak to the amplifier box with a twisted pair cable. Twisted pair bundle cable was run directly from the conflat feedthrough to the amplifier, through the front door of the amplifier box (not through the bellows). Non-sensor pickup was dramatically reduced. All sensors in that bundle now have the same apparent polarity for vacuum shots, versus having 2 distinct sets of pickup. Spreads in nominally axisymmetric poloidal field signals are now ~40% while firing the OH coil alone, and ~10% while firing the VF coil alone. Both of these are down from spreads of over 100%. More testing should be done with improved shielding.

Monday April 25 2011 10:08 pm shiraki 68750-68805 Static phase flips

Today we began static phase flip experiments using the FPGA. The plasmas were standard current ramps with edge q starting at around 4 and falling to slightly below 3. The applied control coil currents had an amplitude of 20A, with resonant 3/1 helicity. Timing of the phase flip was chosen to occur after the q fell below 3 and initial fluctuations were diminished. Initial biorthogonal decomposition analysis of the full magnetics data did not show conclusive results, but further analysis and experimenting will continue tomorrow.

Tuesday April 26 2011 5:48 pm shiraki 68826-68835 phase flip experiments

More data was collected attempting to compare similar current ramp discharges with and without static phase flips in order to extract the plasma response to the external field. Pertubations with both 3/1 and -3/1 helicities were applied. Comparisons so far have been limited by plasma reproducibility and small sample size. This dataset will be expanded in the coming days.

Tuesday April 26 2011 11:59 pm Levesque 68806-68825 Vacuum pickup shots

Ran OH and VF vacuum shots to measure pickup along toroidal array sensor cables. Tested two cables between the tokamak and the amplifiers: a twisted pair bundle cable and a twisted pair ribbon cable. Pickup along the cable was isolated by connecting each to a shorting d-sub connector with no effective NA, instead of the sensor feedthrough. Also tested pickup along the output ribbon cable between the amplifiers and the west rack.

The bundled pair cable and the twisted ribbon cable had similar pickup for vacuum shots. Pickup along these cables does not appear large enough to account for differences in vacuum shots with the sensors connected, suggesting that there is more pickup at the feedthrough or elsewhere within the chamber. Pickup along the output ribbon cable was measureable, but was not enough to account for differences in signals.

Wednesday April 27 2011 7:51 pm shiraki 68836-68858 phase flips

A systematic error was found in the wiring of the power amps, meaning that previously applied fields were not actually resonant perturbations. This was corrected, and the new wiring was confirmed by using the control coils as sensors and detecting the helicity of rotating plasma fluctuations. Static 3/1 phase flips were then applied to plasmas with edge q just under 3, and initial measurements suggest there may be a measurable plasma response, but further analysis is necessary.

Thursday April 28 2011 6:23 pm shiraki 68859-68877

The timing and length of the applied phase flip perturbations were adjusted today, varying from 1ms (0.5ms up and 0.5ms down) up to 2ms (1ms up and 1ms down). In addition to a possible response to the phase flip, there may be some interaction with the pre-flip RMP, i.e. a static response. However, the primary limitation to extracting the plasma response has been discharge reproducibility, so an effort was made at the end of the day to develop a more reproducible marginally stable plasma.

Friday April 29 2011 4:03 pm shiraki 68880-68898

More data was collected with 3/1 static phase flips on similar plasmas as earlier this week. An attempt was also made to apply phase flips on discharges with more of a multimode spectrum. The FPGA and power amp system appear to be working well, but the challenge is still in properly deducing the plasma response.

Tuesday May 3 2011 8:29 pm Levesque 68934-68957 Phase flips

Applied static 3/1 phase flips while attempting an edge q scan. Plasmas were more erratic and non-reproducible than those on April 28; it was difficult to apply the phase flip with the edge q near 3. Also tried applying fields at half the amplitude as part of an RMP amplitude scan. Analysis still needs to be done for the usable plasmas, however lack of reproducibilty should be considered when analyzing these plasmas.

Wednesday May 4 2011 10:25 pm Levesque/Shiraki 68960-68992 Retracted shells, phase flips

Retracted shells 2cm from their fully-inserted positions to try to observe different mode characteristics. Observed 4/1 modes that were more prominent than usual when the edge q was above 3.

Plasmas with large initial currents (~10kA) had difficultly getting below edge q=3. Plasmas with lower initial currents (~9.3kA) and stronger current ramps usually made it through edge q=3 with no problem, including during phase flips. Phase flips were done with helicity -3/1. More shot development is needed to get plasmas with steady q values near 3.

Also did 2 separate phase-flip periods for 3 plasmas (shells still retracted): on for 0.5ms, flipped for 0.5ms, off for 1ms, on for 0.5ms, flipped for 0.5ms. The 3/1 mode typically locked during the first CC on+flip stage, then went away or started rotating when the control coils were off. One plasma disrupted during the second phase flip.

Friday May 6 2011 9:14 am Levesque 68997-69006 Shot development, multimode

Yesterday's run focused on getting a reproducible shot with edge q near 3 for normal operating conditions. This shot type will be used for a q scan at different applied RMP helicities. The shells were fully inserted prior to the run. Plasmas formed around 92.8cm at the end of the start phase, versus 93.3cm for the shells retracted 2cm with the same start settings.

Evidence for multimode activity was seen, especially for shot 68998. BD analysis shows a 6/2 and a 7/2 mode in addition to the 3/1 and 4/1 mode as the edge q crosses 3 from above. This and neighboring shots were similar to shot 68498, which had been our best multimode shot to date.

FPGA code for applying a rotating perturbation was in development, so RMPs could not be applied to these plasmas.

Friday May 6 2011 6:41 pm levesque/shiraki 69007-69014

Some shots were taken today to try to look at naturally present multimode fluctuations, without RMP's. Initial attempts to apply rotating RMP's suffered from lack of synchronization between the five FPGA's, but this issue is being addressed. Plasma experiments with rotating perturbations will begin as soon as possible, possibly this weekend.

Monday May 9 2011 5:59 pm levesque/shriaki 69027-69057 Static phase flips

Due to continuing problems with implementing the rotating RMP's, more static phase flip experiments were conducted today. In particular, a detailed amplitude scan was performed. For control coil currents less than ~12A, the 3/1 static response scales linearly with the perturbation, with a slope of about 2Gauss/Ampere. Between ~12 and 22A, the response appears to saturate at about 3.5G. Above ~22A the plasma seems to always suffer a minor disruption just after the perturbation is turned off. There was some shot-to-shot variability of major radius and edge q, but this was not considered in the analysis so far.

Finally, several vacuum shots were taken to ensure that direct sensor-coil pickup does not affect the response calculation.

Tuesday May 10 2011 7:46 pm Levesque/Shiraki 69058-69100 -6/2 RMP amplitude scan

Applied -6/2 static phase flips to attempt an RMP amplitude scan. At first we saw a linear trend in the n=2 plasma response as measured by the feedback sensors, but later vacuum shots showed that this was mostly/entirely due to direct pickup. Direct pickup for the 6/2 helicity is much larger than for the 3/1 helicity (by an order of magnitude), most likely due to the relative phasing of control coils near each sensor. Toroidal array data were taken for these shots, but have not yet been extensively analyzed.

There was no observed trend in the 3/1 response with changing 6/2 applied amplitude. After stopping the 6/2 scan due to the direct pickup, we continued the -3/1 phase flip experiments and started a q scan. Analysis for the q scan has yet to be done, but only a few shots have been taken so far. We also applied one -4/1 and one -2/1 phase flip (separate shots) for the same equilibrium characteristics. The plasma suffered a minor disruption after the -2/1 perturbation was turned off, though the edge q was close to 2.9. Again, analysis is backlogged for different applied helicities.

Wednesday May 11 2011 11:30 pm Levesque/Shiraki 69101-69127 RMP q scan

Applied -3/1 static RMP phase flips during a q scan of plasmas similar to those from this week's amplitude scans. Phase flips were always applied at 2.5ms to try to minimize the variation in equilibrium plasma properties. So far we have seen the RFA increase as the "mean-edge-q" increases from ~2.6 to ~3, where mean-edge-q is defined as the average q over the period of control coil activation (2ms-3ms). More shots are needed with mean-edge-q above 3 in order to hopefully observe a peak in RFA near edge q=3.

Much of the q variation done so far has been due to ~5mm variation in major and consequently minor radii, which may influence coupling to the control coils and feedback sensors. Systematic reduction of plasma current to raise the edge q with the same major radius was in progress at the end of the run day, and will continue in the morning.

Thursday May 12 2011 6:20 pm Levesque 69128-69153 RMP q scan

Continued edge q scan during -3/1 static RMP phase flips. Took shots with mean-edge-q around and above 3 to extend the range of q's in the scan. The results of the q scan show that the RFA amplitude is largest when the mean-edge-q is between 2.9 and 3. The range of mean-edge-q's in the scan was 2.65 to 3.25. In each shot, the edge q decreased significantly during the 1ms window of control coil activity (e.g. from 3.2 at 2ms to 2.8 at 3ms), which probably spreads out the peak of calculated RFA amplitude. A future q scan should be done during a time window where the edge q is steady for various plasma currents in order to get better RFA peaking.

Friday May 13 2011 6:50 pm DeBono 69163-69173 Bias Probe

Bias probe was run @75Volts into electron saturation current.

The CPCI's suffered a digitization lag of ~150ms. The A14's were not affected. Problem unresolved, will repeat efforts on Monday. Bryan

Sunday May 15 2011 11:55 pm DeBono 69174-69189 Bias Probe

The purpose of this run was to determine the correct polarity of the bias probe voltage and bias probe current signals. It appears the bias probe V,I signals are inverted from their correct polarity by the South Rack A14. Crates only, no bank shots.

Monday May 16 2011 6:44 pm DeBono 69198-69214 Bias Probe

Shots were plagued by same ~150ms CPCI latency as last Friday. However, a couple somewhat useful shots were taken.

Bias probe triggered sucessfully at desired time/voltage. It was necessary to swap the 1V/10A Rogowski for a 1V/100A Rogowski due to high currents collected by probe (For Vprobe = +100V, Iprobe was > 50 Amps).

More data to be taken once CPCI latency problem is solved.

Tuesday May 17 2011 9:39 pm DeBono 69231-69262 Bias Probe

The day's run was made more difficult by the frequent appearance of Store_Action NoX errors in the A14's, which occured primarily in the North Rack but also occured in the Basement, South, Screenroom and West Racks. I suspect that these NoX errors are related to thermal effects in the basement crate: opening both basement crate doors and blowing the high-power fan on the rack seemed to help (although NoX errors continued to occur throughout the runday).

Shots were taken @+25V,+40V, +50,+100,+150 with the bias probe fully inserted. As was seen before, large positive biasing resulted in the rotation frequency of the m=2, m=3 modes to reverse direction from the natural, positive rotation frequency.

Thursday May 19 2011 12:16 pm DeBono 69266-69292 Bias Probe

More work done on using bias probe to slow down mode rotation near 0, as in shot #69265.

Probe voltage was set to floating, 0, +30, +35V for these shots. More shot development needs to be done here to achieve repeatable, large, near 0 rotation modes.

Also bias probe was set to high V values to spin the plasma. Probe voltages set to 200, 250, 300V.

Friday May 20 2011 7:26 pm DeBono 69293-69314 Bias Probe

The goal of the run was to use the bias probe to slow down the natural plasma mode rotation and achieve a repeatable, non-rotating mode. First, the radial position of the probe was experimented with. The probe was biased to 30V and moved so that the probe tip was placed [1.234, 2.234, 3.234]cm inside the plasma. The probe placed at 3.234cm (maximum probe penetration allowed by the bias probe bellows) seemed to have the best results. At the end of the runday, we adjusted the shot to straddle the q=3 surface in order to achieve a stronger mode. Increasing the VFEL to push the plasma inwards raised the edge q closer to 3 and also increased the plasma current ramp. This resulted in a significantly stronger mode and some encouraging shots towards the end of the runday.

Friday May 20 2011 9:47 pm DeBono 69315-69331 Bias Probe

The purpose of the run today was to use the bias probe to slow down the natural mode rotation. This run built upon the promising shots taken at the end of the runday yesterday.

The B.D. applied to the shots taken today with a floating, fully inserted bias probe showed the natural mode rotation around 8-9kHz. This is consistent with natural mode rotations observed earlier (see shot #69142 as an example). The probe was used to slow down mode rotation below 4kHz; possibly as low as 2kHz for a period of 1.5msec after probe activation. Shot-to-shot major r, q, plasma current traces show good repeatability. Shot-to-shot repeatability of the MHD mode rotation is questionable, although all shots show reduced mode rotation compared to the natural mode rotation.

Wednesday May 25 2011 7:34 pm shiraki 69333-69363 static phase flips on biased plasmas

The static response to a m/n=-3/1 static phase flip was compared for plasmas with and without biasing. The probe was inserted inside the plasma in both cases. When turned on, the probe was biased to ~50V, drawing 35-40A. This results in about a factor of three increase in the measured plasma response over non-biased shots. In tomorrow's run we will continue to scan over probe voltage/current.

Thursday May 26 2011 6:21 pm shiraki 69364-69411

The phase flip response as a function of bias probe current was scanned, with bias voltages between 0 and 80V. The plasmas seemed to disrupt more often when the probe was turned on, even when no RMP was present. In cases where the plasma does not disrupt, the plasma response was often delayed relative to the perturbation, making the previously used correlation analysis difficult, even when the raw signals show a clear response. This scan will be continued tomorrow.

Tuesday May 31 2011 3:01 pm DeBono,_Shiraki 69412-69452 Shot Development

The purpose of the run today was to do shot development to optimize the shot for RMP response experiments with edge-biased plasmas. We attempted to optimize the shot for an edge q=3 and also to remove shot-to-shot irrepeatability.

Shots taken throughout the runday suffered from shot-to-shot irrepeatability. In addition, the bias probe suffered from pretriggering problems; instead of firing at 2msec as was programmed, the bias probe would pretrigger around 1.0-1.2msec. This problem appeared pre-HBT upgrade, but has not been a problem post-upgrade until this run.

Tuesday June 7 2011 11:38 pm DeBono 69453-69522 Bias Probe

This run report covers 3 days of running.

The bias probe pre-triggering problem appears to be fixed. It was found that the OHST bank caused the 111A pulse generator to prefire and activate the bias bank SCR prematurely. The problem was fixed by cheating the 111A's power supply.

The rundays were plagued by store_action no-x errors; >9 no-x errors appeared every shot, and sometimes as many as 12 errors per shot. The basement A14_07 was swapped with the west rack A14_15 in an attempt to fix this problem, but did not succeed although perhaps reduced the frequency of basement no-x errors. The lack of a functioning cap room AC could be a culprit: Facilities work order #703420 was placed to fix the AC.

Friday June 10 2011 7:03 pm Levesque 69523-69536 Vacuum pickup tests

Testing vacuum pickup along a new twisted pair ribbon cable which will be used to replace the existing high-resolution sensor cable runs between the tokamak and amplifier boxes. Like the run on April 26, Pickup along the cable was isolated by running the cable from the amp to a shorting d-sub connector with no effective NA, instead of to the sensor feedthrough. Two of the three flat sections along the cable (40" twist, 3" flat, repeat) were manually twisted using the technique we decided upon. When the non-twisted flat section was near the amplifier box, pickup along that flat was small but still measureable (~0.3 Gauss with typical bank settings) though it was 4 feet away from the basepad. This suggests that we should manually twist all flat sections of the cable, including the sections farthest from the tokamak.

Pickups along the rest of the cable and shorted Dsub were ~1-2 Gauss for both VF and OH coils. This is down from ~60 Gauss pickup along the existing flat ribbon cables and feedthrough. When the twisted cable was reversed in order to place the flat part ~5 inches away from the outer VF coil, pickup was ~10 Gauss from the VF. These quoted field strengths are the spurious fields that would be inferred in the poloidal field sensor measurements. More tests may be done next week if deemed necessary.

Thursday June 16 2011 6:28 pm Byrne 69539-69544 Vacuum Pickup Test

A twisted pair ribbon cable (the same as Jeff is using, but unmodified) was hung as it will be when the GPU is connected to the amplifier rack and the VF and OH banks, separately and together, were fired.

The ribbon was shorted at one end by twisting to eliminate NA, and the other end was routed into the North Rack A-14's. Recorded pickup was very low, and comparable to that seen in other channels.

Finally, the other end was unshorted and connected to the Bias Probe trigger, which as a 5V signal is comparable to the signal to be output by the GPU. It was unappreciably affected by the pickup. This confirmed that the small signal was indeed the pickup in the cable. Al shielding is expected to reduce this effect further. Interference on GPU->Crown Amp signals is not expected to be an issue.

Brian Debono checked the basement rack temperature midway through the run, found outside temp to be 27 C, and 19 C inside.

Thursday June 16 2011 6:52 pm Levesque/Byrne 69539-69542 Vacuum pickup shots

Ribbon cables from the feedthrough to the amplifiers for 1/4 of the high-resolution sensors were replaced with twisted pair ribbon cables. Piggy-backed on Pat's vacuum pickup shots to measure fields from the VF and OH in the TA sensors. Updated TA sensors showed much better agreement with each other, versus the wild disagreement when using the flat ribbon cable. More-detailed comparisons will be done after all flat ribbon cables have been replaced.

Monday June 27 2011 7:41 pm Levesque 69545-69551 Vacuum pickup shots

Ribbon cables from the feedthrough to the amplifiers for all of the high-resolution sensors have now been replaced with twisted pair ribbon cables. Ran vacuum pickup shots to measure fields from the VF, OH, and TF banks separately. All high-res sensors now show much better agreement with each other, except for 2 of the PA sensors and 1 of the TA sensors. Discrepancies with these 3 sensors may be due to amplifier problems; this will be investigated.

Two plasma shots were taken (69550 and 69551). Although these two shots were not good-quality plasmas, there should be enough agreement among the high-res sensors for equilibrium reconstructions. Differences in equilibrium fields seen by the axisymmetric TA sensor sets are comparable to the differences in vacuum shots, so subtracting the vacuum fields should help in reconstructions. Paul and Jim will start adding flux loops to the machine tomorrow.

Thursday June 30 2011 7:41 pm shiraki 69552-69587

Two of the new flux loops have been mounted on the machine and were tested today. Raw signal levels were around 1.5V at breakdown and about 200mV during the rest of the discharge. These signals were digitized for all of today's plasma shots. A few shots with a 3/1 phase-flip were taken today, but the plasmas may have been somewhat different from those in previous experiments such as the amplitude scan.

Friday July 1 2011 9:03 pm shiraki 69589-69644 phase-flip amplitude scan

With appropriate bank settings, today's plasmas were close to the target plasma from the last 3/1 phase-flip amplitude scan. However, the "saturation regime" from ~15-30A of control coil current was NOT observed. Instead, plasma response increased linearly with coil current (with the same slope as before), up until about 25A, where the plasma usually disrupted after the perturbation was turned off. In the 20-30A range, there is a noticeable separation between the two datasets (larger than the spread of each).

The shots that resulted in disruptions have not been analyzed yet.

Tuesday July 5 2011 7:47 pm shiraki 69645-69686 phase-flip amplitude scan

More shots were taken as part of the phase-flip amplitude scan, with an effort to consider the variation in edge q from shot to shot. The spread in the plasma response measurement was larger today, for still unknown reasons. The cumulative data so far may be consistent with the theory that the plasma response saturation only occurs for edge q near 3 (~2.85-3.0), while only a linear regime is observed for plasmas with edge q of 2.6-2.85. More data will be taken in the coming days to test this theory.

Wednesday July 6 2011 9:03 pm Levesque/shiraki 69687-69739 Phase-flip amplitude scan

Continued RMP amplitude scan using -3/1 phase flips. Additional data from today is consistent with observations from the previous runs. Only a linear plasma response is observed for plasmas with 2.7<q_*<2.85. Linear plus saturated regimes are observed for plasmas with 2.85<q_*<3.0. The magnitude of the 3/1 plasma response for linear regime shots is consistent with earlier q-scan results.

Thursday July 7 2011 7:33 pm Levesque/Shiraki 69740-69789 Phase-flip helicity scan

Performed a phase-flip helicity scan with n=1 applied fields. The applied m numbers varied between -5.0 and +5.5. The maximum control coil current in each case was ~10A, which is in the linear regime of the recent RMP amplitude scans. Clear peaking in 3/1 static response was measured for m numbers around -2.5 and +4.0. Note that previous RMP amplitude and q scans were done using m=-3. In addition to the m-scan, Bryan took a couple shots at the end of the run day to test the bias probe with a 16-ohm resistor added to its circuit to prevent pre-trigger bias currents.

Monday July 11 2011 8:21 pm shiraki 69790-69829 n=2 phase-flip helicity scan

n=2 phase-flips were applied using 'm' numbers ranging from -7 to +6. All phase-flips had the same amplitude of ~40A. The measured -6/2 response peaks near m=-6 and m=+1, as expected from the corresponding peak in the -6/2 component of the applied field. In addition there may be another unexpected peak at m=+5. However, unlike the n=1 phase-flips, the measured response is not always well characterized by fitting to the passively measured "natural (unstable) mode" structure. Also, while the peaks in the response are higher than the direct vacuum pickup, the pickup may still represent a significant portion of the signal and may require more careful subtraction.

Wednesday July 13 2011 6:47 pm DeBono 69830-69841 Bias Probe

The bias probe was attached to the Crown amp biasing setup today: the setup can place an 85V, 1kHz sine wave on the probe. Plasmas will be taken tomorrow; flux loop installation prevented machine running today.

Thursday July 14 2011 9:59 pm debono 69842-69855 bias probe

The bias probe voltage divider was rebuilt today following an arc. The negative bias supply was re-tested: a 109V, 1Khz sine wave pulse (1 full wavelength) was successfully placed on the probe.

Friday July 15 2011 8:13 pm debono 69856-69873 bias probe

The crown bias voltage supply was tested for the first time today. Shots were taken at 20,40,60,80V sine wave pulses @1kHz. Large pickup voltages were present on the shots with plasmas; the crown amp will be moved either into the south rack or outside the machine room to prevent these pickup voltages.

Monday July 25 2011 5:24 pm shiraki/levesque 69874-69920 Clean-up shots

The bake was turned off yesterday, and clean-up shots were taken today. The discharges improved over the course of the day, lasting up to 5ms with 15kA of plasma current. More clean-up shots will be taken tomorrow if necessary, followed by the high-current (~25A) phase-flip q scan.

Tuesday July 26 2011 10:53 pm shiraki/levesque 69921-70000 high current phase-flip q scan

More clean-up shots were taken in the morning until plasma reproducibility greatly improved. Then the phase-flip q scan was begun with ~25A of control coil current, scanning between (time-averaged) q of 2.6 and 3.1 during the phase-flip.

The initial results are again consistent with a linear response at lower q (q<2.8), and a saturation for plasmas near q=3. It is notable that the installation of the Hall probe and following bake may have changed vacuum and plasma conditions in the time between this and the low (~10A) current q scan.

Wednesday August 3 2011 9:23 am Byrne 70010-10011 Hall Probe Calibration

Two shots were taken with the TF bank set to 500V. Banks fired at this low voltage, but CPCI 12, to which the probe was attached, did not acquire any samples.

Probe was moved to CPCI 10, but then changes to the setup of the probe (probe standoff/leveling cantilever) were noticed, and the run was scrubbed until Thursday so that the changes could be investigated and understood.

Thursday August 4 2011 6:10 pm Paul_Hughes 70026-70027 Flux Loop Calibration

Tested performance of prototype flux loop preprocessing circuit. At full OH, signal saturated. Dividing factor will be increased, and the circuit will be re-tested.

Friday August 5 2011 9:44 am Byrne 70023-70037 TF Only Hall Probe Calibration

Probe was connected and shots were taken with TF @ 500V. Preliminary results look as expected, although data hasn't been fully analyzed. One probe was dead, after invesitgation was found to be a broken lead wire. Wire was repaired but probe now shows an offset of ~70% of signal. Will be investigated 8/5.

TF probe was also scanned along angle to find maximum (Phi direction) and minimum (Theta direction) of signal. Mor work remains to be done however.

Friday August 5 2011 2:30 pm Paul_Hughes 70038-70043 Flux Loop Calibration

Shot 70038 lost to powered-off basement rack. Run actually starts at 70039.

Ran max-setting OH and VF vacuum shots to check for saturation with new circuit prototype. Spike was below 9V with VF at 150, 050 and OH at 295, 105, 02. Success! Prototype will be kicked up to implementation.

Friday August 5 2011 5:42 pm Byrne 70044-58 Hall Probe Angle Calibration

Good data was gathered, but the TF probe shows variation shot to shot, which reflects strongly in hall probe data. Consequently signal is not only a function of angle. multiple shots have been taken for each angle in the region of max signal, TF strength will be normalized out, and the maximum angle extrapolated from the data.

Three bad probes have been located. One is extremely noisy, seems to be a bad amp channel, one seems to be dead, has not been diagnosed, and one (the bad probe from last run) seems to have been blown on the board (Hall current is zero, but signals are output. Very confusing)

Remaining work to be done: Find probe sensitivity (V/T), characterize transverse field effects, and trouble shoot bad probes/amp channels.

Tuesday August 9 2011 5:56 pm DeBono 70059-70092 bias probe

Today brought the first successful tests using the crown amp setup to power the bias probe during a plasma shot. The following waveforms were tested:

Sine waves @500hz, 20V, 100V

Square pulses @-100V, 1msec, 2msec duration

The sine&square waveforms were clearly visible in the voltage/current measurements of the probe. Negative biasing caused positive acceleration (in the natural direction) of the (3,1) saturated external kink, while positive biasing resulted in counter-acceleration.

I-V probe characteristics showed a near-linear plot, with an V/I plasma resistance of 3ohms. -100V was not enough voltage to reach ion saturation current, the old LANL transformer will be hooked up to the crown setup to allow higher voltages to the probe.

Tuesday August 9 2011 7:45 pm Byrne 70093-70112 Hall Probe angular Calibration

Data today was much better than on Friday. Found a cosine-like dependence of signal on angle with respect to toridal field. Peak of plot shows a plateau from ~ -2.5 degrees to +10 degrees away form an arbitrary zero.

Plan going forward is to possibly take more shots (probably no more than one per position) in the plateau region to see if signal really is insensitive to angle.

The shots taken at the decided-upon optimum angle can be immediately used in the next test, which will determine the probe sensitivity (nominally 7V/T). If time permits, the VF banks will be used to quantify signal attenuation due to tansverse field.

Wednesday August 10 2011 7:07 pm Byrne 70113-70134 Hall probe calibration

Run was initially delayed by lack of repeatability from yesterday. A positioning error was found, but signals all displayed a systematically reduced normalized response of ~99% of yesterday's response. Probe currents were the same as yesterday, but the battery voltage was slightly lower (~99.5%). This was the only difference that could be found, and will be tracked in the future.

TF only shots were taken to test probe sensitivity. Data has not been fully analyzed yet, but working probes do show a linear response. VF/TF shots were then taken to determine signal attenuation. During this test it was noticed that the probe amp noise seems to be larger than it was pre-upgrade. This will be looked into moving forward.

Expect to have data analysed and hall probe provisionally ready for use by end of day tomorrow. Systematic day-to-day drift, the malfunctioning probes mentioned in today's meeting and the increased amp noise problem will continue to be investigated and hopefully fixed sometime soon.

Tuesday August 16 2011 6:36 pm DeBono/Levesque 70136-70159 Bias Probe

The runday was shortened today due to a CAMAC software error which took up the morning and early afternoon. Shot development work was done today with the bias probe inserted but floating (i.e not connected to crown voltage source). Shots improved throught the runday, suggesting impurity reduction. More shot development to follow: shots with duration >6msec were acheived today but the edge q profile still needs refinement.

Wednesday August 17 2011 6:31 pm Levesque/DeBono 70165-70190 Bias Probe

Bias probe run today with the following settings

1. Probe floating, no RMP's & static RMP's from 2-3msec

2. Probe biased to approx. floating potential (-45V), no RMP's & RMP's from 2-3msec.

3. Probe biased to (-90V,+45V), with RMP's.

The shots at +45V resulted in slowed plasmas which disrupted during the RMP. Other shots did not disrupt during the RMP.

Analysis pending.

Thursday August 18 2011 3:06 pm Byrne 17191-17210 Hall Probe re-calibration

The probe was recalibrated as before, only this time with the probe gain reduced. Signal did not fall as expected ~30-50%, three previously non functioning probes began working, two previously dead probes began passing 60Hz noise, and noise was reduced across all channels. This suggests that there is something wrong with the 10X setting on the PGA202 amps. An apples-to-apples comparison has been added to the wiki.

During the run it was realized that a toroidal shot measured in the poloidal direction provided a much stronger signal of proper poloidal alignment, as the signal had a zero cross at poloidal alignment, rather than a flat plateau of signal, as was seen with toroidal alignment. Probe was found to be ~5 degrees off axis. Poloidal shots were taken to ensure min n*Bphi corresponds to max n*Btheta. No difference could be seen from one angle to another, meaning poloidal signal is not reduced, while TF pickup is minimized.

Probe reference was redone to allow proper alignment, then measurements of TF field at a variety of voltages (300-700 by 50V increments), and VF field measured with and without a full TF field.

Thursday August 18 2011 6:01 pm Hughes/Levesque 70233-70238 Flux Loop Calibration

We took vacuum shots with full regular settings for VF only, OH only, OH+VF only, and all banks. Also took vacuum shots emulating the bank settings of recent plasma shot 70232 for comparison. * NOTE: we examined reproducibility of VF current, and found VF current is lower for same settings on shots with TF. We suspect this may be due to the VF charge degrading while the TF charges up.

Friday August 19 2011 6:07 pm debono/levesque 70211-70232 bias probe

Bias probe was run with the following settings:
1. Probe biased to (-8,+22,+45V) from 1.5-4.5msec, with static (-3,1) RMP's from 2-3 msec.
+45V reduced the mode rotation velocity of the modes from 6-9kHz to 2-3kHz. Half of the +45V biased shots disrupted after the RMP pulse terminated.
The -8,+22V shots did not disrupt after the RMP.

Friday August 19 2011 6:58 pm Levesque 70239-70266 Top shells retracted

Made plasmas with all top shells retracted 4cm in to try to observe changes in poloidal mode structure. Four shots were done with half of the top shells retracted (sections 1-5). Bottom shells were fully inserted for all discharges. Shots with retracted shells broke down ~5mm further out radially for the same bank settings, assuming the major radius calibration is still valid for the different shell configurations.

Several shots appear to have multimode activity. Mode activity seemed qualitatively similar to modes with fully inserted shells. These have not yet been quantitatively compared to previous shots. Further analysis will be done next week.

Thursday August 25 2011 5:58 pm Byrne 17269-17313 Hall Probe Troubleshooting

Shots 17269-17271 showed very little agreement with expected behavior based on previous rundays. Probe 1 has begun behaving like probe 7, that is, no current is drawn, but signal is output as would be expected.

Furthermore signal levels were down significantly from previous runs with the exact same bank settings/probe position.

Decision was made to once and for all attempt to characterize Hall Probe system's behavior and understand its various pathologies.

Shots from 17272-17313 have been crates only shots, piggy backed on B. Debono's run. Sig gens input sinewaves into the amplifiers, removing probes from the equation for now. Variables controlled for were signal inputs (sinewave, open, shorted) amp circuit (there are two, each servicing 10 probes) pickup to magnetics, and amp gain.

Circuit/Circuit pickup varies from amp to amp, and in some cases can be significant ~6% of signal, however this is only a problem if the amp inputs are left open. Shorted, or with signal, pickup is reduced to roughly the level of the backgroud noise (but still identifiable)

Gain seems to work as expected, which contradicts earlier work whereby signal levels were only slightly changed (not the factors of 10 in the amp spec) and certain probe channels which did/did not function based on gain setting appeared insensitive to the setting this time.

Noise on all amps seems small ~10mV, except for probe channel 12, which outputs slightly more than .5V. Large level signals of 2 V or greater are readable, and filtering may help. Short of replacement I do not know how to repair this amp channel.

Today's work suggests the majority of the problems associated with the hall probe are localised in the probes themselves, or maybe in the cables used to carry the probe power/signal to the amps. This will be looked into tomorrow. And of course the work will have to be checked tomorrow, due to day-to-day variability of probe behavior.

Friday August 26 2011 9:54 am debono 70272-70314 bias probe

Beginning of RMP amplitude scan done today.

Bias probe set @45V from 1.5-4.5 ms, (-3,1) RMP from 2-3 ms with phase flip @ 2.5 ms.

Shots taken @ RMP currents of 1.3, 13.3, 26.6 Amperes. The 1.3 A shots did not disrupt, the 13.3A shots disrupted after the RMP (~3ms) while the 26.6A shots disrupted during the phase flip (~2.5ms).

More shots to be taken tomorrow.

Friday August 26 2011 6:23 pm DeBono 70272-70363 Bias Probe

CC current scan continued today. (-3,1) RMP's were applied to bias probe slowed plasmas from 2-3 ms, with the phase flip at 2.5ms. Shots were taken with the CC current @ currents ranging from 1.33A to 33.3A. The highest CC currents tended to disrupt the plasma during the phase flip@2ms: intermediate currents tended to disrupt the plasma AFTER the RMP @3ms, while currents ~<10A did not disrupt the plasma.

Tuesday September 6 2011 8:12 pm Byrne 70376-70387 Crates Only Hall Probe Troubleshoot

Probe cabling has been refurbished, south rack has input bulkhead installed, signals are properly shielded, Hall/Triple/Dalpha probe breakoutboard is installed. Two broken traces have been repaired, which correspond to non-functioning probe channels. It is expected that no more physical work is necessary for the operation of the Hall Probe

Zero-level signals of the probes have been looked at with crates only shots. Three probe channels display problems.

Probe on channel 7 (numbers are in order from closest to furthest from Plasma Center) displays a .6V offset. Noise on signal no worse than average (4-6 mV), should be easily averaged out by presampling with existing code. Offset has been localized to the probe by checking D-sub output directly with a voltmeter. Amp works fine

Amp on channel 12 displays noise of roughly 100 mV amplitude. Depending on signal levels, this may be problematic.

-Both of these problems are well known from previous work.

Amp on channel 17 seems broken. With gain set at 10X *or* 1X, probe will saturate at -10V output with probe zero-level input (1-3 mV). Probe displays zero-level signal no higher than average when checked with Voltmeter. At 10X gain, probe output shows 1kHz fluctuation with amplitude equal to noise, which is ~3-4X (20mV) average. When shorted, amp outputs zero signal regardless of gain, and noise is reduced to average. Currently unsure how to address this, short of replacement.

A runplan involving calibration-style VF and/or TF vacuum shots is forthcoming to double check that the remaining probes work as previously, and that the repaired probes have been fully brought back into operation.

Thursday September 8 2011 10:27 am Byrne 70388-70402 Hall testing

So it's all in the run report, but basically, I didn't realize the legs of the chips were so delicate, and broke them on Amp chip 14 before I realized what I was doing. This was a channel that had been working fine.

Moving on from there, and keeping myself only to the "busted" chips, I found that:

The noise on chip 12 seems to be due to the circuit, not the chip. With Chip 17 in place, the same noise level is output, and 12 doesn't put out that noise when put in 14's place.

The sensitivity of 17 seems to be *partly* due to the circuit. When 12 is placed in its socket, the DC offset goes to -5V from -10V but that is still WAY higher than any signal I've seen from a magnetic measurement. Oh and also, when 17 and 12 were switched, the noise frequencies of ALL probes, good and bad dropped by ~8X from 40k to 5k. So I guess the circuits aren't independent either?

Does this mean any changes to one circuit, like say, replacing chip 14 means that all the other chips need to be recalibrated as well?

Ideas: I was only working with the busted chips, *maybe* a good chip placed in either 12 or 17 won't behave badly. But I'd rather have someone who knows what they're doing around electronics i.e. you do the switching. Also 17 has a resistor across the terminals, and 12 does not. Maybe the resistor is why swapping them changed the frequency. Although why all channels had the same frequency before they were switched, and then all had a different frequency after, rather than varying board to board, I don't know.

Thursday September 8 2011 3:44 pm Byrne 70403-70410 Hall Probe repair

Amplifier chips had a high frequency noise filter cap attached across two leads. On Chip 12, the one outputting large noise levels, this had come loose. This is not the best method of attachment, and it is possible if not likely it will happen again. A note will be added to the wiki, as this cap is not called out in the circuit diagram and is not visible unless the amp box is disassembled.

Probe 17 had an power input wire broken, but still in physical contact with the dsub pin. Why this would have led to the behavior noticed, which was a steadily declining output voltage, (which may reset itself after a certain point, certain measurements suggest it but inconclusively) is unclear. However, stripping the wire and soldering it properly has removed the behavior.

All probes seem to have been returned, or returned themselves, to operation. Nevertheless they have not actually been used to measure a magnetic field since the repairs.

While it should be fine to use for J. Levesque's upcoming run, 4 of 20 channels were inoperative at the time of the last calibration. Furthermore, while it is likely just due to the delicate nature of the probe, there has been significant run-to-run and shot-to-shot variation observed, as well as strange noise detected when the (nominally constant) transverse TF field was present.

Therefore a separate runplan is forthcoming, in order to fully recalibrate the probe, observe, understand and if possible, repair any time-dependent behavior and allow time for any on the spot repairs.

Friday September 9 2011 7:20 pm Levesque 70411-70439 Toroidal shell asymmetry

Ran with top and bottom shells in sections 2, 3, and 4 retracted 3.9cm from their fully inserted positions. The intention was to break the toroidal shell symmetry to attempt to observe changes in the natural toroidal mode structure. No obvious mode structure differences have been seen yet when comparing to shots with shells fully inserted, but analysis is very preliminary.

Also, Hall probe data were taken with the innermost shield tip at 107cm. This puts the innermost sensor ~1.3cm outside of the limited plasma edge. Fluctuations in Hall probe data correlate with fluctuations seen in the other magnetic diagnostics. Clean-up shots were required at the beginning of the run day, presumably due to the introduction of the Hall probe shield into the scrape-off layer.

Control coil amps were powered on while the FPGA (amp input) was off, which should allow the large control coils to be treated as flux loops when looking at the measured CC currents for all shots from today.

Some interesting shots are:

70420: High frequency counter-rotating mode activity appears around the time that the plasma becomes high-field-side limited (~3.5-3.6ms). This is seen most clearly in the HFS sensors. I have seen this for several shots in the past, but have not cataloged it. The fast mode rotation has been both co- and counter- to the usual mode rotation.

Other interesting shots: 70425, 70428, 70430, and 70433/4.

Monday September 12 2011 7:20 pm Levesque 70440-70472 Toroidal shell asymmetry

Ran with top and bottom shells in sections 2, 3, and 4 retracted 3.9cm from their fully inserted positions. Took 7 shots with shells in sections 1-5 retracted. Tried to reproduce the discharge evolution from shot 69142 in order to directly compare mode activity, but changes to the radial equilibrium with retracted shells made this difficult. Was able to roughly match desired major radius, plasma current, and edge-q evolution for the first ~3.5ms in the retracted-shell shots after changing the VF bank timing by 40-60us.

Hall probe and control coil "flux loop" data were also taken in the same manner as on 9/9/11.

Noteworthy shots:

70449: Large drop in D_alpha light during 2.3-2.5ms. Subsequent spikes in D_alpha are seen during 3-3.2ms, though there are no apparent minor dusruptions (which is when we typically see similar D_alpha spikes).

Other interesting shots: 70447, 70464, and 70468.

Tuesday September 13 2011 5:02 pm Byrne 70473-70484 Hall Probe Calibration

Problems were discovered with the angle finder. There are a few degrees of slop which make repeatable measurements of the angle difficult. This was not discovered as the cause of measurement problems until the end of the run day.

The issue is being corrected by affixing the anglefinder to the probe shaft with two drops of epoxy. This will allow the anglefinder to rotate rigidly with the probe, yet still be removed in the event that proves necessary in the future.

One issue that is not explained by the slop issue:

The point of the angular measurement was to aim the probe further away from the toroidal direction while measuring the toroidal field, in order to pinpoint the angle at which the signal had a zero cross and became negative.

This occurred at different angles for different probes. Despite not being able to say with certainty at what angle the probes are directed, it is certain that the probes are aimed in different directions. Without repeatable measurements, it is difficult to say for sure, but it seems to be of the order of 5 degrees of misalignment.

This will be addressed by redoing the angular measurements once they have been made repeatable, applying a linear fit to the data, and then attempting to find a "best poloidal" by least squares fitting the 20 zero cross angles.

Probe sensitivity and transverse field signal attenuation tests were not done because it is unclear how strongly they are affected by angular uncertainty, as well as time constraints.

Tuesday September 20 2011 3:54 pm Byrne 70492-70518 Hall Probe Calibration

The runplan ran as planned.

The hall probe was subjected to a more rigorous angular calibration, but the suggested change to the nominal poloidal angle was only .03 degrees.

Probe sensitivities were gathered, and in all cases agree well with the results of the previous calibration, in 2007. In addition, two previously inoperative probes are now working, meaning the entire 20 element array is in proper working order. Results will be posted on the wiki this evening

VF/TF tests were run, and the probe seems to be behaving very similarly to the previous calibration, based on eyeball analysis of the plots. More mathematical analysis will be performed, and will be available at tomorrow's meeting.

It is expected that the repair and calibration work on the hall probe is now finished, and that once the analysis and code updates have been made, the data can be entered directly into the tree for use in others' code. Until then, code used in the diagnosis and calibration of the hall probe are being commented and uploaded to the wiki for use. Ask me if you have any questions about their operation.


Tuesday September 27 2011 2:43 pm debono 70519-70529 Bias Probe

The bias probe is connected to the cap bank and is performing normally. However, a BiRa CAMAC power supply in the north rack failed after a couple shots and ended the runday. The affected modules have since been swapped into the (previously) unused north rack crate. DeBono

Friday September 30 2011 6:42 pm DeBono 70597-70625 Cleanup Shots

Cleanup shots done today. Plasmas got longer as runday went on, but base pressure pumps down slowly. Starting base pressure before runday was ~5.6e-9.

Wednesday October 5 2011 6:59 pm DeBono 70664-70735 Bias Probe

(-3,1) phase flips were applied to rapidly rotating biased plasmas. The plasma response appears to show saturated and linear regimes with an amplitude less than that of naturally rotating or slowed modes. DeBono

Thursday October 6 2011 6:16 pm shiraki 70736-70794 RMP timing scan

Plasmas similar to shot 70000 was chosen as a model discharge for the RMP timing experiment. This resulted in minor disruptions early in the discharge (~0.5ms in) which affected reproducibility. The plasmas used instead (see 70781 for example) had a higher initial q and did not cross q=3 until about 3ms (rather than 2ms, in the case of shot 70000). Phase-flips were applied to these shots starting with 3ms up to 5ms, in 0.5ms increments. Only 6 shots were taken in this scan, and there is no discernable trend in the RFA outside the spread of the measurements. Some effort will be made tomorrow to achieve plasmas closer to the target discharge, where the edge q stays constant at ~2.6 for over 2.5ms.

Friday October 7 2011 4:59 pm shiraki 70795-70825

More attempts were made to recreate the desired target plasma for the RMP timing experiments. Bank settings and puff times were adjusted, but reproducibility remains a problem. No RMP's were applied and the Hall probe was not inserted today.

Monday October 10 2011 7:23 pm shiraki/levesque 70826-70882 cleanup shots

The focus of today's run was to clean up the system by creating outboarded limited plasmas to clean the limiting surfaces. This was interspersed with attempts to create the target discharge for the RMP timing experiment. Reproducibility of these plasmas appears to have improved over the course of the day. If this can be confirmed again in the morning then the RFA experiments could be started again.

The runday was ended when the OH electrolytic bank began to have problems fully discharging. Peak currents dropped from about 20kA to 19kA for the same bank settings, with a subsequent shot (without charging) resulting in about 1kA being discharged. This issue will need to be resolved before tomorrow's shots.

Tuesday October 11 2011 6:35 pm shiraki 70883-70931

The issue with the OH bank was not fully resolved, and partially persisted throughout today's run. However, with appropriate adjustments in bank settings this did not seem to affect plasma performance.

Plasma reproducibility has improved since the clean-up shots, and the RMP timing scan was begun. The number of shots is still small, but initial results suggest that the plasma response may be larger earlier in the shot rather than later. This may simply be due to the time-evolution of the safety factor, as the earlier RMP's occur closer to the q=3 crossing which occurs about 1ms after breakdown. The scan will be continued tomorrow.

Wednesday October 12 2011 4:44 pm shiraki 70932-70965

We continued to adjust the timing of the 3/1 phase-flip and measured the plasma response as a function of the timing. Applied RMP's had an amplitude of 10A for all shots, with 500usec in one phase and 500usec flipped. The beginning of the RMP was varied from 2ms to 4ms in 0.25ms increments. The results now seem to indicate that any changes in the measured response are due to the time evolution of q, rather than increased beta over time.

Wednesday October 19 2011 7:40 pm debono/levesque 71010-71070 bias probe

The bias probe was biased to ~-170V,-12A (the target voltage was -300V, loading reduces this to -170V). The mode is torqued in the direction of natural rotation, from ~8-9kHz to ~13-14kHz.A (0<2.5)amplitude scan was done for(-3,1) RMP's applied from 2-3ms, with the phase flip at 2.5ms. Extra measurements were taken at A=0, 0.5 to observe consistency of measured n=1 plasma response phase. DeBono

Friday October 21 2011 9:50 am Debono 71071-71114 Bias Probe

We started a rotation scan for the (-3,1) standard phase flip. RMP amplitude was set @10A. The bias probe was used to accelerate the modes to (+4-5, 14-15) khZ by applying (+13.5,-11.5)A of current from the bias probe. These are the maximum currents the probe can output (in either direction) given its current configuration.

Friday October 21 2011 9:52 am Byrne 71073 and 71114 Hall Probe

2 shots taken: 71073 and 71114

Conditions were: inner hall probe at 103 cm, TF bank at 750V.

70103 was the first shot of the day at 11:50, the Hall probe had just been turned on, and was at as close to room temp as was feasible.

