Neutral gas temperature and densities in the divertor region and pump duct of ITER

A 2-D Monte-Carlo simulation of the neutral atom densities in the divertor, divertor throat and pump duct of ITER was made using the DEGAS code. Plasma conditions in the scrape-off layer and region near the separatrix were modeled using the B2 plasma transport code. Wall reflection coefficients including the effect of realistic surface roughness were determined by using the fractal TRIM code. The DEGAS and B2 coupling was iterated until a consistent recycling was predicted. Results were obtained for a helium and a deuterium/tritium mixture on seven different ITER divertor throat geometries. Recycling, pumping efficiency ratios, temperatures and densities vary markedly. For example, the helium to hydrogen pumping ratio can show a factor of 2.67 ± 0.53 enhancement over the ratio of helium to hydrogen incident on the divertor plate. If the helium flux profile on the divertor plate is moved outward by 20 cm with respect to the D/T flux profile for this particular geometry, the enhancement increases to 4.36 ± 0.90.