Dynamical concentration and static retention of deuterium in tungsten foil studied by low energy D(d,p)T reaction and elastic recoil detection

The deposition behavior of hydrogen isotopes in tungsten is essential in fusion material research. A tungsten (W) foil was pre-implanted by deuterium ions (D3+) with an energy of 20 keV/D and flux of 3.0 × 1014 D/(cm2 s) at room temperature until saturation state was confirmed by the proton yield of D(d,p)T reaction. The changes of D-concentration in surface layer have been obtained by D-D reaction analysis with low flux (0.6 μA) and high energy (75 keV) D+ beam at several storage time after the implantation terminated. Furthermore, the static D-retention in this sample was also measured by elastic recoil detection analysis one year later. The saturated value of nD/nW in surface layer of W foil is (42 ± 3) at.% at fluence of 1.5 × 1018 D/cm2. After beam stopped, the D-concentration decreased, and a static D-retention of about 3 at.% was found one year later. These results showed that more than 92% of deuterium precipitated in tungsten metal at saturated state was unstable.