71114 was the last shot of the day at 6:21, and the Hall probe had been left on the entire time.

Good news: The hall probe's temperature closed 92% of the distance between initial and steady state within 19 minutes. All calibrations were done long after a longer delay between turn-on and turn-off.

The signal dropped as expected, though the data has not been analyzed yet. The probe's De-calibration was not affected from morning to evening, however. All shots seemed to be reduced by the same percentage, but the over all shape of the plot (perfect calibration would be a straight line) was not affected.

The thermal issues can be helped by bleeding in coolant gas, or made irrelevant by allowing the probe to arrive at its steady state temperature (About 35C, or 6.5 kOhm as measured across the thermistor) before attempting to take measurements with the probe.

The de-calibration over time issue remains unclosed, however

Sunday October 23 2011 4:58 pm Levesque/DeBono 71115-71155 TF issues

The following summary pertains to the machine problems and resolutions that occurred during Friday's run. Physics goals and results of the run will appear in a separate run summary by Bryan.


While high-potting, Jim and I found a small continuous arc below chamber section 10 between a TF magnet foot and a bolt in the G10 spacer that the TF magnet stands on. We discussed the arc details with Nick and followed his recommendation for correcting it. The bolt in question has no direct connection to ground -- the arc seems to have been a capacitive effect similar to when the I-beams around the base pad were arcing to the upright support columns a few months ago. There was no apparent immediate danger to the machine, but the problem was resolved with mylar to be cautious. This was done by lifting the magnet slightly to take the weight off the outer foot, and inserting a small mylar sheet in the arc region. The TF magnet shifted slightly while inserting the insulation, but the change should be negligible. A subsequent high-pot test did not show any problems. For the first shot of the day (full vacuum shot), I watched the magnet and arc location to make sure there was no arcing or movement of the magnet. Everything appeared as usual.

In a separate occurence, a very loud noise came from the basement during shot 71121. Bryan, Nick, Jim, and I checked the basement for what caused the sound. Nick found problems with 2 of the TF dump relays. They had clearly arced, and were now stuck in the open position. This was the only abnormality we were able to find. Nick's best guess is that the arc occurred by tracking along insulating components of the relay to its ground. The damage appeared to be only superficial. Nick and Bryan cleaned the 2 relays and surrounding plywood. Nick also added vacuum grease to the those and other TF dump relays to inhibit surface tracking, and gave the okay to continue the run after lunch. We started back up with a half-power vacuum shot, then a full vacuum shot. Bank current traces appeared normal, and we continued the run.

Monday October 24 2011 3:47 pm DeBono 71115-71155 Bias Probe

Machine Report (written by J.P.L); While high-potting, a small continuous arc was seen at chamber section 10 between a TF magnet foot and a bolt in the G10 spacer that the TF magnet stands on. The bolt in question has no direct connection to ground -- the arc seems to have been a capacitive effect similar to when the I-beams around the base pad were arcing to the upright support columns a few months ago. There was no apparent immediate danger to the machine, but the problem was resolved with mylar to be cautious. This was done by lifting the magnet slightly to take the weight off the outer foot, and inserting a small mylar sheet in the arc region. The TF magnet shifted slightly while inserting the insulation, but the change should be negligible.

Shot 71121 was interrupted with arcs in two of the TF bank dump relays. The damage appeared to be only superficial, so the relays were cleaned and reinstalled. Vacuum grease was added to several components of the TF dump relays to inhibit surface tracking. The cause of the arcs was unknown.

Physics Report (written by B.A.D): Rotation scan done with 10amp standard (-3,1) RMP phase flips. Shots were taken with naturally rotating modes, and with modes accelerated in the direction opposite to natural rotation. To achieve the latter, the 1:1 Hammond transformer was reconnected to the bias probe circuit to achieve greater Ibias than was possible with the 4:1 LANL transformer.

Monday October 24 2011 9:44 pm shiraki 71156-71207 Hall probe internal measuremetns

Another arc was found between a TF magnet foot and a bolt in the G10 ring in the basepad. The problem was resolved in an identical manner as last Friday, with the insertion of a mylar sheet between the two conductors, and the run continued as normal.

The Hall probe was recalibrated at the beginning of the day, after powering the electronics for about half an hour to allow thermal equilibrium. This calibration was rechecked periodically through the day, and several channels were found to have drifted by a few percent. It is currently unclear how to compensate for this drift in future runs.

The probe was inserted until the back of the Boron Nitride cap was at the back of the shell, which puts the first channel at 105.5cm, with four channels inside the plasma. At this position, the magnitude of the first two channels are seen to drop relative to the trend of the channels sitting in vacuum. It is hard to quantify this reduction (particularly with the drifting signals), but it is clearly noticeable and repeatable.

Finally, vacuum pickup measurements were taken between the Hall probe and the control coils. With the previously used m/n=-3/1 phase-flips, maximum pickup was about 0.5G/A. However, by choosing an appropriate toroidal phase, the null of the external field can be placed at the location of the Hall probe, reducing pickup on all channels to below .01G/A, which is below noise levels for coil currents as high as 30A.

Tuesday October 25 2011 7:07 pm shiraki/maurer 71208-71259

There was an accident today with the TF bank, although there was no major damage to the machine. The accident was likely caused when the dump relays were reset while the banks were charged. Rather than a full dump which keeps the relays closed, the reset would momentarily close then reopen the relays while the bank was still discharging. Much of the wiring in the dump circuit was damaged, but only one relay was destroyed. This has been replaced with a spare, along with all of the damaged wiring except for the box controlling the power for the relays. As soon as this is repaired, we can begin to test the banks.

Prior to the accident, internal poloidal field measurements were taken with the Hall probe at full insertion, while applying static phase-flips. This was preceded with another calibration of the probe at the beginning of the day. Applied coil currents ranged from 0-30A, which is high enough to induce disruptions.

it was observed today that during the applied RMP, there is an increase in the D-alpha light seen by the spectrometer. This increase over background levels is only observed for coil currents above ~15A, which corresponds to where we begin to see a saturation in the plasma response. At about 25A of coil current, the light is increased by about 50% over the non-RMP shots. This will be studied more closely once the machine is back running.

In addition, the Mach probe was inserted 3cm into the plasma and testing of the probe was continued. I_sat signals appear to now be working, with typical signals of ~100mA.

Wednesday October 26 2011 4:24 pm shiraki 71262-71268 TF bank testq

The TF bank was repaired and tested today. The bank is working fine and two plasma shots were taken. Experiments can resume again tomorrow.

Thursday October 27 2011 9:32 pm Levesque/Shiraki/Maurer 71269-71313 RMP q-scan with Hall & mach probes inserted

Applied m/n=-3/1 phase flips to plasmas with the innermost Hall probe sensor at R0=105.5cm. A q-scan was done with an RMP amplitude of ~20A. Average q_* during RMPs was between 2.75 and 3.05, which is in the saturation regime observed in our previous RMP studies. More shots with lower q values will likely be done in the continuation of the run. Increases in D_alpha light were seen during the RMP periods.

Cleanup and development shots were necessary at the start of the run day. The Hall probe was calibrated at the beginning of the run. The mach/V_float probe was inserted at 104cm. Several shots were taken with the D_alpha-array covered in order to measure non-light pickup.

The TF charge panel has had a minor problem since it was repaired yesterday: The "full charge" indicator remains stuck on after each shot, though the bank fully fires. The resolution is to cycle the power to the TF/VF panel prior to each shot. This does not seem to influence the run, but should be repaired when we have a chance.

Friday October 28 2011 5:43 pm shiraki 71314

There was another arc with the TF bank today, although again there was no damage to the machine. This time the arc occurred when the computer failed to fire the banks, which then timed-out and tried to auto-dump. Six of the dump relays were damaged, and all of these will be replaced with spare 25kV relays from the old LANL system. Several sections of the mylar insulation were also damaged and are being repaired. In addition, the wiring will be reverted to the original configuration with the relays on the low-voltage side of the water resistor, while properly insulating the base of the resistors to prevent tracking along the plywood base.

A J221 in the basement rack was found to be broken later in the day, although it is not known whether this was the cause of the banks failing to fire, or if it is a consequence of the accident. The repairs to the bank will continue on Monday.

Wednesday November 2 2011 12:42 am Levesque 71315-71318 Testing banks

Low power vacuum shots to test bank triggering and currents. All systems appear normal, though a full-power TF shot has not yet been done. The root cause of the banks failing to trigger on 10/28/11 is still unknown. Standard plasma shots will commence Wednesday morning.

All TF bank dump relays have been replaced with clean spares from the old radial positioning system, which have a 25kV rating (instead of the previous TF dump relay ratings of 12.5kV). Dump relays were moved to the low voltage side of the water resistors, which should reduce current in the event of future arcing. The dump resistors have also been raised on PVC pedestals to reduce the possibility of tracking. The TF charge panel issue mentioned in the 10/27 run report has also been fixed.

Wednesday November 2 2011 7:08 pm Levesque/shiraki 71319-71360 Clean up shots

Attempted to continue RMP q-scan with lower edge q values and the Hall probe inserted. Most of the run day was spent doing cleanup shots and trying to achieve the target discharge. Reasonable discharges were reached at the end of the day. Three shots had applied RMPs, but these did not have edge-q's as low as desired. The run will continue Thursday morning.

Thursday November 3 2011 7:06 pm shiraki/levesque 71361-71416 Internal hall probe measurements

More data was taken for the q-scan with internal Bp measurements using the Hall probe. Bank settings were adjusted over the runday to produce plasmas with lower edge q's during the time of the phase-flip. Analysis of Hall probe data from this run is ongoing.

Wednesday November 30 2011 10:34 pm byrne/shiraki 71417-71489 RMP phase scan

The plasmas at the beginning of the day were erratic and reproducibility was poor. The majority of the day was spent running outboard limited clean-up shots. However by the end of the day vacuum conditions were back to normal, and some useful shots were taken. m/n=-3/1 phase-flips with various toroidal phases were applied, all at an amplitude of 15A. There were a total of five such shots that were close enough to the target plasmas, and within these shots, the kink locking-phase tracks one-to-one with the RMP phase. The amplitude of the plasma response had more variation, but is probably within the expected scatter based on previous experiments.

Friday December 2 2011 6:14 pm Levesque/Stoafer/Peng 71490-71536 Hard x-ray noise tests, Phase-flips with fewer CCs

Ran vacuum shots to test for noise and pickup in the hard x-ray system due to the banks. Tests were done with and without a radioactive source near the detector. Analysis is pending.

Phase-flips were done on plasma shots with control coils active in only sections 4 and 5. All large coils were used in the 2 sections, totaling 8 coils versus the normal 40. The applied field had a toroidally localized m=-3 structure. Coil currents were ~22amps peak. A 3/1 global response is seen for most shots. Multiple-shot averaging made the global response very clear. An exemplary is 71530.

Five usable shots were also taken with control coils on in section 4 only. The response is less clear, but may be measurable.

Monday December 5 2011 4:26 pm shiraki 71537-71560 Longer phase-flip RMP's

Some shots were taken with RMP's lasting up to 1ms in each phase. This is in contrast to the 500us in each phase which has been used up to now. Only a few shots were taken, so the experiments will continue tomorrow.

Tuesday December 6 2011 5:15 pm shiraki 71561-71567

Today's run was interrupted early when Facilities arrived to repair the air-conditioning in the experimental hall. The run will resume tomorrow if the A/C repair is completed.

Wednesday December 7 2011 6:22 pm shiraki 71570-71603

Phase-flips lasting 1ms in each phase were applied today at several amplitudes. Several (but not all) shots with 20A in the control coils disrupted towards the end of the phase-flip. This is in contrast to the ~30A which was necessary to induce disruptions when the RMP lasted 0.5ms in each phase.

It is also observed that in many cases, the plasma response tends to be larger in the second half of the phase-flip. This can be seen in shot 71584, for example. It is also common to see a "phase-flip like response" (meaning an n=1 response which reverses phase along with the coil current) with a large rotating mode on top of this. Shot 71591 is a good example of this.

Tuesday December 13 2011 8:20 pm debono/shiraki 71648-71711 Low amplitude phase-flips

Low amplitude (Ic<5A) static phsae-flips were applied today. Analysis of today's and previous shots suggest the possibility of a locked 3/1 mode and a rotating 3/1 mode simultaneously existing. As the perturbation amplitude is increased, the amplitude of the locked mode increases as well.

A few shots were taken at the end of the run with the bias probe inserted and powered with the Crown amp with the 1:1 Hammond transformer. No clean-up was necessary and vacuum conditions remained good. Application of small amplitude phase-flips to these biased plasmas will continue on Thursday.

Thursday December 15 2011 7:56 pm shiraki/debono 71712-71760 low-amp RMP on rotating modes

The bias probe was used at a low positive voltage (+22V) to slow modes down to 5khz (vs naturally rotating 8-9khz), and then (-3,1) 3amp RMP phase flips were applied. Most shots taken today had weak mode amplitudes; however mode locking was observed during the RMP for some shots. Star shots: 71755, 71757, 71758.

Friday December 16 2011 5:42 pm debono/shiraki 71761-71790 bias probe

Continuation of yesterdays experiments to apply Low-amplitude RMP's to bias probe slowed modes. Today A=0.1 and A=0.2 RMP's were applied to slowed plasmas rotating at ~5kHz from 8-9 kHz. Bias Probe set to +22V. Mode locking was not observed in todays best shots (shots that best matched the q,major r profiles of reference shot #70000). Star shots 71766,71744,71784.

Monday December 19 2011 5:40 pm Levesque/Peng 71790-71812 Puff line problems

Attempted to run Qian's experiment with uniform control coil currents for all large coils on 2 neighboring shells, but the run was hindered by problems getting reproducible breakdowns. It looks like there is a problem with some part of the gas puff system. The OH-bias-phase reversed plasma current was inconsistent shot to shot, and was absent for several shots. This suggests that the valve was not puffing in enough gas, or is puffing at the wrong time. The gas bottle pressure, manual valves, and puff valve battery appear fine. Puffs with closed pumping gate valves and no banks showed reproducible static fill pressure at 3.3e-5 torr. The problem will be troubleshot more tomorrow if it persists.

Tuesday December 20 2011 7:18 pm Byrne 71813-71846 Hall Probe Re-commisioning

Shaping experiments were not undertaken today, due to the postponement of the hall probe recommisioning yesterday, and unexpected problems with the hall probe.

While trimming th potentiometers, two of the hall probe chains (there are now 4 chains of 5, rather than 20 individual probes drawing current) had fluctuating currents, from 1-7 mA. This represents the entire range of currents allowable in this configuration, but the potentiometers were barely touched. This was not seen when the probe was tested yesterday. The hall probe was disassembled and inspected, and intermittent losses of continuity were discovered on some probe chips, but the actual location of the loose wires were never found. The probe eventually fixed itself, and has been running well all day.

The run began in the afternoon, and time was lost trying to troubleshoot channels that seemed to be malfunctioning. Two channels turned out to have their gains set incorrectly, while two others, which also output signals much larger than expected, simply fixed themselves. Again, the problem did not recur, and the cause was not discovered.

The full range of calibration tests were performed, and the hall probe does seem to be in good working order.

However, the air pump which was installed to force air and facilitate cooling does not seem to be very useful. The throughput is rather small and the line to the probes is extensive and narrow. There is likely a large pressure drop from the pump to the probes.

The measured thermistor resistance of 6.7 kOhm corresponds to a temperature of ~35° C. 10kOhm represents a 25° C room temp. At the end of the day, the pump was turned off and the resistance was found to drop to 6.29 kOhm. This suggests the pump is cooling the probes by 1 degree C. The pump MAY be useful in holding the temperature constant, and preventing fluctuations, but that will have to be tested over the course of a run day.

Thursday December 22 2011 6:00 pm Byrne/Peng/Shiraki/Angelini 71847-71890 axisymmetric shaping/non-axisymmetric perturbations

The first few shots of the day failed to breakdown, which was resolved by replacing the e-gun biasing battery. The old battery had dropped to 200V, and the new battery measured ~225V. There were no problems with the puff or breakdown for the rest of the day.

Local perturbation shots with no poloidal structure were taken. Unlike the previous partial coverage experiments with m=3 structure, no obvious plasma response was seen. Control coil currents were increased to 40A with still no response.

Shaping experiments were run from shots 71886 to 71890

Due to time constraints, shots were only taken with coils firing at high amplitudes (±35A) shots 886, 887, and 890 were "triangular" shots, while 888 and 889 were "square" shots

In both cases, very coherent, non-resonant modes were created which the plasma survived for its usual lifetime. Triangular shaping seems to draw the plasma's Major radius outwards, while square shaping pushes it inwards. It is yet to be determined if this is plasma coupling or simply the control coils coupling to the MR rogowski. Small effects were also noticed in edge q, but it's still too soon to say if it's an important effect (or a real one).

The modes seen in the triangular shots had a primarily 3/1 component, but the outboard midplane "lobe" was much larger than usual. There was also a coherent n=2 mode, but the m number was harder to distinguish. The square modes were similar, with an 3/1, 5/2 and an n = 3 mode with an unclear m number. The shape of the primary m = 1 mode was similar to that of the triangular mode, but with a phase shift of 180 degrees though the outboard midplane node was much less exaggerated. In both cases the primary modes seen clearly resemble those modeled with Tokamak.

Square shaped plasmas had a longer lifespan than triangular shaped plasmas (comparison to unshaped has not been done yet) Both shaped plasmas had an impurity spike event during their early evolution (~1.8ms) which may have had an effect.


Tuesday January 24 2012 9:34 am Niko 71915-71958 Feedback

First shot did not break down. E-gun bias voltage was 220 V at battery and 200 V on machine. Raising e-gun current from 6.2 A to ~7 A fixed the problem.

Initial plasma shots were short lived and several cleanup shots necessary.

First feedback experiments resulted in unexpected behavior of the control outputs. The problem turned out to be that the data buffers send by the ACQ196 are not ordered by channel number but in some (more or less) random permutation.

With the permutation taken into account, effects of turning on feedback were clearly visible in the mode structure. Modes with active feedback had rotation frequencies down to 0.5 kHz. However, no relationship between mode activity and feedback phase could be observed yet. Reproducibility of plasmas was low.

The feedback system occasionally failed to trigger, or deadlocked while running. Debugging of the problem is not possible with the current hardware configuration and would require to either disable one of the ACQ196s or waiting for D-TACQ to deliver the RTM-T support

The run had to be interrupted once for about an hour due to network problems.

Tuesday January 24 2012 5:44 pm Niko/Daisuke 71960-72011 Feedback

Plasma reproducibility was better today, about 3 out 4 plasmas were usable. A feedback phase scan in 45 degree steps was completed, and a finer scan with 36 degree steps started. Phases around zero resulted in much larger amplitudes and rotation frequencies around 1 kHz. Phases around 100-200 degrees resulted in smaller amplitudes and rotation frequencies of 5 - 8 kHz. The transition, however, seems discontinuous and there is not enough data to tell if the differences are significant or within experimental error.

The digitizer deadlocked two times, so this problem does not appear to be too frequent.

The feedback system did not finish control computations in the available cycles times for roughly 12 samples in every shot.

The run was stopped because plasmas did not break down any longer. The e-gun bias voltage has dropped from 220 V yesterday to 200 V today, which is the most likely reason for the problem. There are no more spares, and this type of battery is not manufactured anymore.

Wednesday February 1 2012 4:50 pm Shiraki/Angelini 72012-72032 Cleanup / D-Alpha

The shots for today were primarily to test the new e-gun and run cleanups. The e-gun worked without any difficulty.

We also had the opportunity to test what the D-Alpha saw. We were able to confirm when a plasma was outboard or inboard limited because of the high emissions at the edge during contact. The lens was covered for a shot to confirm that the measured fluctuations were due to the light and not simply pickup. The light emissions appear to be hollow, but that could simply be due to large emissions from the limiters.

Thursday February 2 2012 6:43 pm Levesque 72012-72032 Feedback

Tested new CPU feedback algorithm which uses fully integrated B_p signals with a smoothed signal subtracted. Gain was set high enough that some control coils reached 30A transiently during feedback. Phasing of the control coil currents tracked the mode phase well, at least for modes at ~5-10kHz. Feedback phase was tested at 4 values separated by 90 degrees. One of the CC current A14s had problems digitizing throughout the run day, making the timebase wrong for 6 of the CC current measurements; presumably these control coils were activated correctly during the shot though.

Lack of plasmas reproducibility hindered the run. Minor disruptions often occurred just after startup and would change the edge q significantly. Non-reproducibility was unrelated to feedback, as shot behavior would diverge before feedback was activated. Shot-to-shot comparison for feedback efficacy at different phase settings might not be possible due to large plasma parameter differences. The time at which edge-q crossed 3 varied by ~1ms among the shots, making it difficult to choose the best time to activate feedback. Within individual shots, feedback did not conclusively enhance or suppress modes while activated -- changes in mode amplitudes were within the standard range of variability.

Friday February 3 2012 7:08 pm Levesque 72070-72098 Feedback

Continued feedback phase angle scan from yesterday. Plasmas were more reproducible than yesterday, but still not enough for good shot-to-shot comparisons. Large -3/1 mode amplification was seen for 2 shots with the feedback phase set such that the measured difference between detected Bp and applied Br was 90 degrees. These 2 shots (72079 and 72080) also had the edge q closest to the target, slightly below 3. For the feedback phase set 180 degrees away from this (72078), no clear suppression was seen. The 180 degree difference in FB phase only changed the angle between detected Bp vs applied Br by 90 degrees, instead of 180.

Monday February 6 2012 7:18 pm Levesque 72099-72140 Feedback with slowed rotation

Applied feedback to shots with the bias probe slowing down mode rotation. Plasmas were fairly reproducible. Modes were non-existent or very low amplitude due to the presence of the bias probe. Feedback did not seem to have much/any effect on the biased shots. Feedback currents peaked at around 10A. Later attempts using a higher gain failed due to a problem with the CPCI outputs; this problem has been resolved and can be avoided in future feedback tests.

Rotating RMPs were also applied to several biased plasmas. With RMP rotation at 2.5kHz, a co-rotating response was seen in the Bp sensors with a phase difference of 90degrees. This was the same phase difference seen in the shots from Friday that had feedback amplification of the mode. This is consistent with a feedback phase instability, where the feedback result was similar to that of the rotating RMP. At RMP rotations of 1.3 and 8kHz, modes did not lock to the perturbation.

The e-gun power supply was found to have a problem in the morning. An indicator light on the power supply was not working, and E-gun bias voltage was measured as ~400V, even though it was set at 250V last week. Nick was able to decrease this voltage to 338V, but it won't go lower. We decided to run with this as is since it's within the design spec of the e-gun. A resistor was also replaced in the power supply.

Tuesday February 7 2012 10:24 pm Levesque/Peng 72141-72183 Feedback phase scan, shot development

Continued feedback phase scan from Friday without the bias probe. Shots were taken at 45-degree increments. Mode frequencies varied shot-to-shot, including natural modes that existed before feedback was applied. During feedback, mode frequencies were 4-10kHz. Results were similar to Friday, with no clear suppression. The closest-matched shots (with programmed FB phase angle) to compare for the 2 run days are: 72078 (90deg), 72080 (270deg), 72146 (0deg), and 72147 (180deg). Shot equilibria had much more scatter for other phase angle settings.

Also worked on shot development at the end of the day to target plasmas that formed with edge q below 3. Delayed VF bank timing by up to 220us to try to get plasma break down with a larger major radius. Breakdown major radius ranged from 92.5cm to 95.0cm. We could not get plasmas with an initial edge q below 3 due to 3/1 tearing modes during and just after the startup.

Wednesday February 15 2012 5:25 pm Hughes/Shiraki 72184-72188 Calibration of The Big Rogowski

Took shots with TBR wrapped around the upper VF coil 1 time, 10 times, and 15 times as noted in shot descriptions. The results are still somewhat puzzling: the VF current curve integrated from the Rogowski signal (accounting for the partial integration of the noise-suppressing RC circuit) is off by what looks like a roughly constant factor of two, but more analysis is needed, and the reason for this is not yet clear. With a little luck, the calibration can be completed with data analysis, and won't require any more run time.

The Big Rogowski is now undergoing an upgrade to improve its insulation for use with the TF magnets. Data from today's shots is recorded in the tree as input 71 from the west rack CPCI; if you use something that references that spot in the tree, it might be worth making note that the above shots are recording something else entirely.

Thursday February 16 2012 7:31 pm Shiraki/Peng/Byrne 72189-72234 Local perturbation + some vacuum test

Get trained on the start up procedure. It takes a long time to get a nice reproducible shot but we finally are able to work on the local perturbation.

The Plasma do give a roughly m=3 response from n=1 local perturbation (only the bottom inboard coils are excited). Control coils are excited when q_edge cross 3. Further analysis is needed.

Another thing is that the background poloidal field fluctuations a bigger when q is around 3. and for all the shots taken, q stays around 3 ( above or blow a little bit). So the response to perturbation is not obviously seen for a single shot, but becomes more clear after average over shots.

A few vacuum shots are also taken in the end.

Monday February 20 2012 6:46 pm Hughes/Levesque 72236-72243 Calibration and Trial of The Big Rogowski

Ran two zero-net-turn calibration shots which are yet to be fully analyzed. Ran several shots with The Big Rogowski around TF #14 (by Jeff's reckoning), starting with only half-normal TF bank charge and working up to a full regular setting vacuum shot with all banks. Next episode: how the B.R. signal compares with the TF Probe!

NB: The Big Rogowski is still on the TF magnet, so watch out for that if you plan to run. Please don't step on the cable in the basement hanging down in front of the basement rack; it really pulls the coil together.

Thursday February 23 2012 9:08 pm shiraki 72247-72291 Long duration phase-flips

Phase-flip RMP's lasting 1ms in each phase were applied to our standard discharges crossing q=3 from above. The FPGA was used to drive the control coils. Vacuum shots show that it takes ~1ms for the eddy currents to decay and for the radial field to soak through the walls.

The most dramatic observation is the occurrence of disruptions at much lower coil currents, usually around 20A but on one occasion as low as 15A. This is in comparison to the approximately 40A of coil current required to induce disruptions when the phase-flips lasted 500us per phase. An example of such a disruption can be seen in shot 72279, which disrupted shortly before the currents were flipped at 3ms.

Applied currents in today's shots were in the range of 7-20A. More shots will be taken tomorrow.

Friday February 24 2012 4:33 pm shiraki 72292-72333 Long duration phase-flips

Yesterday's run was continued to collect more data with long phase-flips (1ms up, 1ms down). Control coil currents were limited to 10A to avoid disrupting the plasmas. Plasmas today were noticeably more reproducible today than they were yesterday.

The bake was turned on at the end of the run day in preparation for next week's shot development.

Monday February 27 2012 11:37 pm Levesque 72334-72353 Cleanup shots

Cleanup shots following the bake. The bake was turned off at 8:40am, and plasma shots started at 4:00pm. The chamber was not fully cool yet, but the base pressure was at 1.1nTorr according to the pressure indicator in the control room (nearly bottomed out) and still falling slowly. Dominant lines on the RGA are deuterium and nitrogen.

Shots started out terrible, presumably due to redistribution of contaminants onto limiting surfaces. Plasmas got longer throughout the run, lasting up to ~4ms. Achieved breakdowns with puff times as low as 100us, while our standard operating puff times have been 1000-1250us recently with the same regulator pressure. D_alpha light in the spectrometer was higher than normal for all shots. Cleanup and shot development will continue tomorrow.

Tuesday February 28 2012 7:24 pm Levesque 72354-72394 Low breakdown q*

Developed discharges where the edge-q starts below 3 then approaches/crosses 3. Was able to do this by delaying the VF bank timing by 100us versus its normal timing, and having higher breakdown current. Successful plasmas finished the "start" phase with 2.5 < q* < 2.7, and 94.0 < R0 < 94.5cm. After settling on a discharge style, between 1/3 and 1/2 of the discharges remained at low q with a smoothly changing major radius and no major disruptions. Shots so far have approached q=3 quickly, or have had q changing slowly but possibly too far below 3. Shot development is still needed to have a better edge-q evolution.

Good shots are: 72374, 72388, 72390, 72392, 72394

Wednesday February 29 2012 9:00 pm Levesque 72396-72434 Low breakdown q*

Continued development of discharges with q* starting below 3. 3/1 and 6/2 modes appear when q* is below 3, thus do not begin as internal modes. More analysis is needed to determine if clear growth rates can be inferred -- the changing major radius complicates interpretation of mode amplitudes. Shot development will continue tomorrow.

Shots that might be good to analyze while q* is rising are: 72398, 72400&1, 72404&5, 72408, 72413, 72415, 72416, 72423, 72433

Thursday March 1 2012 10:57 pm Levesque 72436-72482 Low breakdown q*

Continued discharges that start with q* between 2.5 and 2.8. About half of the plasmas evolve in the style intended, with q* rising toward 3 for 4ms as Ip rises and R0 slowly decreases. The other half of discharges typically fall inward too fast immediately after the startup, and q* rises above 3 within 0.5ms. There are very few shots between these 2 extremes. This bifurcation may be caused by mode activity during startup. The discharges begin with 3/1 activity that usually decays away within 1ms.

In the intended shot style, 3/1 and 6/2 modes grow as q* rises toward 3 later in the discharge. Several shots show clear 3/1 growth that may be fit with a growth rate. The shot set from this week should be extensive enough for a study of natural 3/1 and 6/2 mode activity with q* exclusively below 3. Lots of analysis remains to be done.

Some additional notes from the run:

- cos(theta) rogowski pickup from the VF was recalculated for the delayed VF shots. This had a small but noticeable effect on the calculated major radius and edge q. Future shots with different bank timings may need different compensations for pickup.

- CC amps were on to allow control coils to act as pickup coils for all shots. North rack A14_14 failed to initialize about 20% of the time. I didn't check if its data (6 of the CC currents) were good for any of the shots since the control coils were not energized, but there may be problems if anyone wants to look at that data.

Several good shots are: 72461-3 (steadiest q*), 72464, 72469, 72477

Thursday March 8 2012 5:42 pm debono/shiraki 72483-72524 Bias Probe

The new bias probe 2:1 transformer combo is working well: highest current drawn from probe was ~40amps. More shot development tomorrow is necessary, as we need our plasma parameters to closely match the target shot #70000 from ~1.5-4.5ms for the RMP analysis to be accurate. Although we were able to produce shots that closely matched the target shot from 1.5ms-3.2ms, it proved difficult to obtain shots that closely matched shot #70000 from 1.5-4.5ms.

Friday March 9 2012 6:32 pm debono/shiraki 72525-72552 Bias Probe

Machine report: Although there was no serious damage to the machine, there was a bank failure today. This was most likely due to a water spill in the hallway above the TF bank, which made its way through a metal door in the floor and on to the caps below. The arc occurred while the bank was charging, and the dump relays do not appear to be involved in the accident. Damage is limited to several TF fuses and some mylar insulation. Repairs will begin on Monday.

Physics report: Pre-bank failure, more work was done on the bias probe run from yesterday. Shots proved to be erratic with the probe inserted and activated, limiting the amount of useful data obtained. Star shot #72540.

Thursday March 15 2012 2:44 pm shiraki 72553-72559 Bank test

The TF was tested today, working up in voltage to 6.1kV. A full vacuum shot was taken as well and everything is working normally.

Friday March 16 2012 6:00 pm DeBono 72560-72601 Bias Probe

The new battery-powered egun bias voltage supply has been installed and is working well. More "slowed rotation" bias probe shots taken today. The 2/1 stepdown transformer is working nicely; the bias probe typically drew 33.44 amps during shots today. Plasma's suffered the same irrepeatibility experienced during the run last friday, however a few good shots that matched the standard shot#70000 were taken. Star shots #72598, 72592, 72590.

Monday March 19 2012 7:50 pm Byrne/Shiraki 72602-72646 Control Coil Shaping

Most of the day was spent replicating the model shots (71000 and 70000). Around 3pm, a good equilibrium was arrived at and shots began to be taken.

While running Athena (the eebox computer running the smaller of the two monitors) experienced a glitch. The Ubuntu environment crashed, and the FPGA became frozen and unresponsive. About an hour was lost, but the banks were not charging when it occurred, so no harm was done. Two of the ignitron water outlet cables had been knocked loose, possibly during the repairs last week, and had flooded the area behind the OH power supply to a depth of about 1/8 inch. We shop-vacced up the water and replaced the hoses in the drain channel.

72634-72646 were the shaped shots. Shots 72634 and 35, shots 72641 and 42 are good examples of "negatively" shaped shots, While, 72637 and 38, as well as 72643 and 46 are good examples of "positive" shaping. Due to the fact that it is unknown which direction Br points for a given coil current, I can not say for sure which represents triangularity or squareness.

However, there does seem to be an effect on the plasma edge q and major radius. Depending on the sign of the control coil currents, small jumps in the values in one direction or the other are seen. I have to double check to make sure my code is eliminating pickup from the coils properly, but if that were the case, it's likely we can correlate the jumps to a shaping factor, and from there constrain the direction br points.

The edge q and Mr jumps are the only obvious effect though. Sensor arrays (stripey plots) do not show any obvious changes to mode structure, rotation or strength compared to unshaped shots. It is hoped that the run tomorrow will be able to start shaping sooner, and that more data will be available as a result.

Wednesday March 21 2012 9:25 am byrne/shiraki 72647-72697 Control Coil shaping scan

Was able to return to yesterday's target shot by noon, and many more useable shots were taken as a result. 4 or so shots were taken with each polarity before being switched to ensure that drift in the characteristics of the plasma were adequately controlled for. Additionally, unshaped shots were taken from time to time to compare the shaping currents' effects.

Internal 3-1 modes were strongly apparent as the plasma's edge q fell from ~3.3 to 3. at the crossing, the mode disappeared, and while an external 3-1 established itself some microseconds later in the unshaped shots, the shaped mode spectrum was very "smeary" with no clear mode dominating.

"Positively" shaped shots tended to fall more slowly so that the tearing mode had more time to establish itself. "negatively" shaped shots seemed to kick the plasma out in major radius, and drove q down more quickly, so the internal mode was harder to see. firing the control coils earlier did allow the plasma to be negatively shaped at a higher starting edge q, and the mode behavior did look similar. No B-D analysis has been done yet to determine the actual content of the mode spectra at both these points.

While code has been created to eliminate the pickup in the major radius and IP coils due to the shaping pulses, it is unclear whether it has been correctly integrated into the analysis code, so radial "kickout" can not be said to be a real effect yet, although its magnitude suggests that it is not solely due to pickup effects.

Monday March 26 2012 8:39 pm debono/shiraki 72699-72767 bias probe

RMP phase flips were applied to bias slowed RWM's today. Overall the run day was pretty good: the plasmas tended to disrupt for shots with RMP currents >12A; this is significantly less than that for naturally rotating modes. Shot irrepeatability was still an issue but at least 11 shots were taken that had good agreement with the target shot. Star shot examples: 72734,72764 DeBono

Monday April 2 2012 6:14 pm debono 72769-72809 bias probe

Bias probe run with counter-rotating shots today Maximum bias probe electron saturation voltages/currents are +80V/50-60Amperes in the current setup. Overall the system works well when driven into the electron saturation regime. Unfortunately, well defined contour rotating shots were not seen for our best shots of the day. However, a few shots with q>3 showed defined counter-rotating modes moving at ~-6kHz. Star shots 72789,72804,72806,72805,72807 DeBono

Tuesday April 3 2012 10:55 pm Levesque 72810-78542 Asymmetric walls while approaching q*=3 from below

Began low-edge-q experiments with asymmetric walls. Most low-q shots with walls in the normal fully inserted position were similar to the target shot (72464). After retracting 8 of the top shells 4cm each, achieving the target shot was difficult. Only a couple of shots were similar enough to the target for direct comparison.

Most shots with retracted shells suffered from a strong, quickly rotating 3/1 mode during the startup. This led to minor disruptions which steered shots away from the target discharge. These shots are unusable later in the discharge, but analysis of the startup may be useful. I will continue trying to match the target with the poloidal asymmetry before moving on to the toroidal asymmetry.

Wednesday April 4 2012 8:34 pm Levesque 72855-72905 Low q, poloidal shell asymmetry

Continued poloidal wall asymmetry experiments. The amplifier for the plasma current Rogowski was not working at the beginning of the run day; vacuum and crates-only shots showed a strange oscillating Ip signal. Trouble-shooting showed that the problem was in the AM502 amplifier module itself, not in the rest of the signal path. This problem was circumvented by using the AM502 from the cos(3*theta) Rogowski coil for the plasma current instead. The digitized plasma current should be correct with the replaced module, as long as there are no minor gain differences. However, we're no longer digitizing the cos(3*theta) signal -- we don't have enough working AM502's.

Plasmas were much better than yesterday. Using a longer puff time than yesterday (1000us versus 500us) gave more D_alpha and SXR emission, but did not prevent the strong 3/1 mode from appearing during startup. Shots got better throughout the run. Mode analysis shows presence of 3/1 and 6/2 modes during the target period with q* staying below 3. Tomorrow morning I'll continue with the poloidal asymmetry, then will switch to the toroidal shell asymmetry in the afternoon.

Star shots: 72877, 72881, 72885, 72894 (compare with 72469 with normal shells), 72902, 72905.

Thursday April 5 2012 6:05 pm Levesque 72907-72954 Low q, shell asymmetry

Finished poloidal wall asymmetry experiments. Took more shots with 8 of the top shells retracted, then took a few shots with only 4 adjacent top shells retracted. I will thoroughly analyze the poloidal asymmetry shots next week.

Started toroidally asymmetric shell experiments. Top and Bottom shells in sections 1, 2, 9, and 10 are retracted 4cm. I was able to get close to the target shot by the end of the day. Toroidal asymmetry shots will continue tomorrow.

Star shots: 72913, 72951

Friday April 6 2012 11:57 pm Levesque 72955-73015 Low q, toroidal shell asymmetry

Finished low-q shell asymmetry experiments with top and bottom shells retracted in 4 sections. Most shots had shells in four adjacent sections (sec 9, 10, 1, and 2)retracted, giving an odd toroidal configuration. Also ran several shots with diametrically opposed sections (sec 9, 10, 4, and 5) retracted, giving an even configuration. Equilibrium evolution was slightly different for each of the shell arrangements, which may influence mode behavior. The data set from this week should be extensive enough for comparing mode activity as q* is below and approaching 3 with non-symmetric walls. Next week will be spent analyzing this data set in detail, comparing with shots from March 1st with the standard wall configuration.

3/1 mode activity during startup appeared with all wall arrangements. Characteristics of these startup modes will be compared, in addition to the original intent of studying mode activity that occurs later in the discharge as q* rises toward 3. Qualitatively the modes appear similar in each shell configuration, but detailed analysis has yet to be done.

Star shots: 72961, 72965, 72966, 72968, 72981, 73012

Monday April 9 2012 5:42 pm DeBono 73017-73035 Bias Probe

The goal of the shot today was to do RMP's on rapidly counter-rotating modes. Typical bias parameters were ~80V in-plasma 40-50A. This had the mode rotating weakly (~-4kHz) in the direction opposite to natural rotation, but was not enough to force strong counter-rotation of the mode. RMPs were not done due to the similarity of the shots to "slowly rotating" modes. DeBono

Wednesday April 18 2012 5:11 pm Hughes/Shiraki 73044-73048 Big Rogowski mkII Calibration

Ran preliminary calibration of Big Rogowski against VF current monitor. This data requires some analysis, but suggests a gain factor of roughly 1.65, and if this is accurate, it suggests that the TF probe values are low by about 10%. However, this is still only a preliminary result, and more calibration shots might be needed to more precisely characterize the Big Rogowski's behavior due to some disagreements between the Rogowski and other sensors in the time domain. More on this at the meeting tomorrow (4/19/2012), and results will go on the wiki.

Wednesday April 18 2012 5:54 pm Byrne 73049-73053 Amp wiring check

The amps were fired, first in 0/0 configuration to find reversed polarities (one reversed, many gains moved, a few bad connections), then in 3/1 mode to ensure the correct amps are connected to the correct transformers.

Signals look better, and all connections seem correct. Will re-set all gains tomorrow to ensure that the amplitude spread is due to factors outside the new work

Monday April 30 2012 4:42 pm Hughes/Levesque 73055-73069 VF Shunt Calibration

Hughes: Calibrated VF Pearson against 50mV/600A shunt. Semi-conclusive results, but disagreement seems to be under 2%.

Levesque: Ran VF only and OH only shots to check the calibration of the cos(theta) Rogowski coil pickup. Shots were taken with the unused bank delayed by 50ms in order to remove mutually induced currents. This especially affected the OH-only shots, which previously had significant current induced in the VF coil.

Tuesday May 1 2012 4:35 pm Hughes 73070-73083 TF Calibration Runs

Many hours spent debugging invalid timing setup on basement A14, but once that drama was over, got a few good shots recording data for the Big Rogowski, the TF Probe, and the 50mV/600A Shunt reading the TF current. Some script debugging is still needed to analyze results. However, one immediately apparent quirk was that the Shunt apparently sees the TF current peak at roughly 45ms before t=0, suggesting ~50ms soak-through time between the driven current and the toroidal field seen by the magnetic sensors from outside the TF casings. Further VF calibrations using both Big Rogowski and Shunt will be pursued.

Wednesday May 2 2012 7:17 pm DeBono 73084-73108 Bias Probe

The new Crown amplifier bias setup is capable of putting a ~170V, 3.5ms square pulse on the probe using the current 2:1 stepdown transformer. The VF bank was reconnected today, without a shunt in place. The fast camera has been installed, and a bright lamp has placed in the machine room for illumination. Plasma currents were very low today, approx 5-6kA. The cause of this has not yet been determined. More work to be done tomorrow. Bryan

Thursday May 3 2012 9:14 pm debono 73110-73115 bias probe

It was discovered this morning that one of the three cables (the green cable) connecting the egun to its power supply was wrongly disconnected. The egun is now working normally (~-230V bias). Plasmas taken today appeared to be low current 4.5-6.5kA, the same as yesterday. However, the Bp magnetic signal amplitudes for shots taken today are very comparable to previous "good" shots, suggesting that the Ip measurement is faulty (example: shots 73115,73038). I suspect that the Ip AM502 is broken. Neither CTX or HBT have spare AM502's to swap it out with, and indeed we are already an AM502 short (see April 4th's run report).

Wednesday May 9 2012 7:17 pm Niko 73214-73247 Feedback

Daisuke developed a code for calculating the plasma current from the poloidal arrays. The results were in agreement with the Ip rogowski measurements in earlier shots. However, when plasma shots were taken, the Ip rogowski was found to be working again, so the failure must have been intermittent.
The different control coil current measurements for constant amplifier input were crosschecked with a pearson rogowski for two channels by Pat. It was found that A14 measurements using the shunt resistor agreed with the rogowski measurements. Therefore, the variation is most likely due to varying gains in the amplifiers and can be calibrated for when generated amplifier input.

A short was found in a ribbon cable connecting the FB sensor breakout board to ACQ_388 and ACQ_350. This may have influenced FB sensor data in earlier shots as well. The cable was replaced. A systematic check of all used ribbon cables is probably advisable.

A 0.15 V fluctuation was found in the *input* of the GPU breakout board (i.e., measured in the connector that normally goes to the analog output board). The source of this noise is still unclear. The noise appears even if the downstream amplifiers are turned off.

Plasma shots were taken and a reasonable shot with some mode activity and acceptable reproducibility was found. With the feedback system active, the measured control coil currents, however, were all zero. For further investigation, the output of the FB system was rerouted to ACQ-12. This digitizer saw significant output, so something on the path from AO32 to control coils must have broken again. This was not yet investigated.

A second problem was found in the AO32 output itself. The output did not show any correlation with the control input. Further testing showed that a replay of the sensor data from the MDSplus tree generates correct output, but when the data comes directly from the digitizer, a different output is generated. The problem is being investigated.

Thursday May 10 2012 6:51 pm Niko 73248-73369 Feedback

Plasma shot reproducibility was very good. After the first two shots, all shots were within the target range. A good baseline for mode activity without feedback has been established, but unfortunately no shots with active feedback control were taken today.

The feedback system was further debugged by re-routing control output to another digitizer. The two major problems identified yesterday were fixed. The apparent lack of any control coil currents was due to disconnected A14s. The apparently incoherent control output was because the digitizer does not deliver the channels in order. The correct mapping has already been established previously, but it was assumed that when operating over PCI Express, the channels would be delivered in order. This problem has been fixed.

The state of the control system at the end of the day was unknown: different test scripts generate inconsistent results -- some indicating correct operation and some indicating further problems. I will try to resolve the discrepancies between the scripts first. Depending on the result, either more control system debugging will be required, or plasma shots with active control may be possible tomorrow.

Friday May 11 2012 6:47 pm Niko 73270-73283 Feedback

* The oil pump was found running when the run began at noon on Friday. It was turned off after the last run, so it must have been turned on again sometime between Thu evening and Friday noon. A puddle of spilled oil was found in the basement, most likely because the oil valves in the basement were closed and the piping not designed for the resulting increased pressure.

* At first, the VF bank was not discharging. The problem was fixed by removing the shunt that was apparently not installed correctly.

* The discharge bar for the bank to the left of the basement rack looks broken to me. This should be looked at by someone more competent than me.

* The inconsistencies in the control system data that were observed yesterday have been traced to broken feedback sensors. After these sensors were excluded from all computations, all data is now consistent. Most likely the high-frequency oscillations in the broken sensors resulted in significant differences after partial integration when sampling with 10us (feedback system) vs 2us (normal data acquisition).

* Instead of tracking the n=1 mode in the four toroidal arrays, the control system now tracks the (-3,1) mode and the (-6,2) mode. Motivation for this change was that this is probably a better example for multi-mode control, and that the integration of more sensors would result in a less fluctuation rotation frequency.

* After successful testing on ACQ-12, the control output was wired to the amplifiers and plasma shots with active feedback were taken.

* The control system seems to be working now. Amplitude and phase of the field generated by the control coils (calculated from the digitized control coil currents) track amplitude and phase of the fields seen by the feedback sensors (calculated from the integrated signals in the MDSplus tree).

