Simulation model for lower hybrid current drive

Abstract

A simulation model for steady-state, lower hybrid current drive is described which incorporates a relativistic, one-dimensional Fokker–Planck calculation and a toroidal ray tracing code. Two-dimensional (v⊥) effects are included in the Fokker–Planck analysis in the form of a large perpendicular electron temperature that results from pitch angle scattering. An increase in the parallel refractive index of the lower hybrid waves, arising from toroidal geometry effects, is proposed as a physical mechanism whereby injected rf waves at high phase velocity (ve≪v∥ ≲c) can interact via the Landau resonance with electrons at low phase velocity (v∥ ≲3ve). Numerical results relevant to the Alcator C [Phys. Rev. Lett. 53, 450 (1984)] and PLT [Phys. Rev. Lett. 49, 1255 (1982)] experiments are presented which demonstrate the dependency of the current drive efficiency on various plasma parameters.