Numerical Simulation of Tokamak Electron Dynamics.

In a tokamak, the electron distribution deviates from a Maxwellian. This is because the magnetically untrapped electrons moving parallel to the applied electric field tend to run away. Because of the presence of trapped electrons, the distribution also departs from the Chapman-Enskog solution of the weak electric field problem. Previous analytic and numerical methods have treated this distortion in the limit of vanishingly small electric fields, a vanishing small number of trapped electrons, or both. We present a numerical method which relaxes these limitations, and illustrate the distribution functions which result from it. (Author)