Trapped particle destabilization of the internal kink mode

Abstract

The internal kink mode is destabilized by trapped high-energy particles, leading to a new branch of the internal kink dispersion relation with a real frequency near the average trapped-particle precession frequency and a growth rate of the same magnitude. This trapped particle branch of the dispersion relation is investigated numerically for a variety of particle distributions. Mode growth rate and frequency is found as a function of plasma β, density, and trapped-particle energy and distribution. The high-energy trapped particle sources considered are neutral beam injection, ion-cyclotron heating, and fusion alpha particles. Relevance for various plasma heating schemes is discussed.