Global modes and high-energy particles in ignited plasmas

Publisher Website
Google Scholar
Abstract
Fusion‐produced alpha particles may spontaneously enhance the stability of an ignited plasma against m=1 internal modes. Stable values of the poloidal beta of the thermal plasma component significantly in excess of the ideal magnetohydrodynamic threshold can be attained, provided the region where the magnetic helical parameter q is below unity is not too wide and the ignition temperature is not too high. A comprehensive analysis of the different instability regimes is presented, with special attention to so‐called ‘‘fishbone oscillations’’ and their influence on the ignition energy balance. The theoretical predictions compare favorably with sawtooth suppression experiments in the JET tokamak [Phys. Rev. Lett. 6 0, 2148 (1988)] with high‐power, ion‐cyclotron resonant frequency heating, where energetic ions in the MeV range are produced.