RF effects on neoclassical theory and the bootstrap current in tokamaks

We consider the possibility of synergistic effects in combining bootstrap and RF current drive in tokamaks tl]. In neoclassical theory, the bootstrap current is derived from an electron velocity-space distribution satisfying the drift kinetic equation (DKE), with radial drifts due to magnetic field gradient and curvature. Numerical solutions to the DKE are found with KT3D-NC, a Fokker-Planck code with quasilinear diffusion [2] which calculates perturbations to the electron distribution due to the drift term of the DKE. The resulting bootstrap current is then found by taking the parallel velocity-space moment of the RF-modified electron distribution. A quasilinear diffusion operator is chosen to represent several RF wave scenarios (lower hybrid, fast Alfven waves, electron cyclotron). The numerical results are compared to analytic solutions using several approximate techniques.