High-$\beta$, Sawtooth-Free Tokamak Operation Using Energetic Trapped Particles

It is shown that a population of high-energy trapped particles, such as that produced by ion cyclotron heating in tokamaks, can result in a plasma completely stable to both sawtooth oscillations and the fishbone mode. The stable window of operation increases in size with plasma temperature and with trapped-particle energy, and provides a means of obtaining a stable plasma with high current and high $\beta$.