New mechanisms of minority ion cyclotron current drive

Minority ion cyclotron current drive is studied by solving the Fokker–Planck equation in toroidal geometry keeping the ∂/∂v∥-term in the quasilinear operator, hereby including the important effects of the finite orbit widths of the tail ions and the wave-induced spatial drift and diffusion. It has previously been found that the trapped ion current and the current carried by passing ions detrapped by wave-induced v⊥-diffusion are the two dominating contributions for high levels of coupled power. In this study yet another current-drive mechanism is presented, asymmetric detrapping by inward wave-induced radial drift, which occurs for negative k∥ and is strongest for on-axis resonance where it is the totally dominating effect for high powers.