He bubble growth in a martensitic steel for fusion reactors

Small-angle neutron scattering (SANS) has been used to study the growth of He bubbles in a martensitic steel for fusion reactors. The samples had been homogeneously implanted at 523 K with 400 appm He, then subjected to thermal annealing at temperatures up to 1248 K. Suitable reference samples, submitted solely to identical thermal treatments, were also measured. The He bubble volume distribution functions obtained show that a dense population of bubbles 10 Angstrom or less in size is accompanied by a secondary distribution of bubbles one order of magnitude larger, as expected after post-implantation annealing. These results are discussed in terms of background subtraction and available Q-range.