* The effect of FB control on the plasma has not yet been analyzed, and the number of available shots is still very low.

* The dynamic adjustment of control phasing based on the mode rotation frequency still needs some work. In the tested configuration the phase was adjusted every 1ms. However, since frequency estimates jumped wildly between +15 kHz and -20 kHz, it is doubtful that the adjustment is really beneficial.

Tuesday May 15 2012 10:31 am Niko 73284-73353 Feedback

The feedback parameters were adjusted to compensate for the transfer function of the amplifiers and plasma shots with active feedback were taken.

A total of 20 shots was taken with different base feedback phases (0, 90, 180 and 270). So far, no significant differences in mode activity have been identified (see attachments).

Reproducing the target discharge from last week turned out to be difficult. The shots from today should therefore only be compared to each other, but not with the shots without feedback from last weeks.

Additional problems with the A14s used to digitize control coil currents were observed. In addition to the familiar problems (some signals appear with incorrect time axis or very strong noise), some channels now seemed to record entirely wrong voltages.

Tuesday May 15 2012 6:05 pm Niko 73354-73404 Feedback

Plasma shots were taken with feedback phases of 0, 90, 180 and 270 degrees. In contrast to yesterday's shots, q=3 was approached from below between 4 and 5ms. About 1 out of 3 shots was sufficiently close to the target discharge, other shots tended to fall in rapidly, reaching q=3 around 2.5ms and disrupting at 5ms. Feedback with 0 and 270 phasing was found to result in slightly smaller mean mode amplitude, but standard deviations of all phase sets as still largely overlapping, so the effect may also be coincidental. At the end of the day, plasmas stopped to break down for unknown reasons.

Monday May 21 2012 9:10 pm Debono 73512-73531 bias probe

The new egun filament is installed and is working well.

IMPORTANT NOTE ON IP: The Ip rogowski did not work correctly from the beginning of the runday today, and the problem degraded through the runday. I am now depending on the magnetic sensor measurement of Ip rather than the direct rogowski measurement. Please note that significant differences between the two measurements existed at the end of Niko's last run (ex:shot 73401).

After a number of cleanup shots, shots were taken with excellent plasma parameter agreement with the target shot (#70000), with the bias probe inserted. Biased plasma data to be taken tomorrow.

Wednesday May 23 2012 6:50 pm Debono 73585-73614 bias probe

More accelerated-mode bias shots taken today. (-3,1) phase-flips applied to the plasma with currents from 0-32A. Plasmas looked pretty good; reproducible, and good match to the target shot. Star shot 73613 (30 ampere RMP shot).

Tuesday May 29 2012 6:02 pm Debono 73620-73655 bias probe

CC shots were taken on bias-probe slowed plasmas after the previous run applying them to rapidly rotating plasmas. The plasma response was similar to slowed-rotation shot data taken in the past, and helps to validate the rapidly-rotating plasma response results.

Wednesday May 30 2012 7:05 pm Debono 73677-73700 bias probe

The goal of the run today was to debug the Ip Rogowski. However, the Ip Rogowski problem did not surface today after 10 plasma shots taken over the space of several hours.

We now have two different AM502's amplifying the Ip rogowski voltage into two different West-rack CPCI channels; the prexisting AM502 is connected to CPCI channel 70, and the teaching lab AM502 is connected to CPCI channel 71.

The 2nd AM502 will be left in place in the event that the Ip rogowski problem resurfaces.

Friday June 1 2012 7:55 pm Debono 73725-73750 bias probe

RMP scan taken today with bias probe inserted into plasma and floating (i.e. probe disconnected).

Crate problems in the middle of the afternoon interfered with the run; we were however to get data in the early and late afternoon. More running to be done on Monday.

Monday June 4 2012 9:41 pm Debono 73725-73750 bias probe

The Ip rogowski is working well with the teaching lab AM502 but not with the original hbtep AM502: the hbtep AM502 outputs a significant amount of noise. Today was a model day for excellent plasma reproducability & plasma parameter agreement with the target shot. A (3,-1) RMP phase-flip amplitude sweet was done today with the probe inserted into the plasma and floating. The plasma response to the RMP was very weak, however the mode response was not weak due to the physical presence of the probe.

Tuesday June 5 2012 9:41 pm Qian 73795-73811FeedBack

This is a copy of yesterday's run report. Using the wiki page

I tried to develop the tearing mod shot for torque analysis today. There was some issue with the battery for biasing the Egun in the middle of the day and the plasma didn't break. After re-charging the battery, it works again. I tried to make both the Ip current and Major Radius flat and it kind of works but the duration is short and some fine adjustment of the parameters are need. One can look at 73810 and 73811 for details of the shot information. More time is needed for shot development. .

Thursday June 7 2012 7:55 pm DeBono 73813-73843 Bias Probe

The plasmas today agreed well with the target shot but seemed unresponsive to ~30A (m,n)=(3,1) phase flips, similar to Mondays run. I am wondering if the control coils are actually applying a (3,1) RMP to the plasma. Comparing control-coil only shots 72729 (Slowed-mode run from March 26) & 73845 (today run) shows identical control coil currents, but significantly different FBp sensor pickup. More work to be done... Bryan

Monday June 11 2012 6:13 pm Qian 73889~73919 normal

Control coils are functioning well with the switching. Rotating perturbation is done on normal plasma shots ( not the tearing modes which has not yet developed)

I forget to multiply the frequency with 2pi and the perturbation rotation direction was in reverse to the mode rotation for the first few shots. But positive torque is observed... Then the bug is fixed and I tried some rotation perturbation with 4kHz ~ 13kHz and fixed 12kHz, 10kHz, 8kHz. The torque is always negative.

So I got back to the case where positive torque is observed and did some scan with -1kHz ~ -5kHz, fixed -5kHz, -3kHz~0kHz. -2kHz~1kHz, 0.5~2.5kHz. No matter the rotation is from positive to negative, or from negative to positive. The torque code show that the torque is positive around -1.5~1.7 kHz. ( multiply it by 2pi one gets around 8kHz)

Although I am still not 100% of the validity of my torque analysis code. It definitely shows that something is going on with -1.5kHz frequency. ( The natural mode we usually see is rotating at 7~9 kHz )

Should say that the bug with 2pi factor and direction helped me notice this region accidentally.

The interesting shot with positive torque is 73915~73919

Tuesday June 12 2012 7:44 pm Angelini 73922-73960 Inboard Limited/Fast Camera

The goal of today's run was to make inboard-limited plasmas which may make fast camera analysis easier. After some shot development, I was able to create shots whose major radius didn't vary much. In these shots, the q still changed drastically from around 4 to 2.5 as the plasma current increased. The majority of the shots were taken with the D-Alpha filter and the camera's framerate was 88,000 fps.

Notable shots:

73942 - The plasma is inboard limited most of the shot, and the MR varies the least

73953 - This shot ran for a while between the limiters

73955 - The longest shot of the day (disruption at 7.8 ms)

73958 - Highest current of the day (19.3 kA before the start of the disruption)

During the day I confirmed that the camera was still recording light even if it couldn't be seen in the video. It seems that 88,000 fps was sufficient for all the shots.


Friday June 15 2012 4:46 pm Hughes/Byrne 73966-73979 Big Rogowski mkII Calibration

Shots were taken with the Big Rogowski mkII wrapped 9 times around the upper VF, centered with a used cardboard cable spool. Several shots were dedicated to testing the 500microOhm shunt for safety and minimizing noise (settling on firing only the VF crowbar at 300V as the best approach), followed by shots testing the effects of coil end joint proximity to the VF coils, and proximity of the two coil ends to one another. Analysis still has to be done, but the new shunt has a great SNR, and fills the digitizer range perfectly at 300V (~4.5V peak signal out of +/-5V range). With any luck, no boxcar will be needed, so we'll have ideal time resolution! Note on changes made for this run: The Big Rogowski is still wrapped around the VF, but this shouldn't interfere in anyone's running. The shunt is removed from the VF, the VF return cable is reconnected (although someone misplaced the nut that was used to connect it!), and the associated BNC cable is coiled around the pillar between OHST and VF for safety. The basement A14 is back to TF-esque timing. All krytrons are back on. Everything should be normal, but whoever runs next might want to double-check those affected areas.

Tuesday June 19 2012 6:03 pm cziegler 73981-73998 clean-up

We ran clean-up shots after opening the probe vacuum to the main vessel.

Plasmas were short lived, typically disrupting around 3.5-4ms.

The 5-tip probe's electronics was on until (including) 73989 when it was realized that the voltage sensing circuits are railed. Starting from shot 73990, the probe circuit was off, in order to protect it and the digitizer. On shot 73993, the probe was inserted into the plasma in order to start cleaning the probe tip itself as well as the vessel. At a nominal position of R=107.5cm no effect was detected on the plasma. In the following two shots, the probe inserted a further 1cm each time. The longest and best behaved shot was 73998 (5.5ms). More clean-up shots are required before "real" running.

Wednesday June 20 2012 2:43 pm Hughes 73999-74001 Digitizer test

Three crates-only shots were taken using a 1.606V battery measured before and after with a DVM as a constant-voltage source to check that Basement Rack A14 inputs 5 and 6, and North Rack CPCI Input 69, were recording proper voltages. The good news is that all three recorded 1.606V +/- 1% (the most inaccurate, the North Rack CPCI, appears to have recorded ~1.59V). The bad news is that this doesn't help to explain why the Pearson transformer registers a VF current 25% higher than that recorded by the shunt. I'll take a look at the data again to make sure I didn't miss something by poking at it with only jScope, but it seems pretty cut-and-dry.

Wednesday June 20 2012 6:55 pm Levesque 74002-74020 Cleanup shots

Ran outboard-limited cleanup shots. The bias probe and new 5-tip probe were inserted into the plasmas to clean their surfaces. Both probes were inactive. Plasmas had returned to their normal duration and behavior by the end of the day. External modes were weaker than normal, but this is usually seen when the bias probe is inserted and inactive.

Thursday June 21 2012 5:30 pm Cziegler 74024-74034 5-probe test

We tried to put the 5 tip probe to use today, after the problems noted on Tuesday were resolved - i.e. the probe read-out circuits were re-wired. The machine behaved reasonably well, we ran shot that lasted about 5ms. Unfortunately, the probe recorded negative ion-saturation currents, and at a nominal depth of R=105cm even the floating potential signals bottomed out.

Vacuum shots confirmed that this is not due to pickup. It will only happen with plasma shots. The large negative Isats are even more confusing because

a) the read-out circuit cannot generate negative voltages

b) the problem persists even if the probe is behind the gate valve, BUT (once again)

c) ONLY with the plasma present in the machine.

We will need to re-evaluate the behavior of the probe and the components connecting it to the digitizer.

Saturday June 23 2012 7:51 am Angelini 74035-74053 Fast Camera

Today's half-day run was a continuation of the fast camera run from last week. Using the same settings, I was able to reproduce the inboard-limited plasmas, many of which stayed at a constant major radius for most of the shot. Unfortunately, for the later shots, about halfway through the shot the D-Alpha light intensity decreased drastically. I was able to observe this at different exposure limits, so it may be a physics phenomenon rather than a technical one. I'll see if this drop in intensity corresponds to a particular q or current. One difference in today's run was that the base pressure was lower than last week's.

Good shots for the day are 74044, 74049 and 74053.

Monday June 25 2012 7:15 pm DeBono 74054-74102 Bias probe

Ic amplitude scan taken today for (-3,1) RMP phase flips; the bias probe was inserted and floating in the plasma. Qian's software fix to the CC miswiring appears to be working; data taken today is similar to Daisuke's RMP phase-flip data taken without the probe in the plasma. More running will be done tomorrow. Note: New shorting sticks have been attached to the TF, OHEL, VFEL, and the Ohbias bank. (Note that the originals are still attached at the moment). Bryan

Tuesday June 26 2012 6:37 pm DeBono 74103-74148 Bias probe

More data taken today for the experiment started yesterday (6/25/2012). Plasmas were somewhat irreproducabile today. Overall,the RMP data taken with a floating bias probe is very similar to the data with no probe in the plasma. The plasma(s) disrupted for shots with control coil currents above 25A. No machine problems, although caliban was tempermental in the early afternoon. This slowed down the run somewhat. Bryan

Wednesday June 27 2012 7:20 pm DeBono 74149-74169 Bias Probe

The floating bias probe Ic scan was completed today. Overall the floating probe plasma response is very similar to the plasma response with no bias probe inserted into the plasma. Plasmas readily disrupted at control coil currents above 25A. No machine issues, although the florescent lights above the machine (towards the south rack) need to be replaced. Bryan

Thursday June 28 2012 7:54 pm DeBono 74191-74238 Bias Probe

An easy way to detect broken/missing fuses in the CC rack was found today. 1. Power on the CROWN amps 2. The RED "Clip" LED will light up for ~2s if the fuse is ok 3. The GREEN "Signal" LED will light up for ~2s if the fuse is broken/missing. We replaced several broken fuses today. RMP shots on accelerated modes done today. Bias probe voltage -150V, current -4A. The mode response again was again seen to be slightly less than that of "naturally" rotating modes. DeBono

Monday July 2 2012 6:27 pm Niko 74259-74355 CC Test and Feedback

To ensure that last Friday's rewiring fixed the wiring problems and did not introduce any new ones, every single large control coil was fired individually and checked against radial feedback sensor measurements. The wiring was verified to be correct for every coil.

The amplifier gains for two control coils were found to be set to zero, which may explain problems with these coils in previous runs.

In 3 out of 43 shots, the amplifiers apparently received no signal. This problem was not reproducible and disappeared when taking a second shot (without having touched any system). It is suspected that this may be a result of the RTM-T problems that result in computer crashes at higher sampling frequencies. For now, it is advisable to briefly check control coil currents after every shot.

Reproducing the target shot (approaching q=3 from below) for feedback experiment consumed the rest of the day. With bank timing and voltage settings similar to the reference shot, plasmas behaved drastically different. Towards the end of the day, a new bank voltage configuration was found that resulted in plasmas resembling the reference shot in about 1 of 3 cases. The feedback system was turned on for a few shots and confirmed to be behaving as expected, but no useful feedback data has been gathered yet.

Tuesday July 3 2012 7:06 pm Niko 74356-74450 Feedback

Producing usable shots continued to be difficult in the morning. Plasmas disrupted very early (3-4ms). Therefore, a different target shot evolution (with q crossing 3 at 2 and 5ms) was selected at noon. This target was more reproducible and used for feedback experiments. For all runs, the bias probe was inserted and driven with +60 V from 1.5ms to 5ms, and in later shots 1.5ms to 8ms. Modes were typically found to be rotating with 4 kHz.

CC currents reached peak values of 60 A without breaking any fuses. During one such shot, the voltage across FB02_C2 suddenly dropped to zero and remained there during several test shots. However, this problem disappeared during debugging before any faulty components could be identified.

"Blackouts" (with no signals coming into the CC amplifiers) in either the first 32 or last 8 control coil channels (corresponding to the outputs of the first and second D-TACQ AO32 analog output board) were observed several times.

In feedback shots, feedback was active from 1.5ms to 6ms on the 3/-1 mode. Feedback phasing was adjusted in steps of 45 degrees, and a total of about 3 usable shots was taken for each phase.

Shots with active feedback generally differed from shots without feedback. In shots with feedback, the q evolution stayed much closer to q=3, and often plasmas disrupted early. This did not occur in shots without feedback. A phase dependency was not observed, but an elaborate data analysis has not yet been performed.

Friday July 13 2012 10:56 pm Rath 74452-74495 Pickup calibration

Today's shots were taken to improve the subtraction of pickup currents from OH, TF and VF in the cos 1 rogowski. 4 TF-only shots were taken. Then the VF was disconnected at on top of the center stack and OH only shots were taken. To get a more diverse set of waveforms, some shots were taken with subsets of the available OH banks. After that, the VF was reconnected and the OH disconnected at the same spot. VF only shots were taken with and without VF start bank.

Control coils were then fired individually to determine the physical location of the cos1 rogowski. It was found between FB09 and FB10. No significant pickup from FB08_C1 and FB01_c1 currents was found. Calibration shots were therefore taken with FB09_C1 to FB09_C4 and FB10_C1 to FB10_C4.

Finally, a few plasma shots were taken to evaluate the possibility of reducing the control system cycle time from 10us to 6us. No problems showed up, so next week's runs will most likely be done with 6us.

The interlock at door 2 was found broken and had to be repaired before the beginning of the run. Inspection of the wire strongly indicated the involvement of a postdoc in this issue.

Monday July 16 2012 6:44 pm Niko 74496 - 74555 Feedback

Goal of today's run was to demonstrate feedback effects on a target shot that approaches q=3 from below, while avoiding feedback while q is decreasing at the beginning of the shot.

Initial shots with active bias probe resulted in almost completely suppressed mode activity, so the bias probe was pulled out for the rest of the day.

The control system was configured to track modes from t=1.5ms to t=6.5ms. Control output (and thus feedback) was active from t=4ms to t=6.5ms. Cycle system cycle time was 6us.

Most of the day was spend on shot development. However, at the end of the day good shot reproductivity was established and a total of 14 usable shots were taken in sequence.

Without feedback, the target shot crossed q=3 around t=2.2ms, bottomed out at q=2.4 around t=4ms and reached q=3 again at t=5.5ms before disrupting at t=7.5ms.

When feedback was active with a 180 degree phase, shots resembled the no feedback reference shots until feedback began at t=4ms. Shots then reproducibly disrupted at t=4.5ms, with the major radius jumping from 93cm to 91cm within less than 100us.

When feedback was active with a 0 degree phase, shots resembled the no feedback reference shots until feedback began at t=4ms. After that, the major radius decreased slightly faster than without feedback, resulting in the shot terminating ~0.5ms earlier. Mode activity compared to no feedback shots was generally higher.

Please refer to separate email for illustrating plots.

Tuesday July 17 2012 5:19 pm Niko 75556-75605 Feedback

The scan of feedback phase started yesterday was continued today. Data was acquired for 90 and 270 degree phasing, as well as some additional no-feedback cases. Shots with 270 degree phasing behaved similarly to 180 degree shots and caused a disruption within 1 ms of activating the feedback system. Shots with 90 degree phase behaved similarly to 0 degree shots, having a slightly reduced shot length compared to the no feedback case.

Comparison of perturbation amplitudes between no FB, 0 degree and 90 degree FB is complicated by the large shot-to-shot variability and so far no significant differences have been extracted.

About 1 in 4 shots suffered from failure in either of the RTM-T modules, resulting in only 32 or 8 feedback coils being used.

The amplifier for feedback sensors in section 10 was replaced with a spare. Although this changed the digitized signals, they can still not be considered correcty. Some problem must thus exist in either the sensors itself, wiring or digitizer channels.

Thursday July 19 2012 6:39 pm Niko 74613 - 74670 RWM Shot Development

Goal of today's run was to find bank settings that result in a plasma with distinct RWM activity.

The original plan was to develop a shot with a breakdown at the low field side with the plasma then moving inboard. This turned out to be impossible, as the plasma breaks down on the high field side before any VF bank has fired.

Instead, a shot was developed that started with the major radius increasing to a maximum of 96 cm at 1.3 ms, while edge q fell from +infinity to 2.5 at 1.3 ms. This q value was steady until about 4ms, after which it rose up to 4.5 at 6.5 ms. While significant 3/1 RWM activity was expected for this kind of shot, mode amplitudes at the q=3 crossing did not exceed 4 Gauss, while normal fluctuations were around 2 Gauss for the entire shot. Example: 74658

Attempts to reduce the fluctuation level by staying further away from q=2 generally resulted in very different shots with the plasma immediately falling inward.

Significant mode amplitudes in the order of 8 G were found only in 2/1 and 4/1 tearing modes. Growing 2/1 modes were observed with q=2.3 and r=96cm almost constant for 1ms. This growth was always followed by a minor disruption and the plasma beginning to move inwards. Example: 74632

It was theorized that the lack of any apparent RWMs might be due to the plasma being stable to external kinks. However, an attempt to make the plasma less stable by increasing the puff time and decreasing the toroidal field did not result in any significant changes. However, it was observed that prolonging the puff time from 1.25ms to 2ms results in plasma currents of ~3 kA already during the OH biasing. Example: 74656

It was also found that the edge q calculation was using a hardcoded toroidal field strength of 0.33 Tesla instead of using measurements. The script has been updated to use the measurements of the TF probe, scaled to the current major radius. The resulting corrections are in the order of 10% for a TF voltage of 6.1 kV.

Shots were taken with TF voltage ranging from 5.5 kV to 6.3 kV, thus exceeding the standard 6.1 kV.

In summary, it seems that adjustments of bank timings and voltages in the tested ranges do not result in plasmas with RWM activity. While the parameter space still has large unscanned regions, there does not seem to be any particularly promising direction. However, it seems that in order to demonstrate feedback a new type of shot that exhibits RWM activity is required, so I'm not sure how to best proceed at this point.

Monday July 23 2012 6:26 pm Niko 74671 - 74738 RWM Shot Development

Efforts to find a reproducible shot with RWM activity continued today. Today's attempts were focused on keeping the q evolution from shots like 74658 while increasing the plasma current ramp. So far this has not been achieved, shots with suitable plasma current evolution typically fall too far towards q=2, resulting in significant tearing mode activity, or bounce immediately back above q=3. Shots taken with the same settings fell in either of these categories. It seems that some bifurcation prevents the plasma from taking an intermediate path.

In a second approach, we tried to utilize the control coils in a static m=1, n=0 configuration to move the major radius at breakdown further out. Initial results confirm that we can reprocibly affect the major radius, but so far no shot parameters were found that allowed a return to q=3.

Tuesday July 24 2012 5:45 pm Niko 74738 - 74786 RWM Shot Development

Efforts to find a reproducible shot with RWM activity continued today. The control coils were used for major radius control during startup, but even with this additional know the desired shot evolution could not be achieved. A new parameter set with a large current ramp and a q evolution that drops below q=3 only around 2ms was explored. With these parameters, resistive wall modes with amplitudes up to 12 Gauss were observed in roughly one out of three shots. However, when averaging over multiple modes, this is washed out to 6 Gauss (compared to background fluctuations of 3 Gauss) which still seems too low for use as a base case for comparison with feedback based mode suppression.

Thursday July 26 2012 3:17 pm Hughes 74787-74794 Big Rogowski mkII Calibration, cont'd

In order to verify the calibration of the Big Rogowski, we independently counted wrappings around the VF and fired only the VFEL. All shots of this type produced gain factors (between BR and VF Pearson Transformer) deviating less than 1% from a VF Pearson gain factor from the previous calibration campaign, regardless of geometry of the BR relative to the VF coil, and regardless of the number of wrappings (9 vs 10).

As a second check, we also attempted to calibrate against the OH (wrapping around the upper outer winding), using only the OHEL. This produced a consistent 6%-7% disagreement with the 'characteristic' VFEL shot from the previous campaign. At present, it is not known if this is due to the OH's high dI/dt enhancing some neglected term in the calculation, an error in the calibration of the OH current monitor (a home-made Rogowski, rather than a Pearson), or some other unidentified source of error.

More refinement will follow, in particular, including the Big Rogowski's R and L in the calculation (previously disregarded as insignificant due to the L/R time being around 2us) and calculation of digitization error effects due to the Big Rogowski's relatively small signals. At some point, shots may be taken using the VFST to test the code's ability to keep up with a high dI/dt.

Special thanks to Pat for overseeing, lending a hand, offering some good ideas, and climbing around on the machine a bunch. He really tied the experiment together.

Tuesday July 31 2012 6:53 pm Levesque/Peng 74826-74873 Troubleshooting HD amps

Ran crates-only shots along with several control-coils-only shots to troubleshoot problems with the high-resolution sensors in sections 1-5. One amplifier board which was associated with 3 bad sensor channels was found to have all 12 amplifier channels working; however, 2 of the inputs had bad/loose connections at the ribbon connection for the amplifier inputs. One of the channels (TA03_S3P) was fixed by tightening the connector further in a vice, which is our standard method for these connectors. The other 2 sensors (TA03_S2R and PA1_S17P) are currently working for control-coil test shots, though nothing was done for these other than unplugging and replugging the input and output cables. TA03_S2R may be intermittent -- further testing can be done if the sensor goes bad again.

We also started troubleshooting a second amplifier board which is associated with 2 bad sensors (PA1_S15R and PA1_S16P). This board produces extra unexplained noise, and will be swapped with a working bench-tested board for further tests.

The strong 12-20kHz noise that appeared in all high-resolution sensors in sections 1-5 (refer to crates-only shot 72857) is now gone. This may have been caused by the power source for entire amplifier box, or by some bad connection on the amplifier board for the "TOP 1" signal group -- both were changed before the noise was recorded. The power source (a heavily-damaged extension cord daisy-chained through 2 outlet strips and another extension cord) was the likely culprit, as it was also producing lots of noise when powering an oscilloscope. The box is now powered through a direct source.

Wednesday August 1 2012 6:03 pm Jeff/Qian 74897-74914

*FB10_S3P had a bad connection to the breakout board and is fixed.

*Troubleshooting the FB sensors in section 10 is still in progress. Backup boards were put in and changed the bad sensors on section 10. But there are still bad ones..

*More test to be done tomorrow.

Monday August 6 2012 7:51 pm Levesque/Cziegler/Peng/Rath 74943-74976 Cleanup shots and troubleshooting

Ran cleanup shots. The high frequency noise in the high-resolution sensors in sections 1-5 returned at the beginning of the day. The problem was eliminated by powering the amplifier box through an extension cord to the control coil power rack, but this is only a temporary solution. We should assess the power sources/sinks in the area to look for what is causing the problem, and find a permanent solution. Circuitry for the new mach probe was tested on the machine during cleanup and shot development. Problems in the test setup have not yet been resolved. While attempting to reproduce the target shot for asymmetric wall experiments, the TF and OH Start banks stopped triggering. Troubleshooting of the problem has been inconclusive so far, and will continue tomorrow.

Wednesday August 8 2012 8:01 pm Levesque/Peng 74992-75048 Troubleshooting HD amp problem

For the first shot of the day, only the TF bank was charged to low voltage, and it did not trigger properly and was dumped. Subsequent troubleshooting without charging the banks showed no problems with the krytron firing, implying that the J221 outputs were pulsing. The TF bank was then charged again, and fired successfully even though no connections or software had been changed. All banks fired correctly for the rest of the plasma shots, though only 3 plasma shots were taken.

Most of the day was spent troubleshooting the high frequency noise in HD amp box 1 (for sections 1-5), which returned yet again. It seems that the noise appears under the following conditions, which is consistent with testing from the past week:

-The noise goes away when power to the amp box is cycled.

-The noise does not reappear as long as the high voltage panel is off (and thus krytrons do not fire, though J221 pulses are sent).

-The noise appears when the high voltage is on as soon as the VF Start krytron fires. This occurs even when the banks are not charged.

-After the noise appears, it remains for subsequent shots until the amp box power is cycled. This is true regardless of whether the high voltage is on or off.

Previous troubleshooting was done without considering the state of the HV switch, thus disappearance of noise may have just been due to the HV switch being off after changing power cables. For now, it looks like the problem cannot be avoided for plasma shots as long as all sensors are connected. The problem remains even when the amp box is powered by a UPS on battery.

The noise problem seems to be tied to the "TOP" amplifiers, specifically TOP1 & 3. When all amp outputs except TOP3 are connected to the CPCI, the noise does not appear. When TOP3 is individually connected, it does not produce enough noise to account for when all outputs are connected -- there seems to be a synergic effect between the three TOP outputs. The noise also propagates through the CPCI into the SXR tomography measurement, though the noise is much less pronounced. Troubleshooting will continue tomorrow.

Monday August 13 2012 9:05 am Rath 75082-75103 debugging

Various shots were taken to test and debug the high frequency noise, the automatic triggering and the control system.

The automatic triggering on completed TF bank charging is working fine.

The high frequency noise is still being debugged.

An unexplained phase difference between input and digitized control output was found. The phase difference changes over time, and does not seem to correspond to a constant time lag between the signals. Investigation is ongoing.

Monday August 13 2012 5:27 pm Niko 75112 - 75182 Feedback

The previously observed phase differences between control system input and output were further investigated and an explanation was found. In short, the precision with which the feedback system can compensate for latency depends on how much the average mode rotation frequency agrees with the instantanous frequency, i.e. the phase difference from one sample to the next. Varying sensor gains can cause the measured sin and cos components of a mode to differ in amplitude, which results in a modulation of the apparent frequency, i.e. instantanous and average frequency appear different even for a perfectly rotating mode.

Most of today's shots were "warm-up" shots and not yet reproducible. The target shot has not yet been reached again. At the end of the day, the shot parameters of the target shot seemed to give rise to a mostly reproducible shot with different evolution and less mode activity. Debugging of high frequency noise in high density sensors continued throughout the day as well.

Tuesday August 14 2012 9:59 pm Niko 75183 - 75256 Feedback

Plasmas were reasonably well behaved today. Plasma lifetime increased continuously throughout the day, so that good shots were achieved in the middle part of the run. Early and late plasmas differed too much from the reference shot.

Initial feedback shots were aborted after an unusually high number of broken fuses (about 37 fuses were lost per shot), even though recorded coil currents never exceeded 2 A. The cause turned out to be a race condition at the end of the shot: it was possible that the GPU powered down before the analog output module, resulting in the output module outputting garbage data for a small period of time. Since this happened at the very end of the shot, the digitizers were no longer recording and thus never showed the currents. The problem was fixed by explicitly turning off the output module before the GPU, and no fuses were broken for the rest of the day.

After dealing with the fuse problem, coil FB02_C2 continued showing zero current. The problem was eventually tracked down to a short at the A14 input, where unisolated ends of the ribbon cable touched a metallic component. The ribbon cable was moved to fix the problem, but a proper fix (insulating the ends of the ribbon cable) still needs to be implemented.

Feedback experiments were run on four independent n=1 modes (one for each toroidal FB sensor array). Control cycle time was 4 us, and control latency 16us. The former exceeds our original design goal of 5 us, the later is 4 us larger than the expected value (12us). Shots were taken with 4 different feedback phases spaced 90 degrees apart. Typical control coil currents were up to 2 A. For analysis, shots were aligned by the peak q value. Mode activity generally began to increase when crossing q=2.6.

The following effects have been observed:

Passive observations using the FB coils as sensors indicate that the theoretical phase for mode suppression should around -100 degrees. (assuming an adequate amplifier response model).

Fourier spectra showed distinct frequency peaks at -10 kHz for all modes. However, modes 1 and 3 also showed additional peaks at +10 kHz kHz (zero based indexing). This is consistent with a systematic n=1 error in sensor gain and/or alignment in two arrays.

Comparison of mode phase and control coil phase showed significant variation when feedback was active. I believe this may indicate that the control system latency is too high, so that the mode slips instead of being suppressed, resulting in the changed rotation frequency. Another explanation would be an inaccurate amplifier response model.

The heat lamp for the OH ignitron was found broken, but this seemed not to affect bank firing. Presumably, due to the broken AC the ambient room temperature is warm enough to provide a sufficient temperature grading to the water-cooled components.

From Jeff Levesque:
The source of high-frequency noise in HD sensors in sections 1-5 was isolated to one amplifier circuit (amp 6 in the "TOP3" assembly). The specific problematic component or cable was not found, but the high-frequency noise was eliminated in all sensors by removing the op-amp from this one circuit. Note that the op-amp itself works fine, we just disconnected it because that was the easiest way to disconnect the amplifier circuit. Although the noise only appeared under certain output connection combinations, this change has removed the noise for all further shots, including plasma shots. The end result is that the high-frequency noise is gone (or is as low as other system noise), and sensor PA1_S29R is disconnected.

Thursday August 16 2012 8:24 pm Niko 75275 - 75318 Amplifier Response

Most of today was spent on investigating the variation in control coil current mode amplitude with mode frequency.

Three issues were identified quickly:
Issue 1 was rectified right away, and dealing with issue 3 has been postponed. Correcting issue 2 (in order to verify that the amplitude variation was indeed reduced) turned out to be unexpectedly time consuming.

Elimination of the equilibrium filter introduced a constant drift in all amplitudes. This was first blamed on the function generator running in continous mode, so that the offset subtraction would actually subtract an average over a potentially fractional number of wavelengths.

The straigthforward way to resolve this by triggering the function generator turned out to be less straight, because the low input resistance of the function generator made it impossible to use a single J221 output to drive more than one trigger input.

After this was fixed, it turned out that the signal generator was now outputting a constant non-zero signal (depending on the output phase) in pre-trigger state.

It was attempted to eliminate this problem by using another gate signal for amplitude modulation. However, using amplitude modulation is mutually exclusive with externally triggered operation, so the function generator is running continously on its internal clock and the phases of the two signals are no longer synchronized. This means that the only way to ensure a fixed phase relation between the two signals was to connect them to a scope and manually tune the phase difference after every frequency change. This was considered impractical.

The next attempt was to trigger the function generator externally and set both phases to 0. The phase difference was then produced by sending the second trigger with a (frequency dependent) delay. This produced the desired signals while being zero in pre-trigger state.

At this point, a new problem arose. The partial integration of a pure sinosoidal actually introduced a constant offset. Therefore, even after finally getting the function generator to output the correct signals, the mode amplitudes still showed a constant drift.

It then seemd that it would be easier to keep using the equilibrium filter, but ensure that it would average over an exact period of the input frequency, so that this frequency would not been filtered out. This approach required adjusting the filter for every frequency, but still seemed to be the least complex option.

This test setup has been tested and seems to work. However, due to lack of time the actual frequency scan was postponed. Feedback experiments were then started based on the assumption that introduction of the constant term in the gain would improve the low-frequency response sufficiently.

Shots were taken with 70, 85, 100, 115, and 130 degree phasing. Not enough data is available to draw any conclusions.

A rather different idea to calibrate the amplifier response that did not suffer from any of the problems above only came up at the end of the day. Since the amplifier response is actually independent of the rest of the control system, it should be enough to test a single shell and amplifier on the bench, directly feeding it different sinusoidals without using any control computations. In this setup, it should also be possible to measure the phase of the produced magnetic field instead of the control coil current, so we would be able to include shell eddy current effects without having to rely on the plasma to mediate them. I am considering to do this calibration after the current feedback run cycle is done.

Friday August 17 2012 7:39 pm Niko 75319 - 75412 Feedback Phase Scan

A total of 66 shots with no feedback and feedback with 70, 85, 100, 115 and 130 degree phase were taken today. In this phase area, mode suppression is expected and was previously observed with 100 degree phase. 42 of the 66 shots have similar q profiles and can be used for statistical analysis which is yet to be done.

The current signal for FB02_C2 temporarily failed again today. The problem was resolved by wiggling the ribbon cable of the A14s.

Todays run was again done without a working OH heat lamp. However, a new bulb has been found and is ready for installation.

A few shots with relatively constant major radius near 92 cm were taken at the end of the day for Qian.

Monday August 20 2012 8:41 pm Niko 75414 - 75490 Feedback Gain Scan

The OH ignitron heat lamp was replaced this morning before the run, and the gate valve to Istvan's probe was closed and the probe removed some time before noon. Plasmas became reproducible enough to begin a feedback gain scan shortly after noon.

After about 31 shots were taken the plasma behaviour changed dramatically, preventing the gathering of more data for the gain scan. The last good shot is 75473. In these and all previous shots the plasma current rises from 0 to 4 kA in a few us after the OH start bank fires. Shot 75473 was taken 4 minutes later with the same parameters and without anyone entering the Tokamak room.Bank current traces for this shot are identical to the previous shots. However, the plasma current stays flat even after both OH start and OH electrolytic banks have fired. Only when the VF bank fires, the plasma current slowly rises to a maximum of 7 kA at 3ms. Major radius calculations give results above 100 cm. The e-gun filament is emitting light. All three e-gun batteries have been checked. To be on the safe side, the 9V battery in the circuit was replaced and the 225 V battery fully recharged. Neither changed the plasma behaviour.

The gas valves were checked, and the pressure was confirmed to drop during the puff.

When the VF trigger was moved from 1ms to 1.2ms, the start of the plasma current rise moved from 1ms to 1.2ms as well. When the VF trigger was moved to 0.5ms (before the OH), no plasma current developed at all.

When both OH and VF triggers were moved forward by 0.5ms, the plasma current rise time again stayed with the VF.

Moving the gas puff time from -95ms to -95.5 ms did not result in any changes.

It was found that if the duration of the gas puff is increased enough, the plasma current becomes negative with the firing of the OH bias bank, and then correctly rises with the OH start bank. In these cases the plasma evolution is still very different, and plasmas last no longer than 5ms (compared to 8ms in previous shots). Example shot: 75489. The threshold between the two cases (plasma current rise with VF, and plasma current rise with OH bias) is somewhere between a puff duration of 1.2 and 1.3 ms. Previous shots were taken with a puff duration of 1.1 ms.

Tuesday August 21 2012 6:11 pm Niko 75491 - 75569 Feedback Gain Scan

The unusual plasma behaviour that affected yesterdays shots was gone this morning.

A feedback gain scan was completed. The scan was performed at the phase that seemed most effective at mode suppression in previous experiments (85 degrees). It was found that the gain at which previous experiments were run was very close to the maximum. Attempts to further increase the gain generally resulted in disruptions shortly after activation of the feedback system.

The results of the gain scan confirm expectations. Without feedback, the mode amplitudes are strongest. With higher feedback gain, the mode amplitude decreases. With too much feedback gain, the plasma disrupts. At the highest non-disruptive feedback gain, the mode amplitude is at 78% of the no feedback amplitude.

In the data from both today's and previous runs, it was found that prior to the major radius crossing 92cm, feedback has effects only when running at amplifying phase. Feedback mode suppression only becomes visible once the plasma has crossed 92cm. It should be noted that it this time all toroidal arrays report uniform amplitude increases, so this is not just an effect of the plasma expanding in minor radius and coming closer to the upper and lower arrays.

Thursday August 23 2012 6:52 pm Levesque 75615-75718 Toroidal asymmetry

Made plasmas with toroidally asymmetric shell configuration to look for possible modulations in mode amplitude/frequency with toroidal angle. Shells in sections 1, 2, 6, and 7 were retracted for half of the run. A couple shots overlaid sufficiently with the desired reference shots (refs = 72468 and 73009, matching shots = 75629 and 75706), but most were different. A different reference shot type may be selected tomorrow due to difficultly in matching the original references. D_alpha light from the spectrometer was lower than usual throughout the day. Several "static fill" shots were taken during the day to check for issues with the puff system. Results were as follows. Shot 75698/9: puff=1000us, fill P=3.3e-5torr ; shot 75709/10: puff=1200us, fill P=3.0e-5torr ; shot 75711: puff=1500us, fill P=5.4e-5torr. The puff/fill discrepancy between the two shorter puff cases is concerning, and should be investigated with more static fills at some point. The drop in fill pressure happened despite the regulator pressure remaining at 21psi throughout the day. Niko and Pat also ran test shots to measure the transfer function of a full control coil and amplifier system on a spare shell (shots 75632-75689).

Friday August 24 2012 6:55 pm Levesque 75719-75771 Toroidal shell asymmetry

Continued running with toroidally asymmetric shell configurations. Plasmas were more reproducible than yesterday. The following configurations were used today: Sections 1,2,6,7 out 4cm; Sections 3,4,8,9 out 4cm; and Sections 1,2,3,4 out 4cm. Several shots with mode amplitude and rotation modulation have been observed, as measured by the TAr sensors. These modulations occur later in the shot, as q* rises to ~2.7 from below, though extensive analysis has not yet been done. These have not yet been correlated with the toroidal angles of retracted wall segments, and are not always observed. About 25 shots were close enough to the reference shots to allow direct comparison

Regarding the D_alpha emission problem observed yesterday: light levels jumped up after reinserting shells in sections 1,2,6,7, but not quite to levels from the reference shots, even with a longer puff time (1300us versus 1000us). Note that the spectrometer fiber bundle is between sections 6 and 7, and local shell changes may affect the reflected light seen or the interaction with neutrals.

Monday August 27 2012 7:13 pm Levesque/Rhodes 75772-75851 Toroidal Wall Asymmetry

Finished low-initial-q* experiments with toroidal wall asymmetries. The following configurations were used today: Sections 1,2,3,4 out 4cm; and Sections 3,4,5,6 out 4cm. Mode amplitude and rotation modulation were again observed in TAr sensors in some shots, but in-depth analysis remains to be done. This concludes the wall asymmetry experiments pending further analysis and modeling results. Noteworthy shots: 75834 and 75847.

Control coil amplifier response testing continued in the middle of the run day (shots 75794-75827) to verify the hall probe's frequency response.

Tuesday September 4 2012 5:01 pm Peng 76210-76268 const q round 2.5

* It is found that for such q profile the natural mode is smaller compared to other shots. ( for other shots, the mode amplitude decreases when q reaches 2.5)

* static phase, changing amplitude, perturbation is applied on such shots hoping that we could isolate the effect due to perturbation. However, it was found that for shots in such style, the mode amplitude does not quite feel the perturbation. ( the behavior is similar with/without the perturbation). Later, a phase flip is added to the perturbation, and it still doesn't have noticable effect on the mode amplitude. The phase flip does have some effect on the background trace of the signal on some sensors. The typical shot number is 76264 ( with flipped perturbation)

Thursday September 6 2012 7:16 pm Peng 76269-76340 Steady 2/1 mode

* Shot for steady 2,1 mode is reached.

* Roughly constant Ip, MR, and q for a duration around 3ms, then the trace varies. Star shot is 76320

* This shot style is finally reached around 5 pm so not too much sample points was taken. ( 76320~76340)

* It is not obviously seen that the mode gets locked by the perturbation, but shots with/ without perturbation seems to be different. Further analysis is needed to identify the effect of perturbation on the mode activity.

Sunday September 25 2012 8:05 pm Levesque 76345-76397 Clean up shots

First run day after the recent up-to-air period. The base pressure at the start of the day was 3.8e-8 torr, while normal operating base pressures have been around 1e-8 during the middle of run days. Plasmas were not the standard quality, as was to be expected. Initially plasmas had very erratic major radii, even with standard bank and puff settings. Some plasmas early in the day lasted up to 13ms. Long-duration plasmas had little or no x-ray emission according to the SXRT detector, very large R0, current ~6kA, and erractic q* between 2 and 4. The long shots had very large spikes in D_alpha light as seen by the spectrometer (~3-5 volt spikes, whereas normal disruptions give ~0.4 volts). The first few plasmas of the day seemed to look more whitish, instead of the usual purple. Further plasmas were not observed through a port by eye due to the lack of a control room sightline.

Performance for normal plasma shots improved throughout the day. Plasmas with the standard starting parameters and current ramp lasted up to ~3ms. Cleanup shots will continue tomorrow.d

The fast camera was active for most of the day, however its D_alpha filter was not on. Very interesting rotating high-m structures (m ~= 6-8) could be seen with the camera during disruptions and as plasmas were falling inward. Shells in sections 7, 8, and 10 were retracted for half of the day for the camera sightlines. Shell 7B is presently stuck in the IN position, as the motor spins without gripping the threaded shaft. This can presumably be fixed by tightening a set screw, but the correct size hex key could not be found today (the screw head is either metric, or is slightly smaller than a standard 5/64 english size, which we have seen before in a batch of poor-quality screws -- filing down a 5/64 hex key will work).

Monday September 26 2012 9:18 am Levesque/Peng 76398-76455 Clean up shots

At the start of the day, base pressure on the control room ion gauge was at 3.8e-8 torr again. This is not an improvement from yesterday. The RGA showed the dominant partial pressure to be nitrogen, with water and oxygen down by factors of 3.5 and 5.3 respectively.

Lowering the puff time to 200us (from 1250us) decreased the amount of D_alpha light at the startup slightly, but there was still more light than usual during the main plasma discharge. Eventually we returned to a more standard puff time of 1000us.

Explored a broad range of bank and puff settings, with little or no improvement from yesterday for most of today. At the end of the day, we were able to achieve plasmas that looked more typical after raising the bank voltages significantly. The highest-performance plasma achieved was 76451, with a breakdown current of 14kA and peak current near 19kA. The high-current shots also started having disruptions that looked more normal compared to previous disruptions. Reasonable plasmas still only lasted ~3ms, versus the standard 5 or 6ms..

Monday October 1 2012 7:20 pm Levesque 76671-76679 Testing SXR fan array

At the end of last week, we leak checked and tightened some bolts, then baked over the weekend including the GDC bellows which was not baked previously. The base pressure came down to 2.6e-8 today after turning off the bake. Partial pressures are still dominated by nitrogen, with oxygen down by a factor of 4.4 and water down by a factor of 5.5.

The main purpose of the run was to test the new SXR fan array and filter. So far I have only looked at the raw data, and it appears that 13 of the 16 chords are working well and are in rough agreement with each other. One of the working chords has about 10 times as much noise as the others. All 3 of the faulty chords saturate the CPCI (+10V) at the plasma breakdown. We have not done any troubleshooting yet to see what might be wrong with the bad chords.

Thursday October 11 2012 6:40 pm Byrne 76680-76704 cleanup

Shots were difficult to push outboard, eventually had plasmas centered at 94/95cm by reducing VF (110/3.8k) and increasing OH (300/6k/2k). Shots were taken with base pressure from 30-50nTorr. Base pressure was at 24 nTorr, up from ~20nTorr before opening. Most of the influx seemed to be water. Pressure is at 32nTorr and dropping, although it is not clear what value it will settle at.

Originally trying to increase OH alone led to plasma failing to break down. At 7kV OH St and 3kV OHB, there was no appreciable Ip. This may be due to the plasma not being able to superimpose its own field geometry on the stronger OH field, although Ioh still passes through 0 during "breakdown"

In all cases plasmas were shortlived, had low Ip and had small current ramps, only weakly affected by OH settings. Disruptions seemed not to be caused by resonant surfaces, as q varied greatly, up and down, over the course of a shot, before the plasma crashed (see shots 76702,76704)

All disruptions seemed gentle, as plasmas crashed over a longer time than target shots, and crashed from lower energy. Not sure why this should be so. One interesting shot is 76703, which despite high OH bank settings immediately crashed inwards, while still maintaining a fairly constant Ip profile, even with MR at around 88cm. not sure what to make of that.

