Effect of Toroidal Field Ripple on Fast Ion Behavior in a Tokamak

Abstract

Computational studies have been performed for fast ion behavior in a Tokamak with toroidal field ripple. Collisionless behavior of fast ions relating to rippletrapping, ripple-detrapping and banana drift is of essential importance in fast ion loss processes in case of quasi-perpendicular neutral beam injection. The collisionless ripple trapping and ripple-enhanced banana drift produce a large number of loss bands in velocity space and enhance the loss of fast ions. The fast ion loss associated with ripple can be categorized into two groups; ripple-trapped loss and banana-drift loss. The amount of loss particles due to the respective loss process is significantly influenced by the effect of finite banana size of fast ions. The ripple-trapped loss particles are localized in a specific region on the first wall surface.