Lu, M.; Keckert, S.; Kramer, F.; Prudnikava, A.; Knobloch, J.; Zubtsovskii, A.; Kugeler, O.: Preparation of the Cu-based Nb3Sn Sample via Bronze Route for Quadrupole Resonator Testing. Superconductor Science & Technology 39 (2026), p. 035005/1-20
10.1088/1361-6668/ae496a
Open Access Version
Abstract:
We report the successful production of a Cu-based Nb3Sn sample specifically designed for Quadrupole Resonator (QPR) testing, representing a significant step toward scalable RF superconducting coatings of Nb3Sn on copper substrates. The sample was fabricated using an optimized electrochemical thermal synthesis (ETS) via bronze route, incorporating several key advancements: electropolishing of the Cu substrate, electroplating of the bronze precursor layer, a tailored heat treatment at 700 °C to promote grain growth and suppress tin-rich secondary phases, and a newly developed chemical etching procedure for effective removal of surface bronze residues and contaminants. These improvements address longstanding challenges in the fabrication of high-quality Cu-based Nb3Sn thin films. Subsequent QPR measurements yielded the peak magnetic field and temperature dependent surface resistance Rs, as well as the superconducting transition temperature and quench field. The achieved surface resistance, with a minimum of 47.5 nano Ohm at 4.5K and 15mT (413 MHz), indicates that both residual and BCS losses contribute significantly to the present performance limitations. This behavior is consistent with the observed sub-stoichiometric composition and microstructural inhomogeneity of the film. Although the procedure is not yet fully optimized the results clearly demonstrate the feasibility of this approach and its potential for further improvement through process refinement.