SMuK 2023 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 8: Plasma Wall Interaction I/HEPP IV
P 8.2: Vortrag
Dienstag, 21. März 2023, 17:30–17:55, CHE/0091
Early stages of He cluster formation in pristine and displacement-damaged tungsten — •Annemarie Kärcher1,2, Vassily V. Burwitz2, Thomas Schwarz-Selinger1, Lucian Mathes2, Wolfgang Jacob1, 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, there are no experiments that could clarify the process of early He cluster formation. 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 samples were exposed to a low-temperature He plasma at fluxes between 1017 and 1019 He/m2s and various fluences using implantation energies of 50 and 100 eV. The samples were measured by positron annihilation spectroscopy for defect characterization and elastic recoil detection analysis (ERDA) for quantification of the He retention. For the depth distribution of He, a novel method was applied: thin surface layers of the sample were subsequently removed followed by ERDA measurements in between the erosion steps. The removal was performed by by electrochemical oxidation and dissolution of the oxide in NaOH. The results show a higher He retention in pre-damaged samples by factors up to 10 and a deeper reaching distribution of He in undamaged samples.