TDS Investigation of the Influence of Helium on Hydrogen Isotope Exchange in Tungsten at Sequential Exposures to Deuterium and Helium-Protium Plasmas

In the present work hydrogen isotopes exchange in recrystallized tungsten was investigated after sequential exposures to low energy deuterium (D) and helium-seeded protium (He-seeded H) plasmas at sample temperatures of 403 and 533 K. The total amount of deuterium retained in the recrystallized tungsten was measured by termodesorption spectroscopy (TDS). The results were compared with the amounts of deuterium retained in the top 8 μm layer measured by the D(3He, p)4He nuclear reaction (NRA). It was found that deuterium mainly accumulates in a relatively thin surface layer (10-20 microns) at Texp = 403 K and a thicker layer at Texp = 533 K. A significant part of the deuterium retained in tungsten after primary D plasma exposure was released during sequential exposure to a protium plasma. However, seeding of He ions into the H plasma reduces the amount of released deuterium. Deuterium depletion strongly depends on the temperature of the sample.