Retention of Deuterium in the Surface Layers of Tungsten Preliminarily Irradiated with Helium Ions

The retention of deuterium in tungsten preliminarily irradiated with helium ions is investigated by means of thermal desorption spectroscopy (TDS). Preliminary irradiation is performed with a He + ion beam having an energy of 3 keV and fluence ranging in the interval 10 19 –10 21 He m −2 , in order to produce a defect structure typical of different degrees of damage. The specimens are then irradiated with D_3^ + ions having an energy of 2 keV and a weak fluence of 10 19 D m −2 , with subsequent TDS analysis to characterize the interaction between deuterium and helium-induced defects. It is shown that an increase in the deuterium retention is observed as soon as irradiation with the minimal fluence of helium ions, but it falls to the background level at fluences above 5 × 10 21 He m −2 .