Depth-resolved measurements of the Meissner screening profile in surface-treated Nb

Abstract

We report depth-resolved measurements of the Meissner screening profile in several surface-treated Nb samples using low-energy muon spin rotation (LE-$\mu$SR). In these experiments, implanted positive muons, whose stopping depths below Nb's surface were adjusted between ~10 nm to ~150 nm, 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 employed to prepare superconducting radio frequency (SRF) 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.

15 pages, 5 figures, 2 tables

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Cited by in corpus (9)

• Evidence for current suppression in superconductor-superconductor bilayers
• Comment on "Strong Meissner screening change in superconducting radio frequency cavities due to mild baking" [Appl. Phys. Lett. 104, 072601 (2014)]
• Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier
• Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted $\beta$-emitter ${}^8$Li
• Depth-resolved Characterization of Meissner Screening Breakdown in Surface Treated Niobium
• Search for inhomogeneous Meissner screening in Nb induced by low-temperature surface treatments
• Niobium's intrinsic coherence length and penetration depth revisited using low-energy muon spin spectroscopy and secondary-ion mass spectrometry
• Implantation studies of low-energy positive muons in niobium thin films
• Electropolishing-Induced Topographic Defects in Niobium: Insights and Implications for Superconducting Radio Frequency Applications