SIMULATION OF ULTRAHIGH RECYCLING DIVERTORS FOR TOKAMAKS

The handling of power carried by the charged particles into the scrape-off layer of a tokamak reactor remains a major obstacle for its continuous and reliable operation. Ways of reducing this power through radiation have been studied numerically using fluid models for both the plasma and neutral gas. A new model for the combined plasma and neutral gas transport in two dimensions capable of simultaneously representing regions of fully ionized plasma, partially ionized plasma, and pure neutral gas has been assembled and implemented in the PLANET code [J. Nucl Mat. 196/198, 883 (1992)]. Divertor plasma temperatures of just below 1 eV have been achieved in a pure hydrogen plasma, resulting in an ionization-free region together with ionization and recombination fronts detached from the material walls. In this regime energy reaches the walls almost exclusively in the form of radiation which, in principle, solves the divertor heat load problems.