KINETIC AND TRANSPORT-THEORY NEAR THE TOKAMAK EDGE

Conventional transport orderings employed in the core of a tokamak pla sma allow large divergence-free flows in flux surfaces, but only weak radial flows. However, alternate orderings are required in the edge re gion where radial diffusion must balance the rapid loss due to free st reaming to divertor plates or limiters. Kinetic equations commonly use d to study the plasma core do not allow such a balance and are, theref ore, inapplicable in the plasma edge. Similarly, core transport formul as cannot be extended to the edge region without major, qualitative al teration. Here the necessary changes are addressed. By deriving and so lving a novel kinetic equation, distinctive collisional transport laws for the plasma edge are constructed. It is found that the new edge or dering retains the radial diffusion and parallel flow of particles, mo mentum, and heat to lowest order in the conservation equations. To hig her order a surprising form for parallel transport in the scrape-off l ayer is found, in which the parallel flow of particles and heat are dr iven by a combination of the conventional gradients, viscosity, and ne w terms involving radial derivatives. The new terms are not relatively small, and could affect understanding of limiter and divertor operati on. (C) 1996 American Institute of Physics.