Nature of Monster Sawteeth and Their Relationship to Alfvén Instabilities in Tokamaks

Abstract

A correlation is explored between the presence of energetic particle modes (EPM) and long-period sawtooth oscillations in tokamak plasmas heated by rf waves. The eventual crash of these sawteeth is explained in terms of the loss of the stabilizing fast particles due to the EPM. The absence of long-period sawteeth in high $q_a$ discharges is explained in terms of ion loss due to toroidal Alfvén eigenmodes.