Dose effects in He implanted Eurofer97 steel

Reduced Activation Ferritic/Martensitic steels are being extensively studied because of their foreseen application in fusion reactors. To reproduce neutron irradiation conditions, Eurofer97 samples were implanted at room temperature with helium ions at energies of 500 keV and 2 MeV and doses of 1x10(15)-10(17) He/cm(2). The implantation induced defects were characterized by positron beam Doppler Broadening (DB). The samples were annealed in the range 300 - 1500 K, in 100 K steps. As the temperature increases, the annealing of vacancies and vacancy clusters is noticed and followed by the coalescence of HenVm clusters. At temperatures around 1200 K HeV pairs dissociate and bubbles are formed. Above 1300 K the helium release from bubbles is observed. The S-W graphs reveals that the samples have similar positron traps up to 1200 K. At 1200 K helium bubbles are noticed and the S, W pair shows a clearly distinct behaviour from the S, W values of vacancy type defects. As the temperature increases and helium is release, the S, W pairs shift towards the S,W's of vacancies.