Similarities in divertor erosion/redeposition and deuterium retention patterns between the tokamaks ASDEX Upgrade, DIII-D and JET

The similar poloidal patterns of divertor erosion and redeposition of the ASDEX Upgrade, DIII-D and JET tokamaks are examined by comparing hydrogen isotope retention at the surfaces of divertor tiles. The outer divertor strike point undergoes net erosion. The inner divertor is a region of net redeposition, with deuterium co-deposition rates similar to 20 mu g m(2) s(-1) for all three devices; despite their differences in geometry, size and plasma facing materials. This extrapolates to an unacceptably high tritium retention rate in a DT burning steady state tokamak.