Hydrogen and helium trapping in tungsten under simultaneous irradiations

Hydrogen and helium trapping in polycrystalline tungsten under simultaneous He + -H + and He + -D + irradiation was measured by thermal desorption spectroscopy. At 300 K: He retention and release are affected very little by the presence of H, closely following He + -only irradiations; He is trapped within ∼30 nm of the surface. D retention is similar to D + -only levels but the presence of He enhances D trapping in the near surface, while limiting D diffusion into the bulk; D is trapped within ∼30-35 nm of the surface possibly at interstitial sites surrounding He-vacancy defects. At 700 K: He retention and release are again similar to He + -only cases; He is trapped within ∼30 nm of the surface while no D is observed.