Abstract
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 1×1015-1017 He /cm2. 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.
Highlights
Eurofer97 is a Reduced Activation Ferritic/Martensitic (RAFM) steel used as reference structural material for future fusion reactors
He implantations have been performed in Eurofer97 steel with energies of 500 keV and 2 MeV and doses in the range of 1x1015 -1017 He/cm2
By annealing the samples up to 1500 K it is possible to observe an initial decrease of the S-parameter, associated with the annealing of vacancies and vacancy clusters, followed by a significant increase of this value due to growth of the helium-vacancy clusters
Summary
Eurofer97 is a Reduced Activation Ferritic/Martensitic (RAFM) steel used as reference structural material for future fusion reactors. Low dose (1x1015 – 1x1016 He/cm2) 500 keV and 2 MeV room temperature helium implantations were performed at CEMHTI-CNRS Orléans, France. In the case of the 2 MeV energy implanted samples, the dose range was extended to 1x1017 He/cm2.
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