Deuterium trapping at vacancy clusters in electron/neutron-irradiated tungsten studied by positron annihilation spectroscopy

Deuterium trapping at irradiation-induced defects in tungsten, a candidate material for plasma facing components in fusion reactors, was revealed by positron annihilation spectroscopy. Pure tungsten was electron-irradiated (8.5 MeV at similar to 373 K and to a dose of similar to 1 x 10(-3) dpa) or neutron-irradiated (at 573 K to a dose of similar to 0.3 dpa), followed by post-irradiation annealing at 573 K for 100 h in deuterium gas of similar to 0.1 MPa. In both cases of electron- or neutron-irradiation, vacancy clusters were found by positron lifetime measurements. In addition, positron annihilation with deuterium electrons was demonstrated by coincidence Doppler broadening measurements, directly indicating deuterium trapping at vacancy-type defects. This is expected to cause significant increase in deuterium retention in irradiated-tungsten. (c) 2017 Elsevier B.V. All rights reserved.