Ambipolar transport in a magnetically perturbed tokamak edge-region

Magnetic perturbation of the plasma edge-region of a tokamak may be caused by a number of different sources. Some tokamaks (e.g. Tore Supra, Text) are fitted with ancillary coils yielding magnetic fields which may give rise to ergodicity or may be resonant with the main helical tokamak field somewhere within the plasma. Engineering flaws and tearing instabilities may similarly perturb the magnetic configuration. In this paper we examine collisional effects on particle and energy fluxes in a weakly stochastic magnetic field in a tokamak edge-region. As before, we use the drift-kinetic equation with self-consistent BGK collision term and apply a Chapman-Enskog expansion. Cylindrical flux surfaces are perturbed by a stochastic field having a radial component, and radial transport is dominated by the parallel contribution. We now extend the earlier studies by allowing for an ambipolar electric field, including perturbations in potential on the flux surface and carrying out a parameter survey. (author) 3 refs., 4 figs