Also, when setting up this morning, the cooling water was running, and the sign was flipped to open. When asked CTX was not using it. It was shut off sometime between setup and this afternoon, when Chris discovered it, most likely lunch as the room was not being monitored, and had not yet been darkened and locked up for running. No digitizers seemed to be affected, however, if you're using equipment (racks, cooling water, etc.) that serve multiple users, even if you were the only one using it when you turned it on, please ask around before you shut it off again.

We expect to work on the Thomson scattering Beamline tomorrow, with cleanup shots taking place around that work. Expect to setup in the morning, with hi-pot and most of the running happening after the work in the late morning/early afternoon. Hopefully the new Cryo will arrive tomorrow or Monday, allowing us to take shots at lower base pressure

Friday October 12 2012 5:37 pm Byrne 76708-76720 cleanup/stability/camera calibration

Theme of the run was cleanup shots. Banks were run with very low voltage on VF, and roughly the same voltages as the end of yesterday's run on the OH banks. When the OH electrolytic bank was raised above 300V, it failed to reach a full charge before the TF, and continued charging after the shot. It was dumped and the run was continued

The final four shots are all comparatively long lived, if very low current. VF settings were 2kV on start, and 70V electrolytic, with 5.7kV on the OH start and 270V on the electrolytic. Bias was left at 2kV as there was not time in the runday to vary it. However, it seems likely that the plasma *was* run in a positionally unstable regime for some or most of the shot. Major radius starts at around 95 and moves steadily outward to around 97cm, by 2.25ms, at which time the plasma crashes back inwards, only disrupting around 5ms.

Sarah was able to achieve framerates of 80k fps without the filter, but needs a slower framerate with the filter installed. This may require work to discern plasma dynamics.

Tuesday October 16 2012 5:07 pm Hughes 76721-76731 Magnetic Force Measurements

Aside from some crates-only shots to verify that the baseline signal was coming through properly, took TF-only shots to measure the force on a sample of magnetic material close to the vacuum vessel. After ramping up from 1.1kV, took 4 shots (76727-76730) at the usual 6.1kV. Analysis has yet to be done, but a preliminary glance in jScope showed a lot of shot-to-shot variation that I don't understand yet. More to come.

Friday November 9 2012 10:06 pm Levesque 76732-76782 Cleanup and shot development

Ran cleanup shots and shot development to try recovering our standard shot style and duration. Base pressure at the start of the run was 1.1e-8 torr. Standard-style shots started out short early in the day, then eventually recovered to durations matching those of shots from the end of September (with base pressures at 3.8e-8 and 2.6e-8 torr). Standard shots did not get longer after reaching these reference shots (ending at around 4.5ms). Tried low, medium, and high starting plasma currents (~4.5kA, ~9kA, and ~13kA) to explore discharge evolutions. Several low- and high-current shots lasted slightly longer than the present limit on standard shot duration, but returning to standard shots after these longer shots did not improve their duration. High-current shots appeared to have our normal disruption characteristics.

SXR emission did increase throughout the day, as seen by the high-field-side SXRT diode and the SXR fan array. Modes also became more coherent throughout the day, possibly in part due to larger amplitudes above the noise floor.

Had trouble getting below q* = 3 with the standard shots crossing from above -- shots that began with q* anywhere above 3 could not get to q* < 3 except transiently. Minor disruptions appeared to be caused by, or coincide with, 3/1 and 4/1 mode activity when 3 < q* < 4. 4/1 modes were especially more apparent than they had been in similar discharges before the recent diagnostic upgrades. 4/1 modes often burst to moderate amplitudes after minor disruptions, even when they weren't strong or obvious beforehand. Shots that initiated with q* ~ 2.5 at the end of the startup seemed to evolve as normally expected (but still short), and had large 2/1 modes when going below q* = 2.5. Large loop voltage oscillations, along with small plasma current oscillations, were seen during the 2/1 modes.

One of the new feedback sensors amplifier boards was installed in section 10. All channels in this section now appear to work and are consistent with each other. However, these sensors could not be directly compared with others since this was the only section with the shells retracted (for the fast camera). The run will continue on Monday, with shells in sections 7-10 retracted to improve the fast-camera view.

Monday November 12 2012 7:00 pm Levesque/Angelini/Byrne 76783-76841 Cleanup and shot development

Continued cleanup and shot development. Still unable to get long-lived or reproducible shots. D-alpha emission, SXR emission, and disruption characteristics are looking more like our standard though. The longest shot disrupted at ~ 5ms. Startup parameters were different than Friday's run due to the different shell configuration -- 4 sections were retracted today, while 1 section was retracted Friday.

Nitrogen was the dominant partial pressure before running today and Friday as usual, with oxygen down by a factor of 3.3 (Fri) or 4.6 (Mon). After the end of the run each day, much of the oxygen had combined into water as expected, leaving water as the second-highest partial pressure: Water down from N2 by a factor of 2.5, O2 down from N2 by a factor of 14. Over the weekend, the leak rate was high enough that the O2 partial pressure became secondary and large again.

The run will continue tomorrow, hopefully with the O2 partial pressure lower than this morning due to consecutive run days.

Tuesday November 13 2012 6:54 pm Levesque 76843-76878 Cleanup shots

Continued cleanup shots. Plasmas today improved significantly versus yesterday and Friday, and are much closer to standard operation. Minor disruptions frequently occur near 1.2ms, which also happened before the up-to-air under certain operating conditions. Was finally able to get plasmas crossing q*=3 from above, whereas in the past couple of runs, q* would not cross 3 due to minor disruptions or steady but fast decreases in R0 or Ip. The longest shots disrupted at around 6ms, and had reasonable evolution of all plasma parameters. 4/1 and 3/1 modes have become more clear as well. However, plasmas are still not as long-lived or as reproducible as they were before the up-to-air.

Nitrogen was the dominant partial pressure before running today as usual, with water down by a factor of 4.5 and oxygen down by a factor of 13.4. This was an improvement over the past couple of run days.

Monday November 19 2012 11:42 am Angelini 76879-76899 Inboard limited clean-up shots

The purpose of the run was to continue cleanup shots and attempt inboard limited shots. Each shot was run with a base pressure between 17 and 33 nTorr. On the whole, the shots were short-lived, but that may have been due to the settings for inboard limited shots. While the inboard shots were mostly unsuccessful, there are some interesting shots in which the q drops from 5 to close to 2 almost linearly with time. The poloidal modes are easily seen from the BD. I'd like to see if I can reproduce this BD from the fast camera data. The shots from 76894 to 76899 display this behavior. Shots 76895 and 76897 give especially clear BDs.

The fast camera seemed to be operating correctly. I've noticed "glints" of bright pixels occasionally during the course of a video that may be some form of pickup instead of something physical. This will need to be investigated.

Jeff says that one chord of the SXR fan array has been repaired and the other chords seem to be working. The SXR was turned on for all shots.

Toward the end of the day, the lack of air conditioning started to affect the data storage. Data in shot 76899 may be suspect.

Monday November 26 2012 11:57 am Qian/Sarah/Chris 76900-76911 Plasma shot

This is the run report for last Wednesday.

The objective is to get familiar with the procedure of running the feedback system and using the analyzing code, so that we don't have to re-invent the wheel when Niko left.

I've run the feedback procedure on several shots and system itself is running as expected. ( Plasma is not good though)

Then we tried to run the phase flip on some shots for the fast camera but it didn't work out very well.

For the last shot, OH elect didn't fire. We then dumped it and shut down the machine. ( The reason why it didn't fire is not clear.)

Wednesday December 5 2012 5:13 pm Levesque ****** Gasket replacement and GDC

The chamber was vented, resealed, and pumped down on Tuesday Nov 27th to fix leaks by replacing copper gaskets. The standard 10" copper gaskets in 6 sections were replaced with annealed copper gaskets. The remaining 4 sections that were not replaced include the 2 pump stands (with Teflon gaskets), section #2 (which was not found to have leaks, and could not be replaced quickly), and section #9 (which has not been opened since the shell upgrade in 2010). Note that annealed gaskets were not used after the up-to-air in September since we did not have them in stock. The unused leaky gate valve in section 5 was replaced by blank conflat -- this will be replaced with a better gate valve during the next up-to-air.

While the chamber was open, a brief inspection revealed that the fast-camera background was damaged from the September glow or standard plasma operation. Pitting to the black surface created random speckles of reflective dots. In spite of the speckling, the background is still an improvement over looking directly at the chamber, thus the background was left as is.

After 1 day of leak checking, we glowed with 90% D2 + 10% He for 2 hours, followed by a 100% He glow for 3 hours. Glows were initiated with fill pressures of 50mT. Adding a large inductor to the GDC circuit did not prevent sparks/arcs on the fast-camera black background. Reducing the pressure to < 1mT as read on the convection gauge kept the glow emission only on the plasma side of the shells, and prevented sparks on the fast-camera background. The GDC current only decreased by ~15% with the large decrease in fill pressure. The total time of sparking on the black background with the higher fill pressure was roughly 1 hour, versus 3 hours in the September glow. One of the differential roughing pumps was unintentionally unplugged before/during the glow, and wasn't discovered until the next day, which allowed a significant amount of oxygen back into the chamber.

The bake was on during the morning of Nov 28th through Dec 4th evening. One differential roughing pump seized-up during the weekend, and again allowed more air into the chamber for about a day or less. Both cryo pumps were regenerated (separately) during the bake. After the machine cooled down, the base pressure this morning was 7.5e-9 torr. Two of the differential pumping lines on spool pieces between sections 3 and 6 are suspected to be responsible for significant leaks contributing to the remaining base pressure.

Water resistors in the OH electrolytic bank dump were replaced by heating-element coils. This has decreased the dump RC time to ~8 seconds, versus the previous many-minutes decay time. The bank is now much safer following a dump or power loss.

Wednesday December 5 2012 6:31 pm Angelini 76912-76940 Fast Camera D-Alpha

The first run day after the up-to-air primarily produced short, but reproducible, 4 ms plasmas. The fast camera was used with section 10 open, but with the remainder of the shells left in closed position. This allowed for the shells to be conditioned from the run. While Abel Inversions will not be possible without the black background, the plasmas were cool enough that the D-Alpha filter could be used for a majority of the shots. A quick peek at the fast camera data shows some mode structures that may be able to be correlated with the magnetics data. Further analysis is needed to be sure.

The first shots of the day were unusually long-lived 15ms plasma-filament shots. The shots appear similar to a normal shot until about 3.5 ms where instead of falling into the typical disruption, the plasma breaks into smaller tubes. We were able to capture some of these shots with the fast camera and I can show them at the next meeting.

The new OH dump was tested and performs wonderfully.

Monday December 10 2012 6:08 pm Angelini 76941-76981 Cleanup

There was improvement in the cleanup shots today from last Wednesday. I started with the same run settings, and got plasmas that were virtually identical to the plasmas at the end of Wednesday's run. The plasmas continued to improve from there. The shots today were, on average, 1 ms longer than the ones last week. They are, however, still short at 4.5 to 5 ms. There seems to be an issue with channel #12 on the SXR array. Starting with shot 76955, it displayed strange data that didn't fit with the other channels. The issue is intermittent, though. The SXR data for shots 76974, 76975, and 76981 looks fine. The shells for this run were all inserted except for section 10. I'll open up the rest of the shells for fast camera analysis once we've moved forward from the cleanup phase.

Wednesday December 12 2012 6:22 pm Angelini 76983-77013 Cleanup

Cleanup shots continued today. There was still improvement in the shots. The length only increased on average about a 1/2 ms, but the modes became more coherent. Clear 3/1 modes can be seen on a number of the shots later in the day.

The SXR array channel was fine for most of the shots today. The problem with the channel is intermittent.

The plan is to continue running tomorrow.

Thursday December 13 2012 7:02 pm Angelini 77014-77054 Cleanup

The run today was successful. The shots are on average about 5.5 to 6ms long and are becoming reproducible. The edge q was also lower. Shots that reach q of about 2.4 are 77045, 77048, and 77053.

The SXR array worked for most of the shots today. Channel #15 had trouble earlier in the run day. This is a different channel from before.

Earlier today, Jim found a leak in the Cryo pump in section 7. This is expected to be repaired the next time the pump needs a regen.

Friday December 14 2012 7:55 pm Angelini 77055-77083 Cleanup/Fast Camera

The shots continued to improve. Starting with shot 77075, shells 7,8,9 and 10 were opened for the fast camera. At the end of the run day I was able to get shots whose behaviors were similar to shot 70000. The long shots are 77079, 77081 and 77082. 77076 and 77077 weren't long, but their q profiles got rather jumpy as the plasma reached q=3. The 3/1 mode is strong there.

Jim seems to have fixed the leak in the cryo pump. The base pressure was in the 1e-8 range for most of the shots today.

The SXR array was fine for the run today, but nothing has been fixed yet.

I'm in the process of creating stripy plots from the fast camera data. I'll show those at the next meeting.

Monday December 17 2012 7:00 pm Angelini 77084-77122 Fast Camera Phase Flip

The shots remained long throughout most of the day. I think it's safe to say the cleanup phase is complete.

The primary goal of today's run was to get phase flips working. While there are still a few things to work out, I was able to get the phase flip program running by the end of the day with Niko's help. I haven't done any fast camera analysis yet. I'm not sure I will see much because the q and MR were changing drastically through the phase flip for most of the shots. Tomorrow the plan is to run phase flips while the shot profiles are more constant.

The SXR array didn't show any lost channels today. That's not to say they won't have problems in the future.

Today's shot with the strongest 3/1 mode is 77104. Shot 77116 had the lowest q of 2.28. Unfortunately, I don't think that's reproducible.

Tuesday December 18 2012 5:29 pm Angelini 77123-77146 Phase Flip/Fast Camera

Today the majority of the shots were phase flips. The hope was that something would show up on the fast camera during the phase flips. While by eye, one can vaguely see a "stalling" of the rotation in the video, I have yet to find a way of displaying this numerically. I can show some of the videos tomorrow. The shot with the strongest locked-mode was 77132. 77137 and 77138 get honorable mentions. Shot 77131 had the strongest 3/1 mode.

The six feedback coil currents as digitized by the A14 were terribly off. Jeff assures me that the signal sent to the coils were correct, but they're being recorded incorrectly. I don't think a single shot today had them displaying correctly.

The SXR continued to work fine.

The base pressure was a little higher today, but the shots seemed to be fine. Jim mentioned that we may need to regen the cryo pumps.

Wednesday December 19 2012 4:56 pm Angelini 77147-77173 Phase Flip / Crate Failures

The goal of today's run was to run more phase flips and see how the fast camera responds. I got through about 9 functional shots today. After the meeting, the heat was too much for the server room, and the crates started failing. After being unable to cool them down properly, the run was ended early.

For the shots where the crates didn't fail, the six feedback coil channels operated properly for some of them. I don't know if the heating problem had an effect on them, too.

The phase flip run will continue tomorrow if the temperature will allow for it.

Thursday December 20 2012 2:48 pm Angelini 77174-77191 Crate failures / Phase Flip

The purpose of today's run was to continue phase flip shots with the fast camera. Unfortunately, the temperature problem in the control room and server room has continued to cause crate recording failures. The failures are reported from the basement, south and north racks, which lead me to believe it isn't the racks themselves with the problem, but the server. I ran some crates-only shots before setting up, and everything seemed fine. For the first few shots, the crates performed normally, but they started failing as the run progressed. Until the A/C unit is repaired, I do not think it would be useful to attempt any further runs.


Thursday January 24 2013 6:31 pm Angelini 77192-77230 Cleanup

Today's run was primarily to clean up the machine after the break and ensure everything is working. By the end of the day the shots had cleaned up almost to where they were before the break. The plan is to attempt phase flips tomorrow afternoon if all continues to work well.

The SXR array lost channel 12 during shots 77209 and 77230. The problem is intermittent.

Some shots today showed strong 3/1 modes; 77222 and 77225 are both good. I'll attempt a BD on the fast camera data.

Surprisingly, the crates worked without any problems today, perhaps due to the cold weather. The leak in the A/C was fixed today, and the coolant is supposed to be replaced tomorrow.

Friday January 25 2013 5:18 pm Angelini 77231-77244 Standard plasmas

The goal of today was to do phase flips, but due to problems with caliban, I could not run the program. There may be a hardware problem with the computer. On Monday we'll attempt to debug the problem in depth.

The plasmas today were as good as the ones before the break. They would have made good candidates for phase flips.

I didn't observe any problems with the SXR array today.

Tuesday January 29 2013 5:51 pm Angelini 77245-77280 Debug

Yesterday the dual-channel PCI-e card from caliban was sent back to NI for repair/replacement. Until we get it back, the control coils cannot be used. The goal of today's run was to ensure everything was working for when the card returns. Unfortunately, I had problems all morning. One culprit was discovered to be the pulse amplifier for firing the TF crowbar. The signal was sent through another amplifier instead and that fixed the TF firing problem. Other camac problems were present which may be related to the bad pulse amplifier, but it is unclear whether changing the amplifier was the fix for those.

The ten plasma shots taken today were comparable to the last good shots from the previous week. Shot 77277 shows a rather fast 3/1 mode. Shot 77280 has a slower, but strong, 3/1 mode from 3 to 3.5 ms. Both may be clear to see on the fast camera.

The SXR had issues with channel 12 for shots 77279 and 77280.

The base pressure bottomed out today at 1e-9. This is the best vacuum we've seen over the past 5 months.

Tuesday February 5 2013 6:36 pm Angelini 77281-77325 Mode-seeking

The purpose of today's run was to get camera data of very clean 3/1 modes. In the future the fast camera's spacial resolution will be modified for comparison. Shots today with strong modes were 77314, 77318, and 77324. The 3/1 mode lasted from 2 to 3.5 ms cleanly in shot 77324. Shot 77312 has a short burst of a 4/1 mode.

The first shot of the day exhibited camac problems. A thorough investigation of the connection showed no problems and all subsequent shots went smoothly.

The SXR array continues to have intermittent channel issues.

The base pressure is holding steady in the low nanoTorr range. There seem to be no vacuum problems at this time.

Thursday February 7 2013 6:37 pm Hughes & Angelini 77327-77356 Shells Out 4cm

Several cleanup shots early in the day. Sarah started the run day, but the fast camera was being ill-behaved, so I took over to do cleanup shots. Experimented with shots that swing in and out (77342-77348) with particularly good results on the last two. From shot 77349 onward, all shells are back 4cm. From 77351 VF_ST timing is changed from 860us to 780us. Plasmas bounce around wildly in major radius until shot 77353. Jeff's favorite shots of the day are 77353-77355. 77354 sits at 91cm for a long while, and 77355 is very long. In both shots, q moves very smoothly through 3 from above. 77352 is interesting for a 2-1 tearing mode which causes a disruption, in which the plasma jumps in by almost 2cm, q jumps from 2.1 to 2.8, and a 3-1 kink flares up. Unlike its usual intermittent failures, SXR Fan channel 11 has been dead all day.

Friday February 8 2013 6:32 pm Levesque 77357-77378 Retracted walls

Continued run with walls uniformly retracted by 4cm. 3/1 modes appear to persist to lower q* values than for similar shots with walls fully inserted. Can see nice exponential growth of 3/1 modes for several shots with constant major radii from today and yesterday. Most shots had major radii in the up/down limited range for most of the discharge, with q* crossing smoothly through 3.

The fast camera was active for most of the day. All SXR fan array chords were working for all shots today. Midplane SXR signals from the active tomography chord have been lower than usual in comparison with the normal wall configuration, in spite of plasmas being closer to the diode. Loop voltages have been lower than in runs for the past month or so, but this is most likely due to the lower OH Electrolytic voltage setting. The retracted wall experiments will continue on Monday.

Noteworthy shots: 77362, 77364, 77372, 77374, 77377

Tuesday February 12 2013 3:50 pm Hughes 77379-77397 Ubiquitous Triggering Failures

Today's run was characterized by almost everything going wrong. Most of the run day was spent debugging the misbehaving basement J221s which failed to trigger the TF, the OHEL, and the OHST banks. All banks dumped safely, however. Additionally, there have been intermittent South and North rack failures.

Other than one anomalously successful vacuum shot in the middle of the day, we tried copying the J221 input-5 signal into the input-6 node in the tree, and this improved behavior somewhat: we were able to get all banks to fire on a vacuum shot with the TF lowered to 1100 and all other banks uncharged (77394), and then on a plasma shot at normal bank settings (77396). However, this was the only remotely normal shot of the day, as the VF crowbar failed to fire on shot 77397, causing the VF to ring.

We do at least have some interesting fast camera data from 77397, where we can see the plasma swing in and out, with the plasma current (and brightness) peaking and falling, due to the ringing of the VF.

After the VF crowbar failure, we decided to end the run day rather than risking damage to the banks, and removed the J221 input-6 hack.

77397 is pathological, but the nearest thing to a star shot for the day. 77396 is much more typical, but not very interesting.

Thursday February 14 2013 5:51 pm Hughes 77398-77428 Shells Back 4cm

An actual run day! CAMAC trouble with failure to trigger the OHST and TFST persisted in the morning until we repeated the hack-fix of copying J221_02:5 to J221_02:6 and J221_09:5 to J221_09:6. Good shots followed, but the South Rack consistently produced TR6841_16 and TR6841_17 errors. Additionally, one of the highest-number SXRF channels (14 or 15) was losing signal intermittently throughout certain shots for some unknown reason. The run day ended with another failure of the VFEL to fire, ringing the VF bank, and the decision to debug in the morning.

Plasma shots are from 77401-77428. Shots of particular interest are the following:

Most of the shots today were hampered in approaching 70000 or steady major radius due to the "early mode" where the plasma kicks inward at 1.2-1.3ms on every shot. One notable feature of the recent plasmas is a spike on the leading edge of the current trace which is much larger than the leading-edge current spike on shot 70000. This may be due to one or both of the OH and VF crowbar banks firing a little too late to prevent the current trace from turning over after the start banks peak, but this hasn't been investigated.

All recent plasmas also show SXR midplane traces markedly lower than that of shot 70000, but since their loop voltages are also lower, this may indicate a difference in impurities (that recent plasmas are cleaner) rather than a higher temperature. The triggering system will be examined before attempting to run with banks charged tomorrow. The following modifications to standard configuration are being left in place:

  1. All shells are back 4cm from "fully inserted."
  2. Of the J221_02:6 and J221_09:6 nodes in the tree, each has a signal cloning the corresponding output 5.
  3. The VFST time is set 80us earlier than standard.

Friday February 15 2013 5:26 pm Hughes 77429-77451 Shells Back 4cm

Since yesterday's run day was ended by the VF crowbar's failure to fire, we began the day by testing the krytron triggering. Everything seems to work, although the previously mentioned 6th output trick is still in place. As noted before, the VFST timing is still 80us earlier than normal, and of course all shells are still back by 4cm.

The initial vacuum shot was 77430.

77432, 77440, 77449, 77450, and 77451 are good shots for comparison to 70000. 77440 is probably the closest in R_0 and q*. 77451 is also very close except during the period from about 3ms to 5ms, when it stays outboard longer and then falls in quickly at a later time.

Other interesting shots were 77437, 77439, and 77444.

In 77437 and 77439, q* is extremely stable for about 1ms, starting close to 1.5ms.

In 77444, a strong, steady mode exists from 3.5ms to 5.5ms.

As in most of the recent shots, the presence or absence and the strength of the early major-radial-inward jump at ~ 1.3ms is the strongest determining factor in the traces of R_0 and q*, far outweighing effects of bank settings. It may be worth looking at a population of recent (i.e. shells-back) shots and a population of shells-in shots, and comparing the rate of occurrence and the amplitude of this radial jump.

As of shutdown, the machine is still pretty well-behaved, so the longer startup procedure may not be necessary on Monday.

Monday February 18 2013 6:45 pm Angelini 77452-77488 Fast Camera Shell 8 Asymmetric

The goal of today's run was to determine what effect the shells have on the fast camera data. Once things were working, only the bottom shell in section 8 was fully inserted with the the top shell and all the shells in the other sections extracted 4 cm. It seems that just that one shell has an effect on both the plasmas themselves (leading to a modification of the VFS timing to 760) and the fast camera videos. Once the shell was inserted, all videos showed the long bands, even when the plasmas were more inboard-limited.

To counteract the continuing Camac problems, the two TR6841 modules were deactivated and disconnected from the south rack crate. No further camac errors were occurred during the day.

The PCI-e replacement card was installed in the caliban computer in the south rack. All the RTM-T modules were correctly identified and initialized. Some tests of the control coils were made at the beginning of the day. A modification to the do_awg program was made to address the missed samples problem. Initially this modification was causing spiky currents on the control coils at about 5.5 ms. That error was corrected and the do_awg program now gives reliable phase flips.

During the insertion and extraction of the shells in section 8, an issue with the top shell motor was discovered. The set screws weren't well-placed and the motor was spinning without moving the shell. The motor was removed, repaired and replaced. The top shell in section 8 moves properly now.

The SXR fan array dropped channel 15 earlier in the day, but it seems to be working again.

The run tomorrow will continue the shell effect studies. Good shots for today are 77483, 77487, and 77488. 77483 and 77488 are outboard limited, while 77487 is more top-down limited. All the shots show the long stripes in the fast camera data.

Tuesday February 19 2013 6:53 pm Angelini 77489-77524 Shell 8 effects on fast camera

At the start of the runday, the base pressure was up in the 10^-6 range. The cryo pump in section 6 had shut down and released its trapped gas. After it was gated off, the base pressure came down quickly and it was possible to run. The base pressure throughout the day were higher than typical, but the run was able to proceed.

The goal of today's run was to see what effect the bottom shell in section 8 may have on the fast camera data. At the start of the day, the shell was fully inserted. It was pulled out in 1 cm increments throughout the day. When the shell is inserted, both outboard and inboard-limited plasmas show long banding in the fast camera data. As the shell is set further and further out, outboard limited plasmas are much more difficult to produce. The inboard-limited plasmas show less banding and more of a pinwheel. Inboard star shots are: 77496 (bottom shells in section 8 fully inserted), 77499 (retracted 1 cm), 77505 (2 cm), and 77517 (3 cm). As outboard-limited shots became more difficult to produce as the shell was retracted, further study is needed to form a coherent set of comparable shots.

It is not yet clear whether the proximity of shell 8 to the fast camera view has an effect on the banding in the data. At the end of the day, with shell 8 withdrawn 4 cm, the bottom shell in section 4 was fully inserted. A few shots were taken, but more runtime is needed before any conclusions can be drawn.

There were no camac problems to report. Removing the TR units in the south rack seems to have fixed the problem.

The SXR array seemed to work fine today.

Thursday February 21 2013 6:47 pm Angelini 77525-77550 Fast Camera Shells Retracted

Today's goal was to see the effect the shells may have on the fast camera images when the plasmas are outboard-limited. For the first half of the day, the bottom shell in section 4 was completely inserted while the rest of the shells were retracted. The second half of the run was with all the shells retracted 4cm. I was able to get a few outboard limited shots in each shell configuration, and some shots which transformed from being outboard to inboard limited.

Even when the shells are fully retracted, it is possible to get long-banded fast camera bd images. These images are harder to find because outboard-limited shots often lack the coherent modes typically seen in plasmas which are top/down-limited. As the plasmas move inward, these banded images start to appear more like pinwheels.

The SXR array sporadically lost channel 11 during the day. By the end of the day it'd come back again.

The cryo pump in section 7 had been regen'd. The base pressure held steady in the low 10^-8 range throughout the day as normal.

Star shots for the day:

77535 and 77536 when shell 4b was inserted. They were more outboard limited although the video for 77536 didn't come out properly.

77543 and 77546 when all the shells were retracted. Shot 77543 follows shot 71000 quite closely.

Friday February 22 2013 5:30 pm Angelini 77551-77590 Fast Camera Shells Out Phase Flip

The goal of today's run was to try phase flips with all the shells open. Some of the shots during the first half of the day were successful. In the afternoon the plasmas became less dependable. I plan to continue the run on Monday.

The phase flips were most successful when the plasmas were run outboard-limited. This is possibly due to the proximity of the control coils, but also because outboard-limited plasmas tend not to have q* values near a rational surface. Good shots for 0-degree and 90-degree phase flips are: 77557, 77560, 77563 and 77566. Further runs are needed for other phase angles.

A few of the plasmas went very far outboard and as a result had about 0.5 ms at a very low q*. Two shots in particular are: 77583 and 77584.

The SXR array lost channel 11 intermittently throughout the day.

The vacuum was great today. The pressure at the start of the day was 3e-9 and remained in the low 10^-8 range throughout the run.

Friday February 22 2013 5:45 pm Angelini see previous addendum

I'd forgotten to mention in the last report that the script has been updated to reflect the removal of the TR6841 devices from the south rack. It also has output 5 duplicated in output 6 for the two J221 basement devices. It seems that workaround is still necessary because the first plasma shot of the day failed to trigger properly without it. The script still uses the previous gas puff and VFS timing, so those need to be updated manually in the tree whenever make_tree is run.

Monday February 25 2013 5:15 pm Angelini 77591-77637 Fast camera shells-open phase-flip

Today's run continued last Friday's open-shell phase flips. The shots continued to vary just after breakdown making reproducible shots rather difficult. I doubt I'll be able to take enough shots to make any statistical statements about phase flips with the shells open, but I hope to have enough to give a picture of what the fast camera sees under those circumstances. Tomorrow I'll continue the run, but after that the tests will be closed-shell. I'll compile the shots most representative of their phase angle and show them on Wednesday.

The A14_14 in the north rack threw some initialization errors during "prepare". Re-running the "prepare" phase seems to clear the error and there are no errors during the recording or analysis phases after the shot. I don't believe there has been any loss of data.

The gas puff valve was set a bit too open so the pressure read 22 psi. It was lowered, but now displayed about 20.5 psi so tomorrow it'll probably be adjusted again. I increased the puff time at the very end of the day, but it didn't seem to have a noticeable effect on the shots (they were already unpredictable by that point).

The SXR continues to have intermittent problems with channel 11.

The vacuum is still performing well. The starting pressure was 3.9e-9 this morning and it stayed in the low 10^-8 range all day.

Tuesday February 26 2013 5:07 pm Angelini 77591-77682 Fast camera open-shell phase-flip

Today's shots were rather unreproducible. As far as I could tell, there were no major hardware problems. With the same shot settings, the startup for the shots between 1 and 1.5 ms was very similar, and then after that the shot profiles diverged wildly. The early mode seemed to have a very strong effect today.

I was able to get enough shots to have a basic idea of what a phase flip looks like with the fast camera at different angles. I'll show the images in the meeting tomorrow.

The SXR continued to have problems with channel 11.

While we've had recording problems with the A14 in the north rack for the first 6 control coils, the problem seems to have spread to 6 others. Now all the coils in sections 1,2 and 3 show the phase flip late and spread out. It may be worth checking to see what the problem might be.

After Qian's latency run, I intend to run phase flips with the shells fully inserted.

Wednesday February 27 2013 5:06 pm Qian 77638-77639 crates_only

TR modules are put back in and were not producing errors for the crates only shot.

There are some driver issues that the feedback code could not be compiled and run. Will plan to resume the test after this driver issue has been sorted out...

Thursday February 28 2013 5:34 pm Angelini 77686-77713 Closed shells

The goal of today's run was to attempt phase flips with the shells closed. All of the shells have been fully inserted, except for the shells in section 10 (for the fast camera. Unfortunately, the shots weren't consistent enough for phase flips. Even if that weren't the case, there is also currently some problem with detecting the RTM-Ts in the south rack computer, so phase flips wouldn't have been possible anyway. Instead of running tomorrow, I'll be taking the time to debug the problem.

There were two shots whose edge q started above 3, neared 2.2, and then crossed back up over 3 again before the end of the shot: 77708 and 77710.

For all of the shots today, the SXR array was working fine.

The vacuum bottomed out at 1e-9 this morning and many of the shots had a base pressure in the 10^-9 range.

Thursday March 7 2013 11:50 am Angelini 77714-77753 Closed shell phase flips

This run report is for last Monday, the 4th. I was unable to submit the form at the time.

The goal of the run was to try phase flips with the shells closed. In the morning the plasmas responded well to the RMPs, but in the afternoon I couldn't seem to get the q where the plasmas would respond well. I'll try some different bank settings tomorrow, and then I'll try increasing the control coil amplitude. For the shots with passable phase flips, I was able to see some locking behavior as I did with the shells open. The "good" shots for the day seem to be 77723, 77726, 77733, and 77741.

While I am seeing the locking behavior, the appearance of the flips are more of the long banded style rather than the pinwheel style. This is consistent with what I saw for the shots with natural modes.

The SXR array temporarily lost channel 11 again today. It came back again at the end of the day.

The vacuum's at its 1 nTorr low. The base pressure was in the 8 to 10 nTorr range all day.

Thursday March 7 2013 5:56 pm Qian 77754-77774 crates_only

Feedback latency is tested with osciloscope and the latency is 20us.

Another thing I found is that there might be some mapping error in the feedback signal. When the program is set to take a one-to-one from whatever input to output channel, according to the map, Input FB02_S1P should be sent to control coil FB02_C1, but the signal was instead sent to FB09_C2. If I swap the two SCSI cables on the breakout board for control coils, then FB02_S1P channel would coorespond to FB02_C1. However, individual check with the awg shots suggests that the mapping for control coil should be correct and those two cables should not be switched. Then, there might be some mapping error on the input side. Haven't had time to check that.

The SCSI cable connection is restored to what it was on Tuesday.( Which I think is the correct connection it should be.) But it might worth double checking that the phase-flip is as expected for Friday's run.

Friday March 8 2013 5:32 pm Angelini/Peng 77775-77816 Fast Camera Phase Flip Closed Shells

Today's run focused on phase flips. While the run day was plagued with a succession of small issues, I was able to get shots at the remaining four toroidal angles to complete the phase-flip collection plot. The camera BDs for some of those shots were a bit shaky, but they do show the phase flip. Toward the end of the day, I saw some locking in the first half of the phase flip, but the plasma didn't seem to want to lock during the second half.

The fix to the cooling water system was successful. I didn't have any basement rack errors at all during the day. The pressure on the high pressure valve was 190 psi. We should keep an eye on that.

The TR6841 modules were connected and activated in the tree for all shots today. There were no problems with them. Because they are needed for latency checks on the GPU system, they should stay connected unless problems arise again.

I got more intermittent problems with the North Rack A14_14 module. Sometimes it would fail to initialize. Re-initializing would fix it. On a few shots it failed to store. It wasn't detrimental to the run, but it could continue to cause problems.

The beginning of the day marked issues with the control coil amps. 21 of the 40 fuses needed to be replaced. It seems the fuses we have are different from those recommended on the wiki and are more prone to breaking. For the future, the correct resistors will be ordered.

There was an issue with the control coil signals being switched in section 2. Qian was able to resolve this before the phase flip shots.

I had an issue with the OHE bank when I tried to set it above 320 V. While the sticker recommends keeping it below 350, it seems the voltage cut-out is set to somewhere right above 320. Once the OHE was turned down, everything ran correctly again.

The SXR channel 11 dropped in and out throughout the day.

The vacuum started in the low nTorr range and remained in the 10-15 nTorr range for most of the shots today.

We reached shot 77777 today. It was a simple, short cleanup shot. The longest shot of the day was 77811, which was similar to shot 71000.

Monday March 11 2013 6:42 pm Angelini 77845-77881 D-Alpha filter Fast Camera

The goal of today's run was to see what effect the D-Alpha filter had on the videos. I was able to get a few pairs of similar shots with and without the filter. The primary issue is that there is a lot of light lost with the filter in place. The mean intensity of the light with the filter is about 15% of the intensity without the filter. Even with the substantial light level difference, the dominant modes were similar with comparable shots. However, the "checkerboarding" did show up when the light intensity dropped low enough. To test if this was due strictly to the intensity level, I took some shots at the end of the day without the filter and with the fstop closed down. When the fstop is set to about 6, the checkerboarding becomes apparent. I suspect what I'm seeing is noise from the CMOS when the signal no longer dominates. I'll show some images on Wednesday to demonstrate this.

The first vacuum shot of the day failed to fire the VFE. The connection to the grounding cable was tightened and the problem did not reoccur.

The SXR continues to sporadically lose channel 11.

The vacuum is still excellent.

Monday March 12 2013 5:41 pm Angelini 77882-77910 D-Alpha / Disruptions

The first half of the day was spent taking D-Alpha filtered shots with shells 7, 8 and 10 open. Shell 9 was initially left inserted and later retracted. It seems that when shell 9 is in place, there is a greater amount of light emitted on the outboard side of the videos. This could indicate some plasma-wall interaction. After retracting shell 9, the overall light level with the filter dropped into the noise range. The remainder of the shots were taken without the filter.

The second half of the day was spent adjusting the frame rate and exposure level of the camera to see if the post-disruption modes could be captured. Because those modes only last about 100 to 200 microseconds, the frame rate had to be set to 121000 fps. This rate isn't achievable with the 128x128 resolution. The 128x64 resolution used ends up cutting off the top and bottom of the image, but because the plasma is so small after the disruption, most of those cut pixels wouldn't carry any data. I can get about 20 frames with those settings. Unfortunately, these settings prevent any light from being captured during the remainder of the shot.

For once, there are no major problems to report. The SXR is still losing channel 11 and the vacuum is optimal.

Monday March 14 2013 7:35 pm Angelini 77911-77953 D-Alpha and Color Filters Fast Camera

Today I continued trying shots with and without the D-Alpha filter for comparisons. I also moved shell 9 back in again for the color filter comparisons.

Comparing close-to-identical shots, I'm still seeing similar behavior with and without the D-Alpha filter. I'm confident the phase flip q-scan can be done without the filter. I also have shots I can use to compare the light in the dark region. Abel inversions on comparable shots with and without the filter give similar profiles.

At the end of the day, I ran shots with the color filters to attempt to see the balance of green, blue and red light. The filters are subtractive, so for each of the primary colors I needed to use two filters stacked. The red light gave the strongest response, followed by blue and then green. A reconstructed 3-color image in Matlab displays rather reddish plasmas. I did the color filter tests with shell 9 pushed in so I could see if there might be a difference in how much light comes from the shells. There wasn't. The BDs showed very similar modes for each of the colors. It may be worth repeating this experiment with the shells in different configurations.

The base pressure was up a bit today. The A/C in the test cell wasn't turned on this morning, so that may have affected it. The plasmas were still mostly consistent, although the running base pressure was between 12 and 19 nTorr.

I don't think the SXR channel 11 was on at all today.

The shells are all pushed in except for section 10 in preparation for phase flips tomorrow.

Monday March 15 2013 6:01 pm Angelini 77954-77972 Breakdown Failures

Today's run suffered from breakdown failures. While the shots early in the run were fine, after a while they completely failed to break down even with identical bank settings. Some troubleshooting steps were taken:

The only possible abnormality in the diagnostics is a signal spike in the soft x-ray midplane detector at the time the breakdown should occur. This only appears on some of the failure shots.

Further troubleshooting will continue on Monday.

Friday March 22 2013 6:04 pm Angelini 77885-78036 Fast Camera Phase Flip q-scan

The issue with last week's run turned out to be a short in the e-gun. The e-gun was repaired and the filament was replaced. Yesterday and early today the e-gun was baked and pumped out. The vacuum didn't seem to be too affected by this. The current on the e-gun is set to 10 amps.

The first half of the day was spent on cleanup shots. The plasmas weren't too different from how they typically behave after a week without running. The pressure started at 4e-9 and reached around 1.7e-8 Torr for many of the shots.

In the early afternoon the shots were consistent enough for phase flips. The shot style involved a q somewhat above 3 at the beginning of the flip and typically ended a bit below 3 after the second half of flip. The closer th edge q was to 3, the more quiescent the dominant temporal mode of the fast camera data seemed to be. I'm going to try to classify "quiescence" using standard deviations and see if there's a clear relationship with the edge q.

I'll continue with the phase flips on Monday to try to increase the dataset.

Friday March 25 2013 2:47 pm Angelini 78039-78073 Fast Camera Phase Flips q-scan

This morning we had a small water leak by the north rack on the low pressure side. Nick was able to tighten a clamp and repair it quickly. The water luckily flowed away from anything sensitive and dried soon enough for the run. The high pressure valve did read 200 psi today.

Today's run continued the q-scan from Friday. I have a nice solid set of shots for analysis. A quick look shows there may be a q vs quiescence trend during the second half of the phase flip. I'll show the scatter plots on Wednesday. I intend to continue with this tomorrow, but with the timing of the phase flip changed so it's later in the shot. The lack of a clear trend during the first half of the phase flip might be caused by the lingering effects of the early mode.

The base pressure was up a little today. It started at 3e-9 Torr and most of the shots were in the 15-17 nTorr range.

Friday March 25 2013 7:26 pm Levesque 78074-78087 Perturbations during startup

Ran shots with control coils energized in a few different configurations during startup to see if breakdown would be hindered. Peak control coil current in the strongest cases was ~40amps.

Applying a -3/1 field (78076-78080) with an amplitude of 20amps did not dramatically affect the breakdown. Using a 40amp amplitude reproducibly changed the startup, with breakdown currents ~10% lower and plasmas rapidly crashing inward. This could possibly be compensated for with different bank settings, but I didn't explore that.

Applying an m/n = 0/5 field (78083-78086) with amplitudes of 40amps did not hinder the breakdown at all -- plasmas mostly behaved as if the perturbation wasn't even there. This is good news for the proposed ferritic wall upgrade, which may produce strong n=5 error fields depending on the wall thickness.

6 control coil fuses blew during shot 78086. These were replaced after the following shot.

78087 had a 40amp -1/1 field on during startup, but 6 of the 40 coils had blown fuses. Breakdown was not noticeably affected.

Tuesday March 26 2013 5:38 pm Angelini 78088-78127 Fast Camera q-scan phase flip

Today the q-scan of the fast camera phase flips continued. This time I shifted the timing for the phase flip to run from 3 to 5 ms with the flip at 4ms. It seems to have solved the issue of the first half of the phase flip being too close to the breakdown-induced early mode. However, the later half of the phase flip often took place with the major radius (or the q) changing more rapidly. Subtracting out the shots with problems, I should have enough of a data set to find any trends.

There are no major problems to report today. Even the SXR channel 11 is working.

The base pressure was at 4e-9 Torr and the shots were again in the 15-18 nTorr range. This is a little higher than before, but doesn't seem to be causing problems yet.

Thursday April 4 2013 7:04 pm Angelini 78183-78241 Cleanup and Fast Camera Phase Flip

As expected after a week without running, the plasmas today were mostly terrible. They only started cleaning up after 4pm and as a result, I only got a handful of good phase flip shots. After my talk tomorrow, phase flips with a control coils amplitude of 20 Amps will continue. There weren't any difficulties at that amplitude and even the A14s displayed the flip properly. In the past the first 6 control coils would display with a shifted and extended timebase, but that wasn't present on any of the phase flip shots today.

During the high pot today, there was arcing between one of the TF magnets and the port on the top of section 4. The insulating sheet was shifted to address the arcing.

The first few shots of the day were OH-only to check for problems. Everything behaved correctly.

The base pressure at the start was quite low at 1.9 nTorr, but most of the cleanup shots had a higher-than-normal pressure in the mid-20 nanoTorr range. After the shots started cleaning up, the base pressure dropped closer to the typical running range. I'm hopeful for a good run tomorrow.

All the SXR channels were present for each of the shots taken today.

Friday April 5 2013 7:32 pm Angelini 78242-78289 Fast Camera Phase Flip 20 Amps

Today's run continued the phase flips with coil amplitude of 20 Amps. After some issues, I finally got consistent shots at the end of the day. Monday I'll be moving to larger amplitude phase flips and hopefully concluding this run campaign.

The base pressure came down to normal in the early afternoon, but a breaker tripped and the cryo pump in section 1 was turned off. There has been discussion of moving the cryo to its own breaker to prevent other electronics in the test cell from throwing the switch. The base pressure came down again after some cleanup shots.

The A14_14 in the North Rack threw errors all day during the Init. I had to run the Init multiple times for each shot to get it to activate. Fortunately it didn't show errors during Store, but it is still worth checking out.

The SXR array continues to show all channels. Did someone fix it?

Monday April 8 2013 6:34 pm Angelini 78290-78366 Fast Camera Phase Flip / Disruptions

Today's run was a good one, which made up for last week's poor runs. The goal was to round out the phase flip data set. Shots with a CC maximum amplitude of 20 Amps were taken with lower q values and shots with a maximum amplitude of 35 Amps were captured as well. The high amplitude shots almost unanimously disrupted before 4ms. While this didn't add anything to the phase flip dataset, they consistently disrupted, so I was able to capture disruptions with shells 7 and 8 removed. For the last few I used the D-Alpha filter as well.

I'll have analysis for Wednesday showing the effects of a larger amplitude phase difference on the fast camera data. I'll also show some of the disruption shots from the end of the day.

The vacuum was a drop higher today, probably because the test cell was warmer. Shots ran in the low 20 nTorr range.

The SXR array again seemed to be fully functional today.

Because of the high amplitude current pushed into the control coils, I needed to replace a few fuses in the amplifiers. Only one coil was down at a time, and the failures were few and far between.

Wednesday April 10 2013 5:41 pm Stoafer/Levesque 78367-78369 Thomson Setup

We used crates-only shots to setup the Thomson scattering diagnostic. This included laser and polychromator scope timing. During the run day, laser alignment was also performed.

The run has been very successful so far. We were able to detect stray light from within the chamber from a laser pulse in the polychromator -- this is a promising result so far.

Some tests of the stray light were also performed with the following results. In normal operation, with the collection port opened and the viewing dump open, we saw about 80mV of signal. With the collection port closed, we saw about 30mV of signal, showing some light entering the collection lens from outside the chamber (presumably originating from the beam dump). This was after we enclosed the collection lens in foil to reduce this stray light. When the collection port was open and the viewing dump was closed (no viewing dump), we saw about 550mV of signal. This showed that the viewing dump reduced stray light by about a factor of 7 with our current arrangement. There is a lot of room to improve stray light reduction, including sources outside the chamber.

