Multiple-beam irradiation effects in electron-beam-welded F82H joint

Electron-beam-welded reduced-activation ferritic/martensitic steel F82H, which is one of prime candidate materials for experimental fusion reactors, have been irradiated by electron and helium ion beams using a High Voltage Electron Microscope (HVEM) as the experimental evaluation of the modeling and simulations. Growth rate and saturated number density of dislocation loops have been measured to calculate the migration energies of point defects. Electron irradiation experiment indicated that net migration energy of vacancy in the welded metal of F82H tended to be lower compared to that in base metal, which could be relating to difference of carbon concentration in matrix. In the case of dual beam (electron and helium) irradiation, net migration energies of vacancy were slightly higher than that in electron beam irradiation. This result indicates that vacancy would be trapped by implanted helium due to their strong interaction and appeared to have higher migration energy.