Determination of the BCS material parameters of the HIE-ISOLDE superconducting resonator

Abstract

Superconducting material parameters of the Nb film coating on the Quarter-Wave Resonator (QWR) for the HIE-ISOLDE project were studied by fitting experimental results with the Mattis-Bardeen theory. We pointed out a strong correlation among fitted estimators of material parameters in the BCS theory, and proposed a procedure to remove the correlation by simultaneously fitting the surface resistance and effective penetration depth. Unlike previous studies, no literature values were assumed in the fitting. As surface resistance and penetration depth had a similar dependence on coherence length and mean free path, the correlation between these two parameters could not be eliminated by this fitting. The upper critical field measured by SQUID magnetometry showed complementary constraint to the RF result, and this allowed all the material parameters to be determined.

References in corpus (1)

• The Importance of the Electron Mean Free Path for Superconducting RF Cavities

Cited by in corpus (3)

• Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity
• Two different origins of the Q-slope problem in superconducting niobium film cavities for a heavy ion accelerator at CERN
• Classifying induced superconductivity in atomically thin Dirac-cone materials