Kinetic effects on electron cyclotron emission during electron cyclotron heating in tokamaks

Plasma heating and current drive in tokamaks by means of high-power electron cyclotron (EC) waves results in generating non-Maxwellian electron distribution functions. These distributions intensely emit at the electron gyrofrequency ωc and its harmonics because of their high perpendicular energy content. The properties of the radiation emitted by this specific non-Maxwellian system are studied in the present work. The electron distribution is determined by solving the time-dependent bounce-averaged quasilinear:Fokker-Planck equation by means of a 3-D Fokker-Planck code. The computed steady-state distributioin function is then used to calculate the emission and transmission spectra for different locations of the receiving antennnas, polarizations and harmonics. It results that a detailed analysis of those spectra yields insight in problems like the impact of quasilinear flattening and electron trapping on the form of the steady-state distribution, which are of paramount interest for EC heating and especially for current drive in tokamak reactors. illustrative computational examples discussed. The two most attractive scenarios for EC heating are considered, i.e., by an ordinary (o) mode launched from the outboard side and propagating perpendicularly to the magnetic field B, absorbed at ω = ωc, and by an extraordinary (x) wave, injected obliquely from the inboard side and absorbed at downshifted frequency (ω < ωc). The latter scheme is also representative of current drive experiments. (author). 7 refs.; 7 figs