We will continue the run tomorrow and plan on running plasma shots in the afternoon.

Thursday April 11 2013 7:31 pm Stoafer/Levesque 78373-78400 Thomson Setup

Plasma shots were taken with the Thomson scattering diagnostic for setup and proof of principle purposes. Our first plasma shot recorded successful Thomson scattering data, although signal was rather low.

Throughout the day we attempted to adjust the collection lens alignment, plasma parameters, and laser timing to gain signal with some success. We were able to obtain relatively hot and dense plasmas by the end of the run day, but are still limited in TS signal.

The run will continue tomorrow to optimize collection lens alignment, polychromator alignment, and laser alignment.

We have seen evidence of poor laser beam profiles, which limits the amount of energy we can put into the beam. This will be looked into once the run campaign is finished. For now, we will run with lower energy pulses.

Friday April 12 2013 6:40 pm Stoafer/Levesque 78403-78418 TS setup

We continued in the TS system optimization focusing on the collection system alignment. A good plasma for Thomson scattering has been produced with good reproducibility. Adjustments in collection lens location and fiber bundle position behind the lens were made. We found a significant change in scattered light signal for the fiber bundle position relative to the collection lens, whereas movements of the collection lens relative to the chamber showed less significant changes in signal. Therefore, the next run will begin with optimizing the position of the fiber bundle for collection focus. A shot with good Thomson signal is 78417. A great plasma with mode activity is 78414.

Monday April 15 2013 5:46 pm Stoafer/Levesque 78419-78464 Thomson Setup

The TS system was setup further for optimizing the system. The focus position of the collection fiber bundle was optimized for signal collection. The collection lens was repositioned twice without much of an effect on the signal. Further optimization will take place offline with work on laser power, laser spot, laser alignment, polychromator alignment, and more. A good, reproducible shot was developed and a scan of laser pulse timing was performed. This was to measure the temperature and relative density at various points throughout the plasma. The TS data will be analyzed. Bumping the soft x-ray fan array during collection lens adjustments affected whether certain channels were working or not.

Thursday April 18 2013 8:43 pm Qian 78486~78551 plasma shot

feedback system is tested today with several parameters briefly tried. While some fb shots seems to give positive results on the fb control. It could also due to the shot to shot variation.

The overall shot style does not give a very strong mode when q varies from 2.8 to 2.4. certain gain and phase are tried which seems to give a mild growth or suppress depending on the phase, but the shot is not very reproducible and i cannot confirm such behavior.

one can check 78539 and 78552 and compare with the neighboring shots.

further tests will be make tomorrow.

Friday April 19 2013 8:15 pm qian 78553~78644 Plasma shot

Since the q towards 2. style shot is itself very quiet during much of the time. It is not very suitable for conclusive feedback result. Today's shot is mostly focusing on the q around 3~2.8 shots. The plasma is not very reproducible so the results are not conclusive yet.

Gain for yesterday is found to be actually too high. Lower gain feedback gives less dramatic change in the perturbation (like phase flip would do) and gives better performance. Many fb shots are found to be suppressing the mode overtime. But shot to shot comparison is yet to be made to give more reliable results. A phase scan is performed. (sample for each point is low though) and gives frequency change and amplitude change. Detailed analysis is yet to be done.

Overall, the feedback definitely does some thing to the plasma. But to suppress the mode,if not impossible, the phase window is at least narrower than expect, and needs moderate gain.

Monday April 22 2013 2:23 pm Hughes 78645-78648 Attempt at repairing some sensors...

Jeff and I replaced three array boards and two feedback boards, then took a brief series of vacuum and plasma shots to test those channels. The good news is: 1) The shell 8 topmost poloidal sensor is now working! 2) The other sensor faults that Jeff and I went after apparently aren't due to board problems, so we have lots of good boards. The bad news is: 1) The new array boards are awful. The gain is low by a factor of 5-10 and they have tremendous amounts of noise compared to the other boards. All three array boards will be taken out and replaced with the old counterparts. 2) The shell 6 lower-midplane poloidal sensor has an in-vessel short to the chamber. 3) TA02_S1P, PA1_S01P, and PA2_S14P all look bad compared to other sensors on sharing a board, meaning the fault is probably in their cables or in-vessel. To do: 1) We should add FB06_S2p to a list of things to look into at the next up-to-air. 2) We should investigate the cabling of TA02_S1P, PA1_S01P, and PA2_S14P to see if their problems are in- or out-of-vessel, and decide what to do about them. 3) We need to figure out what we're doing about the lousy new array boards. 4) I'll replace the new boards with their old counterparts, and try to just do plasma shots as per usual tomorrow (Tuesday).

Tuesday April 23 2013 7:09 pm Hughes 78649-78695 Even-Numbered Shells Out

Shots of interest: 78649 - Initial vacuum shot, modeled on 77400 78686 - Closest shot to 70,000 78694 - Characteristic shot type of the day Shots 78651-78659 were spent on deliberate cleanup shots, trying to crash the plasma out toward the shells. Shots 78660-78671 were spent attempting to reproduce shot 70,000 with all shells still in, to find the right neighborhood in bank settings. This was only marginally successful (I suspect the plasmas were still cleaning up). Around 2pm I decided to switch over to the intended configuration with the even-numbered shells retracted by 4cm from their fully-inserted positions (as estimated using the plastic stops that establish maximum insertion of the shells). Shots 78672-78695 were spent attempting to reproduce shot 70,000-style plasmas (based on R0 and edge q traces). The timing of the VF bank firing was modified a few times during this shot series. Shots 78672 and 78673 are at the normal timing (860us); shots 78674-78675 and shots 78679-78695 fire the VF 40us early (820us); shots 78676-78678 fire the VF 60us early (800us). A major factor in plasma performance has been the 'early mode' tendency to jump or deflect in major radius at around 1.3-1.7ms, producing general irreproducibility. However, there commonly appeared a shot style similar to shot 78694 characterized by a very flat R0 around 93cm, a shot length around 8ms, and an edge q profile similar in shape to but displaced away from 70,000. Although it may not be easily comparable to 70,000 style shots, we may be able to use this as a target style for half-shell runs. I'll have to do some analysis Wednesday and figure out where to go next. As of the end of he run day, the even-numbered shells are still retracted. The VF timing has been returned to its usual condition. Some interface thoughts that came up during the run: We should really look at adding an "advanced settings" button to the Dispatch Control to avoid having to muck about in traverser and risk damaging the tree by accident--I'd suggest it should include a "restore defaults" button, as well. We should also try to keep all the changes applied to the current shot, rather than half of them affecting the current shot and half affecting the next shot.

Thursday April 25 2013 5:34 pm Hughes 78696-78743 Even-Numbered Shells Out

The model shot family for today's run was 78674, 78682, and 78694. Shots falling between these were selected; many were close but discarded, and these were marked in terms of how they related to the target family.

Noteworthy shots:

78696 - Daily initial vacuum shot.

78699, 78702, 78707, 78712, 78713, 78714, 78722, 78735, 78738 - Good (or at least okay) shots within target family.

78705 - Characteristic type of shot with R0 a bit too low and q a bit too high.

78706 - Characteristic type of shot with R0 a bit too high and q a bit too low.

As the latter half of Tuesday's run, all even shells are retracted 4cm from their fully-inserted position. Also, the VF_ST time has been set 40us earlier than standard to 820us; as of the end of the run, this has been returned to the standard setting.

Also, the array amplifier board Nick repaired has been installed in amp box 2, Bot3 position to test its performance and to attempt a repair of PA2_S14P. The sensor's signal seems like it might be better, but it's still strange. The board, however, appears to function essentially like any other board, so it seems to have been repaired successfully.

I now have 16 shots fitting a fairly tight envelope in R0 and q, plus at least half a dozen more good ones if the standards for grouping are relaxed. A lot of plasmas weren't awful, but weren't terribly good either. If someone desperately needs Friday, I can probably sacrifice it to more urgent goals (besides which I need to do analysis at some point). If someone wants Friday, please let me know tonight, so we can figure out who's doing what in the morning.

Friday April 26 2013 6:18 pm Hughes 78744-78789 Even-Numbered Shells Out vs. All Shells In

Today's run was intended to compare even-shells-out operation with all-shells-in operation. The main upshot is that each configuration is pretty resistant toward the other's shot style.

Noteworthy shots:
Jeff and I spent awhile playing with bank settings trying to get the plasma to stabilize at around 93cm the way it was doing with half the shells back, but it didn't seem happy doing this long enough for the current to rise and drive q down to a similar region. I also experimented with letting the plasma heat up and then swing out to drop q, at the expense of R0 being somewhat higher.

I suspect the issue may be that the shells which had been retracted haven't really seen cleanup shots since Tuesday afternoon, and that this combined with increased recycling is making for much dirtier (possibly denser?) plasmas. Even with the plasmas sitting a good bit farther outboard than in shot 78674, the SXR midplane sensor sees a considerably higher signal, which seems to corroborate this hypothesis, at least at first glance.

Although nothing came out looking quite like the 78674 shot style, we may be able to at least vaguely compare the behavior of the above-listed shots. It may be more fruitful to compare them against the 78706 shot style, which had somewhat lower q and an earlier q minimum, and tended to sit on a higher R0.

Monday April 29 2013 6:09 pm Angelini 78790-78855 Fast Camera Amplitude Scan

Today's plasmas were rather unreproducible. That meant I didn't get many shots for the amplitude scan, which requires a tighter q range. The plasmas weren't that bad so I'm hopeful for tomorrow's run. I may need more days than I'd originally planned.

The base pressure was typical for a Monday at around 3.5e-9 Torr.

At the beginning of the day the RTM-Ts were unable to initialize. Both the script and the do_awg.cpp program had slots 101 and 102 swapped. Flipping them back allowed caliban to properly communicate with the RTM-Ts. I was unable to find any hardware problems, but changing the software slot references may be necessary in the future. There were no problems with the phase flips after the RTM-Ts initialized properly.

Tuesday April 30 2013 6:20 pm Angelini 78856-78905 Fast Camera Amplitude Scan

The amplitude scan continued today. The shots were somewhat more reproducible and a general trend is beginning to show. I'll show the plots tomorrow.

A few issues came up today. First, the battery backup for athena seems to have a low battery. The workstation just lost power at one point during the run. It's been plugged into the surge protector side.

The other issue was with the CPCIs in the south, west and north racks. They stopped initializing in the afternoon. We tried power-cycling the ones in the south rack, running crates_off and crates_on and restarting the actserv_8002. After that they initialized properly again, but I'm not sure what fixed the problem so it may reoccur.

The north rack A14_14 continued to have problems. It had trouble initializing and during a few shots failed to store its data (even when it initialized without error).

The vacuum is still good. The base pressure at the start of the day was 2.2e-9 Torr and it remained in the low teens throughout the run day.

Thursday May 2 2013 6:30 pm Angelini 78906-78955 Fast Camera Amplitude Scan

The run today was somewhat more successful than the previous days. While I was able to fill out the charts a bit more, it didn't seem that I could get any clean shots with edge q lower than 2.9 when an RMP with a maximum amplitude greater than 25 Amps was applied. They all disrupted right at the phase flip. Despite that, the plasmas were more reproducible today, perhaps because the OHS was set 10 kV lower.

The plots so far still show a saturation for shots with an edge q close to 3. I'll try a few different ways of plotting the data to see if I can find a good q value to mark the division between shots with saturated modes and those without.

The vacuum continues to stay low at 3e-9 Torr and there were no other problems to report today.

Friday May 3 2013 7:55 pm Levesque 78956-78996 Fast camera shot variety

Ran with several very different shot types in order to expand the database of fast camera videos. Shells in Sections 7, 8, and 10 were fully retracted for Shots 78956-78961, then Sections 7 - 10 were fully retracted for the rest of the day. This exposed the black background to allow Abel inversions of the fast camera data. Shot groupings are as follows:

78961-78971: High start-current: ~12-17kA startup current, versus our typical ~8-10kA in most recent runs. Noteworthy shots are 78961, 78965, and star shots 78969, 78970. Several shots had very large 2/1 modes. The fast camera showed typical emission behavior in preliminary analysis.

78977-78983: Double-puffs. These shots had typical or short initial puff durations, then had an additional gas puff during the plasma (at 2ms or later). With the second puff duration programmed to be as short as 10us, the fast camera saw bright emission (about the same intensity as the breakdown) at the high-field-side for ~2ms, or until the disruption. Note that we are not sure how quickly the puff valve closes (i.e. it might actually be open longer than 10us). The 2nd puff emission typically appeared in the fast camera view about 0.3ms after the valve was set to be opened. Extra emission in the normal spectrometer view took longer to appear and was not as strong; the emission slowly rose starting ~0.8ms after the puff. Note that the puff valve is at the high-field-side of Section 9, the fast camera views tangent to this region, and the D_alpha spectrometer views a vertical chord at Section 6.5. The camera/spectrometer discrepancies suggest that the extra neutral interactions are localized near the puff valve for a substantial amount of time, and do not quickly spread around the machine in comparison with the equilibrium evolution. The loop voltage began rising 0.5ms after the puff, accompanied by a decreasing plasma current, suggesting that the plasma was cooling down. The midplane SXRT chord also had a delayed rise from the puff. Plasmas disrupted within ~2ms of the second puff.

78984-78993: Drastically different VF/OH bank timings. These shots are very bizarre, and produced some exciting fast camera videos. Small plasmas are seen to move vertically -- most start near the top of the machine and expand/drift downward to being vertically centered. 78984 broke down near the bottom of the machine, then the plasma rapidly moved up to the top shell over ~0.1ms before later expanding downward. Shot 78987 has an exception video including filamentary structures during a double puff. 78988 had a triple-puff, but the third puff didn't have a clear effect the could be unambiguously separated from the standard behavior of those shots (many bright flashes after a slow decay of emission). Star shots are 78991 and 78993, which had clean 4/1 and 3/1 modes respectively after the initial mayhem.

78994-78996: Targeting Niko's feedback shots (similar to 74780). Didn't have much success here, but ran out of time after only 3 shots. It looked like it may not be possible to reproduce the target shot with the 8 shells retracted.

Plasmas that were transiently far inboard or far outboard appeared throughout the run.

Tuesday May 7 2013 5:42 pm Rhodes 79037-79087 Phase Flips

Continued yesterday's excitation of internal resonant surfaces.

First few RMPs after 5ms did not work because of limitation on control coils. They are now set to sample 11ms into shot.

Today obtained long lasting plasmas with lower q*, closer to 2. RMP was applied towards the end of the shot, when the major radius was between 90 and 92 cm. Amplitudes were kept low with the hope of seeing a torque but not complete locking of internal mode. This remains to be seen.

Thursday May 9 2013 6:59 pm Angelini 79088-79130 Fast Camera Gas Puff Imaging

The purpose of today's run was to capture modes and disruptions with the shells fully retracted. At the beginning of the day, the standard exposure (9 microseconds) was used with shots naturally disrupting from high mode activity. We attempted to get the shots to disrupt near the midplane with some success. After that, the exposure was dropped to its lowest (1 microsecond) and a second puff was fired in the middle of the shot. Shot 79109 was the only shot which didn't disrupt immediately following the puff. Because of the limits of the puff circuit, there doesn't seem to be a way currently to lower the strength of the puff and prevent the immediate onset of a disruption.

Shots with edge q less than 2.5 were attempted in conjunction with the gas puff. It seems there is still 3/1 mode activity even with very low q, and the disruptions were primarily due to that mode. Some 3/1-2/1 hybrid modes were seen in the magnetics. I'll attempt to pull some of this out of the fast camera data for next week's meeting.

Strong condensation was seen on the cooling water line to the basement rack during shutdown. It doesn't seem that any electronics are in danger of shorting due to the condensation, but please keep an eye on this as the weather gets warmer.

The loop voltage diagnostic is currently disconnected in section 10 for the tests tomorrow.

Friday May 10 2013 5:52 pm Byrne 79131, 79132 Vacuum/crates only

The Loop Voltage output box failed today on the first shot. The first shot was un-divided, leading to an overvoltage condition in the CPCI at the firing of the OH start bank.

Rather than BNC feedthroughs, the LV coil was fed directly into the divider box. Torques to the box shorted the internal voltage divider, either through moving the internal wires relative to each other, or breaking a solder joint leading to loose wire contacts.

A crates only shot was taken with a low level sig-gen sine wave input after this to ensure that the CPCI was not damaged. This was an identical signal to one input yesterday, and the digitized signals were equivalent before and after, with a high degree of fidelity. It seems that no damage was done to the digitizer. Furthermore, the voltage divider has been re-constructed using better solder joints and BNC feedthroughs to eliminate mechanical stresses on the electronics. Bench testing (9v Battery) shows equivalent voltage division to before, but has not been tested on the LV coil as yet.

Repairs to the voltage divider meant that pre-positioning shots could not be taken, as facilities was working in the cap room AC the rest of the day. It was decided to begin moving the coil without shots, and compare the post-positioning shots to vacuum shots taken during earlier runs.

The loop voltage re-positioning is 40% done (The coil is hanging from zipties on 4 of ten braces), and work is accelerating as methods for reliably threading the LV coil and attaching the ziptie holders to the radial braces are developed. There is no reason to suspect that one more day would be insufficient for completion.

I have two finals on Monday, so will be unavailable to work for much of the afternoon. I don't think it would be a good idea to have work-studies on the machine unsupervised, and the only qualified people in the lab with experience up on the "roof" are Jeff and Jim. I don't want to let this job run to Tuesday, or require other people to step in and do my work for me, so I'm hereby requesting clearance to work Sunday to get a jump on the threading.

There is little to no risk of harm to myself or the machine, as all tools I will be using are light, plastic, and unpowered. It will be necessary to do a safety check when the work is done regardless of how, so all Sunday work will be inspected before the machine is brought back on-line.

While repositioning was always going to be difficult, the expected "unexpected problems and delays" have arisen. Though they have been dealt with, I'm recording them so that a post-positioning safety inspection takes full account of them.

Certain PVC covers are positioned such that they completely occlude the TF-chamber gap. They had to be removed. So far 5 (of 40) covers have been removed. They have been labeled with masking tape as to which TF (case and side) they belong.

The loop voltage coil, as it turns out *is* fixed in place. It is run though one tab in one chamber piece. It is a rather tight fit, so while care is being taken to pass the wire through gently, some nicking in the second, outer plastic insulation has been noticed. It is the same type of insulation used for the flux coils (thick, translucent plastic, not heatshrink).

I'd like to show this to someone knowledgeable to determine whether there is still enough of a safety margin with TF arcing. If it is not, the only real option I see is to completely remove the LV coil, strip the outer insulation, re-insulate, and install. Or simply insulate a new length of wire and replace the LV coil, as it may be tough to straighten it enough to swap jacketing. In any event, the coil will have to be completely pulled through the tab, so after inspection, that work will continue.

Two radial sensors, on chambers 3 and 8, which were hung around the inboard midplane conflat flanges, were removed to make way for the re-positioning (and later, the Shaping coil holders.) One was disassembled and removed intact, but the thin wire connecting the sensor was broken due to rough handling. The sensor wire on the other one was already broken before work began. The conflat nipple at the second sensor was connected to the spare puff valve. Short of gating the CF off, and removing the attachment, the only way to remove the sensor was destructively. Since it was already broken, it was destroyed.

A small hand saw was used, and the sensor was split in two and removed. There is significant plastic sawdust at the point of removal. Though it is not an arc hazard, the plan is to use canned air to blow it to the ground and vacuum up what can be reached. This has not been done in case there is a reason not to do so, or a better way to remove the plastic dust. The sensors themselves have not been used on the machine for many years, were not connected to any digitizers, and the general state of neglect and disrepair they were found in means that they should not be missed.


Friday May 10 2013 6:36 pm Byrne 79131, 79132 Vacuum,Crates

On Shutdown, it was noticed that the feedthroughs for the ion gauge have come disconnected. Two of the 7 feedthroughs (at 11 and 1 o'clock on the face) pulled loose. Rather than risk damaging the ion gauge, by reattaching them, they have been left as is.

Tuesday May 14 2013 6:06 pm Byrne 79133-39 LV calibration

Took a few low level OH shots to check for loose tools. None were found.

Took a VF only and OH only shots with identical bank settings to previously taken shots. In all cases, the gross features are the same, and it seems that noise has been reduced. This may be due to better electrical coupling at the voltage divider.

A full vacuum or plasma shot has not been taken, but all indications are that performance will be as good or better than it was before.


Thursday May 16 2013 5:14 pm Qian/Dov 79139~79179

Some clean up shots are performed today. Plasma shot traces seems normal towards the end of the day. A OH coil connector over the top of the machine was found to be torn broken after OH elect was set to 400mV. Jim fixed it and it works fine so far. So, it seems not safe to set OH elect that high. Plasma is not reproducible for the current bank settings. Further adjustment need be made so that the result of fbtest would be easier to identify.

Friday May 17 2013 4:53 pm Qian 79181-79234

Today's plasma is reproducible. Plasma response is quite distinguishable with different phase set. It seems that when the phase is set for suppression, the mode will drop, but the equilibrium starts to vary heavily. (Another way of saying it is: when a fast mode get suppressed, a slow mode get excited.) This seems to be consistent with the gain-response diagram.

I will test some other possible improvement for the feedback algorithm on Monday.

Monday May 20 2013 4:57 pm Qian 79235~79292 feedback shots

Further improvement with the feedback algorithms are made and tested today.

Demonstration shots: 79269,79270,79271, 79291,79292 where 79271,79291 are reference shots without feedback and others are feedback shots with the most promising parameters tested so far.

Friday June 7 2013 4:26 pm Peng 79548~79593 plasma shot

Shots with slowly rotating perturbation are tested today. With freq around positive 0.3~0.5 KHz, the plasma behaves similarly to those suppressed fb shots.

With only section 6~10 of the control coil turned on, this behavior is not seen. This effect is also not seen for negative freqs.

Monday June 24 2013 5:14 pm Levesque/Stoafer 79601-79632 Cleanup, SXR fan testing, Thomson scattering

Cleanup shots following up-to-air for Thomson scattering Rayleigh calibration, SXR fan array filter replacement (now 100nm Al instead of 400nm Be), and Section 5 10" conflat replacement with a gate valve. The bake was on for 1 week. Base pressure at the start of the day was 6.9e-9 torr, which is better than the last up-to-air, and was about as good as expected. The partial pressure is dominated by N2, with water and O2 about equal and down by a factor of roughly 3. The TF cooling/insulating oil level was very low at the start of the day, meaning that the leaks are pretty severe, though the oil hadn't been refilled in the last 2.5 weeks.

The SXR fan array signals are heavily saturated, as was expected from the filter having more transmission at lower UV energies. The gain will need to be reduced by changing resistors on the amplifier boards. Three of the channels are not working -- this will be investigated. The disconnected m=3 Rogowski signals looks the same as one of bad SXR chords, even though this Rogowski signal is usually zeroed out, suggesting there is some connection between the two strange signals.

Thomson scattering was active for the last 2 hours of the day. All TS data were collected at or before 4ms. Observed temperatures were in the range of 10eV to 100eV, depending on the shot parameters. High versus low temperature shots were in agreement with x-ray emission. Densities were in the range 1.8 to 3.4e19m-3. Cleanup will continue tomorrow along with more TS data collection.

Everything with spitzer and the run seems to be working fine, except one minor issue with the auto-updating of plotting shot parameters. This is being investigated.

Tuesday June 25 2013 5:57 pm Peng_Stoafer 79635~79425

A good many of shots are taken today. Shot duration has been close to that before up-to-air. The Thomson scattering diagnostic was used in the run today. The laser worked well throughout the run. We were able to make reproducible shots which we could do time scans on for temperature and density; more to come. Temperatures ranged from 60-150eV on normal shots. The density ranged from 1-3.5 e19 m^-3. A more thorough scan of shots will be performed tomorrow.

Wednesday June 26 2013 6:41 pm Stoafer/Levesque 79726-79795 Temp/Dens scan

The run today was aimed to use Thomson scattering for a temperature and density scan of various shot styles. Overall, the day was successful with reproducible shots and reliable Thomson system.

The first shot style was similar to yesterday's with a current ramp from 11 to 14kA and constant major radius around 92cm. This was a very reproducible shot on which a full scan was performed from 2-7ms. Densities ranged from 1.5e19to 3.6e19 and temperatures ranged from 70 to 190eV.

An attempt at low density shots was taken by lowering the gas puff time from 800us to 150us. The shots were not reproducible and densities were not much lower than the previous shot style, so this scan was not carried out. Densities ranged from 1.5e19 to 3.2e19, but the values were similar in the previous shot style for the time windows sampled.

A shot with high current was developed, based on previous shot development, to look at a new regime with higher Greenwald density limits. The shots have a current ramp from 14 to 18 kA. These shots are not very reproducible, but we are working on performing a scan regardless. We find these plasmas to be very hot with a relatively reliable measurement around 170eV (see discussion about high temperature readings below). So far densities range from 2.6 to 3.6, but we have just begun the scan; this scan will be continued tomorrow.

Currently, we are only able to use two TS channels for every shot, which creates a problem in relying on the data. We have found that this is especially true for high temperature readings (above 150eV). However, at high temperatures we are able to use a third channel as well. We will start to include the use of this channel when possible and look into improving the analysis of the signals (there is evidence of systematic noise).

The plasmas are looking very good and lasting a long time. Star shots include 79744, 79768, 79771, 79783, 79787, 79794.

Thursday June 27 2013 5:48 pm Stoafer 79796-79866 TS scan of high current

The goal of today's run was to perform a TS scan over time of high current shots. This shot style showed much higher temperature and density, as expected, which was also seen in the soft x-ray signals.

The shot style was not very reproducible, so not many samples were taken at each time point.

I will continue to work on analysis of the TS signals based on the discrepancy of using the high temperature channel or not.

Friday June 28 2013 9:00 pm Angelini 79867-79880 Fast Camera

Today's run was supposed to focus on collecting videos of long shots with more quiescent modes for comparison with prior shots. While I was able to get a few clean shots, a leak in the cooling water pipes (high pressure side) above the North rack sprang a leak and we ended early. A collar around the pipe was tightened, but a more thorough check and repair will happen on Monday. A potential contributor to the leak may have been a further increase in pressure. The gauge now maxes out.

Jeff has started replacing the resistors in the circuit for the SXR array. The new resistors will fix the over-saturation problem.

There is a small leak in the cooling water for the ignitron near the TF bank. It seems to be small enough not to be a critical problem.

The vacuum is holding steady around 7 nTorr.

Monday July 1 2013 7:50 pm Angelini 79881-79918 Fast Camera

The goal of today's run was to try to get tearing mode shots. Toward the end of the day I was able to get some shots with a constant major radius and a q just above 3. I'll do some analysis and see if the fast camera sees anything different from previous shots with the q just below 3.

Both the water leak near the north rack and the leak in the ignitron in the basement have been fixed.

All but two of the SXR array channels have had their resistors replaced and are now at a lower gain. The SXR plot now tracks much more closely with the major radius.

The base pressure seems fine. It started in the mid nTorr range and reached 25 nTorr during the run.

Tuesday July 2 2013 5:54 pm Peng/Levesque 79919-79967 RMPs and SXR data.

More shots with rotating perturbation is done today. To affect the Bp pattern, one needs the (3,1) mode perturbation. (0,1) or (3,0) perturbation doesn't have much effect. This rules out some possibilities of the explanation

More test with rotating frequencies is done, but the mechanism is still not known. Will try to figure out some model before doing further tests

At the end of the day, ran shots with widely varying major radii in order to observe movement of the SXR fan array emission centroid. In at least one case having major radius above 94cm and q* near 2.1, a 2/1 mode in the magnetics was accompanied by an apparent inversion radius in the SXR data.

Friday July 5 2013 2:51 pm Rhodes 79968-79992 RMP

The goal was to calculate m number of the mode based on the phase shift between control coil signals (used as sensors). This proved difficult to do within reasonable error.

Then could not get 'do_awg' to initialize the ACQ for resonant perturbations. Problem not resolved.

Turns out there's an early campus shut down today. Will try again Monday.

Monday July 8 2013 6:39 pm Rhodes 79993-80053 RMP and low q

Took a few RMP shots with q*>3, trying to excite 3/1 tearing mode activity. Then spent most of the day trying to create reproducible low q* shots near q*=2. Had a few good shots but none were reproducible, which made it difficult to apply RMP.

Tuesday July 9 2013 3:58 pm Qian 80054-80100 plasma shot

More low q shots were tried today.

Slightly delaying the VF start timing will result in a bigger major radius and lower starting q. The shots are not very reproducible, which makes it hard for comparison with/without perturbations. Increasing the puff timing would reduce the possibility of minor disruption, but will also make the MR falls in quickly.

80083, 80086 is a pair of shots that have similar equilibrium traces. The 0.5kHz rotating perturbation does not seem to much effect in this case.

Thursday July 11 2013 6:23 pm Stoafer 80101-80132 TS scan of double puff

The goal of the run was to obtain a T_e and n_e evolution of a discharge with a secondary gas puff. The puff occurred at 4ms into the shot and TS measurements were taken before and after the puff. Increasing densities were seen after the puff with a crash 1-2ms after the puff. Plasmas with and without the second puff were very reproducible all day; without the second puff, plasmas were lasting onwards of 10ms.

The TS system was relatively easy to get up and running after it had not been used in 2 weeks. The alignment did not seem to change significantly (no alignment adjustments were made in order to retain the alignment of the Rayleigh calibration). The beam dump had shifted out of place; a problem which will be addressed.

Friday July 12 2013 4:37 pm Stoafer 80133-80187 TS scan of outboard plasmas

The theme of the run was to obtain the T_e and n_e evolution of discharges that start outboard limited (around 95cm) and progress inwards. The plasma current was ramped to increase the temperature throughout the discharge.

Plasmas were relatively reliable after a target shot was obtained, so a TS scan was performed.

Target shot was 80164.

In the beginning of the day, the VFE bank would not charge. We found the issue to be that the shorting bar was in contact with the VFS shorting bar, which share a bucket. Future issues will be avoided by adding another bucket.

Thursday July 25 2013 8:02 pm Hughes 80198-80212 Ferritic segment force testing

Success! Starting with the TF at 200V (~100G) we gradually ramped up to higher fields, using the lab camera to record video of an edge-on view of the control coil end of shell 9T.

Below 4kV (~2kG) the deflections of the shell were too small to measure clearly, since the edge-finding algorithms all have some finite precision, especially when tracking a moving object with imperfect focus and finite contrast. This gives us a roughly estimated error of +/-0.3mm on most shots (about 2 pixels). This error estimate is, if anything, a conservative underestimate, to avoid shrugging off deflections as merely reading error.

At 4kG, we observed a deflection of roughly 0.6x0.15mm (machine-radially and vertically, in that order), which rose to about 1.67x0.6mm at 6.5kV with all other banks also firing at maximum normal settings. This is well below the 2.5mm limit we had set. Although analysis is slightly complicated by changes to camera position between shots, there is no evidence of any change in resting shell position from the beginning of the run day to the end (4 shots at or above full normal field). Any changes are well within the conservatively estimated reading error of the edge-finding algorithm.

Installation was occasionally frustrating and not always pleasant, but went fairly smoothly, and some aspects can be easilly improved with better planning (e.g., preparation of a smaller hex key with a ball tip).

The greatest standing concerns are the buckling of the prototype's shimstock panels when on the bench (which may or may not be an issue when installed), and avoiding the chamber flange when retracted. As to the first, we may need to add toroidal ribs to the design; this would also simplify assembly in some ways, which might make it easier to shop out construction. As to the second, we may have to choose whether to lose a centimeter or so of either retraction or insertion, unless another acceptable design solution approach can be developed.

Images will be uploaded to the wiki before the next meeting.

Tuesday August 6 2013 6:36 pm Peng/Levesque/Byrne 80229~80301

Today's main purpose is to do clean up shots. This is the first run day after a 3-day up-to-air followed by a 1-week bake.

Several chords in the SXR fan array were fixed during the bake last week. Two more gain resistors were changed to reduce the gain to an appropriate level; now only one chord is left with the high gain (it's the first channel, which is at the innermost tangent radius). The power connection for the first chord's amplifier board was repaired, which seems to have fixed the intermittent low-saturation problem on that channel. Two chords were fixed by reconnecting the crimp-connections at the vacuum feedthrough, within the copper bellows.

There are now only two apparent issues with the fan array: 1) Chord #1 has the higher gain by a factor of 8, which can be corrected in software when the signal doesn't saturate, and 2) Chord #15 appears to have reduced sensitivity, which is likely related to a poor connection upstream of the amplifier board -- that ground side of that channel has a higher-than-normal resistance to ground.

The voltage induced on the shaping coil was measured during high-power OH-only shots.

The base pressure this morning is around 1e-8 torr. Mass mainly around 4, might by He or D2. A good many clean up shots were taken today and the duration of plasma increased gradually during the day. The clean up shots will continue tomorrow.

Athena and other workstations got frozen several times today. Luckily, it hasn't caused any auto-discharge on banks. This problem is under investigation.

Thursday August 8 2013 5:42 pm Qian 80303-80382

The main purpose of today is clean up shots.

Cryo pump finished regen later in the afternoon and the base pressure is brought down. At the end of the day, the pressure is 2.4e-8 torr.

Plasma got good enough in the late afternoon and some feedback test is done. The plasma is not very reproducible so the drift subtraction is not working verywell. Highpass filter version, which suffer less from drift effect is firstly tested. No suppression effect has been observed so far. Nor is any slow mode being excited. Further tests are expected to be done tomorrow.

Friday August 9 2013 6:20 pm Qian 80383~80451

clean up shots and feedback tests are performed today.

base pressure is 6e-9 at the beginning of the day. puff time was decreased to 100 and the plasma breaks down normally. Shots similar to those before up-to-air are obtained. This suggests there might be some thing loose about the puff valve.

further feedback test with high pass filter is done today. Without high pass filter, the feedback would excite big slow mode at around 95 phase shift, which was observed before. With high pass filter at around 45 phase shift, the mode would be slowed, but one do not see a big dominating slow mode as before. The mode is not obviously suppressed. a rough phase scan does not seem produce much effect.

Monday August 12 2013 5:34 pm Peng 80452~80514

feedback tests are performed today.

The main algorithm tested are highpass filter version. It was found that at a narrow region of phase shift parameter, the plasma is affected a lot. A slow mode is still excited despite the highpass filter. But the overall mode is slightly suppressed as in contrast to those with only Bp feedback previously.

BpBr version is tested later. But the plasma is not very reproducible later in the day and the drift subtraction is not working very well.

The AC in the machine room seems to be not working, and the temperature is getting warm .

Tuesday August 13 2013 6:13 pm Peng 80515~80579

feedback tests are performed today.

It is found that the slow mode is self-excited by the control coil when the mode is slowed down. So the omega dependent gain parameter is adjusted to make sure that the gain decreases at low omega. Also, since the Br mode is quicker in detecting the slow mode, mode coupling setting was used. The phase shift introduced by high pass filter is taken into consideration and compensated. When the feedback is on, the mode frequency would still vary, but the control coil would no longer excite severe event that leads to disruption. Mode suppression can be observed in some shots, but not much.

Thursday August 15 2013 4:31 pm Levesque 80580-80602 Problems running

Tried to run far-outboard plasmas with R0~96cm, but encountered too many problems with the run. Only shots 80581-80587 were plasma shots; the rest were from trouble-shooting. I was not able to achieve the desired plasmas before problems ended the run day. The final gain resistor in the SXR fan array amplifier box has been replaced, so all channels now have the same gain. Note that chord #1 is exceptionally noisy even with the lower gain though, so we may want to change this channel back or hunt down the noise.

At the beginning of the day, the VF Start bank was charging much slower than usual. It was slow enough that the bank would not fully charge before the TF completed. We were unable to find significant problems around the bank itself, and ended up raising the current control on the VFST power supply. This current control knob may have been accidentally lowered by a passerby in the control room. The bank appears to charge at a reasonable rate now.

The banks failed to fire after they fully charged for shot 80588. The data storage cycle initiated, but the triggering pulse was not delivered. Upon storing, all CPCIs and the two TR modules in the south rack failed to store, and all successful stores happened suspiciously faster than usual. Subsequent crates-only tests all had the same problem: the PULSE_ON delivery was not able to fire the puff valve or krytrons, and the same devices always failed, despite all INIT events reading success. Restarting various parts of the system did not help.

Thermal problems in the south rack are the suspected culprit. The air conditioner in the machine room hasn't been working for the past week, and the south rack was too hot inside. The solenoid valve delivering cooling water to the south rack was found closed due to lack of power. We found the unplugged connection, restored power to the valve, and the chiller started blowing colder air. If the next run day proceeds without issues, then this was probably the problem. If not, more trouble-shooting will be required.

Monday August 19 2013 6:44 pm Levesque/Peng ****** crates_only

Some of the crates_only shots are tested later this afternoon to prepare for tomorrow's run.

CPCIs were still producing errors during the storage phase. We did further check in the basement and found standing water in the basement rack, and a powers trip in it was not working. After replacing the power strip, the storage works fine. The source of the standing water is not clear.

Some of the bank cryotrons are not working and need to be looked into tomorrow.

Tuesday August 20 2013 6:01 pm Peng/Levesque 80609~80657 plasma shot

The standing water in the basement rack is due to the slight leak in the water pipe going through the fan. It is fixed and water is mopped out.

Feedback system is tested today with passing the total mode amplitude through a lowpass filter. The result is quite promising.

comparison groups: 89631,80639 and 80650,80651,80653,80657

each group have similar shot styles. and 631,653 are reference shots. One can choose their own mode amplitude analysis tool and the suppression should be seen during the feedback is on.

Thursday August 22 2013 6:30 pm Peng 80658~80736

feedback tests are continued today.

While the frequency variation due to feedback algorithm is seen. The suppression cannot be seen conclusively. Some phaseshift calculation check will be done later to see if the code's output is expected.

Monday August 26 2013 6:20 pm Peng 80744~80798

Feedback test is continued today. an invert transfer function for the amplifiers are constructed later today and makes the actual control coil current more like the requested one. a brief phase scan is done but the mode still cannot be suppressed. Phase acceleration/ deceleration and mode amplification is seen at corresponding phase shift. But the suppression phase shift still have a frequency oscillation.

The frequency oscillation will be further looked into and see if adjustment can be made.

Tuesday August 27 2013 6:19 pm Byrne 80799-80825 Rogowski Calibration

The Rogowski seems highly susceptible to noise.

The function generator's signals passed with no trouble and integrated well last night, so the cabling is continuous and the integrator and software work well.

The first shots of the day proved unrecognizeable as the VF trace. A huge noise pulse at the firing of the VF was the culprit.

The noise existed with a 50 Ohm terminus at the end of the cabling, rather than the rogowski

The noise was reduced, but still significant when the Triax cable connectors were tightened to provide better shielding.

The noise persisted no matter the level of the banks (down to 20V VFE, 200V VFSt)

The noise occurred at different times depending what banks were on.

The noise persisted when the original rogowski was used to measure the OH rather than VF current, and when a random other rogowski was hooked up to the VF cabling and the current was measured through that

The last three suggest there is still a problem in the interference shielding. I re-inspected, and rebuilt in a few cases, the triax connectors. This had no effect.

I think this means I am officially out of my depth. The noise is definitely coming from the krytrons, and I seem to have hit the limit of what I can do to the connectors to make things better. There may be breaks in the shielding away from the connectors, both cables were inoperable when I first found them, but it will be difficult to inspect the full length of both of them.

The fact that the first two random triax cables we selected were both initially unuseable has me hesitant to try replacing them with others from the lab, as even pulling them enough to check for continuity and proper insulation will be a full-day job.

We can look at what at what I was able to do tomorrow, and with the understanding that signal levels will be ~3 times what I saw on the VF and that the noise does not scale with signal, we might decide it's ok.

If it's not, I'm going to need some input. Personally I would vote for making brand new Triax cables and re-running them, it's the only way to be sure there's nothing wrong with the cabling. The shunt into a Jensen is another option, but we'll have to see if it can handle the load.

Wednesday August 28 2013 3:50 pm Peng 80827~80849

some feedback tests are done today. With the improvement on control coil currents, it's now much less likely to excite a dominant slow mode. The modes could still be slowed down at some phase shift, but it is higher than 2kHz.

Thursday August 29 2013 6:53 pm Peng 80852~80913

feedback tests are done today. While amplification, slow and acceleration can be observed at corresponding phase. The suppression is still not ideal. Slow mode would always arise. The slow mode does not keep increasing and becoming dominant. But we cannot get rid of it. Typical shots are 80911 and 80913.

Thursday September 5 2013 5:34 pm Peng/Levesque/Byrne ******

Triggering system for the banks are not working properly today. This might due to the high temperature in the server room and the Kamac is probably producing errors. A facility guy is sent in today to look at the AC problem

The triggering system are left to cool overnight to see if problem goes away tomorrow.

Friday September 6 2013 6:06 pm Peng/Levesque 80975~81039

Banks are triggered normally today

feedback system with Kalman filter are tested today. The slow component cannot be filtered out very well. The Bp/Br ratio for the slow mode changes when Kalman filter option is on and this makes the fast mode detection not working as expected. Reasons for this will be looked into.

Tuesday September 10 2013 6:05 pm Byrne 81050-81065 Shaping Coil Discharge

Low shot numbers since many shots were crates only with multiple pulses.

81055-81065 are shaping coil shots. 81063 and 81064 the bank was charged but deliberatley not discharged to look for susceptibility to tripping by bank room EMF interference. None was found.

Bank was stepped up to a 200V Start, 80V crowbar discharge. After an initial shot with myself in the bank room to get the timing right, all other shots were performed with the cap room empty and locked. Crowbar bank voltage will be roughly +- 5V from 80 in any given shot, but current traces with the rogowski show good agreement from shot to shot.

PA pickup shows ~130G on edge, and very localized, as would be expected.

Pulse shape looks similar to what was predicted by SPICE, but the resistance measured is too high to give the pulse shape we are getting. This may be due to the difficulty of measuring order 10^-2 Ohm resistances. Inductance was measured at 40uH, rather than the 49 predicted, but that is still quite close.

More analysis work is required on the Rogowski output before we can compare it to simulations however.

But as of now we have a working, chargeable, dischargeable shaping coil system. Remaining work is mostly learning how to use it and interpret the data from its use.


Tuesday September 17 2013 4:50 pm Byrne 81066-81077 VF qualification

We ran the VF coil up from 50V El/1kV St to the maxima of 350V El/10kV St. The purpose was to ensure that the coil had been put back together properly after it was disconnected from its leads to allow access for shaping coil work.

In no case were there any problems with the coil. All shots fired, and the traces on the VF current monitor look fine.

We did lose some time trying to track down the cause of a trigger failure. As it turns out, the crate in the server room needed a reboot. This crate is never turned off under normal conditions, and we saw last week how extended operation can degrade the Camac systems. With the AC out, the problem is compounded.

After a reboot, we get the same errors on calling 'crates_on' that we used to get before an upgrade, which requires the re-running of the program. During this time we never had trouble with the server room crate, suggesting that it was a) reset at the end of the day when it was hooked into Matterhorn, and b) that the resetting is what prevented the errors.

We can talk about it at the meeting, but it might be worth it to turn that crate on and off with the others at the beginning and end of the run day. It can't really cause harm so the worst case scenario is the present status quo.

Wednesday September 18 2013 6:30 pm Byrne 81078-81110 Shaping Coil!

The run day ended when a start cap blew. We were running the coil up to a 600V/200V start/crowbar shot. This was done with charge solely on the coil banks. As the start bank reached 600V, a high leakage current was noticed. Just as the power supplies were cut, a loud snap was heard. Checking the bank, one cap was found with charring near its blow-off valve. The MOV was blown, as was the fuse. This is the failure mode we had expected and designed for.

Since the caps are individually rated for 450V, there would have needed to be greater than a 3/1 charge imbalance for an overvoltage on any cap. Initial, low current burn in tests did not indicate this would be a problem, nor did tests up to 200V with the higher amperage power supply we currently use. No autopsy has been performed, but at the moment, I would put it down to a 30 year old cap with high leakage cascading to a short failure. If the problem is limited to that one cap, we have multiple replacements ready to go.

On the lighter side, several shots were taken with the banks charged up to 400V/160V. These shots show a significant departure from our usual modes of disruption. Rather than an inward crash of several milliseconds, the plasmas suddenly slam inward over the course of tens of microseconds.

The other characteristics of the shots do not seem markedly different from what we normally see. Shots tended to disrupt around 5.5ms, but we were still in the clean-up phase of the run due to Jorway problems early in the day. Shots tended to last longer as the voltages were developed and as more shots were taken.

No analysis has yet been made, but start shots are 81098 (1st shaped shot settings 200V/80V), 81106 and 81108 (400V/160V)


Thursday September 19 2013 6:24 pm Qian/Dov 81111~81167

Feedback shot tests are performed today.

for state-space model, some problem was found in the matrices which overflow the output on the control coil currents. Several fuses were blown and replaced, the coils seems fine. The units of the model will be further checked to make sure the output is reasonable.

for single-helicity model. algorithms using four array individually were tested today. Modes can be accelerated and decelerated, yet the suppression is not reliably achieved. While the fast mode decreases, a steep gain curve edge depending on freq is made such to prevent the feedback acting on itself once the fast mode is suppressed. This results in some pulse-like suppression.

Friday September 20 2013 5:50 pm Byrne 81168-81177 Shaping Coil

After determining the problem was the MOV's (which are used to prevent overvoltage as fuses are to prevent overcurrent) low voltage rating, the banks were fired in isolation, starting at 120V/120V, and stepped up gradually to 250V/250V.

From there we increased the start bank to 500V, for a 500V/225 V. All crowbar bank shots beyond the one 250V shot were taken at 225V.

The bank fired fine, with no problems. The crowbar bank is now completely qualified for operation up to it's max rating of 250V, and the start bank up to 500 of 900V. The GDC power supply's voltage dial has been set to a level to top out just below 250V.

