108 research outputs found
Depth-resolved measurements of the Meissner screening profile in surface-treated Nb
We report depth-resolved measurements of the Meissner screening profile in
several surface-treated Nb samples using low-energy muon spin rotation
(LE-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.Comment: 15 pages, 5 figures, 2 table
- …