OEDGE modeling of the DIII-D double null [formula omitted] puffing experiment

Abstract

Unbalanced double null ELMy H-mode configurations in DIII-D are used to simulate the situation in ITER high triangularity, burning plasma magnetic equilibria, where the second X-point lies close to the top of the vacuum vessel, creating a secondary divertor region at the upper blanket modules. The measured plasma conditions in the outer secondary divertor closely duplicated those projected for ITER. 13CH4 was injected into the secondary outer divertor to simulate sputtering there. The majority of the 13C found was in the secondary outer divertor. This material migration pattern is radically different than that observed for main wall 13CH4 injections into single null configurations where the deposition is primarily at the inner divertor. The implications for tritium codeposition resulting from sputtering at the secondary divertor in ITER are significant since release of tritium from Be co-deposits at the main wall bake temperature for ITER, 240°C, is incomplete. The principal features of the measured 13C deposition pattern have been replicated by the OEDGE interpretive code.