Path-sum calculations for rf current drive

Path sums and Gaussian short-time propagators are used to solve two-dimensional Fokker-Planck models of lower-hybrid (LH) and electron-cyclotron (EC) current drive (CID), and are shown to be well suited to the two limiting situations where the rf quasilinear diffusion coefficient is either relatively small, D-rj approximate to 0. 1, or very large, D-rj --> infinity, the latter case enabling a special treatment, Results are given for both LHCD and ECCD in the small D-rf case, whereas the limiting situation is illustrated only for ECCD. To check the accuracy of path-sum calculations, comparisons with Finite difference solutions are provided.