Synergistic Effect of He and H on the Surface Swelling of Ion-implanted Ti/Ta-added Reduced Activation Ferritic/Martensitic Steel for Fusion Reactors

Surface swelling caused by He implantation was studied for newly-developed Ti/Ta-added reduced-activation ferritic/martensitic (RAFM) steels. Post-implantation annealing at 623 K for 2 h of He-implanted RAFM-steel samples led to surface-step formation because of surface swelling induced by He bubbles formed inside the samples. Pre-implantation of a small number of H ions was found to cause an increase in the surface-step height, which was not expected. A possible mechanism for this synergistic effect of pre-implanted H is proposed.