The role of electron-electron collisions in the neoclassical theory of ECRH current drive

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Abstract
The effect of electron trapping on ECRH driven currents in Tokamak magnetic field configurations has been calculated using the full Fokker-Planck collision operator to take account of the electron-electron collisions. Relativistic effects are also included in the electron cyclotron resonance condition. The treatment is linear, two-dimensional in velocity space and applies to large aspect ratio Tokamaks. For suprathermal, non-relativistic resonant electrons the inclusion of electron-electron collisions is found to substantially reduce the effect of trapping compared with predictions based on the Lorentz gas model. For thermal electrons the fractional reduction in current is similar to that obtained when electron self-collisions are neglected. When relativistic effects become important, trapping affects the current on the low field side of the resonance considerably less than the current driven on the high field side.