Effect of Damage Introduction and He Existence on D Retention in Tungsten by High Flux D Plasma Exposure

Both of radiation-induced damages and helium (He) existence effects on deuterium (D) retention in tungsten (W) by D plasma exposure were evaluated using high flux divertor plasma exposure device, called Compact Divertor Plasma Simulator (CDPS). The results were compared with 3 keV D ₂ ⁺ implanted W with low flux and fluence. The thermal desorption spectra were consisted of three desorption stages at 400, 600, 780 K. Comparing to the undamaged W, the D desorption stages were shifted towards higher temperature side and the values of D retention increased. It can be said that the formation of stable trapping sites by damage introduction enhances the D trapping in the damaged W. For He ⁺ irradiation, D desorption at lower temperature was enhanced, due to the formation of dense dislocation loops. In case of sequential Fe ²⁺ and He ⁺ implantation, D desorption at higher temperature was reduced, comparing to that for only Fe ²⁺ damaged W. These facts show that the accumulation of He near surface region reduces D diffusion toward bulk, leading to the reduction of D trapping by voids.