COMPARISON OF A SIMPLE RECYCLING MODEL AND A COMPLEX RECYCLING MODEL IN EDGE PLASMA TRANSPORT CALCULATIONS

The results of a significantly more efficient model (molecular model) for computing particle and energy sources from recycling in edge plasma transport codes, such as b2, are compared with results from more detailed calculations using the b2 code coupled with the neutral transport code, DEGAS. The molecular model considers the reflux both of cold molecules and of energetic backscattered atomic neutrals from the divertor target plates and has been implemented to function internally within the b2 code. The molecular model calculations are shown to be in reasonable agreement with more detailed calculations done with the coupled b2/DEGAS codes for seven cases typical of conditions in the scrape-off layer of the Doublet III (DIII-D) tokamak. Because the molecular model is a far less expensive computational tool, it represents a significant improvement over the existing (coupled) edge transport recycling model. Thus, it may find wider application in design studies for future devices, such as the International Thermonuclear Experimental Reactor (ITER).