Higher rated MOV's are en route, and can be replaced as soon as they arrive and access to the bank is available. I have a rough algorithm for determining the proper post processing and gain, which would be good to put into the tree, so that those interested have more than the raw data (North rack cpci input 96) to look at. If anyone knows how to do that and is willing to show me, I'd be much obliged.


Tuesday September 24 2013 6:52 pm Qian 81178-81219

some static perturbation test was done today to check the Bp,Br mode response to the control coil. With static perturbation and phase flip, the phase difference between Bp and CC mode is roughly -55deg and Br/CC is roughly -150 deg. This was used to obtain the expected phase shift parameter for feedback system, which is -35 deg. This is within the phase window where we saw fast mode got suppressed with slow mode arising.

Tuesday September 24 2013 7:02 pm Byrne 81220-81227 Shaping Coil

Shots were taken at the end of Qian's run to test the new MOV's

Banks were progressively charged up to 250V/900V, and discharged. In all cases, the banks held their charge well and discharged properly.

Finally a shot (81227) was taken with plasma and a fully charged bank. No shot development was done, and a rather dramatic disruption occurred. Within .5ms the plasma had basically crashed inwards.

Python code has been developed to give us the actual current in the coil. Looking at that shot, the current seems to be briefly in excess of 9kA.

We were expecting a max current of roughly 8kA. This could be due to the lower than expected inductance, or it could be that the resistance of the coil is also lower than expected. We have not been able to accurately measure it yet.

The phidget has been giving us some trouble, currently it does not measure voltage on the banks accurately, and thus does not stop charging when the specified voltage is reached. Nick and I are looking into the code and expect to find a solution soon. We also need to modify the Take_shot script to allow entering of the bank voltages into the tree for recording. If anyone has any familiarity with this, your help would be appreciated.

At the moment, the shaping coil can be used. It can be charged (manually) to whatever voltage you'd like and be discharged at a set time (currently set by the fast camera timing in the tree) in the shot. Current is recorded (on CPCI channel #96 in the north rack, currently no dedicated tree node), and viewed (using my code). We should be eliminating each of those inconveniences one by one in the upcoming days.


Thursday September 26 2013 6:19 pm Hughes 81228-81279 Odd Shells Out

Not the best run day ever, but not the worst. This run featured the odd-numbered shells retracted 40mm +/- 0.15mm, and the target shot has major radius steady just inside 92cm, with a current ramp from 11kA to 15kA. Attempts at the second shot style (12kA to 16kA) didn't accomplish much, mostly due to intense early-mode activity making plasmas extremely capricious toward the end of the day. Since the real objective isn't to raise current, but to reduce q, I may try adjusting the TF tomorrow, instead. We'll see.

The VF was set early by up to 170us to prevent the plasma flying out to the 94cm region where it likes to hang out. Plasmas had okay breakdowns, but unpredictable and messy early behavior.

There was also a failure to dispatch jobs on the first shot (81228), but this resolved itself after restarting the takeshot program. I suspect tokamak elves were involved.

Shots of interest:
81229 - Daily Vacuum Shot
81255 - Probably the best shot of the day
81251-81262,81265,81273 - Good enough to be used

At the current rate things are going, I'll probably need Friday just to finish the set of three q traces for the half-out configuration. Maybe things will go super fast and every plasma will be awesome, tomorrow, but I wouldn't put a lot of eggs in that particular basket.

Friday September 27 2013 6:21 pm Hughes 81280-81326 Higher-current, steady maj. radius

The objective was to continue the runs from Thursday (9-26) pursuing higher-current, lower-q shots with major radius steady at 92cm. This didn't turn out terribly well. Intense early mode activity, possibly instigated by plasmas breaking down with q just above 3, made plasmas extremely irreproducible and generally uncooperative. The few shots close to the target shot of this style briefly hovered nearer to 91cm; some were not very steady at all.

Later in the day, another series of shots was taken with the start current raised so q at breakdown would be slightly below 3, and the current ramp would evolve the edge away from the resonance. This had at some success, producing a couple of shots with much better-behaved plasma current and R0 traces.

Notable shots:
81280 - Start-of-day vacuum shot.
81282, 81294, 81298, 81302, 81304, 81306 - Tolerable current traces, but R0 doesn't match target shot very well.
81325,81326 - Best shots of higher-current style.

Since Pat needs to do setup work with the phidget on Monday, I'll do some more running then, and see if I can get some more decent high-current/low-q plasmas, as well as some high-q shots. If there's time, I'll also experiment with changing the TF.

Monday September 30 2013 6:13 pm Hughes 81327-81399 Odd Shells Out + Different TF Settings

Today was rather more productive than Friday! A couple of decent high-current shots were taken, as well as several pretty good lower-current/higher-q shots, with q_min around the 2.8-2.9 neighborhood. There was also some time to play around with TF settings and see how the plasma handles it.

Last things first, with only a few shots, I was able to get a plasma with the TF at only 4.6kV, 75% of our usual 6.1kV setting. Making a halfway decent plasma required cranking up the OH quite a bit, probably to compensate for reduced confinement. There seems to be a general trend that you want to raise the OH *roughly* by the same proportion as you drop the TF, at least as a rule of thumb for starting with something that looks like a plasma.

Shots of note:
81327 - Start-of-day vacuum shot. There's some peculiar noise on the loop voltage monitor, but it seems just to be an unidentified curiosity.
81333, 81338 - Marginally acceptable high-current/low-q shots.
81365, 81376, 81386 - Best low-current/high-q shots.
81368, 81373, 81385, 81388, 81389, 81391 - Reasonably good low-current/high-q shots.
81396, 81398 - Best shots with significantly reduced TF.
81399 - TF just above 60% of normal; didn't even break down! This *may* be the limit.

Anyway, I've got a couple dozen decent shots to chew on, so analysis will come later. The odd shells will be inserted as per normal configuration, the VF start time will be reset to 860us, and the puff time will be returned to 200us as it's been during recent operations.

Tuesday October 1 2013 6:19 pm Qian 81401~81461

Feedback tests are done today with low q shots. Modes would interact with perturbation, but are not suppressed. The response can still be seen with half the gain we used to set, which might suggest we were operating with too much gain.

Thursday October 3 2013 5:55 pm Byrne 81462-81464 Phidget qualification

Some harmless flooding was seen today. During the day, the ignitron water was turned on, as the phidget is wired into our system to the point that even bench testing requires all interlocks closed. At the end of the day, as I was tuning on the basement crate power I noticed a large puddle forming under the OH power supply.

It turned out that the trough was slightly blocked on the other side of the wall separating the drain from the cap room by a mop, and that the ignitron outflow hoses were directing their water outside the trough to begin with. Nick and I fixed the problem, although we have no idea how the hoses could have ended up like that between the last runday and today. No damage.

As of today, the phidget and its programming are working properly to prompt for operating voltages, dump, switch power, cut off power when desired voltages have been reached.

At the end of the day attempts were made to fire the coil using the phidget. The south rack Jorway outputs would not trigger, however so we were unable to fire.

However, since the point of this week has been to get the phidget up and running, we can declare success. The banks were charged to the voltages we had specified at which point their supplies were cut. The banks dump when the phidget sees a dump signal. The interface is still a bit wonky, but that has more to do with my coding those bits, instead of Tyler. If we can get the Jorway running tomorrow I expect the bank will be fully integrated into our system. Next step will be pickup subtraction in our IP, MR, and Cos(3-theta) rogowski coils. Pickup is very low, so if a Daisuke-style response function can't be hacked together quickly, we'll just do a proportional subtraction. Should not take more than tomorrow.

Friday October 4 2013 6:06 pm Byrne 81465-77 Shaping coil

The Jorway problem from yesterday turned out to be intermittent. Was able to run all day no problem.

Phidget interface code still ahs some bugs to be worked out, but as of now, accepts voltages, charges, cuts off, adn gives realtime graphical data as to bank voltages

problems with the rogowski (it was routed incorrectly) slowed us down, but some good flattop shots have been taken. It is my understanding that step-function like shots are the easiest to model using response functions.


Tuesday October 8 2013 9:58 pm Levesque 81478-81521 Far outboard plasmas with low q*, RMPs

Ran far outboard, low q* plasmas to study internal RMP effects on 2/1 modes with dark SXR fan array chords on the high field side. Having dark SXR chords on one side of the plasma implies that there are no emission contributions at minor radii outside the tangent minor radius of the last bright chord, which allows easier interpretation of SXR mode data. Target plasmas had R0 near 96cm and q* near 2 for 1ms or longer.

Most shots were unusable for the present study due to minor disruptions at low q*, but there is a good dataset of usable shots. Successful discharges showed magnetic and SXR evidence of the 2/1 mode locking to the applied perturbation. Without applied fields, large oscillations in the entire emissivity profile are seen at the frequency of the magnetic-observed 2/1 mode. Additionally, a ~40kHz mode is often seen simultaneously with the ~8kHz 2/1 mode.

Noteworthy shots:

81498 and 81519 -- Good reference shots with no applied RMP.

81509, 81511, and 81506 -- Good RMP shots with CC currents peaking around 18amps. Phase angles were 0o, 90o, and 180o respectively.

81489 -- Very clear high-frequency (~40kHz) modulations in the SXR data during 2.8-3.4ms.

Wednesday October 9 2013 7:42 pm Byrne/Levesque 12860-12869 crates only - tree updates

The Take Shot Make Tree and Shot Browser scripts have all been updated to reflect the new addition of the Shaping Coil.

From here on, if you'd like to see the output of the shaping coil, it can be found at .Sensors.SH_CURRENT. The timing of the bank is stored at .timing.SH_ST. and the voltages for any given shot will be stored in .metadata.SH_ST/SH_CB

Since the shaping coil has the capability of being fired at an arbitrary time during a shot, it's most likely this will be taken advantage of. Therefore in addition to the bank voltages, you can also browse the Start Bank's trigger time (the CB always happens ~.8ms after) in the shot browser.

The Take_shot frontend now has a checkbox for the Shaping coil, which allows you to run without triggering the switch, (please do, since the eventual plan is to move the phidget, with it's myriad garbage warnings and errors, to an automatic linkage with the tree.) a text field similar to that for the gas puff and VF timing for the shaping timing, and text fields for the voltages. You will still need to call the phidget program and manually insert the voltages to get the banks to actually charge, at the moment, however.

In looking around the top of the machine, we found that one of the leads was zip-tied badly, and not canceling the bundle - crossovers. This was fixed. The main source of error, the SXR passage, may be harder to fix though. Fortunately it is a strengthening of the field, so a nominally diverted plasma will remain so, but with an N=1 error overlaid. It seems likely this is due to the bundles being forced apart rather than pushed closer to the chamber, but it hasn't been thoroughly investigated yet.


Thursday October 10 2013 6:15 pm Byrne 81532-81552 Shaping Run

Very interesting data for our first real shaping run.

Lost the first half of the day to a series of brain farts. Jscope error was due to a typo (not the period/colon thing, apparently either will work) and subsequent noise discovered in the basement was just intrinsic noise caused by a bad choice of frequencies and gain to integrate/amplify out of the func-gen.

The first shaped plasma shots are 81544 and 81545. We were getting quick inward crashes as soon as the coil was turned on. Dropping the VFE and raising the VF ST and OHE (Shaping begins at 2ms) we were able to create a mid-plasma outward push to counteract the shaping coil's pull

The plasma was *extremely* repeatable, for HBT-EP, and shots 41548-52 are the star shots.

49 and 50 are unshaped shots. They fly outwards and have a sharp inward crash as soon as q~2.1. The shots were bookended by 48, 51, and 52, which fly out more slowly once the shaping is on, and on reaching q~2.1 hover for nearly 1ms before a much more gradual crash inwards than the unshaped shots. There's still no pickup subtraction in the MR rogowski, but a strong 2-1 mode is seen on the HD arrays for the entire time q is indicated to be near 2.

Zero crossings on the both PA arrays' poloidal sensors suggest the plasma is diverted in these shots, though Ish is ~4.5kA. This makes sense, as my simulations predicted diversion would be easier with an outboard plasma, or a low current (Ip was ~10-11kA in all cases) or by implication a real plasma, as outward shafranov shifts are not modeled in my simulation. Since we had all three, it's a definite possibility.

Definitely will be investigating this further tomorrow


Friday October 11 2013 6:30 pm Byrne 81553-81580 Shaping

Went looking for a higher IP shot so that I wouldn't be so dependent on extreme outboard plasmas, and was unable to find one.

Star shots are 81563 and 81565, low q, briefly dropping below 2 in 65 before experiencing a crash. The crash is similar to an unshaped shot, but with a q about .15-.25 lower. I'll have to look at the modes and any sources of pickup on the relevant diagnostics to see if we actually are getting a lower q.

81578 and 81579 are interesting in that the plasma is stopped right at or below q = 3 for a prolonged period with shaping. It would be interesting to compare these shots to another run's unshaped ones to compare multimode specta. (if I were to not shape that particular shot it would fly outboard and have a q=2 crash, so I don't have an apples/apples comparison from circular to shaped yet)


Monday October 14 2013 7:09 pm Byrne 81582-81609 Shaping

Attempted to get a steady shot around q = 3 to observe mode behavior/differences from unshaped plasmas.

Started seeing large jumps in current in shaping coil at ~15ms, beginning at 81604. Checking the banks, found that the mylar wrapping at the leads had come loose. At the time of work, these leads were tightly enough captured between TF and chamber that mylar sheets had to be slid in, rather than wrapped and taped around. Modifying the leads Friday seems to have loosened them and the mylar had fallen loose. We are operating on the assumption that this is the location of a short to chamber ground, though we will have to test it to be sure. Mylar was wrapped around the central bundle and taped to the cable to keep it in position.

Spacers were inserted in the 2-bundles to hold the wires stiffly in the coil holders. These were found to be inserted in the wrong location poloidally in some holders, and were removed, and partially replaced (the job will have to be completed before the next shaping runday.) This will increase the spacing between the central bundle and the mis-spaced 2-bundle. No prediction on what this will do to the assymetries of the coil.

Tuesday October 15 2013 9:06 pm Qian 81610~81686

feedback test with inverted cc-Br transfer function has been tested. frequency dependent gain compensation is no longer needed with this feature. Phase scan is performed and it seems that the plasma response also depends on the major radius a lot. with the same settings, there can be big response or even no response depending on the major radius varying from 90 to 92 cm. So the relation between response and phase shift can not be easily seen. Further analysis will be done.

Wednesday October 16 2013 6:39 pm Byrne 81689-92 Short-location

Three shots were taken, Shaping only, TF only and TF + Shaping. On the third, the current bump was seen. The scope had triggered (on what I'm not sure, the level was set at 1V, and there should be no noise across the resistor, but I was using the old, beat up o-scope.)

A fourth shot was taken with people in the machine room, looking and listening for sparks. Dov located the spot as the leads. Large gouges were found in the insulation.

The twisted pair was secured only at the outer, lower VF coil and at the entry to the coil proper. It seems that it had been jerked around (and possibly unwound, as there was a large un-twisted gap on the line to the coil itself. pics will be sent out in a separate email.

Lugs are on order. When they arrive we will cut each wire in the twisted pair at a different location, along the length where they pass through the floor. This will isolate each break from the other, and from accidental access by anyone near the coil. The coil-end will be drawn up and through and inspected for any other cuts. It will then be wrapped in mylar, taped, and heatshrunk. Running the heatshrink down the length of a twisted pair will be difficult, but the large amount of oil leaking at its location should make it possible.

While we wait for the lugs to arrive, I will machine a plank of wood left over from the bank construction. It will screw into the G-10 footings the TF feet attach to. It will be located beneath the chamber, and run from the inner to outer footings. The twisted pair will be lashed to this plank with zip-ties, to keep it clear of sharp objects, and hold it securely long term.


Monday October 21 2013 7:55 pm Byrne/Levesque/Peng 81695-81750 Shaping/cleanup

Shots 81696-81701 went well. They were taken to make sure the coil was properly attached, polarised, and measured. As the bank voltages were stepped up, it seemed that the crowbar bank was having difficulty charging to more than 200V, even with large (2A) currents. Also the phidget seemed to be reporting large noise on the banks (127V on a 100V shot, 650V on a 700V shot, both on the Start bank) Again, the actual voltage as directly measured with a DMM shows no such noise spikes.

A cause for the inability to charge the crowbar bank has not yet been discovered, but the plan for tomorrow is to: A) test to make sure the phidget is reading the voltage correctly B) Discover the source of the leakage current. - a shorted cap should be immediately removed by its charging circuit.

Jeff subbed in in the afternoon to take some shots, but found that the differential roughing pump near section 9 was switched off. This was probably kicked off while work was being done locally on the shaping coil. The pump seized up upon turning it on. Jim replaced the pump with a working spare.

Also, the small pump stand cryo was turned OFF, and it's gate valve was OPEN. "Cold head" switch was on, but "Compressor" switch was off. Checking the temperature shows the head at room temperature, and there is no condensation outside the pump chamber, meaning that it was off at least overnight (probably over the weekend, since today is Monday) and was outgassing into the chamber. It looks like it would be very difficult (but still possible) to accidentally turn the cryo off -- could the switch flip to the off position if there is some problem with the pump or power?.

Jim says the temperature on the other cryo pump is okay.

Present status: Large pump stand cryo is pumping, small pump stand cryo has been chilled and is pumping. Baseline pressure is 30nTorr, and RGA shows roughly equal parts D2, H2O, and N2.

Rest of runday was taken up with cleanup shots. Base pressure dropped significantly from 80nTorr to 30nTorr, and plasmas were made with lifetimes of ~5ms, and currents of ~12kA. These were outboard-scraping cleanup shots, so a centered plasma should be able to do better. A night of pumping should help as well.

These plasmas are similar in behavior to my shaped shots, so we can probably use them to take some data with the new coil, if the problem with charging can be found and worked out.


Tuesday October 22 2013 6:30 pm Byrne 81751-89 Shaping/cleanup

Day began late due to troubleshooting the charging issue in the crowbar bank. This turned out to be a holdover from the original code that was not corrected, and causing the bank voltage to be mis-measured. It was fixed, and the banks work well enough, within the bounds of the phidget noise. This work enabled us to take another look at the bank voltages during charging, and they are definitely not as spiky as the phidget makes them out to be. No ideas on how to fix it yet.

After that came shot development. A high OH, low VF shot, with a late (1 ms) VF start was developed. This gave a steady (~6ms lifetime), far outboard plasma. Shaping with 2/3 max current (600V st, 145V cb) gave a series of plasmas with q dipping to 3 +/- 0.1 for about .5ms. These shots are 81784-89

These shots will be studied to look at their multimode spectra. If anyone else has unshaped shots with similar behavior in their portfolios, i.e. outboard, with q =3 , I'd greatly appreciate being able to compare the two.

Other strange behavior was the plasma suddenly jumping *out* when the shaping coil was turned on. It may be uncorrelated, but it does happen frequently. the last shot of the day -89, gives a good example of that. Will have to check to see how the fields and fluxes develop during the shots to get an idea of why. Plasmas still crash inward quickly at the end of these shots, and strong shaping definitely causes a centrally located plasma to fall inboard to disrupt.

Base pressure was still high today, 10nTorr equilibrium, 30-40nTorr when taking shots. Jim said that both cryos may need to be regenned.


Wednesday October 23 2013 9:35 pm Levesque/Byrne/Hughes 81796-81844 Cleanup and inboard SXR shots

Cleanup shots were taken to recover from the poor vacuum quality earlier this week. Although the base pressure is still a little high, we were able to return to standard plasmas by the end of the day.

Fired the shaping coil only near its maximum rated voltage with 4 people observing around the machine to look for coil motion and listen for sounds of coil impacts. Substantial noise and motion were observed. Decided to hold off on further shaping shots until a large chunk of time can be dedicated to improving components around the coil after/during the APS DPP conference. Analysis in the near term will be done using the existing data. More detail was given in the email that Pat sent around earlier today.

Made far-inboard plasmas to collect SXR fan array data with little or no emission in the outermost chords. This is a companion experiment to shots taken on October 8. Was able to get modes in plasmas that were transiently as far inboard as R0=86-86.5cm. Saw clear 4/1 modes in the magnetics with q* slightly below 3, and 3/1 modes with q*=2-2.1, suggesting that there are problems with the major radius and/or q* computations this far inboard. Problems with the major and minor radii measurements are likely for plasmas this far inboard since they are far from the well-calibrated radii. SXR data has not yet been analyzed in depth.

The TF charging electrode plate has been fully eroded away, and needs to be replaced as soon as possible. The TF bank can still be charged now, but the threaded rod which normally holds the electrode is eroding away. Note that the electrode was seen to be very thin but still present a couple of weeks ago, so it hasn't been missing for very long.

Thursday October 24 2013 6:42 pm Hughes 81845-81900 All Shells Out

Today's run was a followup to my previous run campaign (shots 81228-81399 from 9/26-9/30) with the odd-numbered shells retracted. After a couple of attempts to run with a full high-density poloidal array inserted (first shells 8T&B, then 3T&B), it was determined that inserting only a single pair of shells made achieving breakdown difficult or impossible. Jeff suggested manipulating other settings (OHB>2kV, driving control coils, etc) may help achieve breakdown, but I opted to run with all shells out and figure out a way to do mode analysis later.

I took shots in the medium-current and high-current regimes from the previous run campaign, characterized by shots 81255 and 81325, respectively. Noteworthy shots of the day are:

Other reasonably good 81255-style shots:
81854, 81855, 81858, 81866, 81867, 81869, 81870, 81871, 81875, 81876, 81877, 81878

Other reasonably good 81325-style shots:
81881, 81882, 81883, 81885, 81887, 81889

The most obvious trends in this run compared with the previous (odd shells out) campaign were:

  1. needing to set a significantly earlier VFST time (up to 100us earlier) to keep a similar initial major radius, and
  2. plasmas almost uniformly lived much shorter lives, generally disrupting at 4-5ms, compared with 6-8ms as seen in most shots of the previous series.

This reduced lifespan may be due to increased mode activity; the m3 Rogowski signal seemed more lively than usual, and there was no evidence of any other cause. This obviously begs analysis. As is, it's often difficult to identify a poloidal mode number even by eye, and codes are almost always worse at it. I may be forced to look at "n=1" modes rather than sorting them by m-number, unless I can do something very clever with the inboard (ergo, stationary) halves of the two poloidal arrays.

Friday October 25 2013 4:40 pm Hughes 81903-81941 All Shells Out

Today's run started a bit late, and ended a bit early due to no one being available to co-pilot, but got a pretty high density of good-quality shots. All shells were kept retracted throughout the run. The first hour or so of the run was dedicated to filling out the high-current (81325-style) shot library, and the remaining shots targeted the low-current shot style typified by 81376.

Notable shots include:

Other high-quality 81376-style shots from this run day include: 81923, 81924, 81926, 81928, 81932, 81933, 81934, 81938, as well 4 medium-quality shots that could be used in case more data is needed.

Plasmas tended to live longer than the high-current (81325-style) shots, with generally lower m=3 Rogowski signal, but didn't live as long as the characteristic shots of the previous only-odd-shells-retracted run campaign, typically disrupting between 5-6.5ms.

I am planning to try using an angle-correction algorithm to compensate for the angular displacement of the retracted high-density array sensors; hopefully this will make the poloidal structures easier to analyze. Analysis will follow in the coming week.

All shells will be fully inserted by the end of the [run] day.

Monday October 28 2013 6:09 pm Qian 81942~82024

feedback tests were done today. With MR around 92cm and q below 3. More mode suppression can be seen. But since the shots are not very reproducible and q often goes to 2.5. It cannot be completely assured that the mode suppression is not simply the effect of q trace. More analysis will be needed.

Wednesday December 11 2013 6:35 pm Byrne 82054-82095 cleanup/shaping

Run was delayed due to problems with the crates.

Firstly, the west rack was not initializing when crates_on was run. A fiber optic cable was found between the door and the crate. When jiggled, it seemed to cause the no sync light to light up. The power on the crate was also cycled. When crates on was next run, everything initialized, and worked fine all day. The fiber optic may need replacing, but we'll keep our eye on it. as we continue to run

Next, the CPCIs were not digitizing. After several attempts to diagnose the problem, it was found in Traverser that all the inputs were disabled, which was why no errors were returned by the shot dispatcher. make_tree was run and everything was well. It's unclear how this happened. If anyone has any ideas why the cpci's would have been disabled in this way, please let the lab know.

Most of the rest of the day was spent on cleanup. Most of the shots were the typical shots, low current, short life, high light output, but some, for example 82074 and 82076 had extremely long lives, and an *outboard* crash which is usually not seen, following large MR fluctuations. Ip decayed in stages, stopping for ~.5ms between each decay. The bank settings were the same as for the shortlived shots.

Eventually the shaping coil was turned on, and the plasma seemed to crash inwards after about .5ms. The mode structure was analyzed, and it seems to be due to a strong mode locking. 82089 and 82090 are good examples.

Reducing the startup current, so that the slower crowbar bank was forced to push the shaping current to its max value also seemed to allow the plasma to develop more naturally. The effects of wall eddies as the shaping field soaks through, or simply the rapid imposition of the shaping field (timescale of the wall, rather than the crowbar bank) could be the cause of the early disruptions.

Shots had been taken recently with 250us long gas puffs. This was continued on this run, but towards the end, longer puffs were taken. 350us was very similar to 250, but 1250us, the tree default led to higher post-breakdown Ip, higher initial Dalpha and larger SXR emission during the bulk lifetime.


Thursday December 12 2013 6:21 pm Byrne 82096-82128 Cleanup/Shot development

Forgot to turn on the oil pump during setup this morning. Was called to my attention by Jim close to 5pm. Plasmas ran well all day, and on inspection the only thing we could find was that the cases were slightly warm to the touch, due to the oil not being cycled through. Sorry everyone, I'll try to be more mindful in the future.

The e-gun battery had not been charged in a long time (probably pre-APS) and died after the first plasma shot of the day. It was recharged for 20 minutes to get back up and running, and another hour during the holiday party. It seems to have died again on the last shot of the day, as all banks fired, the gas puff and e-gun were on, but no breakdown occurred. It is recharging now and should be at full charge by tomorrow morning. It seems a waste of time to charge the e-gun after each run, but it is probably worth it to save the time that is wasted when it eventually runs out.

The first good shot of the day was dialed into the same settings as the first shot of yesterday. In all indicators (plasma life, IP current, Dalpha and SXR) the plasma was similar but better than the previous day. However, trying to match other reference shots of Sarah's and Qian's gave shots that disrupted earlier, at lower Ip. We are progressing, but still have some way to go to clean up the machine.

I was not able to develop a good shot today, though I am somewhat close to the shot used in my APS poster (81597). The e-gun dying interrupted development of the shot. Like the pre-APS run, it demonstrates that the plasma can survive for periods when the shaping current is ~6kA.

Shots taken with a slower risetime yesterday and today gave reason to worry about that, as they disrupted later, but still at around the same current as "step function" shaping shots

The idea is to get a plasma that sits stably at q~3 for a millisecond or so. The reference shot was repeated several times, so there is no reason to expect that we can not return there with time.

Tomorrow morning will be devoted to finishing installation of the new water cooling system. It should not take too long, perhaps an hour to 90 minutes. I'll continue with the shaping run then. If shot development goes well, and I get a database of a few promising shots, I'll try reversing the polarity for a few "bean" shots.


Friday December 13 2013 4:55 pm byrne 82129-82158 Shaping

Run went significantly better today than previous days. Not much time to run with morning work, colloquia and APAM friday, but several interesting shots were taken.

Most important result is shot 82158. This shot was taken with the start bank at 810V, and the crowbar bank at 190V. This is the practical maximum (assuming we don't go above 90% rated voltage) for 'flattop' shots. The crowbar bank can be raised, but the shot will peak later, and will be changing appreciably throughout the shot.

The plasma did not disrupt immediately (this is so far the only shot we have taken that did not, at these shaping current levels). The plasma ran very far outboard. This has two interesting effects. One, the plasma is very likely diverted, as the shaping current is ~8kA and MR is > 94cm. Two, the large MR led to a low q. The plasma sits at q~2 for almost 2ms with little trouble. Shots taken with all settings but the shaping the same have quick disruptions right at q~2 and crash. Several shots of this type have been taken, with varying shaping currents.

82152 was also interesting. An 'early mode' disruption reduced its MR before the coil fired, meaning that its q was very close to 3. This was the original target, before the difficulty of getting there, the interesting q=2 behavior, and the time left in the day conspired to look at shots as described in the previous paragraph. Shaping current was 110% of that used in the q~3 shots analyzed for APS. Will try to get a q = 3 database Monday.

As the comparison of shaped and unshaped q~2 plasmas showed, if we want stable equilibria in both cases that are similar to each other, we will have to develop them seperately. So far I don't have an unshaped plasma that sits near where the shaped plasma sits, with similar q. Getting that might be tricky, while a shaped q~3 seems to be hard to get to, which would be easier in an unshaped case. Work will be done on all these fronts tomorrow.

Have a good weekend.


Tuesday December 17 2013 7:09 pm Byrne 82159-82251 Shaping

This is a run report for Tuesday the 17th, and Monday the 16th, on which I forgot to send out a run report.

Yesterday's work on developing a shaped shot that had a steady q = 3 did not exactly pan out. I was hoping to have analogues to the unshaped shots with long lives, and steady q's that did not vary from 3.1-2.9 over multiple milliseconds. I was able to get many unshaped shots with this behavior.

The best I was able to develop have been shots that come close to q =3, but have more variable behavior than I'd like. shot 82200 and -05 are a good example. I should be able to look at these shots and get some information out of them. I would like to continue to develop the shots at a later time, but I think it would be wasted effort until I have a chance to analyze my data from this week's run.

Today was dedicated to doing a few 'bean' shots. This morning on inspection the leads of the coil were found to have snapped two of the zipties holding them together. They were tightened and trimmed using the only gun that could fit in the available space, which may have been too heavy duty and over tightened them. Additionally, when installing replacements, one of the zipties cracked in half as I was tightening it. The zipties we used may be old and becoming brittle. This will be observed carefully in the days ahead.

The bean shots were interesting, they tended to fly outwards when the shaping coil was turned on, and did not show the 'hard crash' in MR at disruption that the shots shaped with positive polarity do. Only a few shots were taken, the initial shots were shaping plasmas that tended to go down near q =2. The bean plasmas showed a tendency for a minor disruption at higher q levels, while normal shaped shots seemed able to accomodate lower q than unshaped. This is obviously speculation as no real analysis has been done.

Next a plasma with a normal q of ~ 3 was shaped, and again, the plasma was pushed outwards, giving it lower q than an unshaped shot. However, two shots, 82243 (unshaped) and 82247 (shaped, with higher VF settings) are somewhat similar in their deveopment at 3-5ms, so this might be an interesting area to look at.

This will probably be my last run for a week or so as I sort out all data analysis and the other related work. If anyone else needs machine time, the coming days will be available.


Thursday December 19 2013 5:45 pm Byrne 82253-82291 Cleanup

Problems with the CAMAC highway kept us from starting up until 1pm. The u-port in the basement rack was apparently not receiving a signal from the north rack. a spare f.o. cable was found in the conference room closet. Replacing the cable from the north rack to the basement rack gave was found to fix the problem. However, re-replacing the cable and cycling the power made the highway work as well. Unplugging and replacing this original cable and cycling power had no effect. I have no idea why transiently inserting a new cable should fix things.

One of our first ideas might have been that the crates were overheating because the coolant water is still under construction. The large fan was plugged into the same circuit as one of the cryopumps. Some time around 1:30pm the circuit tripped. Work was done on the shaping coil charging circuit first, which meant that plasma shots were not taken until 2:30. It was at this time that we noticed pressure was at 10-5 Torr.

The cryopump on chamber 1 was on the breaker and lost power. Unfortuately the gate was not. So the cryo warmed to 100K before we caught it and outgassed into the chamber. At the same time, the gate on the other cryo WAS on the circuit. So one cry was off, warming into the chamber, while the other was gated off. I think we should definitely have our failsafes on the same circuit as what they are supposed to ensure fails safe.

Fortunately the problem was not allowed to progress for too long. The pressure has been coming down steadily, especially after the one cryopump cooled sufficiently to open it back up. As of this writing, the pressure is in the low 10's or nTorr ~(20-30) by the time a new shot is taken. Shots have been steadily improving over the course of the day, and will probably be useable tomorrow, especially as the day progresses.

Star shot is 82291. Delayed the VF by 200us. Plasma starts outboard at around 95cm and q begins under 3. Tons of development is needed to make this a good kink-mode shot (and then to make another shot, which is also shaped.) but still.


Friday December 20 2013 6:11 pm Byrne 82292-82340 Shot development

The of the day was trying to get shots with a q that sat below 3, while Ip still had a strong ramp. Late start to day kept us from taking many shots, but we got close to an unshaped equlibrium that looks good.

Star shots are 82338 and 82307. Slightly different settings, but they illustrate the basic idea. We would like to move the steady state q from 2.25 to 2.5+.

Plasma was highly resistant to this development. 82307 was reached around 2pm, but not much progress was made beyond it. A lower Ip to start, with the same ramp should be a pretty good start, but the current was not greatly changed by increasing OHSt (varied from 6-9kV over the course of the run)

A big change was in the puff time. Decreasing the puff time to below 1ms gave low Initial Ip plasmas, but strong ramps, while puffs longer than that (standard is 1250us) gave lower initial Ip, but flatter ramps. Effect seemed bimodal, as decreasing puff steadily did not give a continuum of Ip behavior, but that may be due to insufficiently statistical numbers of shots taken. This is where the investigation will resume on Monday.

Have a good Christmas and safe travels if you're taking off this weekend.


Monday December 23 2013 4:33 pm Byrne 82341-82404 Shot development

During hi-pot, a clicking sound was heard. It was established that this was the breakers tripping again. They were found and turned back on, and there was no change in the base pressure.

Base pressure is significantly higher than Friday, nearly 2X10^8, vs 5X10^9 before. This is likely due to the increased temperature today vs. Friday. AC is still out.

Shot development was hampered by the battery for the gas puff dying around 2pm. It took about a half hour to diagnose, and once the new power supply was inserted, the plasmas were differently behaved than in the past. This would explain things seen in previous days, like small changes to gas puff timing leading to largte changes in plasma behavior.


Friday December 27 2013 5:43 pm Byrne 82405-82466 Shot development

Today's run delays were:

Despite the dispatcher not showing any errors, the shot triggers for OH,VF, and SH banks did not fire. It's my understanding that the TF trigger comes from a different location. This bank fired. Cycling the crates on and off had no effect. Eventually athena was cycled, and the triggers worked.

After that a shot was taken, the same moment of which a breaker (not the one in the machine room that has been giving us problems) tripped, cutting power to the control station. The cap room was checked, everything was fine. The tripped breaker was found in Nicks room. No idea on the cause. This shot, again, only fired the TF, but after power was restored, the banks all fired well.

The machine seems to have been dirtied by its days inactive. the last shot of Monday was taken several times, but I was unable to return the plasma behavior to what we saw then.

Attempting to run some aggessively outboard cleanup shots, I discovered that the change in Ip with the gas puff duration seems to have been a function of the dying battery we were using. Previously, a gas puff of 250us would start with significantly lower Ip Dalpha, and the Dalpha spike would be noticeably delayed. After replacing the battery with the power supply, there was no difference between a 1250us shot from before, a 1250 us shot after or a 250us shot after. This suggests that the battery had trouble fully opening the gate during a short puff.

This removed a "knob" for control of the plasma, but reduced the space in which to search for our shot. A few shots were taken with delayed VF start(to increase initial MR), increased OHE (IP had a 'saddlebacked' droop between startup and crash, almost certainly an effect of the dirty chamber.) boosted VFE (to hold the plasma, which starts further out, at a constant MR for as long as possible)

Star shots are 82457, 451,446. These shots all have q just below 3 for roughly 1.5-2ms. 457 in particular is very flat below q = 3. There is some early mode activity in this shot though (perhaps 4 in 5 shots today displayed early mode activity, scrapping most) so it was not repeatable.

The 'early mode' in my case often seems to come about by approaching the q = 3 line too slowly. The faster you punch through, the less likely the mode becomes. However, for me this means q is much too low after the plasma establishes itself. I'd like to find a similar equilibrium without the early mode, but I'm unsure if anyone's found shots that are less likely to have them (so far I'e only heard of shot styles in which they are more likely)

At least I have a few q = 3 shots, at early times, so the current gradient should be high, unshaped. Shaped will be its own problem, and post New Years, the machine will probably need another day of cleanup. At least the base pressure is down below 10^8, thanks to the low ambient temperature. The weather should be extra cold next week, so that should help.


Thursday January 2 2014 7:10 pm Byrne 82467-82516 Shot Development

As usual, problems with the crates on startup. No visible source of error. This was anticipated, though, and the crates_on script was the first thing I did. Jeff rebooted the system while the rest of the startup checklist was run down. No time was lost. It stinks that the problem still exists, but it may be worth while to check that crates on will not throw an error first thing in the morning to avoid missing the time it takes to reboot either Spitzer or Athena.

Machine was dirtied up again, as expected. Eventually was able to return to the start shots of last Friday. Apologies for my mistake, but I entered the numbers in the book incorrectly, and that made it into last run report. I mentioned a star shot as 82446, but it was 82445. Not only was I able to replicate the shot to within the limits of a dirty chamber (short life, so shorter time below q =3), but I was able to do so in a repeatable manner. Previously, up to 5 or 6 shots were required to get one that was not scotched by an early mode.

These shots are born just below q =3 and stay roughly constant for up to 1.5ms, but IP ramp is almost non-existent. We see the 3-1 mode pre-existing, but then declining in amplitude, which may be due to the current profile relaxing after startup in the presence of constant IP.

Since we were sure that we can get more data on those shots if need be, the decision was made to try to replicate Niko's thesis shots. Reference was shot 74780. These shots are far outboard (which is helpful for future shaping) low Ip(t=0), and long lived, with a constant dIp/dt. q is constant at ~2.25, but a growing 3-1 mode is seen. It happens late, though when Ip has pretty much peaked. The idea is to run the plasma slightly more inboard to to increase q across the shot. These shots were excellent cleanup shots, as can be seen if you stack the IP traces of shots 82502-82506. Leaps and bounds in terms of lifetime, and when the shot style of -445 was run, it too lived longer and less disruptively.

To try to hold MR out Jeff and I experimented with using the control coils as a pseudo-VF coil. The coils all had the same step function voltage spike, with the polarities switched between to and bottom. Shots 82513 and 82514 have "anti-VF" pulses at different times and amplitudes, but in both cases, we see a very strong effect. That the plasma is far outboard, and so is strongly coupled to the control coils doesn't hurt. We definitely have the ability to arrest the plasma's inward crash, or even draw it outwards, though how finely we can control MR, and thus q, and for how long, remain open questions

In other hardware news, the plasma is definitely insensitive to gas puff duration now that the new power supply has replaced the old battery. Puffs of duration from 1250 to 250 us were taken, and very little difference in Ip or Dalpha at breakdown were seen. Jeff actually has a shot development primer on the wiki that demonstrates the effect that varying puff time used to have.

When the puff time was reduced below 250us, the plasma did not breakdown initially. However IP did rise after about 1ms. I don't know why the OH pulse wouldn't cause breakdown but OH+VF would, but that seems to be the case as you can see in shots 82496,82498, and 82516. This last shot was taken with a gas puff of 250us. I left the power supply on after Friday and its battery died. We gave it a quick charge during set-up, but it probably died. It seems that without enough juice, there is some effect on it that leads to these types of shots. So if you want to fire a non-fast startup shot, the option seems to be on the table. At any rate the Gas Puff power supply will probably need recharging at least monthly, assuming we remember to turn it off at the end of the day.


Monday January 6 2014 6:16 pm Byrne 82517-564 shot development

Star Shots are 82553, 82545.

Replicating the same style of shots used by Niko for his thesis. As before, the cleanup nature of the shots meant that the equilibrium was highly dynamic from shot to shot. I was able to get several shots, of which the star shots are good examples, where q was below 3 by 2ms, and rose steadily from 2.5 or so back up to 3 over the course of 3 ms.

Attempted to switch to shaping but there were problems with the phidget controller. The shaping coil fired well during the vacuum shots at the beginning of the day, but when the coil was energized for the first shaped shot, 82547, it only fired with about 1/3rd the expected current. The bank gauges indicated full charge.

Attempting to repeat the shot, the interface software correctly identified when the start and dump buttons were pressed, but neither interlocks on the dump, nor the two Shaping power supplies were thrown, suggesting that the problem lies in the phidget controller rather than any one of the three other instruments. I was unable to diagnose or repair the problem by myself with the time allowed (this was at about 4pm) so I continued to take shots to build a database.

The plasmas began falling in slower and slower, keeping q too low. I tried to fix this by boosting VFE, but that was a was as the VF's Ohmic drive cancelled any gains in the MR crash with higher IP. I should hve reduced OH instead.

The crate highway turned on with no trouble for the first time in several runs.


Tuesday January 7 2014 7:00 pm Byrne 82565-82597 Shaping

Morning was spent debugging the phidget. No problems were found in hardware, and we were able to use software snippets to perform each phidget operation independently. It seems that the phidget is able to get into a state which the normal operation of the software is unable to get it out of. This can be fixed by a hard reset - removing and replugging the usb cable. On the bright side several errors and possible problems in the phidget code that we have not encountered were caught and fixed, on the dim side, we weren't able to fix the problem that we currently have, but at least we have a way around it

Star shots are 82586, 82589 for large m=3 activity, as compared to an unshaped shot, 82588. Have not analyzed, only looked at stripey plots and m=3 rogowski.

Other shots of interest are the run from 82590-97. This was a shaping scan. All shots were flattop-style, each one involved stepping current up by 1kA per shot, from 1kA to start. Saw a 1ms drop in plasma lifetime from 3kA-4kA of shaping, and from 5kA to 6kA of shaping, vs .25ms per kA in others. 82593 and 82594 (4 and 5kA) have a nice q ramp, similar to the model unshaped shot, 82545, which will be helpful in comparing the effect on the MHD.

See you all at the meeting tomorrow,


Friday January 10 2014 5:58 pm Byrne 82598-82642 Shaping

Base pressure was at 1.3x10^-8 Torr at the start of the runday. It has been rising steadily, despite the recent cold. I think it's likely that one or both cryo's ought to be regenned.

The hook-and-loop type velcro on the new PVC has begun to come loose. The installation of the shaping coil holders meant that we needed to replace the old style of PVC installation with a two-piece system to allow for removal. This was done on the old, grey PVC when the coil was installed. The loop section of the velcro, which has been on since the upgrade in August, is still sticking well, likewise, the hooks, which were on from august until we replaced the PVC in November were fine. It's likely the hook velcro on the new PVC was a different type, that was not high-adhesive. I have ordered high adhesive Velcro from McMaster and will replace it all when it arrives. For the meantime, the panels were stuck back on, as the adhesive still had some tack, but not enough to serve long term

The high base pressure and the cleanup style shot I am shaping meant that the equilibrium was highly variable. Only the last 5 shots or so did not develop from shot to shot. This made comparing the effects of a shaped and ushaped shot very hard. The intention was to repeat each of the shots in my shaping progression from Tuesday's run at least twice, so that I could speak with some confidence as to the effects of shaping. I have 100V and 200V done, and intend to shape up to 800V, so much remains to be done.

Star shots are 82625 and -34, simply because they are unshaped shots that are very similar to my reference shot, increasing the database for unshaped plasmas.

Monday January 13 2014 5:02 pm Byrne 82643-82669 Shaping

Base pressure started at 12nTorr, but increased steadily throughout the day, until after a long break it had settled at 30ntorr. During running at the end of the day, the base pressure was seen to be at settled at around 50-60nTorr between shots. Cleanup shots had little effect with the base pressure this high.

The cryos were at 30K and 18K when measured. 30 Kelvin is pretty high, and the pump should probably be regenerated once the liquid nitrogen on order arrives.

So not much to report on the plasma front. Several machine issues to report, though. One of the OH charging resistors was found to be too low by roughly an inch. It must have been too low for a long time, and it's not obvious how the banks were able to charge during all this time. The reason the banks were not able to charge, however, was found to be a tripped breaker in the bake oven room. This was fixed, but not before we opened the supply box for the TF, which required work to put back together.

Also, in the last few run-days, a strange noise spike has been seen in the loop voltage sensor at around 4ms. Sometimes it occurs, sometimes it doesn't. When it does, the time varies from 3.5-6ms. The shaping and VF coils have not been shown to have any effects. When the OH or TF is off, it does not occur, but when both are, it does. It's not clear why this should be so.

Also, after the TF/OH banks were worked on, we re-high-potted. A low, frequent popping sound was heard near the feet on one TF case at chamber 10. We were unable to isolate exactly where it is arcing and what to, but the power supply had no trouble holding voltage, and we've run with a similar issue before with no problems. Nevertheless, we should monitor to make sure it doesn't get worse, for the obvious reason but also because it would make it that much easier to isolate and fix.

Also, I finally sat down with the pickup subtraction code, and it seems like 1) Qian's pickup subtraction is more accurate than the current method, at least when trying to zero out a pickup signal. It stands to reason that a full plasma shot, which is harder to quantify the performance is just as good. 2) The differences in the MR can be rather large, up to 1cm. In shots like mine, where MR is far outboard, this is a large effect on mr, and thus on q. I'll be putting some plots together and sending them out for perusal tonight.


Wednesday January 15 2014 6:36 pm Byrne 82681-82728 Shaping

Spent most of the day developing the shot again. Fortunately I was able to get back to the reference equilibrium for the last few shots.

The second Cryo was turned on around 5pm, as of this writing (6:30) the base pressure is around 24nTorr. Since the pressure after firing is usually much higher than the base pressure in the morning, it's safe to say our base pressure will be significantly lower tomorrow.

82722-27 are shaped. The coil was run with 800V on the start, and 200V on the crowbar, giving 8kA of step-function like current. IP never rises above 10kA. There is no doubt the plasma is diverted in this case.

Again, large amplitude is seen on the m=3 rogowski, though I haven't done BD analysis. 825, 6 and 7 have the SH start delayed by 1.5ms to see what effect that would have. The coil essentially came on as the plasma left it's low q region naturally. m=3 rogowski signal is more muted in this case.

