Fokker–Planck studies of high power electron cyclotron heating in tokamaks

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Abstract
A Fokker–Planck formalism has been developed to interpret experimental data from high power electron cyclotron heating of tokamak plasmas in which the electron distribution function can be substantially distorted. The Fokker–Planck equation is solved using a 2-D code which incorporates electron trapping, a steady Ohmic electric field and a bounce averaged electron cyclotron heating term. The quasilinear RF diffusion coefficient is calculated using a single particle model which includes the mildly relativistic resonance condition and takes into account localized RF power injection and tokamak rotational transform effects. Comparisons are presented of the calculated and observed soft X-ray spectra from 60 GHz second harmonic electron cyclotron heating experiments on the CLEO tokamak. Good agreement between theory and experiment is found. In addition, predicted RF current drive efficiencies for the COMPASS tokamak are presented.