Damage evolution and its impact of the W/Cu flat-type component for divertor target in EAST

Abstract W/Cu flat-type components are promising candidates for plasma-facing components in future fusion devices due to their flexible and efficient heat sink design. They are expected to be used in the inner/outer Reflector plates and Dome of ITER. To investigate their damage behaviors, a high-resolution infrared camera was employed to monitor the damaged C4 W/Cu flat-type component with a hypervapotron heat sink, located in the outer horizontal target (OHT) of the EAST lower divertor. The results show that the formation of W protrusions (‘Hills’) connects the early crack initiation stage with the final W exfoliation. To prevent further damage progression, it is recommended that for tokamaks, the damaged area be located two decay lengths away from the strike point—this distance is sufficient to guarantee safety. In such a scenario, if the damage lies within the private flux region, the parallel heat flux will be reduced to nearly zero. Although thermal performance degraded over time, the damaged OHT component was still able to maintain an approximate thermal equilibrium during each discharge, and no abnormal W impurity levels were observed. Linear fitting analysis estimates a total lifetime of approximately 3257 ± 277 shots, with a plasma stored energy of 298 ± 20 kJ corresponding to the onset of W melting in the surface protrusions. These findings shed light on the damage behavior of W/Cu flat-type components, provide key support for the development and validation of finite element analysis models, and offer practical guidance for the design and evaluation of ITER-like W/Cu flat-type components.