Deuterium retention in single crystal tungsten

The retention of deuterium in single crystal tungsten (SCW) has been measured at 300 and 500 K, as a function of incident ion fluence over the range 1021–1024 D+/m2. Irradiation of SCW with 1.5 keV D3+ ions at 300 K leads to saturation at a much lower incident fluence than seen in polycrystalline tungsten (PCW), but with the same levels of D retention at saturation, ≈5×1020 D/m2. Implantations at 500 K reached saturation at a very low incident fluence, below 1021 D+/m2, with the amount of D retained at saturation ≈1.5×1020 D/m2. This level is 3–4 times lower than the saturation value for 300 K implantation of the same single crystal of tungsten. Deuterium depth profile analysis by secondary ion mass spectrometry (SIMS) shows D trapping primarily within the 500 eV D+ ion implantation range for both 300 and 500 K profiles. SIMS also revealed that the depth profiles for oxygen and deuterium were similar. When the tungsten was annealed at 500 K for 1 h after implantation at 500 K, SIMS indicated that the deuterium retention decreased by an order of magnitude.