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Abstract. Recent DIII-D experiments have shown that the n=1 resistive wall
mode (RWM) can be controlled by an external magnetic field applied in closed
loop feedback using the six element error field correction coil (C-coil).
The RWM constitutes the primary limitation to normalized beta in recent
DIII-D advanced tokamak plasma experiments. The toroidal rotation of DIII-D
plasmas does not seem sufficient to completely suppress the RWM: a very
slowly growing RWM (growth rate
1/
) is often
observed at normalized beta above the no-wall limit and this small RWM slows
the rotation. As the rotation decreases, there is a transition to more rapid
growth (
1/
). The application of magnetic
feedback is able to hold the RWM to a very small amplitude, prolonging the
plasma duration above the no-wall limit for durations much longer than the
growth time of the RWM. These initial experimental results are being used
to compare control algorithms, to benchmark models of the feedback
stabilization process and to guide the design of an upgraded coil-sensor
system for stabilization of the RWM at normalized beta values closer to the
ideal-wall limit.
IAEA 2001