Characterization of helium ion implanted reduced activation ferritic/martensitic steel with positron annihilation and helium thermal desorption methods

Low energy 3 keV He implantations were carried out on Eurofer97 steel to reproduce the radiation damage induced by the creation and thermal evolution of the defects and the behavior of the implanted He is studied with the positron annihilation Doppler broadening technique (PADB) and thermal desorption spectroscopy (TDS). PADB results show that annealing at 1200 K for 1 h removes the majority of pre existing defects. The 3 keV He+ implantations were carried out in two sets of samples – ‘surface polished’ and ‘annealed’ (1200 K, 1 h), up to doses of 1018–1019 He/cm2. The samples were implanted at temperatures of 375 K and 525 K. The preliminary TDS studies show that when implanting at 375 K, the majority of He is released at desorption temperatures below 1000 K and is likely to be related to trapping at vacancies and small He clusters. At 575 K, the larger part of the desorption takes place at higher (>1000 K) temperatures and is associated with the formation of larger He–vacancy clusters, such as bubbles or voids. The migration of He during implantation towards the bulk is observed as a decrease in Doppler broadening parameter at depths much deeper the He implantation range.