Comparison of D retention for advanced plasma facing materials by D ion implantation

For the evaluation of hydrogen isotope retention behavior for advanced plasma facing materials like W-Ta, W-Mo alloys and K-doped W, D₂⁺ implantation with different incident energies of 1 keV and 3 keV was performed up to the fluence of 1x10²² D m⁻². Thereafter D retention behavior was evaluated by thermal desorption spectroscopy (TDS) up to the temperature of 1173 K. 6 MeV Fe²⁺ irradiation was also performed to introduce the irradiation damage up to the damage level of 1 dpa, followed by the evaluation of D retention. In addition, positron annihilation spectroscopy (PAS) was performed to clarify the density and size of irradiation defects among these advanced W materials. The HIDT (Hydrogen Isotopes Diffusion and Trapping) simulation was applied to evaluate the activation energies of D trapping and their trap densities based exclusively on D₂ desorption. The results showed that no large D retention enhancement was found for W alloys, but the D trap density with higher trap energy was reduced. In especially, the formation of large voids was refrained and D trapping by small trap energy like mono-vacancy was the major D trapping sites for K-doped W. For W-Mo and W-Ta, the addition of minor element would occupy the irradiation defects leading to the refrain of D trapping with stable D trap energy.