Feedback stabilization of current-driven resistive-wall-modes (RWMs) near $q_{95}\sim 4$ in DIII-D

Complete feedback stabilization of current-driven RWM at $q_{95}\sim 4$ has been demonstrated in DIII-D. Taking advantage of the reproducible RWMs in ohmic plasmas with fast current ramps, we assessed the RWM feedback algorithm that had not been fully evaluated with pressure-driven RWMs. Using the internal control coils powered with a broadband supply, we suppressed the current-driven RWM at $q_{95}\sim 4$; successful feedback is attributable to both error field correction and direct mode feedback. The use of derivative gains expanded the stable range of proportional gains. The current-driven RWMs are frequently accompanied by magnetic island-like structures near $q=2$ surface: the evolution of such internal structures is also used to assess the efficacy of feedback stabilization. The experimental results will be used for a benchmark of RWM feedback models.