Predictive modeling of EAST divertor target power loading with varying chemical sputtering conditions

The Experimental Advanced Superconducting Tokamak (EAST) is being built in China to achieve high power and long pulse operation for studies of reactor-relevant issues under steady-state conditions. A major concern for EAST is the power handling capability of the divertor target plates, which is a critical issue for future high-powered steady-state tokamaks, such as ITER. Detailed modeling using B2/EIRENE code package and the most recent chemical sputtering data shows that the presence of strong chemical sputtering at the main chamber wall leads to strong carbon radiation in the periphery of the confined plasma, significantly reducing the heat fluxes to the target plates and facilitating plasma detachment at a lower density desired for lower hybrid current drive in EAST, with only a slight increase in Z_eff at the edge. The target heat load can be further reduced by operating with a double-null divertor configuration, which also leads to a significant reduction in the edge Z_eff. However, the code predicts that the double-null operation would result in a strong divertor asymmetry in target power loading, favoring the outside targets.