SMuK 2023 – scientific programme

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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 11: RF and SRF Research

AKBP 11.2: Talk

Wednesday, March 22, 2023, 17:45–18:00, CHE/0184

Nb3Sn Co-Sputtering for Interlayer-Free High Performance Copper SRF Cavities — •Nils Schäfer, Carl Jung, Matthias Mahr, Carl Jung, Christian Dietz, Sebastian Bruns, Márton Major, and Lambert Alf — Technische Universitaet Darmstadt (TU Darmstadt) Institute of Materials Science FB 11

Nb3Sn thin film coatings are a promising candidate to replace bulk Nb to increase performance and energy efficiency of SRF cavities. Replacing niobium by Nb3Sn coated copper would not only reduce material*s cost, but would also allow optimal heat removal for higher cryogenic efficiency. The challenge is the detrimental interdiffusion of Cu into Nb3Sn at the typically high deposition temperatures conventionally used for Nb3Sn synthesis. We have recently introduced a novel kinetically driven low-temperature co- sputtering process that overcomes the copper diffusion challenge. In this break-through process, even a diffusion barrier layer is not needed, because the Cu diffusion is minimized to an extent where the superconducting properties of Nb3Sn are not negatively affected. Magnetization versus temperature measurements demonstrate the good shielding performance in parallel orientation of the Nb3Sn thin films on the copper substrate. Mechanical nanondentation and scratch tests demonstrate that even after thermal cycling of the sample, the adhesion properties the Nb3Sn thin film coatings are excellent. Work supported by the German Federal Ministry for Education and Research (BMBF) through grant 05H21RDRB1 and the German Research Foundation (DFG) via the AccelencE Research Training Group (GRK 2128).