Feedback Suppression of a Large-Growth-Rate Flute Mode

Abstract

A very large growth rate, large saturation amplitude, hard-onset flute mode in a multipolelike magnetic field is suppressed by a factor of 60 in power by negative current feedback to the plasma. Upon suppression of the instability, the center-line density increased 7%. The required feedback gain and phase are in rough agreement with a linear slab-model theory.