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Title: Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG

Ambient magnetic field, if trapped in the penetration depth, leads to the residual resistance and therefore sets the limit for the achievable quality factors in superconducting niobium resonators for particle accelerators. Here, we show that a complete expulsion of the magnetic flux can be performed and leads to: (1) record quality factors Q > 2 × 10{sup 11} up to accelerating gradient of 22 MV/m; (2) Q ∼ 3 × 10{sup 10} at 2 K and 16 MV/m in up to 190 mG magnetic fields. This is achieved by large thermal gradients at the normal/superconducting phase front during the cooldown. Our findings open up a way to ultra-high quality factors at low temperatures and show an alternative to the sophisticated magnetic shielding implemented in modern superconducting accelerators.
Authors:
; ; ; ;  [1]
  1. Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)
Publication Date:
OSTI Identifier:
22395510
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 23; 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; MAGNETIC FIELDS; MAGNETIC FLUX; MAGNETIC SHIELDING; NIOBIUM; PENETRATION DEPTH; QUALITY FACTOR; SUPERCONDUCTING CAVITY RESONATORS; SUPERCONDUCTIVITY; SUPERCONDUCTORS; TEMPERATURE GRADIENTS; TRAPPING