(Color). Experimental arrangement of conducting shells, mode control coils, and poloidal field sensors.
Normalized overall feedback gain illustrating the frequency variation of the magnitude and phase. Shown are: dotted line intrinsic to analog hardware, dashed line with the effect of filter , solid line with the effect of filter .
Shot-averaged evolution of the plasma current and edge safety factor. Investigation of feedback effectiveness was performed during the time interval between , when rotating external kink instabilities appeared.
(Color). Poloidal field measurements of Rogowski oscillations for four cases: no feedback wall retracted by , no feedback with wall fully inserted, positive feedback (amplification), and negative feedback.
(Color). Amplitude of the frequency spectrum of Rogowski coil oscillations as a function of the feedback toroidal rotation angle for filter . Angle represents phase difference between applied radial magnetic field component and sensed poloidal component. The large phase margin is obtained with effective phase compensation.
(Color). Amplitude of the frequency spectrum of Rogowski coil oscillations for filter . Angle represents phase difference between applied radial magnetic field component and sensed poloidal component. Because of the appearance of oscillations at , the phase margin nearly vanishes with ineffective phase compensation.
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