THEORY OF FAST-ION TRANSPORT DURING SAWTOOTH CRASHES IN TOKAMAKS

An approach is suggested for the description of fast ion transport in tokamaks during sawtooth crashes, which takes into account the orbital motion of the particles and the temporal evolution of the magnetic co nfiguration. The approach is based on a kinetic equation for the distr ibution function of fast ions derived using different scales with char acteristic times of the sawtooth crash and of the fast ion motion. The evolution of the magnetic configuration in the process of the crash i s assumed to be known, and its analytical description is suggested for the case of the Kadomtsev type of crash. The derived kinetic equation is analysed for both trapped and circulating particles, and conclusio ns are drawn concerning redistribution of particles of various energie s and pitch angles during crashes. The physical nature of fast ion tra nsport induced by the sawtooth crash is elucidated.