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

Abstract

Depth profiling of light elements in the surface layer of solids by means of ERDA is limited to depths smaller than about 1 μm. In order to measure the distributions of hydrogen isotopes in larger depth regions such as needed for the divertor tiles from the tokamak fusion experiment ASDEX-Upgrade in the Max-Planck-Institut für Plasmaphysik, samples cut from the divertor tiles (about 0.6 mm tungsten on carbon) were bevelled at different angles by mechanical cutting and polishing or by ion beam slope cutting. The mechanically cut slopes were additionally cleaned and polished by oblique incidence ion beam sputtering with target rotation to avoid anisotropic etching.The surface composition along the slope was measured by ERDA with the Rossendorf Nuclear Microprobe. A 10 MeV Si ion beam was focused to about 3 μm and scanned linearly across the slope. The hydrogen and deuterium recoils were detected by a surface barrier detector at a recoil angle of 30° after passing through a 10 μm thick Al foil for stopping scattered primary ions. Deuterium was found at depths up to about 25 μm and hydrogen up to 750 μm on the samples analysed.