Deuterium distribution and behavior of blisters in pre-damaged and undamaged tungsten

Tungsten (W), as a plasma-facing material, is subjected to high fluence plasma, resulting in both radiation damage and deuterium (D) retention. This study explores the blistering behavior and D supersaturated layers in both pre-damaged and undamaged W samples. To achieve a uniform damage profile similar to neutron irradiation, carbon (C) ions with multiple energies and angles were employed. The samples were further irradiated with low-energy D ions under two fluences at temperatures from ~ 380 to 640 K. Using various experimental techniques, we found that pre-damaged W samples can effectively suppress the formation of blistering and lower the threshold temperature at which the surface remains free of blistering. We also observed the prominent D supersaturated peaks within the depth of 20 nm in both pre-damaged and undamaged W. Furthermore, a close correlation between blistering and the D supersaturation was investigated. The results suggest that neutron irradiation in the fusion reactors could increase the critical D concentration for blistering, while a greater depth of damage facilitated the inward diffusion of D, thereby reducing the D concentration gradient and alleviating surface blistering.