The last shot of the runday had a louder snap when the banks fired. The only thing I was able to find was that a few of the zipties had broken at the bundle, which is reasonable given the high currents involved. Nothing was seen on the ISH trace to indicate any shorting.

If the pumps continue to cooperate, it should be much easier to return to the unshaped equilibrium, so there should be a much larger cohort of shaped shots.


Thursday January 16 2014 6:38 pm Byrne 82728-82774 Shaping

HUGELY improved performance now that the base pressure is down in the single digit nanoTorr range. Returning to the reference equilibria took 4 shots, as opposed to 3-4 hours.

First shaping only shot saw the rare 'Start Only' discharge. According to the phidget, the crowbar bank charged, and on the next shot, the bank was found to be completely discharged. Not enough time had elapsed for the crowbar bank to have discharged through the dump, but according to the rogowski it had not discharged through the coil. There is no obvious damage to the bank, and nothing in the current trace suggests a short. This was also the only instance of this shot seen all day. The shot was immediately repeated and the bank discharged properly.

A large database of high-power shots was taken. The first six shots of the day were 4 700V-175V shots and two 800V-200V shots. After this the leads were inspected. They had been double ziptied, and at one of the locations had broken both ties. The OH leads on top of the machine had also come loose. The OH was bound more tightly, and at the end of today, has not broken loose. The Shaping coil was re-bound and shots were taken at 600V-150V instead. The zipties on the SH leads are also fine at the end of the day. We will probably need a new solution if we hope to put >6kA through the coil, though Nick and I have some ideas.

At any rate, we now have a multi-shot cohort for 800/200, 700/175 and 600/150. Analysis to come.

At the end of the day, I moved the shaping start back to the same time as the VF start - 1ms. The expectation was the plasma would disrupt before forming, but we actually saw an improvement in performance. The plasma lived longer and fell in more gently than when the coil was turned on to a full formed plasma at 2ms, though it still ended in a hard MR crash. These shots all had trouble getting through q of 3 though. It may be worth investigating a bit more.

On inspection, there seems to be a 50us delay in firing the SH coil vs the VF coil. The last shot of the day, the VF start was moved back 50us, but when the values are backed out of the tree, they seem to rise at almost the same time. Anyone know why this should be so? Are the krytrons that much faster than an SCR?


Tuesday January 21 2014 6:56 pm Byrne 82775-82832 Shot development

This report covers Friday's run as well as today's.

The run Friday began with the no-breakdown 'triangular IP' plasmas. The gas puff was orignally set to 500us. This had worked previously on Thursday, but on Friday (The first day to begin with the AC system fixed) it did not. Increasing the Gas Puff turned out to be necessary. This *may* be because the background pressure was lower, requiring more gas? How much of the background would be deuterium, which I would imagine the OH is optimized to ionize? I can't imagine a background pressure that was mostly nitrogen or oxygen would have the same paschen curves as hydrogen.

After this, most of Friday was spent trying to get plasmas below q = 3. This was seen on Thursday, but developed as the machine pumped down, and was not recognized as a feature of the new equilibrium. Plasmas are subject to small, frequent bursty activity as they approach q = 3 from above, keeping MR low and preventing the plasma from breaking below q = 3. 82794 is a good example, or 82821, which is from today.

Anecdotally, the reason for this was the aggressive current ramp. Backing off the OH did not have much effect, though raising OHE to 300V did allow us to get the q =3 surface outside the plasma. It was at this point that q =2 crashes became an issue, as the plasma would go too low once through q = 3. Eventually we were able to get unshaped shots that passed through q = 3 and lived, quiescently, between q = 2 and q = 3.

Friday's run started after lunch. I had a class in the afternoon, so the theme of the run was about re-conditioning the chamber after the 3-day weekend and getting back below the q =3 barrier. 82831 and 82831, the last two shots of the day, look pretty good on that front. We can resume shaping tomorrow.

Friday morning was spent cleaning up the cap room. The oil leaks may be getting worse, or the neglect may have reached a tipping point, but there were 1/8" deep standing pools of oil beneath the krytrons for the OHE bank, and near the barrels of oil. The metal walkways, which are bolted to the floor, have piles of saturated absorbent beneath them.

The oil filters, and the line, to them seem to be a big culprit. I suspended a catchment bucket beneath the filters with wicks to direct the oil, and moved a wick from the top of the filters' feedline to the low point, as plenty of oil seemed to be leaking past it anyway. This seems to be helping, at least the catchment is about 1/8 full after today's run. I think there's probably still a leak above the OHE ignitrons (which may be the PVC routing pipes at the southwest end of the Tokamak) which we'll have to watch. The loose oil and absorbent was covered with dry stuff to prevent leakage in the garbage, swept up and replaced with new absorbent. Conservatively, about 50 lbs of absorbent and oil came out of the basement. I'll try to be around to help Glenn, our custodian, cart it out tomorrow morning, but if I'm not around, please lend him a hand. It's in the trash near the sink.

Maybe we should talk during the meeting about who's responsibility it is to tend to the oil/absorbent in the basement. If it were part of startup, that might help people find the time. It's dirty work, but if it's done more often it shouldn't be that big of a deal.


Wednesday January 22 2014 6:25 pm Byrne 82834-82852 Shells Out Shot Development

Today we retracted the shells to full-out positions, and began running to develop a shot.

Interesting shots are 82835, as compared to 82832. This would be the first and last shot of today and yesterday, respectively. It illustrates pretty starkly how much radial stabilization we get from the walls.

Usual trouble with developing a shot. Plasmas were either highly susceptible to activity at q = 3 or fell through to q = 2, where they would suffer one big disruption, which would then lead to the ultimate death of the plasma within 1 or 2 ms. Shot 82839 is an interesting one. The plasma fell below q =2, and then held there, steadily, for about 1.5ms, before a minor disruption kicked it above q =2

At the end of the day, we were able to get shots that fell to q ~2.25 and were stable, so we began shaping. The best shot of the bunch is 82851. This shot has *no* activity as it falls below q = 3, and when the shaping coil fires, at 2.75ms, it rises pretty linearly to q of 3 and sits there, just before disrupting.


Friday January 24 2014 1:17 pm Byrne 82853-82877 Shaping

Computer trouble on friday aborted the run. This report is for Thursday, which was not sent out.

The computer trouble seems to be spitzer related. The TF phidget does not initialize when the take_shot_hbt script is run. running th script with the phidget disabled shows that every CPCI in the crate chain is not initializing. Everything else works. Not sure how to debug this, and the small amount of available time on Friday between morning and afternoon talks means that I'm going to see if this straightens itself out the way it seems to have broken itself.

As for Thursday, shots began perfectly with no development! The repaired AC and regenned cryo are working wonders in terms of preventing wasted time. Shots were taken shaped. Currently, the unshaped equilibrium does goes below q=2 and does not rise to q=3, while shaped shots do. We'll try to fix that later.

The shaping start bank had its voltage dialed down to cause a longer rise to peak current. After checking with the flux simulation code, it was found that at a certain point the plasma stopped being diverted. The voltage was brought to just to the point of marginal diversion, and the Shaping coil was fired progressively earlier (when the plasma was further out and IP was lower). These shots should be interesting to look at as they take place right at, and on either side, of the diverted/limited transition, and all disrupt near q =3


Wednesday January 29 2014 5:27 pm Byrne 82881-82920 Shaping

No plasma shots were taken today. After some troubleshooting, the problem was found to be the e-gun filament. The bias voltage on the filament would drop as the heating current was turned up. This would be slow at first, with a large discontinuous drop around 6 Amps. The normal operating current is 10 Amps so this is roughly a 3-fold decrease in filament temperature. A few runs were taken with different filament temps and biases, in the attempt to get useful plasmas. Voltages of 167V, 100V, 60V and 14V were all taken, and in no case did the plasma ionise. This is a current range of 5-7A. Nominal voltage is 171V.

We have not been able to identify the cause of the problem, but have confidence it is limited to the e-gun itself. A power resistor was hooked to the e-gun supply, and bias was not found to vary with current. The filament itself, which had the form of a tight solenoid when installed is extremely kinked now. Pictures will be sent to the group through normal email.

The gas puff problem, however, was found to be a dead 9V battery in the power supply. I had not had anything to do with this battery previously, and did not think to check it yesterday. The shots that did not break down WERE seen to have a pressure spike, so that issue at least seems to be settled.

This seems to be the end of the shaping campaign for now. We'll check the operation tomorrow once we've retracted the e-gun behind the gate valve, but if that doesn't work the only option is to remove the e-gun and replace the filament. This will probably end up dirtying the vacuum to some degree when it is replaced. We will still take a few shots to ensure everything is ok for Paul's campaign.

The phidget problems were solved by attaching the shaping phidget through USB to spitzer. The drivers used to operate the phidget are located on Spitzer and Nick suggested network issues might be to blame, especially considering the errors are generally related to checking the phidget state, as well as how often these calls are made. Two vacuum shots were taken with the shaping coil, and though this is a VERY unrepresentative sample, unplugging the phidget and re-plugging to Athena was tried right before this, and did not fix the issue, so it was not the hard reboot that returned the phidget to operation.

Shots taken on Tuesday (Sorry for not having sent the report out last night) were 82881 and 82905. The first few shots were an attempt to get q below 3. 82891, we had a pretty good shot. By 82896 we noticed the Dalpha, initial Ip and SXR were dropping, and began to boost the gas puff time, but as it became clear that we would not be able to keep it operational we ended the runday.

Plasmas should still be possible Friday, though what condition the vacuum will be in after the repair to the filament, I couldn't say.


Friday February 14 2014 4:45 pm Hughes 82949-82953 Vacuum shots testing Fe wall effect on sensors

First shot of the run was TF only to check for unexpected noises. No problems were observed. All other shots were in reference to shot 82681, a vacuum shot from one of Pat's recent(ish) shaping runs. 82950 is TF and VF only. 82951 is TF and OH only. 82952 is a full standard vacuum shot. 82953 is identical to 82952, but with the TF reduced by 80% to increase the residual permeability of the ferritic wall by 25% from ~8 to ~10. Since the shaping coil and glow discharge use the same power supply, which is still hooked up for GDC use, and the run being delayed by the shell motor controller breaking yet again, we decided to put off shaping coil vacuum shots until another time. -- Paul

Friday February 21 2014 5:35 pm Hughes 82954-83015 Cleanup shots after Fe installation

Since this run has been cleanup shots (and will continue to be cleanup shots, unless plans change), there isn't a huge amount to report as far as star shots. Machine performance is pretty good for being right after a long up-to-air with lots of material installed, followed by just a week or so of baking.

My shots are 82954-82968 (some vacuum shots, some attempted plasma shots without breakdown), 82974-82983, and 82992-83015. Pat took over cleanup shots 82969-82973 on Thursday, and Qian and Ryan took crates-only shots 82984-82991 today.

Base pressure Thursday morning was about 7.2nTorr and up to 9.4nTorr this morning (Friday). Not sure what accounts for this change.

Noteworthy vacuum shots:

Noteworthy plasma shots: While shutting down I'll turn on the RGA, record vacuum status before I leave, and check it again on Monday morning to see how the vacuum has been evolving since we shut off the bake.

Wednesday February 26 2014 6:12 pm Stoafer 83016-83028 Multi-Point TS

After installing the new collection optics and aligning the laser, some plasma shots were taken to test the new multi-spatial point Thomson scattering system. On shot 83028 we saw TS light in three spatial channels (light not in the laser wavelength channel)! Optimization of collection optic alignment still needs to take place. We had a few issues with start up including the puff valve battery not being charged and the strangely behaving e-gun. It seems that setting the current of the e-gun to 8A gets breakdown, even though the measured voltage is low. Breakdown did not occur when the current was set to 6A and the voltage was around 200. There is too much stray light in the system currently, which needs to be reduced for proper running of the TS system. Also, I had trouble opening the shutter to the viewing dump. This was resolved by moving the bottom shell in section 6 in. Although it is designed to be able to open and close with the shells retracted, it seems to get stuck on the shell. For now, please do not fully retract the bottom shell in section 6.

Monday March 3 2014 6:25 pm Hughes 83059-83101 Cleanup and Shot Development

Today's run went pretty well despite some snags here and there. In particular, the puff PSU battery hadn't been charged, and dropped to 7.8V during the run, wasting a good chunk of time on lost shots and recharging.

With a bit of tinkering and fairly similar settings (with the exception of OHEL raised by 20%), it was possible to reproduce shots of the style for which 81932 was developed with a steady R0 between 91 and 92, a fairly steady current ramp, and q starting near 4 and dropping below 3 at around 3ms.

Some especially good shots with fairly arbitrary grades:

Here are some other notable shots: Several shots died with abrupt inward crashes at around 2.8-3.2ms, suggesting higher than normal disruptivity. Loop voltages have been about 20% higher than otherwise comparable shots from October. SXR midplane signals have also been noticeably higher, suggesting the plasmas are still not terribly clean. Elevated base pressures seem to tell the same story. I think the next step is to insert the non-ferritic walls for continued cleanup and shot development.

Tuesday March 4 2014 6:17 pm Hughes 83102-83159 Cleanup and Shot Development

Another day of cleanup shots and testing how willing plasmas are to behave as they did prior to the up-to-air. All even-numbered (i.e. non-ferritic) shells were inserted, and all ferritic shells retracted for this run. Plasmas generally were less similar with even shells in than with all shells back, perhaps due to greater impurity injection due to proximity to the wall surface. After seeing this, shot style changed from pursuing 81255 to producing plasmas that flew far outboard late in time. A final 81255-style shot was taken at the end of the day for comparison. None of the shots of the day are really great for my purposes, but there is some lively activity if anyone wants to dig through for analysis.

Noteworthy shots:

Jeff also did some analysis during the day and sent notes on observations: 83140: 3/1 mode grows almost instantly during 4.0-4.1ms, from zero amplitude to pretty strong (auto-scaled PA2 plot is near +- 13G limits). This could be a good example of a mode growing on an ideal time scale (e.g. the ideal kink mode going unstable). q* is near 2.4 at this time.

83147 (and maybe others around this shot): looks like higher-order mode activity is dominant, at least from 2-3.5ms, while using boxcar smoothing. I think this is due to the 3/1 mode locking. Plotting 1.5ms onward with standard contour plots, it looks like there's a 3/1 mode that slows down and probably locks, then disappears from my analysis since it's treated as equilibrium.

Both 83137 and 83159 show a rolloff of plasma current starting around 3ms, as well as higher loop voltage and SXRMP signals than the target 81255 in spite of very similar IP and R0. This may just mean a lot of cleanup shots are needed.

Thursday March 6 2014 6:59 pm Hughes 83160-83262 Cleanup and Shot Development

Today was mostly dedicated to aggressive cleanup of the stainless (even-numbered) shells, with a bit of shot development at the end of the day to test progress of the cleanup shot campaign.

Cleanup shot style (83162-83237) was intended to give the plasma some time to heat up and then throw it outboard; shot development (83238-83262) targeted shot 81255 and its relatives.

For a series of shots longer than their immediate neighbors during the day, the time in ms at the current-peak of the disruption were:

shot: 83168 83174 83181 83193 83220 83231

t(ms): 4.99 5.50 5.87 6.43 6.65 6.86

Noteworthy shots include:

Although all of these shots followed the current, R0, and q* of shot 81255 quite well, none of them lasted as long after the loss of a steady major radius/decline of the plasma current. Although still somewhat higher, loop voltage and SXRMP traces were much closer to the target for a magnetically-similar plasma today. Loop voltages, for example, tended to be 1-1.5 volts higher, rather than reaching up to 4 volts higher. There are still large (2-4V) jumps in loop voltage, which correspond to changes in plasma current as well as SXR fan brightness.

Tomorrow morning, the new stoppers for the ferritic shells will hopefully be ready. The plan, then, is to insert the ferritic shells and undertake another aggressive cleanup program.

Friday March 7 2014 7:26 pm Hughes 83263-83334 Cleanup shots with Fe walls inserted

We finally started cleaning up the new Fe walls! That's pretty much the big news for the day, as it was otherwise just a string of cleanup shots without a great deal of time in-between for analysis, the focus being to produce lots of hot, outboard, long-lived plasmas. Most had their disruption current peaks between 5 and 6ms; not bad for cleanup shots, although not fantastic.

Base pressure at the start of the day was definitely down from previous run days, so the barrage of cleanup shots approach employed yesterday seems to have paid off. Today saw 68 plasmas, down from yesterday's 100, due to various interruptions. Shots 83265-83281 were shots in the same configuration as yesterday (even/nonferritic shells in, odd/ferritic shells back) to establish a baseline, make sure the nonferritic shells were clean, and buy some time to find the missing spectrometer lens mount.

Noteworthy shots:

We had hoped to use the spectrometer to check for the appearance of iron/cobalt or other impurity lines when the ferritic walls were inserted, but a mounting clamp for the spectrometer lens has gone missing, so we were unable to do so. Jeff has been looking at other ways to set up spectrometer optics that might be usable in upcoming run days.

PS: On a maintenance note, Qian observed that the south rack doesn't seem as well cooled as it ought to be. I checked the thermometer on the high pressure water line, and it was at 50F, which ought to be pretty cool. I'm wondering if something might have been altered or valved off (wholly or partially) during the work on the new cooling water system.

Monday March 10 2014 6:45 pm Hughes 83335-83380 Cleanup and Shot Development (Attempted)

After a few cleanup shots, shot development was started based on shot 82545 as a general model. This did not go very well. Shots either went completely awry or suffered minor disruptions around 2.5ms, followed by another disruption around 4-6ms destroying the plasma. Lower-puff shots were also tried, as low as 125us, resulting in very erratic starting plasma currents, generally jumping between ~6kA (target) and ~3kA.

Toward the end of the run, this behavior began appearing on higher-current shots. An attempt to counteract it by raising the puff time to 1ms didn't help, and resulted in a plasma with almost no breakdown. The e-gun bias battery and puff PSU battery have both been checked, and were still well charged. The 9V in the puff circuit has not been checked, and any other problem in the puff or e-gun systems could be at fault, as well.

The disruptions tended to occur at a q* of around 2.4-2.5, abruptly shifting from a modest 2-1 mode to a strong 3-1 as q* jumped up to 3 or higher with an inward jump in R0 of about 1.5cm, after which the strong 3-1 mode would generally fade away over about 500us. This *might* be a sudden 3-1 external kink, but the 1-0 structure of the sudden inward jump dominates all other signals, and I can't offer a totally convincing reason why the 3-1 kink would wait so long to appear.

Pat took a few shaping coil only vacuum shots during the day (83346-83348), and Jeff worked on getting spectrometer data.

Shots of note:

Two leads apparently connected to the spectrometer came loose during attempts to diagnose the failure to get breakdown. I'm not sure how or where those plug in, so I'm leaving it as-is. Obviously we'll need to fix some things before we can run tomorrow.

Thursday March 13 2014 6:55 pm Hughes 83387-83426 Shot Development for FWM

Not the greatest run day. Several shots and perhaps two hours or more lost to chasing intermittent and poorly-understood breakdown problems. Targeted plasmas with a strong current ramp (>2MA/s) that start outboard limited (R0~93-94) and swing inward so that q* approaches 3 from below.

Shots that had good breakdown showed the same behavior seen on Monday where a moderately strong (perhaps a few Gauss) 2-1 mode would develop around q*=2.5, followed (sometimes after sitting quietly) by a minor disruption which kicks the plasma inward and kicks q* up just above 3, leaving a 3-1 mode which fades away over 0.5-1.0ms.

This suggests all the modes are internal, at least while they're relatively steady. The disruption could be caused by a severe internal mode; it could also be the sudden onset of a 3-1 external mode which survives and fades away after the q* jumps up and the mode becomes internal.

After shot 83408, the non-ferritic (even-numbered) shells were retracted. Other than the breakdown trouble that showed up and lasted until the e-gun heating current had been tweaked, there was no obvious effect, based on the 10 or so successful plasma shots that followed.

Noteworthy shots:

The cause of the breakdown problems hasn't really been resolved, although fiddling with e-gun heating current seems to (sometimes, maybe) help. Once we're past the IAEA deadline, we should probably make a scan in e-gun settings and see what effect it has, if any; it sounds like there have been some cursory efforts to do this while trying to fix it, but not as a dedicated experiment to understand the e-gun's peculiar behavior.

The spectrometer was set up to record for shots 83416-83425, but it's hard to tell whether any of the data is useful until I can sit down and put it into an analysis code. I'll try to get that done tonight and send out a report on what I see.

Friday March 14 2014 5:37 pm Hughes 83427-83451 Shot Development for FWM

Mostly bad news on this run. After hearing some fairly loud snapping sounds which were initially identified as cable ties breaking on the OH leads, we discovered an OH lead had broken its lug and was arcing across the gap (and also breaking cable ties). Fixing this took a big bite out of the run day.

After the repairs, several plasmas were made with the same configuration as before, having the non-ferritic walls fully retracted and the ferritic walls inserted to their new stoppers. Then on a hunch, I retracted the ferritic walls by 5mm. Comparing these two configurations with a few shots (8+ each), the limiting lower q boundary had been about 2.5 with the ferritic shells fully inserted, but this dropped to around 2.25 by retracting the ferritic shells slightly, a boundary very close or identical to the lower q limit often seen by Pat and others in this shot style.

This suggests to me that with the insertion limits as they stand, at least a part of at least one ferritic wall is acting as a limiter, so the real q* of the plasma is 5-10% lower than our calculated q* suggests. Without a deliberate study of each wall's effect, which could easily take a solid week to do right, I'm not sure what to recommend other than keeping the ferritic shells 5mm back from the insertion stoppers until we have more information.

I'll compare against some older shots, but I suspect we don't need to retract farther, and may be able to re-insert some shells some amount. I have taken spectrometer recordings of both configurations (although as usual the recording may or may not show anything), so I'll look and see if there are any suspicious lines in one that I don't see in the other.

Noteworthy shots:

As with Monday's run, today's run ended with plasmas suddenly refusing to break down. I suspect it's an e-gun issue, because I remember we had set the e-gun heating current to 7.5A before, and when I looked, it was down to 5A, and the filament seemed dimmer than usual. Maybe someone fiddled with it and didn't tell anyone; I don't know. Someday we should probably do a proper characterization of the e-gun behavior and propensity for failed breakdown in the I_heat-V_bias parameter space.

And that's the run. Happy Pi day, everyone.

Monday March 17 2014 6:16 pm Hughes 83452-83509 Shot Development for FWM

Today was mostly spent attempting to get a different kind of shot that starts out around R0~94 to drive q* down quickly to 2.5 or lower, rather than the gradual shots before. These efforts did not meet with a great deal of success. Only a few individual shots produced anything like the q* trace desired, with especially significant shot-to-shot variability, very vulnerability to early disturbances around t=1.3ms, as well as difficult to predict response of the plasma to changes in bank settings.

This may be due to operating in a regime where insufficient VF pressure can cause the plasma to lose energy quickly to the limiter and then crash in. The strong current ramp may also have influenced the vulnerability and unpredictable response at early times.

Noteworthy shots:

As has been a recurring theme lately, the run day was ended by plasmas suddenly no longer breaking down. Since it was almost 6pm already, it wasn't a catastrophe, but it is a somewhat distressing trend. So far the only fix I know of is going home and coming back in the morning.

Wednesday March 19 2014 6:13 pm Hughes 83510-83527 Shot Development for FWM, and prelim e-gun & puff testing

Today was a mixed bag of trying to get a really good shot for FWM study, plus some dabbling with the e-gun and puff. While we made a few interesting and rather wild plasmas, perhaps the most important result of the day has been finding that the puff system is highly erratic across the run day.

Notable shots:

Comparing shots 83519, 83522, and 83527 and looking at the bias current (the negative plasma current preceding the OH start), what stands out is that both the 4ms and 2ms puffs showed about 3 times more bias current than the intermediate 3ms puff, and their bias currents also peak about 100us earlier than the intermediate puff.

This suggests something highly erratic in the puff system over timescales on the order of a run day. We don't know yet whether this is an electronic or mechanical problem. I would suggest we dedicate a run day to hooking up all the signal sources to record their performance, and doing a series of fill tests at different points in the day. We can then compare shots with similar puff settings and different fill performance, and see where in the system the behavior begins to diverge.

As things stand, we don't even know whether the puff is reasonably stable shot-to-shot except that in a 3 shot series (83516-83518) the fill increased with longer puff times, although not in a particularly linear way:

Time vs Fill
Shot no. Puff Time (usec) Fill Press. (uTorr)
83516 125022
83517 250037
83518 400056
83526 300068
I suspect we will have to lock down the issues with the puff before we can pursue reproducible plasmas, but we'll see what can be done tomorrow.

Thursday March 20 2014 6:32 pm Hughes 83528-83568 Shot Development for FWM, puff testing

Today began with some diagnosis of the peculiar puff behavior observed yesterday. The results weren't absolutely conclusive as to the problem, however, and the puff seems to have behaved itself throughout the rest of the run day.

The only sign of a possible puff issue while making plasmas was variability in the bias-stage negative plasma current amplitude, varying between about 300A and 160A with a general decreasing trend from the beginning of the run to the end. Jeff has said this is within the expected variability, but since we haven't tried to characterize the puff before (or so I understand), this might represent an inherent variability which becomes intermittently worse.

A few plasmas with q* that drops quickly to around 2.5 and then sits relatively steady and/or rise toward 3 were made, but at first glance, none of them seem to exhibit strong 3-1 activity near R0=92. Although there is often reasonably strong mode activity, it's always 2-1, as far as I've seen, even though the current ramp has been pretty consistently in the 1.5-2+ MA/s range. I'm not sure what to make of that.

Notable shots:

I'll also send around a set of plots of static fill data from yesterday and today, showing that the puff has some unreliable behavior, needing at least three fit lines to fit its behavior reasonably well.

Monday March 24 2014 6:05 pm Hughes 83569-83593 Shot Development for FWM

Another day of trying to wrangle the shots that jump sharply to q*~2.5 and rise up toward 3 from below. Still no very promising results. A lot of 2-1 modes blending into a variety of hybrid 2-1/3-1 structures for reasons that aren't entirely clear. The high dR0/dt when R0 is near 92 may contributed to this messy mode structure. Big 3-1 modes mostly showed up only after the plasmas fell in to R0 around 88 or lower, where wall coupling is comparatively quite poor.

No really great shots were made, although there were a few where the q* stayed between 2.5 and 2.7 for most of the shot. Even modest (~15V) changes to the OHE setting in either direction would produce plasmas that fell sharply inward, suggesting the run campaign has led to a very strange, ill-behaved regime, where gradual development will be difficult. I'm planning to try a different shot style, tomorrow, and see if that's easier to work with.

Notable shots:

Some of the other plasmas were passingly interesting for various reasons like peculiar SXR fan plots, but not really what I've been looking for.

Thursday March 27 2014 7:35 pm Hughes 83594-83632 Preliminary Fe/non-Fe Comparison

We finally had a run day comparing ferritic vs. non-ferritic shells with the same shot style! This was done using steady major radius shots of the style I developed last summer. This shot style was combined with phase flips to test stability to an imposed -3/1 (with some sizeable n=5 sideband due to only energizing the inserted shells); the phase flip started at 3.0ms, flipped at 3.5ms, and ended at 4.0ms. Due to lack of a copilot much of the day, there are many fewer shots than I would have wanted, and I haven't been as picky about them as I'd like, but there are some interesting correlations.

I first took a series of shots without changing the preset amplitude of the waveform, which came out to about 1V (roughly 10A). A number of these shots disrupted around 3.75ms. The average disruption time (as measured by the current spike) for this family of shots is 4.37ms (7 shots). Interestingly, the plasmas that fell inward to 90cm or farther tended to live longer.

Observing this trend, I tried a few shots at 5A (0.5x amplitude). These had a mean disruption time (MDT) of about 5.08ms (4 shots), ignoring one that fell out past 93cm and died earlier than the other 4 of this type.

I then reversed the shell configuration so that the ferritic shells are now retracted to their full safe retraction (5mm in from the old stoppers) and the non-ferritic shells are 13mm back from full insertion to compensate for the ferritic shells having been between 10 and 15mm back from the old insertion stoppers; this means the stainless shells were (on average) at roughly the same radial positions in both configurations.

All the shots after reversing the configuration were relatively long-lived. Shots with amplitude x1 had a MDT of 5.62ms (6 shots); another set with amplitude x2 (not 1/2!) had a MDT of 5.47 (3 shots).

Obviously, 3 to 7 shots in a set do not great statistics make, but there does seem to be a trend. To put it another way and sneak in an XKCD quote, "Correlation doesn't imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing 'look over there'." While this isn't a huge result, it definitely suggests ideas for the next FWM campaign.

Notably, Jeff and I didn't see evidence of big mode excitation or locking on the Fe-in/SS-out shots, although I was only looking at the stripy plots, and Jeff can say better than I what analysis he used (or if I misunderstood what he said). I honestly don't have the experience with RMPs yet to make a meaningful statement about this result, other than that it strongly suggests greater disruptivity (and hence reduced stability) in the presence of the ferritic wall.

Notable shots:

Note that since only half the coils are energized, if comparing against Daisuke's results, the gain on all of these shots (in the sense of the quantity of flux pushed toward the plasma surface) is essentially half the gain he used. I believe he also had the shells more fully inserted, which will further reduce the effective gain-at-plasma-surface during my run, compared with his, although I may have bought back some of that by running at R0=92 rather than 93 or 94.

As an aside, Jeff and I discovered that the unused flux loop cables jump during TF-only shots. These cables are twisted pair connected to the flux loop box through a D-sub connector and isolated (fixed to an unplugged connector terminal rated to hundreds of volts) at the other end, since the inner set were never installed. These have been lashed down with cable ties to avoid the unlikely case of them jumping enough to contact a TF casing; they only jumped a couple of inches when we watched, however, and shouldn't be able to reach the uninsulated part of the TF casing. However, this is a bit of a puzzle, since there should be no current flowing. It may or may not be worth figuring out what exactly is happening there.

Monday March 31 2014 5:30 pm Stoafer 83633-83663 TS Alignment

The goal of the run was to align the collection optics to maximize TS signal using plasma shots. Overall, the day was successful with signal in channels B and C, which are not laser line channels, for all views. I was planning sending an image with the data, but had issues in the latter part of the day with the laser, so was unable to get an image of the signal.

In the beginning of the day, I spent time aligning the laser and fixing an issue with the laser triggering system. This all seems to working properly now, except I had a couple of shots at the end of the day where the laser did not fire. I will look for this issue in the following run days.

I was developing a shot the stayed relatively constant in major radius and got hotter through the shot (based on SXR emissivity data). Target shots are 79717 and 79755. I got reproducible shots towards the end of the day.

I will continue tomorrow with lens alignment. There is still a lot of room for improvement (I have not even tried adjusting fiber bundle focus location), showing we will have good Thomson data, at least for views 92cm through 100cm!

Tuesday April 1 2014 3:12 pm Stoafer 83663-83701 TS Alignment

Today was spent making adjustments to the collection system for Thomson scattering. The day went very smoothly, with reproducible plasmas, allowing rather efficient alignment of the system. The collection system is now aligned to gather decent signal in all views. A more optimized alignment will require the chamber to be filled with dry nitrogen to see Raman scattering to optimize the light in a non-stray light channel.

The following run days will be spent doing temperature (and relative density) scans for various shot styles. The current shot style is interesting and will be scanned first.

Wednesday April 2 2014 6:28 pm Stoafer 83702-83731 TS scan attempt

Today was spent debugging the laser triggering setup. The triggering worked fine for the previous run days, but became flaky towards the end of the day. Today we had intermittent problems all day. I plan to continue debugging before tomorrow's run, so hopefully tomorrow will be successful.

Thursday April 3 2014 6:27 pm Stoafer 83735-83785 TS scan

Today's run was rather successful for doing a time scan in looking at TS signal. The laser trigger now seems to work as expected; we had no problems at the end of the day. I was able to get reproducible plasmas, so was able to do a time scan over the shot for TS signal at 3 spatial locations. The major radius also varied during the shot, which is seen with the TS signal. I will complete a full analysis after the run campaign and send out a report. From preliminary analysis, when the plasma is centered around 92cm, I found the plasma temperature to be between 100 and 140 eV in the 92cm and 96cm views and a plasma temperature of 40 and 70 eV in the 100cm view.

In order to fix the laser triggering issues, I rewrote the arduino triggering program to make it more intuitive for myself. There were issues with laser triggering early in the run today, but I found that the issue was pickup along the cords that run from the control room to the laser room to be able to turn on and off the flashlamps. I changed the code to account for this pickup (just ignoring the signal from these buttons during a shot) and the triggering worked as expected for the rest of the day. It might be helpful to reduce the pickup along these cords in the future.

In the beginning of the day there were crate issues. When running crates_on we got an error for every crate. It ended up being a communication problem between Spitzer and the server room crate. Jeff helped sort out the issue. The issue was not fixed when rebooting Spitzer initially, but we tried rebooting the server room crate and rebooting Spitzer while that crate was on, which fixed the problem.

Tomorrow I am going to try a different shot style to perform a scan and, perhaps, change the 100cm view to a different location.

Friday April 4 2014 6:06 pm Stoafer 83786-83827 TS scan

The run today was designed to be able to gather TS signal before and after a minor disruption with a SXR crash. We have found that we were able to do this by starting with an outboard plasma around 95cm and bringing it inwards with a large plasma current ramp. The edge q approached 2 and the plasma ends up having a minor disruption at around 5ms. We also used the control coils to induce a disruption by applying a 2/1 RMP for 0.2ms at 4.5ms. Afterwards, we used the control coils to apply an additional vertical field, opposing the VF from the VF coil. This keeps the plasma outboard, prolonging the plasma, as well as allowing TS signal in all three views 92cm, 96cm, and 100cm. The plasmas were working out pretty well, but we had an issue towards the end of the day, which ended the run.

Late in the run, an unusual noise was heard near the machine, sounding like loose parts moving around. It was identified as a G10 insulating shim that had dislodged from its normal position between the TF and OH coils. Without this piece in place, there is less material supporting the weight of one of the TF magnets, and less insulation between the local TF magnet (at the Thomson scattering section of the machine) and the lower-outer-OH coil. This insulating shim should be repositioned before further running of the machine. Neighboring shims may also dislodge soon without remediation, and continuing runs before fixing this issue could pose a risk of arcing between the TF and OH in the future.

Wednesday April 9 2014 7:45 pm Hughes 83843-83862 Ion Gauge

Today was a repairs/upgrades testing day. Shots 83855 and 83856 were primarily to check for any more unfortunate noises during vacuum shots. The machine sounds okay, so it seems the problem has been fixed.

All shots including the above included a gas puff to test behavior of the digitized ion gauge signal. There are some very peculiar quirks, in addition to the 60Hz signal which we assume comes from the 60Hz temperature variation of the ion gauge filament.

We found that the effect of firing the banks on the ion gauge signal was much more complicated than the scalar signal reduction we had discussed in the meeting. The signal goes totally wild when any banks at all are energized (see Fig1). To get a base pressure (averaged over the gray area on all plots) and a fill pressure (averaged over the green area on all plots), we had to change the start time and basement_tf time to -240ms, and the puff start to -220ms (the black dotted line on all plots).

As visible in Fig1 comparing vacuum+puff shots 83852 (black) and 83853 (red), as anticipated from what we saw with the 60Hz signal, the SNR is roughly constant, meaning the higher the signal (i.e. the more gas puffed in) the more the noise is amplified. We can also see that 500us and 1000us puff times are pretty much equivalent, although 2000us and 3000us are markedly different.

An even more striking feature of Fig1 is seen in plasma shots such as 83854, 83855, and 83857, where the ion gauge signal is very strongly suppressed over a period far outside the lifetime of the plasma (the light blue area). No vacuum shot had this behavior. As far as I know, everything should look the same between a vacuum shot and plasma shot at t=200ms... but the ion gauge apparently does NOT. It also seems that--at least fir the first fraction of a second following the plasma--the machine actually pumps down FASTER with a plasma than without.

Fig2 shows shots 83854, 83855, and 83857 from above, as well as a puff-only shot, 83856, to compare the pumpdown characteristic. We should expect 83853 (green) to be higher and 83852 (red) to be lower than 83857 (blue), which should have about the same pumpdown as 83856 (black); however, the plasma shot is notably lower than all three non-plasma shots, whereas firing the coils doesn't seem to upset the trend.

We also took a few static-fill shots in order to compare the front-panel readout of the gauge against the digitized and processed signal. The results are somewhat puzzling. Although there is relatively good agreement between observed base pressures and analyzed base pressures ("p1" on each plot) to within 10-15%, the fill pressures do not agree nearly as well.

The following table compares the gauge readings and deuterium-corrected fill pressures, compared against the fill pressures calculated and displayed in Fig. 3
Shot # p_gauge(uTorr) p_gauge_D(uTorr) p_calc(uTorr)
83858 50143100
83860 318963
83861 277754
83862 5114699

I'm not sure where this disagreement could be coming from.

In short: the good news is that we can get a base pressure and a fill pressure; the bad news is that there is a lot of stuff going on we don't entirely understand. I'll leave the tree changes in place while doing my FW+RMP runs, so we can go back and use the data retroactively if we want, but I won't be messing with this until that run series is finished.

Fig. 1 Fig. 2 Fig. 3

Thursday April 10 2014 6:29 pm Hughes 83863-83926 RMP-response FWM study (baseline)

Today's run objective was to get several shots with a range of control coil amplitudes, in order to find a response/amplitude curve for the Fe-retracted configuration. There isn't much analysis to offer at this point, since my RMP-response analysis code isn't working at all, yet.

However, plasmas were very reproducible, today, yielding at least 6 reasonably good RMP shots at each of six control coil currents (5A, 10A, 20A, 25A, 30A, and 40A). The only plasma that disrupted near 4ms were one or two which pushed up against the outboard limiter and a couple of 40A RMP shots on which the TF was lowered, pushing q* closer to 2.7.

Since these were only a couple of shots, it's hard to say what they mean, although it does point to the importance (which we already know about) of q* for the RMP-response effects. A more comprehensive study may have to dedicate additional time to enhancing the amplitude scan with q* scans.

Noteworthy shots
I tried to take a few non-RMP shots, as well, at the end of the run (as well as one in the middle), but for whatever reason those shots were generally less well-behaved, with more wandering in R0 and q*.

Friday April 11 2014 7:17 pm Hughes 83927-83938 Attempted FWM+RMP run

Not much to say. Had breakdown problems all day, couldn't find the problem. The puff seems to be fine. The shells are in a configuration used recently without such severe breakdown problems. It's possible the e-gun has been moved, or that something else has changed, but unless the machine magically fixes itself by Monday morning, we'll have to poke around and see what could be going wrong. I would argue that even if the machine *does* magically fix itself by Monday morning, we should spend Wednesday at least on trying to track down the problem systematically.

Shot 83931 and shots 83935-83938 were used by Kyle and Qian to test some feedback code, but I can't say much about that.

Noteworthy shots:
Hopefully Monday will go a little better.

Tuesday April 15 2014 9:46 am Hughes/Byrne 83940-83984 Attempted FW+RMP, diagnosis, shaping coil

This would have been sent yesterday, but the wiki was down.

Not much to report. Plasmas were uncooperative all day, and eventually failed to break down. After some fiddling with the e-gun, a setting was found in which it reproduced plasmas more similar to those on Thursday, with similar bank settings. It seems to prefer a heating current (at least, in the "Fe-in/SS-out" shell configuration) that puts the bias right on the cusp of the sharp transition.

Targeting 83918 was difficult, because the plasmas had to pushed considerably harder (e.g., 10-12% higher bank settings) to produce similar equilibrium parameters, which seemingly led to greatly reduced reproducibility. Only three not-awful shots with RMPs were made before plasmas stopped breaking down and the focus shifted to diagnosis. For shots 83980-83984, I handed the remainder of the run day over to Pat for testing the shaping coil, so I can't really say much about those shots.

Noteworthy shots:
Below is a table of the e-gun heating currents and (active) bias voltages measured while diagnosing breakdown failure:
I_H [A]: V_B [V]:
8.5 8
8.0 9.6
7.5 11.6
6.5 175
7.0 ~25
Notably, where most of the bias voltages varied by a couple percent on the multimeter, the roughly 25V measured at the 7A setting varied continually by at least a few volts. It doesn't seem to be a matter of poor contact with the multimeter leads. My guess is that the system was at a cusp in the nonlinear relationship between heating current and bias voltage (about 230V with the e-gun turned off) and the voltage changed significantly with small variations in the current; but I don't know of a reason for the current to be unstable.

Tuesday April 15 2014 6:12 pm Hughes 83989-84020 FW+RMP w/ various problems

Today was another attempt at getting RMP response with the ferritic wall inserted, which was met with moderate success at best, due to problems with Caliban as well as breakdown problems. The Caliban issue was resolved with multiple reboots--apparently, Caliban sometimes boots up well, and sometimes it doesn't, and we don't really know why.

This is not dissimilar to the breakdown problems, although we have some guesses. Having found yesterday that the best breakdown performance seems to be found at a point on the V_B vs I_H curve where V_B is highly I_H-dependent, we tried increasing I_H (thereby lowering V_B) and increasing the bias power supply from 250V to 400V (thereby increasing V_B for a given I_H), hoping to get a nice V_B at a more stable part of the curve.

This met with at least some success, as we had no failures to get breakdown after this adjustment, but plasmas were still not as good as they had been on Thursday, whereas one of the settings we stumbled across yesterday while trying blindly seemed to produce a more Thursday-like plasma. While the Monday-esque plasmas aren't totally useless, they exhibit a roughly 10% lower plasma current (and thus, higher q*); correcting the plasma current with higher OHST tends to throw them out to a higher R0, and the behavior around t=1.3ms is extremely variable, shot-to-shot. Some plasmas jump in almost to 90cm. Others sit at 92 but then swing outward, driving q* down and away from the target profile.

Part of the difficulty is that I_H changes on its own; after setting it to 7.5A around midday, by the end of the day it was hovering around 7.9A, and visibly wavering by perhaps 100mA. Nick has suggested this might be solved by replacing the supply's variac. We may spend a part of Wednesday exploring the parameter space of the e-gun at long last, in order to make a more deliberate and less ad-hoc choice of settings. We are also discussing how we might record the bias voltage and/or emission current, to be better able to diagnose future breakdown issues.

Problems aside, I did get a few reasonably good shots with 0.5 and 1.5 helical amplitudes (-3/1 structures on at 3.0ms, flip at 3.5ms, off at 4.0ms). I'll probably need more to make for really meaningful analysis, but I also need a working analysis code, so I can't say too much about it just yet. Although some shots flew in or out and died young, it's interesting to note that at least a couple of relatively well-centered plasmas died around 3.8-4.2ms, but only (as far as I recall) on the A=1.5 series.

Notable shots:

Thursday April 17 2014 6:36 pm Hughes 84035-84089 FW+RMP

Today was a very mixed bag. After adjusting the e-gun settings yesterday afternoon, plasmas were very strong with considerably higher start IP for the same bank settings, and relatively reproducible after a bit of shot development/cleanup. However, before long, the e-gun's filament heating current began wandering erratically by significant fractions of an amp.

Although we now operate in a *less* I_H-sensitive part of the e-gun's V_B/I_H curve, we are still at the edge of that rollover, so fairly small changes in I_H can change bias voltage by more than 10%, changing the breakdown characteristics. Between shots, I_H changed by as much as 2.25A in one extreme case; since it can only be checked by entering the tokamak room, it's impossible to say how much it actually changes regularly, and impossible to correct it before firing the banks.

While the plasmas were cooperating, I was able to get 2-3 good RMP shots each with an amplitude setting of A=0.5, 1.0, and 1.5... I also attempted to get shots at A=2.5, but these disrupted around or before 4.0ms or had undesirable R0 and q* traces. However, at least one A=0.5 shot also disrupted at almost the same time as the early-dying A=2.5 shots, so it isn't clear that this had anything to do with the RMP.

Noteworthy shots:
Hopefully things will be more settled during the day tomorrow.

Friday April 18 2014 6:43 pm Hughes 84090-84138 FW+RMP

Today was a more successful study of RMP response with the ferritic shells inserted and non-ferritic shells retracted. Plasmas exhibited quite a bit of shot-to-shot variation; only 1 in every 2-3 plasmas was useful. Although the e-gun is now set to parameters such that we don't seem to have breakdown problems, the changes in bias voltage due to the wandering heating current seems to drive significant changes in the breakdown characteristics, changing the startup plasma current by +/-10%, roughly.

As Jeff pointed out today, it is possible that configurations with the ferritic wall inserted and the plasma well-centered at breakdown (with a very early VFST time) are more responsive to these variations than far-outboard plasmas with non-ferritic walls inserted.

All RMPs were -3/1 helicity, turning on at 3ms, flipping at 3.5ms, and turning off at 4ms. Analysis will have to wait until next week, when I have some code up and running, although interestingly, I did often see rotating modes suddenly appear at the phase flip, especially at higher amplitudes. I'm not yet certain whether this is caused by the RMP, or an intermittent feature of the shot style.

Noteworthy shots from today:
I believe the next run day is Chris'. I'll be reversing the configuration to ferritic walls fully retracted (less 5mm padding) and non-ferritic walls fully inserted. I'm also working on a --showgas flag for the code to replace the big current shot # display with puff/base pressure/fill pressure information (since there's really nowhere else to put it). Anyone who wants to take a look at it and give feedback on alternatives for displaying this information can find and run it in "home/peh2109/Scripts/hbt/bin/". I won't send it on to the repository until I have some approval, though, so the regular we use will remain untouched for now.

Monday April 21 2014 5:58 pm Stoafer 84139-84146 TS scan

Today I was attempting to do a TS scan on a plasma that disrupts around 4.5ms. However, I immediately had problems with breakdown with 2 attempted plasma shots. It was found that the puff valve was stuck open, filling the chamber with deuterium gas. The small deuterium gas bottle was noted to have around 400psi towards the beginning of the run day was empty.

It was found early that the cryos were frosting up, so the gate valves were closed, causing no damage to the cryos. They are being re-genned.

