Depth distribution of deuterium in single- and polycrystalline tungsten up to depths of several micrometers

Depth profiles of deuterium trapped in W single crystals and polycrystalline W irradiated with 200 eV D ions at 300–323 K have been measured up to a depth of 7 μm using the D(3He,p)4He nuclear reaction in a resonance-like technique. The proton yield as a function of incident 3He energy was measured and the D depth profile was obtained by deconvolution of the measured proton yields using the program simnra. The depth at which deuterium is retained can be tentatively divided into three zones: (i) the near-surface layer (up to a depth of ∼0.2 μm), (ii) the sub-surface layer (from ∼0.5 to ∼2 μm), and (iii) the bulk (>5 μm). Low-energy D ion irradiation modifies the W structure to depths of up to about 5 μm, both for W single crystals and polycrystalline W. Up to this depth trapping sites are created at a fluence of 5 × 1022/m2 for the retention of deuterium at about 0.1 at.%.