Damage dose dependence of deuterium retention in high-temperature self-ion irradiated tungsten
Recrystallized tungsten (W) samples were irradiated by 20 MeV self-ions at 1350 K to peak damage doses in the range of 0.001-2.3 dpa. The irradiation-induced defects were then decorated with deuterium (D) by a gentle D plasma exposure ($<5$ eV/D, $5.6 \times 10^{19}$ $\text{D} / (\text{m}^2 \text{s})$) at 370 K. The D depth profiles in the samples were measured using $\rm D(^{3}He,p)α$ nuclear reaction analysis. The maximum trapped D concentration evolves differently with the damage dose compared with the previously studied irradiations at 290 K and 800 K. At the damage doses below 0.1 dpa, the D concentrations are lower than those after the irradiation at 800 K. At higher damage doses, the D concentrations exceed the 800 K values and reach 1.7 at.% at 2.3 dpa, showing no clear tendency towards saturation. Transmission electron microscopy revealed the presence of nm-sized voids in the samples irradiated at 1350 K, in contrast to the ones irradiated at 290 K and 800 K. Thermal desorption spectroscopy (TDS) indicates that the dominant D trapping sites are different compared to the irradiations at 290 K and 800 K. Reaction-diffusion simulations show that the TDS spectra can be described by assuming that D is trapped as $\rm D_2$ gas in the void volume and as D atoms at the void surface.