We were able to pump out the deuterium from the chamber safely by bleeding in dry nitrogen while slowly pumping on the chamber with a roughing pump. The chamber is now roughed out and valved off while the cryos re-gen.

We have another bottle of deuterium, but tomorrow we need to fix the problem with the puff valve.

While the chamber was a relatively high pressure, I performed alignment of the collection system using Raman light.

Monday April 28 2014 5:27 pm Byrne/Stoafer 84192-84229 TS/Shot development

OH lead broke around 3pm, stopping the run. The cause has been isolated, and the leads have been removed and stripped and are ready for installation of a replacement. I will be stopping at an Electric supply wholesaler tomorrow to have spare parts first thing in the morning. We should be running again by the afternoon. No damage to the machine, other than the broken lead was detected.

From Chris:

Thomson scattering measurements were taken throughout the day. Plasma center temperatures ranged from 30eV to 60eV throughout the day with higher temperatures being reached as more cleanup shots were taken. There were a series of shots taken where the TS measurement was taken when the plasma was centered at 96cm. In these cases, the temperature was read to be around 45eV in the 96cm view and 30eV in both the 92cm and 100cm views.

After switching off with Chris at lunch time, shots 84206-84226 were fired with the aim of developing a longer lived shot and cleaning the chamber.

Base pressure from shot-to-shot was roughly 35-40nTorr, which is rather high for a clean chamber. Currently the chamber is at 11nTorr, and has not had gas puffed in in 2 hours. At the start of the day, the pressure was ~9nTorr. We'll see if there has been any improvement.

Ferritic shells are still pulled back, and are not being cleaned. They can be inserted if we think the represent a virtual leak as is, or if not, it should be held in mind that they will require cleanup on the next ferritic experiment.

Wednesday April 30 2014 6:08 pm Byrne/Stoafer 84230-84273 Shot development/cleanup

Lost the morning when it was discovered that the high voltage power supply providing the e-gun bias had died. We currently have no idea what happened, but as a stopgap, eleven 9V batteries were daisy chained together to provide a 103V DC power source. With the e-gun at full heating current, the e-gun has a 25V drop, and a 0.75mA output. The batteries are rated to 350mA hours, so we should have plenty of time to work out a new solution, as long as we remember to turn off the e-gun when not in use.

Day was ended when the Shaping coil stopped discharging. on shots 84271 and 84272, the bank was seen to fully charge, but only released around 10% of the expected current. A shaping only vacuum shot, 84273, with 1/3 the previous voltage (200VSt, 50VCb) did not seem to discharge at all. The batteries on the pulser for the SCR switch were inspected, and stood at 9.21 and 8.9V. The 8.9V battery is a bit low, but not really in the range where we would expect to see its performance change. It's not been ruled out yet that the SCR is undamaged. Let's hope that's not the case. Bank was dumped (still works) and shorted.

Otherwise, the day went rather well. Lots of shots were taken, almost all shaped. There was some trouble getting MR to behave the way we want - to rise then fall *gradually*, rather than crashing in, but we seemed to be making good progress until the problems discharging arose. Chamber seemed to clean up as the run progressed - this is only the second half-day of cleanup since the leak in the gas-puff, so the shots are still quite variable. Running the shaping coil decreases plasma lifetime by around 1ms across the board, but nevertheless, it seems that if we were to run a shot optimized for high IP and/or long life we would be able to hit star shots like 70000 and 71000.

I'll start work on the Shaping bank first thing tomorrow, and hopefully we'll be able to run.

Thomson Scattering seems to be working well too and the data is saved in the tree if anyone wants to look at it. Node is Sensors.Thomson.


Thursday May 1 2014 5:57 pm Byrne/Stoafer 84274-84299 Troubleshooting/RMP Shaping

Issue with the shaping bank turned out to be the trigger pulser. Two 9V batteries run it, one was at 8.97V. This was apparently enough to cause the SCR to not trip. Checked the pulse shape once I replaced the low battery, and the pulse is only 2V peak into an Oscilloscope. According to the SCR's datasheet, it should require 3V to turn on, so we may be marginal and very sensitive to the batteries drooping.

Shaping bank ran well all day. Began with the control coils running as pseudo-VF coil. This actually worked quite well, and by 84292 we had a q* trace very similar to shot 69642, from Daisuke's RMP run, used as reference, in the time of interest.

Began having crate troubles by the end of the day. Shot 84293 carried the first 3-1 RMP, overlaid on top of the VF pulse. 10A of VF, 10A of RMP. Concerns over the 50% shell coverage led us to boost the current to 10A VF and 30A RMP for subsequent shots. No indication of blown fuses. 84295 and 97, the TF did not digitize. This was seen once yesterday. Paul had apparently encountered this in his campaign as well. q* can not be reconstructed using tree data in this case, though we can assume the toroidal field is very similar from shot to shot and use a reference without introducing too much error.

82498 and 99, the RMP would not fire. No clue as to why yet. Will look into it tomorrow. Run day was closed down by the 4:10 class Chris and I had to attend.

Star shots are 82492 to compare our base shaped equilibrium with reference 69642, 84293-97, to look at 3/1 response in a shaped plasma


Friday May 2 2014 7:25 pm Byrne/Stoafer 84300-84346 Shaping + RMP

Tested Caliban with 2 crates only shots first thing, no problems with getting the control coils to fire. Control coils worked fine all day afterwards. Not sure why it would have failed at the end of the day Thursday

shots 84318 - 339 represent the compass scan. The python function I called to get a random angle seems a little busted, as the values tended to cluster together for several shots, before a big jump to a new cluster zone. Last couple shots were chosen deliberately to fill in some of the larger gaps. Still, we covered the compass pretty well. Lost a fuse in one of the RMP coils at 319 (made worse since we are only pulsing half of our coils) and did not notice until 33 but the 3-1 component of the RMP should still be dominant.

Shots 340-46 represent the amplitude scan. Phase is set to zero, amplitude is varied from 3-.5 (or 30-5A in the coils, unsure the Gauss strength of the 3-1 field). All fuses were fine for all of these shots.

All shots were very close to Daisuke's shot 69642 in q* during the time of interest. The 'VF' pulse on the RMP coils was extended .5ms before and after the 3-1 RMP so that we have time to examine the effects of the one in isolation from the other. q* is a pretty rough parameter considering all the issues with the shaped geometry, but it's the best we have so far. Turn-on,flip and turn off times are visible in the stripey plots, so there should at least be something worth looking at.

Computer problems:

Take shot script hung at one point early this morning. Banks failed to auto-fire, and Take Shot script needed to be force quit. Command line control did not return even then, until a Ctrl-C was given, at which point a segfault was reported. Chris said he saw something similar before the gas puff failed, so Athena was rebooted just to be safe. The gas puff was not triggered at any time up to this error, and no irregularities were seen after the reboot.

The TF probe is often failing to digitize. This was seen yesterday, and it seems to occur more often around the end of the day. Heating in the rack shouldn't be an issue, but I can't think of why else. Jeff has suggested that the extra-long time base of the TF digitization may mean it is still digitizing when the store command comes through, causing an error. Suggestion is to disable the TF phidget, and fire manually, hitting pulse, store and analyze separately. This is impractical for my run, but may be worth trying later.

This may not be the case for anyone else, but running with Athena can be a pain. Despite running as much code as I can on Spitzer or Caliban, I still need to switch between many programs to analyze and prepare each shot using an interface run on a computer that has trouble supporting it's own load. If a reboot is necessary, that's another 10 minutes wasted. I feel a lot more could be gained from a runday if computer latency weren't a time-limiting factor. Athena is a pretty central part of any experiment we do, so if it can be done without messing things up too badly, the next time we have the opportunity and means, we should probably see about replacing Athena with a computer with at least an average amount of oomph.

Monday May 5 2014 6:07 pm Stoafer 84347-84411 TS scan minor disruption

The goal of the run was to do a TS scan of a shot with a reproducible disruption to see the Te profile before and after the disruption. I am still working on shot development to reproduce shot 83817. Shots are getting caught with an early 3-1 mode, which prevent them from getting to lower q. I try to get the plasmas to approach q=2 and use an RMP to induce a disruption at 4.5ms.

Changing plasma and machine conditions have slowed shot development, but I am starting to get shots I can use. Since my previous run the gas puff valve has been changed, making the back pressure different.

We had breakdown issues in the morning, which was found to be problems with the gas puff valve. We increased the back pressure on the valve from 9PSI to 10PSI and increased the gas puff time from 75us to 1000us, which resolved the problem. This dramatic increase in the gas puff timing shows that the valves can have different characteristics week to week.

Tuesday May 6 2014 6:26 pm Stoafer 84412-84474 TS scan minor disruption

Today's run continued to perform a TS scan of minor disruptions. Towards the end of the day we were consistently getting a minor disruption at around 4.5ms or 5.5ms (shots typically deviated to either on of those). The TS laser timing was varied to determine Te and relative density distributions throughout the shot.

Plasmas were not reproducible in the morning and it was found that the neutral gas pressure was varying. The cause ended up being the battery for the gas valve circuit was not charged. The battery was had a full voltage reading yesterday, but had apparently not been charged over the weekend (it was outside of the gas valve circuit box and near the charger on Monday morning, but not connected to the charger).

The low battery voltage made, what seemed to be sporadic behavior is the gas puff, with changing fill pressures from shot to shot. Once the battery was replaced, the fill pressures leveled out, but required a longer gas puff time (1500us instead of 1000us) to get to the same fill pressure.

Thursday May 8 2014 7:05 pm Byrne 84475-84533 Shaping + RMP

Star shots are 84506,84527, 84529, 84530, 84531, 84533. They are shaped shots, with RMP, that persist for at least as long as the RMP. 84533 has 30A of RMP current, the others have only 16. Had to reverse the VF RMP polarity, to push the plasma in rather than pull it out. shot 84506 is from before that switch happened, so it is comparable to the last run for comparing 3/1 to -3/1, but probably not much else.

Unfortunately that's about all I got. Was unable to match the shots from last Friday well for most of the day. Took a lot of development to bring the plasma around, but we do have a reasonably repeatable shot. Hopefully we'll still have it tomorrow morning.


Friday May 9 2014 4:25 pm Byrne 84535-84588 Shaping + RMP

Spent a lot of this morning trying to improve on the equilibrium from yesterday. Ended up settling on the original equilibrium, with the tweak of only imposing the VF cc pulse early in the shot, at the time the early mode causes MR crashes. This did not eliminate the occurrence of early modes, but did help reduce the frequency. Star shots are 84577, 84574,73, and 71. These shots all had q and MR close to the model shot of 70000, Shaping that started at 1.2ms, and RMP phase flips with 30A of current from 2-3ms.

Tried to get an unshaped equilibrium, but it was too late in the day to do anything useful. This will have to come later.


Friday May 9 2014 5:11 pm Byrne/Levesque 84589-84594 Unshaped + RMP

Added a few more shots to the end of the run day. Was able to get a couple of unshaped RMP shots that are similar enough for direct comparison to the shaped shots from today. Additional good shots are: 84589 and 84591.

Monday May 12 2014 7:18 pm Hughes 84595-84644 FW+RMP extension

The objective of today's run was to fill in the high-amplitude gap in the ferritic wall part of the response-vs-RMP amplitude plots I showed in the last couple of meetings. I started by taking some non-ferritic RMP shots to make sure the response is comparable to my previous shots before casually inserting new data. However, on reversing configuration to insert the ferritic walls, the plasma became much less cooperative, displaying erratic breakdown problems and intense major radius jogs sometimes over 1cm, at around 1.3ms, as well as being extremely sensitive to bank settings and varying widely from shot to shot.

More shots will be required to say anything definitive, although a majority of shots that weren't rejected for excessive deviation in major radius and q* instead disrupted between 3.4ms and 4.2ms. All of these were at RMP code amplitude of 4 (est. about 50 Amps); I may try A=3 or A=3.5 RMPs tomorrow, instead of pushing for A=4.0 as I did today. Thomspon Scattering was running today, but Chris can say better if it saw anything noteworthy.

Due to breakdown problems shortly after switching to the ferritic configuration, the e-gun settings were changed. The e-gun is now set to a supply voltage of 151V; with the heating current at 8A, this yields about 35V filament bias. Plasmas broke down much more willingly after this change, but also displayed the large major radius jumps (possibly due to early mode activity) mentioned above.

Noteworthy shots:
Analysis will follow when there's more data to look at and I'm not busy running, hopefully in time for the Wednesday meeting.

Tuesday May 13 2014 6:10 pm Hughes 84645-84681 FW+RMP extension

Although plasmas continued to be somewhat uncooperative in the same manner as Monday afternoon, several shots with RMP amplitudes of 4 and 3.25 in code were taken. The resulting calculated response show considerable shot-to-shot variation, with some data points agreeing with the slope of the A=0.5-2.5 series and others suggesting a saturated behavior.

The interpretation of the new data is therefore not obvious, and will probably require more detailed shot-by-shot analysis and careful reasoning to decide whether a particular shot is "bad"--i.e. having an equilibrium that changes radically, making subtraction difficult, or with an equilibrium different enough from the other shots to experience very different MHD damping/amplification and therefore exhibiting different saturation behavior for the same RMP.

This seems like highly subjective territory, so my inclination for the present is to set the extended data aside as Not Yet Understood, and focus on the prior set of data which is at least relatively consistent with itself.

Noteworthy shots:
One interesting observation is that the rate of disruptions between the time of the phase flip and a short time after the RMP ends seems to be MUCH higher for high-amplitude RMP shots.

Monday May 19 2014 5:46 pm Qian 84684~84732

The run was for experiment data to apply subspace identification method. Most of today's run are spent on shot development. Shots are not very reproducible during the day. Ferritic walls are in and perturbation is applied on those shells. The perturbation doesn't seems to disrupt the plasma so the data should be able to be obtained from this method. More shots will be tested tomorrow.

Tuesday May 20 2014 5:54 pm Qian 84733~84798

all the shells are put in today and the plasma becomes more reproducible. plasma with randomized peturbation are performed and data is obtained to test the subspace identification method.

Wednesday May 21 2014 5:15 pm Stoafer 84799-84852 TS scan of 92cm plasma

The goal of today's run to do a TS measurement scan of plasmas that stay at 92cm throughout the shot. These are the shots that Qian has been using for preparing his state space feedback algorithm. For these shots both the ferritic and stainless shells are inserted. The stainless shells are inserted 13mm back from their nominal position to match the location of the ferritic shells.

We saw high temperatures throughout the shot with a relatively low density compared to other shots with TS with the new alignment. This makes sense because the soft x-ray signals are low compared to other shot styles. Temperatures in the 92cm and 96cm views ranged from 100 to 200eV based on the measurements.

I have been looking at the analysis I use for determining Te from TS measurements and have been working to improve it to be more reliable. Ideally, we would be able to do some Raman scattering shots to get a good averaged shot that I can fit each plasma TS measurement to to reduce the affect of noise in the measurements.

For now, I believe the measurements might be high, but I do believe the plasmas get to be at least 150eV towards the center based on the raw signals from TS.

Thursday May 22 2014 4:26 pm Qian 84853~94912 feedforward shots

Perturbation with fixed rotation frequency has been applied today. These data, along with the randomized frequency obtained on Tuesday, should be able to give an estimation for the response matrix for the system. More data analysis will be done later.

Shots are quite reproducible with current wall configuration. Plasma sometimes disrupts suddenly around 4~6 ms. This is not correlated to the perturbation that this applied.

Tuesday May 27 2014 3:03 pm Stoafer 84914-84955 TS scan higher density

The purpose of the run was to perform a TS scan of a similar shots to the previous scan (shots 84799-84852), but with higher density. The fill pressure was increased from 74uTorr to 135uTorr, which more than doubled the density. I was able to develop a shot similar to the low density shots.

The temperatures were lower than the low density shots, but I believe the density is raised enough to have a net increase in pressure.

I will continue with taking data tomorrow and will perform analysis of the two shot styles.

Tuesday May 27 2014 8:17 pm Levesque 84956-84976 TS scan, normal density

Ran more shots to extend the run day and collect TS data with a different discharge evolution. Developed a shot that starts with R0 near 96cm and q* near 2.5, then gradually moves inward as the current rises and q* stays roughly constant. Good overlaying discharges of this type were 84959, 84962, and 84963. The fill pressure and density were typical of our recent shots, being lower than Chris' run earlier today. The discharge evolution was not too reproducible, but it did provide reasonable TS data as the laser timing was changed. Temperatures were typically around or below 125eV throughout the shot, and were generally lower than data taken during recent runs. I attribute this lower temperature to the lower starting current that was required to maintain q* above 2 with a small minor radius.

At the end of the day, I started developing a discharge similar to the high-current plasmas from June 2013 (reference shot 79771), but ran out of time before getting a good shot.

Wednesday May 28 2014 4:31 pm Stoafer 84977-85032 TS scan of 92cm steady plasmas

I finished the TS scan of the higher density plasma shots with a steady 92cm major radius. The density measurements were significantly higher, but the temperature measurements were lower. I will perform a quick analysis looking at the temperatures, densities( arbitrary), and pressures (arbitrary) between the shot styles to see if we can develop similar plasmas with different pressures.

Thursday May 29 2014 4:44 pm Hughes 85033-85048 Extended timebase ion gauge measurements

Today's (brief) run was aimed at studying the behavior of the ion gauge data on longer timescales than the normal t=1s limit (~120k samples x 10us/sample) by increasing the clock divide from 10 to 100. This provided a ~12s long basement A14 timebase.

We have long observed that plasma shots take longer to pump down and establish a higher base pressure than shots in which gas is puffed but no plasma forms. Since digitizing the ion gauge earlier this year, we have also observed that, contrary to the long-time (~10+ seconds) behavior, the pressure following a plasma shot drops below the pressure seen at the same time in a puff-only or non-plasma puff+banks shot.

With the extended timebase, we can see that (given a plasma shot and a puff-only shot with similar fill pressures) there is in fact a crossing point, generally between t=1.5 and t=3.0 seconds. The crossing time seems to be determined by fill pressure and vacuum condition at the time of each shot. Before the crossing point, even after all significant electromagnetic perturbation of the ion gauge dies down (around 1.0-1.2 seconds), the plasma shot exhibits a lower pressure than the non-plasma shot with puff; after the crossing point, the plasma shot's pressure is higher.

The best theory I can put forward is this:
When a healthy plasma forms, it sputters impurities off the walls, making the walls very clean; gas is pumped out fairly quickly by the cryopumps, but due to this wall cleaning, the walls help to accelerate the pumping until they saturate on a timescale of 1-3 seconds. The material knocked off the walls resists cryopumping much more than deuterium, suggesting helium as a top candidate. As a monatomic gas, helium should be more able to soak into the outer layers of the wall's lattice, which might help to explain its persistent abundance in the wall; its presence in the vessel would also be cloaked by the identical mass of the deuterium.

There may be other possibilities, and there are some puzzling aspects about this theory--particularly the persistent abundance of helium after every shot, months after it was last introduced during glow discharge cleaning. If anyone has clever ideas, it would be interesting to hear them either by email or in our next meeting.

One no-puff, no-banks shot was also taken in which the e-gun was switched on after hitting PULSE ON: this shot shows the time characteristic of the pressure rise we observe whenever we switch on the e-gun, revealing a surprising amount of temporal structure with a large-scale risetime of about 2 seconds, but unexplained perturbations with ~0.5s timescales.

Noteworthy shots:
I'll be setting the timebase back to its usual settings to avoid the risk of breaking code that doesn't anticipate alternative timing arrangements. For future reference, extending the basement A14 timebase requires changing CLOCK_DIVIDE in the basement A14_04 node, as well as modifying the trigger settings in .devices.basement:J221_09>"Setup Device">"01" from [5000000] (5,000,000us) to at least 13,000,000us (I used 15,000,000 for simplicity). I'll be sending around plots of the data discussed here.

Friday June 13 2014 5:53 pm Stoafer 85049-85085 Bias probe at floating potential

Today we ran with the bias probe after it was re-installed on the machine. The plasmas cleaned up very quickly, with the bias probe retracted and the gate valve open, it only took 4 shots to get back to normal-operation plasmas.

This bias probe was disconnected from the biasing electronics, so it would remain at the floating potential, with a voltage divider to measure the voltage. The bias probe was fully inserted, with the front of the probe tip at 103cm. After about 10 shots, the plasmas looked similar to before the probe was inserted.

The reference shot used was 84941. 85073, 85076, 85077, and 85078 were good shots with the probe at 103cm. 85080 and 85081 were good shots with the probe tip at 107cm. 85085 was a good shot for the probe tip at 106cm.

During the run, we noticed that the voltage on the probe was reading positive, which did not make sense. We checked the electronics and found that there is a sign inversion associated with the A14. Bryan found this as well, as noted in his run report on May 11, 2011. The inversion is now accounted for in the tree (sensors.bias_probe), which also accounts for the voltage divider.

On shot 85060 we noticed large voltage measurements on the probe, which were caused by ground loops. Jeff found that the grounding wire of the BNC cable inside of the south rack was very close to the rack casing, which might have been causing the ground loop. The grounding wire was pulled back from the rack casing to resolve the problem and we did not see the issue again.

In all of the plasma shots today, we saw additional noise in the major radius measurement than usual. Jeff suspected a ground loop either associated with the bias probe or other work done in the area and worked to resolve it, but the issue is still not fixed. This is not a very bad issue, but we will continue to try to resolve it. Note the cosine rogowski is in the west rack, which is the same ground as the chamber. The bias probe circuit uses the chamber ground, but its voltage is measured in the south rack, which uses a different ground. The plasma current measurement is also in the west rack, but the noise is not seen. This might be due to different RC circuits for making the measurements.

The run will continue on Monday to see how the floating bias probe affects the plasma conditions. TS measurements will be taken. We also plan to run the bias probe in a grounded configuration to measure how that affects the plasma. Tests are planned to measure the crown amp output through the transformer to figure out how to properly run with biasing the probe.

Monday June 16 2014 5:39 pm Stoafer 85086-85106 Bias probe floating and grounded

Today we ran in three configurations: bias probe retracted (shots 85087-85091), bias probe inserted to 103cm and floating (shots 85092-85096), and bias probe grounded at same location (shots 85097-85106).

There was no extreme noticeable change in running with the probe retracted versus floating, perhaps a decrease in natural mode amplitude, but this needs to be analyzed.

The natural modes seemed to slow down and become larger in amplitude, as expected, when the probe is grounded compared to when the probe is floating. This is exciting and will be looked at further.

We stopped the run to install a more appropriate Pearson for measuring the current to the probe, which was done at shot 85106 and works well. We also plan to change the voltage divider for measuring the voltage on the probe.

Towards the end of the day we started setting up the Crown amp to be run with a function generator triggered from the south rack. This setup will be completed for tomorrow's run, where we will control mode rotation by biasing the probe in various ways.

Star shots include:

Tuesday June 17 2014 6:09 pm Stoafer 85107-85128 Bias probe with amplifier

Today's run goal was to run with a bias probe connected to the crown amplifier to affect mode rotation. Shot 85127 and 85128 were plasma shots with the bias probe driven at +18V from 2ms until 6ms, which confirmed that we are biasing the probe as expected. More shots with different probe voltages are planned.

Most of the day was spent troubleshooting issues with the bias probe. This included Jorway triggering and using a function generator as input to the Crown amp. These seem to be resolved currently, so we were able to take a few plasma shots.

Tuesday June 24 2014 5:40 pm Stoafer 85130-85144 Bias probe

Qian and I setup the bias probe to be controlled by the same system as the control coils. This allows us to easily change the signal we apply to the probe and do feedback with the bias probe in the future.

A short run was performed after the setup was complete with a triangle wave applied to the bias probe. For shots 85140 and 85141 a triangle wave was applied from 2ms to 6ms with a period of 1ms ramping from 0V to about 45V. We saw mode amplification (possibly slowing) at the peaks of the triangle wave, which is expected. Shots 85143 and 85144 had a negative triangle wave with the same parameters and the mode did seem to speed up, but not at the same time the the triangle wave peaked negative.

A run with similar ramps will continue tomorrow.

Monday June 30 2014 5:36 pm Byrne 85151-85177 Cleanup/conditioning

Started around Noon, as the shells needed to be repositioned to begin the runday.

Plasmas were very short lived and SXR light was very high for most of the day, suggesting a high amount of impurities. A High, steady outboard limited plasma was developed and run several times. Following that a few shots were taken with the same settings as the target shot (82575).

Ip was lower, LV was higher, lifetime was shorter, and SXR was marginally higher. Plasmas seemed to have trouble getting below q=3. the final shot of the day, 85177, is a good example. Whether it's a coincidence of Ip and MR development or not, it holds almost constant at ~3.25 before the plasma begins an inward crash ending in disruption.

Plasma is developing, and despite the heat, things seem to be improving. Hope to have good data by the end of Tuesday.

Tuesday July 1 2014 6:09 pm Byrne 85178-85236 Shot development

Progress, however slow. Shots have finally begun approaching a lifetime of 5-6ms, roughly the standard, as well as reaching high current, and straight current ramps, instead of a 'slumpy-saddle backed' trace (see early shots,85182 for example)

Still having great difficulty getting q below 3. A very high OHramp (OHE at 340 out of 350V) shot was able to push q down, but IP was obviously too high for suitability for shaping. (shots 82523,24,25) dropping OHE, in parallel with VFE, and TF to attempt to reduce IP, while keeping the ramp and MR/q trace intact has not worked yet, though only a few shots have been taken and development is still in progress.

Hope is to scale down the IP trace, while maintaining the plasma's transit through the chamber and it's q, to allow us to ensure diversion when we shape. The few shots taken with shaping have disrupted too early for useful data to be gathered. There will probably be extra development needed once an unshaped equilibrium is arrived at.

Wednesday July 2 2014 6:22 pm Byrne 85236-85275 Shot development

Am still unable to find a shot that reliably goes below q =3. Any suggestions are welcome.

Have been experimenting with a 'VF' type control coil pulse, to push the plasma quickly outboard, dropping q below 3. Have had some success, however, I have not successfully managed the actual VF bank such that the plasma is not immediately pushed back, and q sent above 3 again.

85245 is a good example. passes through q =3 twice (passes back out again due to q =2 disruptions) but even at late times, has trouble getting through q =3. My theory before today was that there was something about the breakdown (hollow IP profile, strong eddies in the shells/chamber...)that was causing the plasma to exhibit this behavior. Since we see it at times after 4ms, I think it might a permanent feature, at least with the shot settings I am using.

Have heard that this is due to high OH settings, but that was not seen to be the case in a previous run. Have been steadily dropping OHSt and OHE over the course of today and have yet to see the behavior significantly affected.

Ran a study of moving the VFstart later and later to force q through 3 via large MR/low a, (shots 85245-49) and it seems like there are two very different operating regimes on either side of the q = 3 line. A plasma that is finally pushed through q of 3 is suddenly very positionally unstable, and flies out until q~2 causes a large excursion in MR back to a more stable position. If that position is above q of 3, there will be more hitching. If the plasma can then pass through a second time, the same thing will happen

If anyone has run in the last few weeks/months, with q below 3 and MR above 92, please let me know

Also, the control coils in chamber 1, top shell, midplane were found to have shorted to the shell. Last time they worked was shot 84890. There is pickup due to the OH bias firing seen in the shunt, which suggests that the wires are not broken, but that the insulation has worn away somewhere, providing a second ground path to the coil. Repair work may be possible in the future, or it should be possible to remove the large coil from the circuit and use the medium or small coils as well.

Thursday July 3 2014 6:25 pm Byrne/Levesque 85278-85340 Shaping

Quick heads up, the leak rate of the silicon oil seems to be going up. Not sure why, but the reservoir was completely filled on Monday, and by Thursday morning, the level had fallen below the 'T'. As a head's up to anyone else who may be operating the machine in the near future, the new automatic pump fills the reservoir much faster than it empties into the system. I got a bit of an oil shower this morning waiting when the reservoir filled before the line had even filled to the yellow rope. Best to turn it on for 5-10 seconds, then proceed with the startup checklist.

Early part of the day was spent cleaning up the machine. At about 1pm, the 'hitching' behavior of the plasma at a q of 3 suddenly stopped. Since the day and week were ending, rather than develop the shot further we took what we could get and ran the shot as is, along with a shaped equilibrium that was very similar.

q goes below 3 early, drops to about 2.5, then rises to 3 or above after ~2ms as the plasma falls in. It may be difficult to BD these plasmas, as they move a lot in the chamber, but they are very repeatable, and we were able to overlay shaped shots on them quite well. Star shots would be anything from 85318 to 85328 for unshaped, and 85330 to 85340 for shaped. in particular 38 was run with 7kA of shaping current, and had good q behavior, so there is a very good chance it is diverted.

Monday July 7 2014 7:29 pm Byrne 85341-85408 Shaping

Got many more star shots, in that they were repeatable in the main, and went below 3 and back up again, with some time after before disrupting.

Shots are still highly variable in their actual MR/q, but that was an inescapable feature of this campaign. The shot database is much larger than for others, however, so that should help us determine what is an actual feature of shaped MHD and what is unrepeatable 'noise'

Took two shots at EOD with 3-1, 20A RMP on the 10 inserted shells. the shell with the broken coil is not among them. Have not analyzed, but figured it would help to plan the next campaign. As always, I would not read to carefully into any differences with a sample size of one, but if you care to look, they are shots 85403(unshaped) and 85404 (shaped, disrupts right as RMP ends. Did not see this at all without RMPs) and 85408 (shaped, does NOT disrupt despite similar q evolution.)

Total Star Shot (as in comparable data) database is:
From today:

Unshaped: 85368,70,72,93,96,97,99,401,402

Shaped: 85378,83,84,85,87,88,89.

From yesterday:

Unshaped: 85318-28

Shaped: 85311,13,30-40

There is a lot of variation within these shots, due to the large amount of early mode activity, (which antedates the shaping, if any) and causes unpredicatble behavior as q=3 is crossed. should still be plenty to work with


Tuesday July 8 2014 6:26 pm Qian 85409-85459 feedback shots

The purpose is to test the improved feedback algorithms with phase dependancy.

All shells are inserted for the current configuration. non-ferritic shells are backed by 13mm from fully insertion. Early today, the ferritic shells were fully inserted and the plasma was behaving quite unstable: minor disruptions happens on the frequency of 1/0.3ms and the major radius behaves like piece-wise step function. Example shot is 85421. These could be interesting shots to examine later but are not suitable for the current purpose.

Later it was found out that ferritic shells should also be backed by 5mm and that got rid of the strange behavior of the plasma.

desired shot style was reached later today and feedback shots are tested. There was a bug in the code found during testing and took some time to fix it. So we didn't have much time in fully test the performance of the algorithm.

Some feedback shots without phase dependency was performed to reproduce the previous result. It seems that non-feedback shots have a tendency to disrupt when q reaches around 2.2. With feedback at a given phaseshift, this disruption is avoided. and plasma lives longer. feedback shots: 85450,85456 non-feedback shots: 85451~85455 which all disrupts when q reaches certain point.

Further tests with phase dependent algorithms will be tested tomorrow.

Wednesday July 9 2014 6:39 pm Peng 85460-85505 feedback shots

The them of today's run is to test the feedback algorithms.

The shot style has a roughly constant MR around 92cm. q drops across 3 around 2.5ms and reaches 2.2 around 4ms. When q reaches this low value. a strong m=2 mode appears and grows, usually leading to disruption. The growth of this mode is nearly exponential and can be used to calculate a growth rate.

feedback coil are turned on at 2.7 ms and turned off at 5.5 ms. It can be seen that with proper value chosen, the growth rate of the m=2 mode is reduced. It still disrupts finally, but q stays at the critical value around 2.2 for longer time. star shots for comparison are:

non-fb shot: 85502, 85505

fb shot: 85503,85504

the phase dependent algorithm is used in the above feedback shots. But it seems that the phase shift and gain parameters affects the performance more. even with the reversed phase dependence, with the proper phaseshift and gain, the growth rate is still reduced to an extent: 85501

more tests will be done tomorrow.

Thursday July 10 2014 6:03 pm Peng 85506~85584 feedback shots

today's theme is feedback test. Plasma current is lower compared to yesterday's run with the same settings. Increasing the puff time or OH start or OH elect does not have much effect on boosting the plasma current to yesterday's level. This resulted in a different q trace and yesterday's shot styles could not be reproduced.

For today's shots. The early activity still occurs frequently and I think this is related to the instability introduced by ferritic walls. MR is chosen around 93 mm where this effect is sort of mitigated. q traces are higher today compared with yesterday's shots because of lower plasma current. Feedback effect seems to be observed when q drops across 3 and stays around 2.4~2.7. with MR around 93mm. Suppression can be seen when the plasma parameters are in this region.

star shots are 85581 (nonfeedback) ,85582 (feedback). the control coils are turned on after 3.5 ms.

The plasma is not very reproducible and shots with different parameter traces are hard to compare. more tests would be done tomorrow.

Friday July 11 2014 4:47 pm Peng 85584~85640 feedback shots

Shots similar to Wednesday was performed today. Shots disrupts with a exponentially growing m=2 mode as q reaches near 2.2.

When feedback is on, such growth rate can be reduced.(not fully stop the exponential growth, but the time is extended.) More analysis will be done over the weekend to show a more clear result.

Monday July 14 2014 5:36 pm Stoafer 85641-85684 Exploratory Bias Probe

Today's run goal was to explore how the bias probe interacts with the plasma. I had recently tested the crown amplifier on a resistive load to determine optimal settings and limits on the input voltage. With this information, I setup triangle waves and square waves to see how the bias probe interacts with the plasma. We also explored medium density and low density plasmas by varying the puff time.

For triangle wave plasma, we saw expected IV curves, which will be sent in a separate email. We did not see the probe clearly get into the electron saturation regime.

With the square waves, we applied a positive voltage from 2 to 3 ms, then a negative voltage from 3 to 4 ms. We also reversed the voltage with negative from 2 to 3 and positive from 3 to 4. We saw the plasma mode reverse direction, as well as lock, for the maximum amount of positive voltage applied.

The following are lists of shots taken and their conditions:
You can find bias probe data saved in the tree under sensors.bias_probe:voltage and sensors.bias_probe:current. You can also find a useful jScope configuration under bias_probe_new.jscp

Tuesday July 15 2014 5:09 pm Stoafer 85685-85726 Bias Probe feedback

Today's experiments with the bias probe focused on getting feedback working with Qian's help. We were able to get a simple algorithm to feedback on the bias probe voltage to maintain a certain mode frequency. For a first try, this worked very well, but it will be tricky to optimize it because the bias probe suppresses mode amplitudes making it difficult to determine the mode frequency.

A scan of bias voltages using step functions was also run, which will be used as a reference for the feedback algorithm.

Star shots for feedback:
The following are star shots for the scan of input voltages into the Crown amp:

Thursday July 17 2014 4:39 pm Peng 85728~85771 feedback shots

Today's shot is for feedback tests. There was some problem with turning on the crates this morning. It might be caused by the thermal issue in the control room. Shutting spitzer down, cooling it and then rebooting fixed the problem. Plasma shots are not very reproducible today. We still got some shots that is similar to the target shot and did a brief phase scan. More tests will be done tomorrow.

Friday July 18 2014 3:02 pm Peng 85772~85808 feedback shots

more feedback shots are performed today. Plasma shots are not very reproducible. The MR radius swings between the target style (outboard) or falls inboard. This is largely due to the early mode activity which cannot be controlled by now.

a brief phase scan is performed and the results will be analyzed.

Monday July 21 2014 9:27 pm Levesque/Stoafer 85809-85842 Low q* shot development

In the beginning of the day we performed rotation feedback with the bias probe. The target rotation was 9kHz, using a positive bias to drive faster modes. The feedback worked well with the simple feedback algorithm and plasmas seemed to be more stable, however only a small number of shots were taken with this focus. Following the brief feedback run, shots were developed which have a centered major radius and q* decreasing to near 2 at 4ms. These shots will be used for later magnetic feedback attempts.

Starting at shot 85824, the focus changed to developing plasmas that have the initial q* in the range of 1.5 < q* < 2 at the breakdown. We had moderate success, and were able to reproducibly get plasmas with initial q* down to around 1.5. These plasmas were very unstable, with the major radius always crashing in quickly and/or plasma current falling quickly to move q* above 2. When q* rose above 2, the plasma current tended to rise as programmed unless R0 had decreased too far (and led to a major disruption before the plasma could recover). Strong 2/1 modes were seen while q* was below 2. This q* < 2 time window lasted less than ~0.5ms, and the major radius was always changing quickly. 3/2 modes were also seen in the magnetic sensors for these shots. Further shot development is needed to see if it's possible for us to maintain these discharges for longer times; not much exploration has been done yet.

The method for getting to low initial q* today was to have high Ip at breakdown and use a much lower TF than normal. Typically we run the TF bank at 6.1-6.5kV, while today we ran it at 3.6-4.0kV. We ran the OH Start bank at our maximum comfortable limit, which is still well under the rating of the bank. We will soon clean and evaluate the OHST bank to see if we are willing to raise our present maximum charge limit.

Noteworthy discharges are:

Tuesday July 22 2014 4:41 pm Stoafer/Levesque 85843-85876 q<2 shot development

We continued with shot development for plasmas with q* less than 2. A good base shot for the early development of the shot style is 85866. The plasma moves outward to about 94cm with a large starting plasma current, bringing the q* below 2 quickly in the beginning.

However, there is not enough OH ramp to keep the plasma outboard, so it crashes inwards. We were able to adjust the settings to get this good starting behavior, but are having trouble in keeping the plasma going. We used a high OH bias of 5000V and set the OHE at its max of 350V to get a good current ramp. We also raised the limit of the OHS bank from 10kV to 12kV with Nick's approval after inspecting the bank. For this shot to be developed more, we would need to raise the limit of the OHS or OHE settings, which we are not interested in doing at this time.

We can still explore regimes in reducing the TF for lower q shots. In these shots, the TF bank is set to 4700V, about 2/3 the normal setting. We have seen that we can lower it even further and still get breakdown.

No specific plans for continuing this shot development are in place.

Tuesday July 29 2014 4:48 pm Peng/Stoafer 85877~85920

Shot developments are done today to make a shot style with q starts below 3 and reaches 2 around 4ms. The shots are not very reproducible and gets worse towards the end of the day. But progress is made and more tests will be made tomorrow.

Monday August 4 2014 5:50 pm Peng 81921~81975

Feedback tests was done today. q was maintained roughly stable with a low q rather than a decreasing case. shots have less tendency to disrupt with this q trace. When feedback is on, the modes frequency can be changed but the amplitude is not affected much. maybe the mode amplitude is saturated and is maintained at a certain level.

Wednesday August 6 2014 6:07 pm Peng 81975~81925

More shots developments are done today. We can let q reaches below 3 quickly and rise up approaching q=3. The major radius is roughly maintained constant. The shot style is reproducible at a rate about 3/4. So we should be able to do more feedback tests on such shot style.

Wednesday August 6 2014 6:30 pm peng 85975-86025

This is a correction to previous run report. the shot numbers are 85975~86025

Thursday August 7 2014 5:42 pm Peng 86025~86065

Shots today are targeted to have q stays below 3 and have a kink mode. Feedback control is tested on such modes and suppression effect can be seen.

star shots are 86060 and 86061.

Thursday August 14 2014 6:01 pm Peng 86066~86115 plasma shot

most of the time today was spent on getting the same shot styles as last Thursday. Should be able to perform feedback tests tomorrow.

The broken CC06_S1 control coil continues to give the spike around 1ms even after the fuse in the loop has been taken out. It suggests that the signal is coming from the digitizer side.

Friday August 15 2014 5:47 pm Peng 86116~86160 Plasma shot

Shots today are still not very reproducible and much time is spent on tuning the parameters. Some comparison is finally obtained in the end though.

86155 (fb shot) compared 86157 (ref) and 86156 (fb) compared with 86160 (ref) shows the feedback suppression effect. Feedback is turned on at 3.8 ms.

Tuesday August 19 2014 6:52 pm Peng 86162~86109

feedback experiments continued today to see the effect of turning it off early. The targeted shots are not easy to reproduce. The comparison pair is 86190(ref) and 86205(fb) where feedback is turned on between 2.5ms and 4.2 ms. Suppression can be seen during this window.

Thursday August 21 2014 5:26 pm Peng 86211~86258

fbshot tests are done today. And the targeted shot style was obtained and tested. a good example group are: 86229, 86232,86240,86242. where 86232 and 86242 are reference shots. and 86229and 86240 are shots with feedback turned on at 2.5ms and turned off at 4.5ms.

Friday August 22 2014 5:27 pm Peng/Stoafer 86259~86309

Rowgowski coils are tested today. signals can be measured by the oscilloscope. But the noise level is big in the circuit and has to be further reduced to provide reliable measurement.

Biased prob is put in and used to drive a slowed mode. This certainly makes the plasma more stable and led to early disruption events. We are still working on this to obtain a target shot style.

Monday August 25 2014 5:53 pm Peng/Stoafer 86309~86347

The code to control bias probe and feedback control coils together are tested today and working. Plasma becomes very unstable when the bias probe is turned on to slow the mode. feedback might delay the disruption a little bit but is not conclusive.

Tuesday August 26 2014 5:47 pm Peng 86348~86390

feedback shots with bias probe inserted in were tested today. With the bias probe inserted in, plasma behave quite differently. It is find out that with bias probe maintained at -40 volt (floating potential) the plasma could last pretty long sometimes. Most of the shots have a roughly constant MR around 93 cm and q around 2.4 The plasma shows a strong rotating 2,1 mode. When feedback is tried on such modes, no suppression effect can be seen. This is consistent with the previous observation that a tearing mode cannot be suppressed. A kink mode style is targeted later in the day but can hardly be achieved.

Wednesday August 27 2014 4:56 pm Peng 86390~86429

More shot developments are done today but the targeted shot style are hard to obtain.

Friday August 29 2014 3:29 pm Hughes 86430-86452 Shot development for bias probe

Today's run was meant to retrieve the 83918-style equilibrium with bias probe slowed modes. For most of these shots, the bias probe voltages were -2 and +4 at the amplified input (corresponding to about -40 and +90 real Volts at the probe), the negative voltage being the floating potential. For most shots, the bias ramped from 2.5-3.0ms or 1.5-2.0ms later in the series. All shots showed significant variability in R0 traces, and significant disruptivity, with only a few relatively good slowed plasmas with steady R0. Nearly 50% of plasmas with slowed modes disrupted by 5ms, as compared with all plasmas with negative or zero bias lasting longer than 5ms; this is merely an interesting observation, however, as the sample sizes are very small for both sets. With that cavet, since the ferritic wall is inserted, the higher disruptivity at slowed rotations MAY indicate increased mode amplification as rotation drops to 1kHz and slower, as various simulations and tests (Mike's simulation, the freq. rolloff on the mu tests, the amplification of ~1kHz phase flips but relatively unchanged natural mode amplitudes) have suggested. More shots are needed, however, and I would strongly suggest once we're satisfied with the shot programming, we should start swapping between ferritic and stainless walls again, even without RMPs.

Shots of interest:

One problem of note is that the mode analysis built into the bigplot script (including Chris's version that plots the bias probe traces) doesn't pick up slow modes well at all. At some point, I want to overhaul it to make a smarter polynomial smoothing code that knows to skip the disruption. Might do that early next week, or over the weekend if I can get a stable connection to the lab server.

Tuesday September 2 2014 2:01 pm Hughes 86453-86467 Shot development for bias probe

More shot development with bias probe. Mostly saw plasmas with highly reproducible IP, R0, and q traces but disrupting early (mostly between 3.5ms and 5ms) at bias voltage ~80V. Turned slowing bias voltage down by half, and saw mean disruption time of 5 shots move back from ~4.6ms to 5.2ms, suggesting relationship between bias voltage and disruptivity, but this could be due to the radial current or the bias itself or the rotation or something else entirely.

Handing the run over to Chris at 2pm.

Wednesday September 3 2014 11:05 am Peng 86468~86476

this is a run report for yesterday's run after Paul. A brief test was done on feedback using the shot style developed early in the day. Major radius a roughly constant around 92cm. q drops gradually over time, acrossing 3 around 2.5ms. Bias probe was initially floating at -40V and then quickly ramp up to 40V around 2ms, then maintained at 40V.

suppression can be seen with 3000gain at 270 deg. The gain is higher than previous cases without bias probe (2000 gain at 330 deg). But the current on the control coil is around 20mA which is at the similar magnitude. Then phase shift is also changed from 330 deg to 270deg. The effect is not much at 330 deg.

refshot. 86470,86475. fbshot: 86473, 86474.

Thursday September 4 2014 5:48 pm Byrne/Levesque 86486-86515 Shaping vacuum shots, bias-slowed plasmas

Took vacuum shots to measure pickup from shaping coil on sensors for a variety of shaping currents. Also took some control-coil-only shots with a 3/1 applied field to check for pickup on sensors. Note that all shells are at the same radii as for the previous few weeks (all SS portions of shells are at the same radius, slightly retracted from the SS full insertion location).

Also took plasma shots with the bias probe set near floating or set near ground. These expand on the shots taken earlier this week at higher voltages. Only a few shots were taken (86509-86515) before running out of run time.

Monday September 8 2014 6:33 pm Hughes 86517-86560 Fe wall bias w/ long RMP

Today's run was meant to gather a series of shots with long RMPs and positive (slowing) bias to begin a Fe/SS comparison. For this run, the Fe shells were inserted (back 5mm from maximum insertion) and the SS shells retracted fully. Unfortunately, plasmas were not very cooperative, and most disrupted between 4ms and 5ms, and often even earlier. As a result, the usual 3ms-4ms phase flip wasn't suitable. A new shot style that crosses q=3 at about 2.5ms rather than 3.0ms was developed, although the major radius is considerably less steady in this shot style. The bias probe begins ramping from floating potential (-40V) at 1.5ms and reaches full bias (+80V) at 2.0ms, holding until 8.0ms; the RMP amplitude is set to 2.5 (roughly 25 amps), turning on at 2.5ms, flipping at 3.4ms, and turning off at 2.5ms, giving 900us of soak-through time. Analysis will be performed later, but as a preliminary observation, the disruptivity and general fussiness of the plasmas seemed greater today than on other days.

Noteworthy shots: