A theoretical framework for understanding thefeedback mechanism for stabilization of external MHD modes has beenformulated. Efficient computational tools - the GATOstability code coupled with a substantially modified VACUUM code - have been developed to effectively design viable feedbacksystems against these modes. The analysis assumed a thin resistiveshell and a feedback coil structure accurately modelled in θ andϕ, albeit with only a single harmonic variation in ϕ. Timeconstants and induced currents in the enclosing resistive shell arecalculated. An optimized configuration based on an idealized modelhas been computed for the DIII-D device. Up to 90% of theeffectiveness of an ideal wall can be achieved.
Circuit equation formulation of resistive wall mode feedback stabilization schemes