Ion cyclotron range of frequencies stabilization of sawteeth on Tokamak Fusion Test Reactor

• Published in: Physics of fluids. B, Plasma physics Plasma physics, 1992-07, Vol.4 (7), p.2155-2164
• Main Authors: Phillips, C. K., Hosea, J., Marmar, E., Phillips, M. W., Snipes, J., Stevens, J., Terry, J., Wilson, J. R., Bell, M., Bitter, M., Boivin, R., Bush, C., Cheng, C. Z., Darrow, D., Fredrickson, E., Goldfinger, R., Hammett, G. W., Hill, K., Hoffman, D., Houlberg, W., Hsuan, H., Hughes, M., Jassby, D., McCune, D., McGuire, K., Nagayama, Y., Owens, D. K., Park, H., Ramsey, A., Schilling, G., Schivell, J., Smithe, D. N., Stratton, B., Synakowski, E., Taylor, G., Towner, H., White, R., Zweben, S.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 700340 - Plasma Waves, Oscillations, & Instabilities- (1992-); 700350 - Plasma Production, Heating, Current Drive, & Interactions- (1992-); CLOSED PLASMA DEVICES; CONFINEMENT; Exact sciences and technology; FLUID MECHANICS; HEATING; HYDRODYNAMICS; INSTABILITY; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MECHANICS; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; PLASMA CONFINEMENT; PLASMA HEATING; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; STABILIZATION; TFTR TOKAMAK; THERMONUCLEAR DEVICES; TOKAMAK DEVICES; Waves, oscillations, and instabilities in plasmas and intense beams
• ISSN: 0899-8221; 2163-503X
• DOI: 10.1063/1.860484

Results obtained from experiments utilizing high‐power ion cyclotron range of frequencies (ICRF) heating to stabilize sawtooth oscillations on Tokamak Fusion Test Reactor (TFTR) [Hawryluk et al., Plasma Phys. Controlled Fusion 33, 1509 (1991)] are reviewed. The key observations include existence of a minimum ICRF power required to achieve stabilization, a dependence of the stabilization threshold on the relative size of the ICRF power deposition profile to the q=1 volume, and a peaking of the equilibrium pressure and current profiles during sawtooth‐free phases of the discharges. In addition, preliminary measurements of the poloidal magnetic field profile indicate that q on axis decreases to a value of 0.55±0.15 after a sawtooth‐stabilized period of ∼0.5 sec has transpired. The results are discussed in the context of theory, which suggests that the fast ions produced by the ICRF heating suppress sawteeth by stabilizing the m=1 magnetohydrodynamic (MHD) instabilities believed to be the trigger for the sawtooth oscillations. Though qualitative agreement is found between the observations and the theory, further refinement of the theory coupled with more accurate measurements of experimental profiles will be required in order to complete quantitative comparisons.