Comparison of RWM Stabilization Strategies in DIII-D

S. Yang, E. Schuster, D.A. Humphreys, M.L. Walker, Y. In, J-S. Kim

Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Dallas, Texas, November 17-21, 2008

Abstract

One of the major non-axisymmetric instabilities under study in the DIII-D tokamak is the resistive wall mode (RWM), a form of plasma kink instability whose growth rate is moderated by the influence of a resistive wall. The FAR-TECH/General Atomics RWM dynamic model represents the plasma surface as a toroidal current sheet and represents the wall using an eigenmode approach. This dynamic model is used for the design of model-based controllers that have the potential of outperforming present proportional-derivative (PD) controllers. We report on validation of this dynamic model, a required step before implementation of any model-based controller in the DIII-D plasma control system. In addition, simulation results are presented comparing the performance of advanced controllers synthesized using the validated dynamic model and present non-model-based PD controllers.