Finite element modelling D-alpha radiation and impurity transport in tdev

Particle and energy transport are modelled in TdeV using the multispecies f inite element simulation code TOPO. For every charged species, equations ar e solved for the conservation of particles, parallel momentum, and energy. For neutral species, equations are solved for the conservation of particles and energy. For simplicity, all neutral fluxes are assumed to be diffusive . The transport equations are discretised with finite elements on a triangu lar unstructured mesh. This allows a realistic description of the TdeV dive rtor geometry, with segmented divertor plates arbitrarily oriented with res pect to the local flux surfaces. The use of an unstructured mesh also allow s local mesh refinement in the vicinity of the X point, and at selected loc ations near the divertor plates. Comparisons between simulated and experime ntally measured density profiles are presented. Detailed comparisons betwee n calculated and measured D-alpha specific intensities are also presented. Finally, an assessment is made of the single ion temperature approximation commonly made in other edge transport models. (C) 1999 Elsevier Science B.V . All rights reserved.