Power Balance Investigation in Long-Pulse High-Performance Discharges with ITER-like Tungsten Divertor on EAST

The Experimental Advanced Superconducting Tokamak (EAST) research program concentrates on demonstrating steady-state high-performance H-mode operations with ITER-like tungsten divertor. Calorimetry was applied to actively water-cool the plasma facing components (PFCs) by increasing the water temperature for power balance investigation. Considering the energy balance of EAST long-pulse high-performance discharges with upper single null (USN) con?guration, thus far, approximately 78% of the injected energy could be accounted for. The method of estimation of heat flux on upper tungsten divertor target with a high time- and spatial-resolved infrared camera has been developed, and the sum of its heat load was found to be significantly consistent with that measured through calorimetry. The record longest steady-state H-mode plasma #73 999 was sustained for up to 101.2 s with net injected energy exceeding similar to 0.25 GJ in the USN configuration. Heat load analysis of this discharge using calorimetric measurement indicates that the modification of heat load distribution was observed and this was induced by a slight change in the magnetic configuration. Not all temperature increments in the five cooling water modules reached the saturated state for the 100 s level discharge, which means that 100 s timescales are insufficient as compared to the thermal transport timescale in the targeted PFCs. The heat load on the tungsten divertor targets is not evenly distributed with the ratio of similar to 2 in favour of the outer divertor.The experimental results and analysis of the physics involved in these USN configuration discharges are reported and discussed.