Hydrogen and deuterium depth profiling in divertor tiles of a fusion experiment by micro-ERDA

Depth profiling of light elements in the surface layer of solids by means o f ERDA is limited to depths smaller than about 1 mu m. In order to measure the distributions of hydrogen isotopes in larger depth regions such as need ed for the divertor tiles from the tokamak fusion experiment ASDEX-Upgrade in the Max-Planck-Institut fur Plasmaphysik, samples cut from the divertor tiles (about 0.6 mm tungsten on carbon) were bevelled at different angles b y mechanical cutting and polishing or by ion beam slope cutting. The mechan ically cut slopes were additionally cleaned and polished by oblique inciden ce ion beam sputtering with target rotation to avoid anisotropic etching. The surface composition along the slope was measured by ERDA with the Rosse ndorf Nuclear Microprobe, A 10 MeV Si ion beam was focused to about 3 mu m and scanned linearly across the slope. The hydrogen and deuterium recoils w ere detected by a surface barrier detector at a recoil angle of 30 degrees after passing through a 10 mu m thick Al foil for stopping scattered primar y ions. Deuterium was found at depths up to about 25 mu m and hydrogen up t o 750 mu m on the samples analysed. (C) 1999 Elsevier Science B.V. All righ ts reserved.