| Deuterium and Helium trapping in polycrystal tungsten under D-only, He-only, sequential, and simultaneous implantation was studied as a function of He fluence and implantation temperature. Deuterium implanted at 300K gets trapped at surface sites and extended defects. No deuterium was trapped in 700K implantations. Implanted helium was trapped within 30nm of the surface. It is suggested that He trapping occurs via the formation of He clusters, He vacancy complexes, and He bubbles from He self-trapping, and punching out of self-interstitial atoms (SIAs). In sequential implantations at 300K, He and D de-trap each other and re-trap at different configurations; at 700K, helium re-traps at the same configuration but at a much reduced amount. In simultaneous implantations, He mitigates D diffusion, and D limits He trapping; D may enhance He trapping at vacancy complexes. No enhanced D retention was observed, and no D was trapped at 700K simultaneous implantations. |
