Helium behaviour and vacancy defect distribution in helium implanted tungsten

Influence of MeV helium implantation on deuterium retention in self-ion implanted tungsten

“…For our implantation energy range it was reported by other authors before that up to 2000 K no He desorption was observed [8].…”

“…It has to be mentioned though that in contrast to the He particles from the plasma, which can not penetrate deeper into the material, the neutrons are able to penetrate -and cause He production, in the bulk material. The behavior of He introduced into the bulk has for example been investigated by Ullmaier and Chernikov [6,7] and recently by Debelle et al [8,9]. He was in all cases introduced at ~ MeV energies, the authors focused on the He behavior and trapping in tungsten.…”

“…Recent work [8] assumes He trapping in vacancy complexes which may cluster to larger structures as gas filled bubbles under thermal treatment. In this work we continued the previous studies [5] of hydrogen retention in radiation damaged tungsten and focused on the influence of bulk He introduced into the damaged zone on hydrogen retention.…”

Positron annihilation studies on the nature and thermal behaviour of irradiation induced defects in tungsten

“…Note that positrons do not probe the stopping zone of the 800 keV 3 He ions but only the track region (TR) between the surface and the cascades region (CR). Moreover it has already been shown [6] that there is no diffusion of implanted 3 He from CR to TR as a consequence of thermal annealing up to 1773 K. Positron Annihilation Lifetime Spectroscopy (PALS) was performed in the track region of 800 keV 3 He with the Pulsed Low Energy Positron beam System [7,8] (PLEPS) installed on the NEutron-induced POsitron source MUniCh [9] (NEPOMUC). The time resolution (FWHM) was 280 ps and the count rate was ~10…”

Effect of the displacement damage from argon ion irradiation on the synergistic effect of helium–hydrogen in tungsten

“…Iwakiri et al [20] proved that the formation of helium blisters at high fluence mainly depended on irradiation temperature, e.g., at elevated temperatures. Vacancies created by helium ion irradiation distributed along the running path of the helium ions, and vacancy concentration varied as the irradiating fluence [21]. Vacancies migrated and merged by means of irradiation heat, and formed defects such as dislocation loops and voids.…”