ITER edge-plasma conditions versus pump configuration

Two-dimensional fluid simulations of ITER double-null divertor scrape-off layer plasma conditions have been limited to considerations of a single outboard divertor plate with up/down symmetry assumed. The present work evaluates the effect of pumping at only one plate on particle flow patterns and divertor power loads. Pumping only at one plate reduces sheath temperatures at both plates, but increases the heat flux at the pumped plate. The physics assumptions for separatrix density (nSEP=/3.5) and for radial particle diffusivity (D=0.66 m2/s) used in the simulation of ITER edge plasma result in particle throughputs two orders of magnitude greater than that required for acceptable fusion-product ash removal rates. The main-plasma particle confinement time, however, is an order of magnitude shorter than the transport energy confinement time, τE. Plasmas (D=0.04 m2/s) which would have τp∝τE are evaluated and are found to have unacceptably high plasma temperatures and heat flux at the plate. Ash removal rates are still acceptable. A plasma recylce coefficient (at the divertor plate) of R=0.965 reduces the particle throughput by a factor of 2.8 below the case without recycle. (orig.)