MODELING OF CORE-WALL PARTICLE DYNAMICS IN TORE SUPRA PUMPING EXPERIMENTS

Particle control experiments in Tore Supra have shown that the change in core plasma density with pumping at the outboard pump limiter amounts only to a small fraction of the total number of particles extracted by the outboard pump limiter system. To develop a model for the core-wall particle exchange at the level of individual basic physical processes, the particle exchange between the core plasma and the wall has been modeled in detail for a series of Tore Supra discharges. Core and scrape-off layer particle balance and wall diffusion calculations were performed using a radial transport code and a 1D wall diffusion code. Core-wall particle exchange for the case of the outboard pump limiter is found to be mediated by the localized charge exchange flux in the near limiter region. The wall particle efflux required for detailed balance does not match that calculated to be available from the near limiter wall region unless some local heating of the wall is assumed.