Comparison of RWM Stabilization Strategies in DIII-D

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.