- Prof. Gerald Navratil -
Thomas Alva Edison Professor
My research concentrates on applying experimental plasma physics to the problem of developing controlled thermonuclear fusion as a source of energy. The national research program to develop fusion energy is now more than forty years old and has been receiving substantial amounts of federal funding since the period of energy shortage in the mid-1970's. Fusion energy has the potential to provide a virtually unlimited source of power with a very plentiful fuel supply (deuterium and lithium) and a greatly reduced environmental hazard.
The U. S. Department of Energy funds the High Beta Tokamak Research Program carried out on the HBT-EP tokamak in the Columbia Plasma Physics Laboratory. The objective of this research is to discover what processes limit the stability of a magnetically confined plasma in a tokamak device when the pressure of the plasma becomes comparable with the magnetic field pressure and how to extend these limits to higher pressure. These 'high beta plasmas' are needed to make fusion a practical source of electric power since the fusion power density scales as the square of the plasma pressure.
Our investigations of high-beta plasma physics are carried out on the HBT-EP tokamak located on the Columbia campus and on the Tokamak Fusion Test Reactor (TFTR) located at the nearby Princeton Plasma Physics Laboratory. The HBT-EP tokamak is the third and largest (R = 1 m) in a series of tokamaks built at Columbia and was dedicated in 1993 after a two-year construction period. The unique design of the HBT-EP tokamak includes a 1 cm thick aluminum 'shell' which can be positioned near the plasma edge to provide passive stabilization of pressure-driven plasma instabilities. These passive stabilization techniques are now being studied in combination with the first high-power, active feedback control experiments being carried out with the Los Alamos National Laboratory which has provided a total of 32 megawatts of feedback control power amplifiers for use on HBT-EP.
The work we carried out on the TFTR tokamak, which is the largest fusion facility in the United States, led to the discovery of an improved mode of operation at reduced electric current in the plasma. We have studied these 'high poloidal beta' plasmas using both deuterium-only plasmas and deuterium-tritium plasmas. In our experiments with tritium-fueled plasmas on TFTR, significant amounts of power have been produced which exceeded 6 megawatts of fusion power output.
- Recent Publications -
"Feedback control of the proximity to marginal RWM stability using active MHD spectroscopy" J. M. Hanson, H. Reimerdes, M. J. Lanctot, Y. In, R. J. La Haye, G. L. Jackson, G. A. Navratil, M. Okabayashi, P. E. Sieck and E. J. Strait, Nucl. Fusion 52 013003 (2012)
"High resolution detection and excitation of resonant magnetic perturbations in a wall-stabilized tokamak" David A. Maurer, Daisuke Shiraki, Jeffrey P. Levesque, James Bialek, Sarah Angelini, Patrick Byrne, Bryan DeBono, Paul Hughes, Michael E. Mauel, Gerald A. Navratil, Qian Peng, Dov Rhodes, Nickolaus Rath, and Christopher Stoafer, Phys. Plasmas 19, 056123 (2012)
"High-speed, multi-input, multi-output control using GPU processing in the HBT-EP tokamak, Fusion Engineering and Design", N. Rath, J. Bialek, P. J. Byrne, B. DeBono, J. P. Levesque, B. Li, M. E. Mauel, D.A. Maurer, G. A. Navratil, D. Shiraki, Fusion Engineering and Design, online May 2 (2012)
"The high beta tokamak-extended pulse magnetohydrodynamic mode control research program", D. A. Maurer, J. Bialek, P. J. Byrne, B. De Bono, J. P. Levesque, B. Q. Li, M. E. Mauel, G. A. Navratil, T. S .Pedersen, N. Rath and D. Shiraki, Plasma Phys. Control. Fusion 53 074016 (2011)
“A Kalman filter for feedback control of rotating external kink instabilities in the presence of noise,” J. M. Hanson, B. DeBono, R. W. James, J. P. Levesque, M. E. Mauel, D. A. Maurer, G. A. Navratil, T. Sunn Pedersen, D. Shiraki, Physics of Plasmas 16 (2009) 056112.
