Result and discussion on the evolution of in-situ leading edge-induced melting on W divertor targets in EAST

Abstract The application of ITER-like W/Cu plasma facing components in current tokamaks is of special concern by ITER. In 2014, ASIPP successfully upgraded upper divertor of EAST to a full tungsten component structure through independent research and development, and adopted W/Cu monoblocks as the divertor targets for high power exhaust. During recent plasma operations, the leading edge-induced thermal loading caused the melting of W/Cu monoblocks and the melt layer occur motion mainly by electromagnetic force. It was found that the melt layer migrated to neighboring W/Cu monoblocks, solidified into a hill structure or filled the gap between W/Cu monoblocks. Meanwhile, the large sized chamfering structure was residual on the molten W/Cu monoblocks. The thermal analysis shows that the W /Cu monoblcoks with large sized chamfering structure has an increased heat load capacity and it is not prone to secondary melting with the same heat flux in subsequent operations. And the removed melted layer may gradually migrate far away from the strike point and eventually solidify into stable structures. The improvement of the heat load capacity of the molten W/Cu monoblock and the melt-layer motion may be a benign situation, thereby achieving a healing effect to avoid further deterioration of plasma facing components. The evolution behavior of such leading edge-induced melting on ITER-like W/Cu monoblocks in EAST provides significant reference for ITER.