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Nb3Sn superconducting microwave cavity tunable over 1 GHz for dark-matter searches

D. Maiello1,2,*, R. Di Vora3, D. Ahn2, G. Carugno2, R. Cervantes4, B. Giaccone4, A. Ortolan3, S. Posen5, G. Ruoso3 et al.

G. Sardo Infirri1,2, B. Tennis5, S. Tocci6, and C. Braggio1,2,†

  • *Contact author: dora.maiello@phd.unipd.it
  • †Contact author: caterina.braggio@unipd.it
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Phys. Rev. Applied 26, 054032 – Published 10 November, 2026

DOI: https://doi.org/10.1103/k4tb-q2pd

Abstract

We demonstrate a wide-frequency tuning mechanism for superconducting microwave cavities designed for dark-matter searches. Using a NbSn-coated cigar-shaped cavity operating at approximately 9 GHz, we achieve continuous frequency tuning exceeding 1 GHz by mechanically separating the two cavity halves: a “tuning-by-opening” technique. Finite-element method simulations predict that radiative losses do not degrade the quality factor even for large openings, as a closed cavity with an intrinsic quality factor maintains this value for apertures up to 9 mm, corresponding to a tuning range from 9.0 to 7.5 GHz. Experimental validation using both copper ring spacers and a continuous sliding mechanism confirms values exceeding the dark-matter quality factor across the entire explored frequency range, despite mechanical imperfections and film nonuniformities. This tuning approach avoids inserting elements into the resonant volume, making it particularly suitable for high-Q superconducting cavities in axion haloscope experiments and readily applicable to rare-earth barium copper oxide (REBCO)-based implementations capable of operating in multi-tesla magnetic fields.

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Phys. Rev. Applied 26, 054032– Published 10 November, 2026
  • Received 19 March 2026
  • Revised 3 July 2026
  • Accepted 9 October 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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