Effects of divertor geometry and pumping on plasma performance on DIII-D

摘要

This paper reports the status of an ongoing investigation to discern the influence of the divertor and plasma geometry on the confinement of both ELM-free and ELMing discharges in DIII-D. The ultimate goal is to achieve a high-performance core plasma which coexists with an advanced divertor plasma. The divertor plasma must reduce the heat flux to acceptable levels; the current technique disperses the heat flux over a wide area by radiation (a radiative divertor). To date, we have obtained our best performance in double-null (DN) high-triangularity (delta approximately 0.8) ELM-free discharges. The overall mission of the Radiative Divertor Project (RDP) is to install a fully pumped and baffled high-delta DN divertor. To date, however, both the DIII-D divertor diagnostics and pump were optimized for lower single-null (LSN) low-delta (delta approximately 0.4) plasmas, so much of the divertor physics has been performed in LSN. As part of the first phase of the RDP, we have installed a new high-delta USN divertor baffle and pump. Both divertor and core parameters are discussed in each case.