Surface Cracking Behaviors of Ultra-Fine Grained Tungsten Under Edge Plasma Loading in the HT-7 Tokamak

Tests of the candidate plasma facing materials (PFMs) used in experimental fu- sion devices are essential due to the direct in°uence of in-situ plasma loading. A type of ultra- fine grained (UFG) tungsten sintered by resistance sintering under ultra-high pressure (RSUHP) method has been exposed in the edge plasma of the HT-7 tokamak to investigate its performance under plasma loading. Under cyclic edge plasma loading, the UFG tungsten develops both macro and micro cracks. The macro cracks are attributed to the low temperature brittleness of the tung- sten material itself, while the micro cracks are generated from local intense power flux deposition.