“A digital control system for external magnetohydrodynamic modes in tokamak plasmas,” J. M. Hanson, A. J. Klein, M. E. Mauel, D. A. Maurer, G. A. Navratil, and T. Sunn Pedersen, Review of Scientific Instruments 80 (2009) 043503.
“Feedback suppression of rotating external kink instabilities in the presence of noise,” J. M. Hanson, B. DeBono, R. W. James, J. P. Levesque, M. E. Mauel, D. A. Maurer, G. A. Navratil, T. Sunn Pedersen, D. Shiraki, Physics of Plasmas 15 (2008) 080704.
"Critical b analyses with ferromagnetic and plasma rotation effects and wall geometry for a high beta; steady state tokamak," G. Kurita, et al. (G.A. Navratil), Nuclear Fusion 46: 383 (2006)
"Overview of the National Centralized Tokamak programme," M. Kikuchi, et al. (G.A. Navratil), Nuclear Fusion 46: S29 (2006)
"Measurement of Resistive Wall Mode Stability in Rotating High-Beta DIII-D Plasmas", Reimerdes, Holger et al., (G. A. Navratil), Nuclear Fusion 45: 368 (2005).
"Scaling of the Critical Plasma Rotation for Stabiliation of the n+1 RWM in DIII-D", LaHaye, R.J., A. Bondeson, M.S. Chu, A.M. Garofalo, Y.Q. Liu, G.A. Navratil, M. Okabayshi, H. Reimerdes, and E.J. Strait. Nuclear Fusion 44: 1197 (2004).
"Suppression of resistive wall instabilities with distributed, independently controlled, active feedback coils", Cates, C., et al. (G. A. Navratil). Phys. Plasmas 7:3133-6 (2000).
"Sustained rotational stabilization of DIII-D plasmas above the no-wall beta limit", Garofalo, A. M., et al. (G. A. Navratil). Phys. Plasmas 9:1997 (2002).
"Modeling of active control of external MHD instabilities" Bialek, James, et al. (G. A. Navratil). Phys. Plasmas 8:2170 (2001).
"Active control of 2/1 magnetic islands in a tokamak", Navratil, G. A., et al. Phys. Plasmas 5:1855 (1998).
"Higher fusion power gain with profile control in DIII-D tokamak plasmas", Lazarus, E. A., and G. A. Navratil et al., Nucl. Fusion 37:7 (1997).
"Initial High Beta Operation of the HBT-EP Tokamak", M. K. Vijaya Sankar, E. Eisner, A. Garafalo, D. Gates, T.H. Ivers, R. Kombargi, M. E. Mauel, D. Maurer, D. Nadle, G. A. Navratil, Q. Xiao, J. Fusion Technology 12, 303 (1993).
"High Poloidal Beta Long Pulse Experiments in the Tokamak Fusion Test Reactor", J. Kesner, M. E. Mauel, G. A. Navratil, S. A. Sabbagh, M. Bell, et al., Physics of Fluids B 5, 2525 (1993).
"Operation at the Tokamak Equilibrium Poloidal Beta Limit in TFTR", M. E. Mauel, G. A. Navratil, S. A. Sabbagh, M. G. Bell, et al., Nuclear Fusion 32, 1468 (1992).
"Study of High Poloidal Beta Plasmas in TFTR and DIII-D", by G. A. Navratil, R. A. Gross, M. E. Mauel, S. A. Sabbagh, et al., Plasma Physics and Controlled Fusion Research 1990 (IAEA, Vienna, Austria 1991), Vol. 1, page 209.
"Transition to the Second Region of Ideal MHD Stability", S.A. Sabbagh, M.H. Hughes, M.W. Phillips, A.M.M. Todd, G.A. Navratil, Nuclear Fusion 29, 423 (1989).