A quasilinear, Fokker–Planck description of fast wave minority heating permitting off‐axis tangency interactions

The off‐axis quasilinear fast wave minority heating description of Catto and Myra [Phys. Fluids B 4, 187 (1992)] has been improved and implemented in a code which solves the combined quasilinear and collision operator equation for the minority distribution function. Geometrical complications of a minority resonance nearly tangent to a flux surface in the presence of trapped as well as passing particles are retained. The tangency interactions alter the moments and the fusion reaction rate parameter in a model which explores heating on a single flux surface. The strong tangency interactions enhance the more familiar interactions due to trapped particles turning in the vicinity of the minority resonance. An asymmetry in off‐axis heating effects occurs because heating on the low field side of the magnetic axis heats more trapped particles than high field side heating. This asymmetry is responsible for the better performance of the low field side case relative to the high and on‐axis cases and provides some control over the power absorbed by and the energy stored in the trapped particles.