Accurate predictions of hydrogen isotope/tritium inventory in tungsten (W), used as a plasma-facing material in fusion reactors, can reduce the uncertainty associated with the self-sustaining fuel cycle. It is well-established that displacement damage generally enhances deuterium (D) retention in W, whereas helium (He) typically reduces it. However, the synergistic interaction between these two factors on D retention in W remains poorly understood. This study investigates the combined influence of displacement damage and plasma-implanted He on D retention in W, with focus on their dependence on D-induced blistering. High-energy (3.5 MeV) Fe13+ irradiations were conducted at 300 K to introduce displacement damage (0.1 dpa) in W. Low-energy (60 eV) He plasma exposure was then carried out at 600 K to generate a He-rich layer at the near surface of both pristine and Fe-irradiated samples. Subsequently, the samples were exposed to D plasma at 500 K, with the ion energy set to 38 eV. The results show that displacement damage increases D retention at low fluences (5 × 1024–1 × 1025 D m−2), but slightly decreases retention at higher fluences (3 × 1025–5 × 1025 D m−2). The impact of He on D retention in W is competitive, depending on the level of irradiation damage. In cases with minimal D-induced blistering (area ratio <13%), the trapping effect dominates, with He-induced defects acting as strong D traps, leading to increased D retention. However, in highly damaged W, where high-density defects are induced by displacement damage or severe surface blistering (area ratio >33%), the diffusion barrier effect of He-rich layer outweighs the trapping effect, leading to decreased D retention. The combined effect of displacement damage and He increases D retention at low D fluences and decreases it at high D fluences, with the magnitude of these changes deviating from a simple linear addition of their individual effects, indicating a complex, non-linear interaction.
This study investigates how radiation damage and helium affect the storage of deuterium, a hydrogen isotope, in tungsten used in fusion reactors. It shows that radiation damage increases deuterium retention at low levels but decreases it at high levels, while helium can have both trapping and diffusion barrier effects depending on the damage level.