NEOCLASSICAL IDEAL INTERNAL KINK MODES IN HIGH-TEMPERATURE REGIMES INTOKAMAKS

Previous results on the theory of neoclassical ideal internal kink mod es are generalized to the case of a finite ion-orbit width, which is r elated to both the ion motion along the drift trajectories in a curvil inear tokamak magnetic field and the ion Larmor rotation. A dispersion relation is derived for the ideal internal kink modes in high-tempera ture regimes for which the singular-layer width does not exceed the wi dth of the ion drift trajectories. A new substantially neoclassical re gime corresponding to the singular-layer width of the order of the ion drift orbit is found and studied. The drift effects are shown to stab ilize the neoclassical ideal internal kink modes, and the influence of ion collisions on the stabilized modes is investigated. It is found t hat ion collisions result in the growth of the modes with frequencies close to the ion drift frequency and in the damping of the modes with frequencies that are much less than the drift frequency.