Helium retention behavior in simultaneously He+-H2+ irradiated tungsten

The purpose of this study is to elucidate helium (He) retention behavior in tungsten (W) under simultaneous He and hydrogen (H) irradiation. Polycrystalline-W was irradiated by He⁺ and H₂⁺ simultaneously with the energy of 1.0 keV and 3.0 keV. He⁺ fluences were (0.5, 1.0, 10) × 10²¹ He⁺ m^-2 and H₂⁺ fluence was 1.0 × 10²² H⁺ m^-2,respectively. After irradiation, He desorption behavior was investigated by high temperature thermal desorption spectroscopy (HT-TDS) in the temperature range of R.T.-1773 K. Micro-structure changes of W after irradiation were observed by TEM. It was found that simultaneous irradiation with different H₂⁺ energy significantly changed He retention behavior. 1.0 keV H₂⁺ suppressed the He bubble growth and no bubbles can be observed at room temperature. On the other hand, 3.0 keV H₂⁺ facilitated the formation of He bubbles and increased the He retention due to the additional damage introduction by energetic H₂⁺.