Conditions for stabilization of the tokamak plasma vertical instability using only a massless plasma analysis

The practical implications of the results presented provide substantial insight into some long-standing issues regarding feedback stabilization of the vertical instability with PD controllers and also provide a rigorous foundation for the common practice of designing controllers assuming m=0. For controllers that operate only on the plasma vertical position, we settle the question: when are m=0 models predictive of actual plasma behavior?