SMuK 2023 – scientific programme

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P: Fachverband Plasmaphysik

P 8: Plasma Wall Interaction I/HEPP IV

P 8.3: Talk

Tuesday, March 21, 2023, 17:55–18:10, CHE/0091

Low Energy Ion Scattering investigation of dynamic surface segregation of chromium in the WCrY SMART material — •Pawel Bittner, Hans Rudolf Koslowski, Andrey Litnovsky, and Christian Linsmeier — Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung, 52425 Jülich,Germany

Self-passivating Metal Alloys with Reduced Thermo-oxidation (SMART) are promising candidates for the first wall of the DEMOnstration power plant (DEMO). These materials should feature an increased oxidation resistance during accidental conditions and tolerate plasma loading during regular operation of the power plant. In this work, the effects of segregation, diffusion and sputter erosion on the surface Cr concentration of a tungsten-chromium-yttrium SMART alloy (WCrY - 68 at% of W, 31 at% of Cr and 1 at% of Y) are studied with low energy ion scattering (LEIS) measurements at 800 K, 900 K and 1000 K and numerical simulations. The LEIS is operated with He⁺, Ne⁺ and Ar⁺ ions at 1 keV in sputter mode. The time resolved measurements show a build-up of Cr at the surface directly after increasing the temperature, followed by a slow decrease with evolving time. A comparison to a discrete layer model, in which the segregation enthalpy, entropy and atomic mobility are taken into account, indicates that this decrease is caused by a slower bulk diffusion rate compared to the rates of sputtering and surface segregation.