The effect of inert gas pre-irradiation on the retention of deuterium in tungsten: A TMAP investigation combined with first-principles method

Thermal desorption of deuterium in tungsten pre-irradiated with the inert gas (helium, neon, argon) is modelled by TMAP (Tritium Migration & Analysis Program). Each TMAP model incorporates three activation energies linked with three types of traps respectively. First-principles method is performed to calculate the activation energies of deuterium detrapping from different kinds of defects. By comparing the activation energies modelled in TMAP with that obtained from first-principles method, the types of traps are determined. The pre-irradiation of helium can suppress the deuterium retention in vacancy clusters. Neon and argon pre-irradiation suppresses deuterium retention in mono-vacancies due to decreasing the number of mono-vacancies caused by the occupation of the inert gas atoms into mono-vacancies. The pre-irradiation of neon can facilitate deuterium retention in vacancy clusters through generating vacancy clusters during the injection process. Argon pre-irradiation facilitates deuterium retention mainly through generating voids, which are of a larger scale than vacancy clusters and can serve as effective traps.