Effects of dislocations on thermal helium desorption from nickel and iron

Helium atoms in metals have a strong tendency to accumulate at defects. Unfortunately, the experimental identification of the trapping sites of helium atoms is difficult. In this paper, the effects of dislocations on the trapping and desorption of helium atoms in nickel and iron were studied by thermal desorption spectroscopy. Defects were introduced in well-annealed high-purity metals by cold rolling. Positron annihilation spectroscopy was carried out to identify defects by measuring the positron lifetime before annihilation with various defects. The trapping and desorption of helium atoms at dislocations were investigated by implantation with low-energy He+ ions, both without irradiation damage (0.1 keV or 0.15 keV) and with irradiation damage (5.0 keV).