Active feedback stabilization of the resistive wall mode on the DIII-D device

A proof of principle magnetic feedback stabilization experiment has been ca rried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing re sistive wall, on the DIII-D tokamak device [Plasma Phys. Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159; Phys. Plasmas 1, 1415 (1994)]. The RWM was successfully suppressed and the high b eta duration above the no-wall limit was extended to more than 50 times the resistive wall flux diffusion time. It was observed that the mode structur e was well preserved during the time of the feedback application. Several l umped parameter formulations were used to study the feedback process. The o bserved feedback characteristics are in good qualitative agreement with the analysis. These results provide encouragement to future efforts towards op timizing the RWM feedback methodology in parallel to what has been successf ully developed for the n=0 vertical positional control. Newly developed MHD codes have been extremely useful in guiding the experiments and in providi ng possible paths for the next step. (C) 2001 American Institute of Physics .