Bubble Formation in ITER-Grade Tungsten after Exposure to Stationary D/He Plasma and ELM-like Thermal Shocks

Plasma-facing materials (PFMs) in the ITER divertor will be exposed to severe conditions, including exposure transient heat loads from edge-localized modes (ELMs) and plasma particles neutrons. Tungsten is material chosen as PFM for divertor. In previous tests, bubble formation ITER-grade tungsten was detected when fusion relevant conditions. For this study, simultaneous ELM-like D/He (6%) linear device PSI-2. Bubble then investigated via SEM micrographs FIB cuts. It found that 100.000 laser pulses of 0.6 GWm−2 absorbed power density (Pabs), only small bubbles nanometer range were formed close surface. After increasing Pabs 0.8 1.0 GWm−2, size went up about 1 µm deeper below Increasing fluence had an even larger effect, more than doubling 2 diameter. When using deuterium-only plasma, samples showed no reduced cracking, showing such caused by helium plasma.