Fishbone Mode in Spherical Tokamaks

Abstract

It has been shown that the diamagnetism of toroidal high-pressure plasmas and the concomitant magnetic valley in the equilibrium magnetic field affect features of the precessional motion of fast ions, which may result in the absolute stability of the fishbone mode in spherical tokamaks with sufficiently high $\ensuremath{\beta}$. The obtained stability conditions agree with experimental observations and pave the way for fishbone-free plasmas in spherical tokamaks.