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Depth-Resolved Measurements of the Meissner Screening Profile in Surface-Treated Nb

Ryan M. L. McFadden1,2,*, Md. Asaduzzaman1,2, Thomas Prokscha3, Zaher Salman3, Andreas Suter3, and Tobias Junginger1,2,†

  • 1TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada
  • 2Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, British Columbia V8P 5C2, Canada
  • 3Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen, Switzerland

  • *rmlm@triumf.ca
  • †junginger@uvic.ca
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Phys. Rev. Applied 19, 044018 – Published 6 April, 2023

DOI: https://doi.org/10.1103/PhysRevApplied.19.044018

Abstract

We report depth-resolved measurements of the Meissner screening profile in several surface-treated Nb samples using low-energy muon spin rotation. In these experiments, implanted positive muons, whose stopping depths below Nb’s surface are adjusted between approximately 10nm and 150nm, reveal the field distribution inside the superconducting element via their spin precession (communicated through their radioactive decay products). We compare how the field screening is modified by different surface treatments commonly used to prepare superconducting radio-frequency cavities used in accelerator beamlines. In contrast to an earlier report [A. Romanenko et al., Appl. Phys. Lett. 104, 072601 (2014)], we find no evidence for any “anomalous” modifications to the Meissner profiles, with all data being well described by a London model. Differences in screening properties between surface treatments can be explained by changes to the carrier mean free paths resulting from dopant profiles near the material’s surface.

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Phys. Rev. Applied 19, 044018– Published 6 April, 2023
  • Received 22 December 2022
  • Accepted 28 February 2023
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