Title: Smooth transition of neoclassical diffusion from the banana to Pfirsch-- Schlueter regime

It is shown that neoclassical transport previously obtained by numerical evaluation of variational procedures can be reproduced analytically by taking account of the energy dependence of the collision and bounce frequencies through the separation of velocity space into banana, plateau, and Pfirsch--Schluter regimes. (AIP)

Particle transport rates for a trace impurity are calculated for a Pfirsch-Schlueter regime plasma consisting of a main ion and all the charge states of a background impurity. The main ion is taken to be much lighter than all impurities, but masses and charges are otherwise arbitrary. Qualitative trends of the transport rates with variations in the trace impurity mass and background impurity concentrations are discussed.

A prescription for constructing the plasma pressure profile in the vicinity of an equilibrium magnetic island is derived by solving a sourced pressure diffusion equation near the island region. For pressure sources and sinks that are relatively constant in space, it is found that the plasma pressure profile is insensitive to pressure sources; thus the pressure profile can be constructed by assuming that the net pressure flux across any topologically toroidal magnetic surface is constant. This construction of the pressure profile is also valid for magnetic islands that are slowly evolving in time. By coupling the pressure evolution equation withmore » the magnetostatic equilibrium equations, the theory is applied to the case of self-consistent construction of pressure-gradient-driven magnetic islands. In particular, we address the question of resonant Pfirsch-Schlueter current induced magnetic islands and the role of thermal effects on nonlinear magnetic islands.« less

The particle and heat flux problems were solved in the collisional or Pfirsch-Schluter regime for a two-ion species tokamak plasma using a kinetic approach with exact Fokker-Planck collision operators. These solutions are appropriate for analyzing the behavior of impurities in the low temperature plasma edge region where impurities first enter the plasma from the outside. One finds that low charge states of low mass impurities can be screened effectively from further penetration of the plasma.