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P: Fachverband Plasmaphysik
P 9: Poster I
P 9.4: Poster
Dienstag, 29. März 2022, 16:00–17:30, P
Early stages of He cluster formation in tungsten — •Annemarie Kärcher1,2, Vassily V. Burwitz2, Thomas Schwarz-Selinger1, Wolfgang Jacob1, Lucian Mathes2, and Christoph Hugenschmidt2 — 1Max-Planck-Institut für Plasmaphysik, 85748 Garching, Germany — 2Technische Universität München, 85748 Garching, Germany
In future fusion reactors, tungsten as plasma-facing material will be subjected to intense fluxes of helium (He). While the consequences of high He fluxes on the surface properties of tungsten have already been thoroughly studied, the mechanisms behind the early stages of the He cluster formation are still unclear. To understand the initial steps of the interaction of He with W, especially the impact of pre-existing defects, annealed, polycrystalline W samples were irradiation-damaged to various damage levels. Then, these were exposed to a low-temperature He plasma at low fluxes and fluences using an implantation energy of 100 eV. These He-implanted samples were measured by Doppler-broadening positron annihilation spectroscopy for defect quantification and elastic recoil detection analysis (ERDA) for quantification of He retention. To obtain information about the depth distribution of He, thin layers of the sample surfaces have been removed and ERDA measurements have been repeated subsequently until the signal intensity dropped to the sensitivity limit. In the irradiation-damaged samples, the He penetration into larger depth is significantly reduced compared with the depth penetration in undamaged samples, while their overall He retention is higher.