Sawtooth stabilization by barely trapped energetic electrons

Abstract

The barely trapped energetic electrons produced by the electron cyclotron resonance heating can interact efficiently with the internal kink mode and stabilize sawtooth oscillations. The effects of the spatial distribution and the pitch angle distribution of the energetic electrons are considered. The most effective stabilization is obtained when the peak of the spatial distribution locates on the q=1 rational surface. This machanism gives a reasonable explanation of the difference between the high-field-side heating and the low-field-side heating on tokamaks.