Quantify typical trapping sites of deuterium in tungsten by sequential thermal desorption coupled with a dedicated numerical diffusion model

Pure tungsten (W) was irradiated by low-energy deuterium (D) at 335 and 500 K to investigate the effects of irradiation temperature on the concentration depth profiles (CDPs) of D-induced trapping sites and the retention behavior of D at these trapping sites. To quantify typical D trapping sites, a novel approach was developed by combining experimental and theoretical analysis, including the sequential constant temperature thermal desorption to fast release D from irradiated W, in-situ ion beam analysis to obtain CDPs of retained D after desorption, and a one-dimensional diffusion model to simulate the diffusion, trapping and detrapping of D during desorption. The approach was verified through the microstructural characterization of irradiated W. It was revealed that the retentions of D in both near-surface and sub-surface layers were larger at the lower irradiation temperature (335 K) because of a higher density of D-induced dislocations and cavities in the corresponding regions. Employing the approach, the releasing behavior of D at four typical trapping sites, i.e. dislocations, mono-vacancies, grain boundaries and cavities was quantitatively analyzed. The approach with the capability to quantify typical D trapping sites provides a powerful tool for understanding the retention mechanism of D in the damaged W.