Study on the interaction between He and defects induced by He-ion irradiation in W and W5Re alloy

Abstract To investigate the interaction between He atom and irradiation-induced defects in W and W5Re, multiple energetic He ions with damage dose ranging from 0.84 dpa to 1.63 dpa were selected in the present study to implant into W and W5Re samples. Doppler broadening spectroscopy (DBS) and coincidence Doppler broaden spectroscopy (CDB) based on slow positron beam and synchrotron X-ray diffraction technology were employed in the current work. Under the same dose (≤ 1 × 1021 ions m−2) irradiation at room temperature, the depth distribution of vacancy-type defects in W and W5Re is similar. With the increase of irradiation dose, the vacancy-type defects in W continue to grow through absorbing and merging. However, Re atoms are more likely to hinder this growth mechanism, leading to an accumulation of high density but small size vacancy-type defects in W5Re. The HenVm complexes in W continuously attract the mobile interstitial He atom and then induce the trap mutation in the implanted region. Micro-voids and large He bubbles (∼ μm) exceed the recognition of positron. Re atoms has strong the attraction to vacancies and positron affinity. The possible compound of Re and HenVm complexes makes it easier for positron to characterize the He-related and Re-related information around the defect sites. The lattice swelling is similar for the W and W5Re because the structure of HenVm cluster or He bubble can destroy the lattice periodicity and increase the lattice stress in the implanted region.