Impact of detailed radiation transport on volume recombination

Recently both the Alcator C-Mod and DIII-D tokamaks observed significant re combination of major ion species in the divertor region during detachment. For sufficiently low temperatures the mixture of neutral atoms and ions can be optically thick to line radiation. The optical depth of the recombined region to Ly, radiation can be very large and opacity effects and radiation trapping can dramatically change the heat flux to the divertor walls. This paper presents an analysis of the effect of line radiation on volume recom bination using CRETIN, a multi-dimensional, non-local thermodynamic equilib rium (NLTE) simulation code that includes the atomic kinetics and radiative transport processes necessary to model this complex environment. (C) 1999 Elsevier Science B.V. All rights reserved.