Comparative Modeling of Particle Deposition and Impurity Generation from Large-Area Inner Walls in Tore Supra, TFTR, JET and DIII-D

The use of the large-area tokamak inner wall to reduce peak heat fluxes has been proposed as a potential alternative to the use of divertors. This paper uses detailed modeling of inner wall processes on several existing tokamaks to understand the differences among them and the cause for deviations from ideal performance. The present analysis shows that the typical deficiency in overall performance for inner-wall limited plasmas to date is largely sui generis: that is, each of the cases has unique performance-limiting features, rather than representing an intractable general problem