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Title: Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

We investigate “hot” regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λ{sub L}=23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ>100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.
Authors:
; ;  [1] ; ; ;  [2]
  1. Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)
  2. Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)
Publication Date:
OSTI Identifier:
22283139
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 7; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BCS THEORY; CONCENTRATION RATIO; HYDRIDES; MEAN FREE PATH; MUON SPIN RELAXATION; NIOBIUM; PENETRATION DEPTH; RADIOWAVE RADIATION; SUPERCONDUCTING CAVITY RESONATORS; SUPERCONDUCTIVITY; SUPERCONDUCTORS; TRAPS; VACANCIES