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Field of first magnetic flux entry and pinning strength of superconductors for rf application measured with muon spin rotation

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  • T. Junginger
  • S. H. Abidi
  • R. D. Maffett
  • T. Buck
  • M. H. Dehn
  • S. Gheidi
  • R. Kiefl
  • P. Kolb
  • D. Storey
  • E. Thoeng
  • W. Wasserman
  • R. E. Laxdal
Article number032002
<mark>Journal publication date</mark>16/03/2018
<mark>Journal</mark>Physical Review Accelerators and Beams
Issue number3
Number of pages15
Publication StatusPublished
<mark>Original language</mark>English


The performance of superconducting radiofrequency (SRF) cavities used for particle accelerators depends on two characteristic material parameters: field of first flux entry H-entry and pinning strength. The former sets the limit for the maximum achievable accelerating gradient, while the latter determines how efficiently flux can be expelled related to the maximum achievable quality factor. In this paper, a method based on muon spin rotation (mu SR) is developed to probe these parameters on samples. It combines measurements from two different spectrometers, one being specifically built for these studies and samples of different geometries. It is found that annealing at 1400 degrees C virtually eliminates all pinning. Such an annealed substrate is ideally suited to measure H-entry of layered superconductors, which might enable accelerating gradients beyond bulk niobium technology.