Helium isotope exchange in tungsten irradiated sequentially with 4He and 3He ions

Helium (He) isotope exchange in tungsten (W) during sequential irradiation by 3 keV 4He and 3He ions at room (RT) and elevated temperatures (70 0-120 0 K) was investigated. The total He fluence was in the range of 5 x 10 21 -1.8 x 10 22 He/m2 to provide a saturation of the surface layer. The amount of He re-tained in W after irradiation was measured using in-situ (up to 1500 K) and ex-situ (up to 2500 K) thermal desorption spectroscopy (TDS). Air exposure influenced TDS spectra, but clear were no notice-able differences between 3He and 4He TDS spectra after single irradiation. Subsequent irradiation with different He isotopes demonstrated a very efficient isotope exchange already at room temperature. The substitution of He atoms goes even faster with increasing irradiation temperature. Mechanisms of ob-served processes are discussed on the base of a simple model.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The study investigated helium isotope exchange in tungsten during sequential irradiation by 3 keV 4He and 3He ions at different temperatures. The retention of helium in tungsten was measured using thermal desorption spectroscopy. The results showed efficient isotope exchange even at room temperature, with a faster substitution rate at higher irradiation temperatures. The mechanisms of the observed processes were discussed based on a simple model.