A low energy muon spin rotation and point contact tunneling study of niobium films prepared for superconducting cavities

Abstract

Point contact tunneling (PCT) and low energy muon spin rotation (LE-muSR) are used to probe, on the same samples, the surface superconducting properties of micrometer thick niobium films deposited onto copper substrates using different sputtereing techniques: diode, dc magnetron (dcMS) and HIPIMS. The combined results are compared to radio-frequency tests performances of RF cavities made with the same processes. Degraded surface superconducting properties are found to yield lower quality factors and stronger Q slope. In addition, both techniques find evidence for surface paramagnetism on all samples and particularly on Nb films prepared by HIPIMS.

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Cited by in corpus (7)

• Depth-resolved measurements of the Meissner screening profile in surface-treated Nb
• High Frequency Nonlinear Response of Superconducting Cavity-Grade Nb surfaces
• Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier
• Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted $\beta$-emitter ${}^8$Li
• Search for inhomogeneous Meissner screening in Nb induced by low-temperature surface treatments
• Niobium's intrinsic coherence length and penetration depth revisited using low-energy muon spin spectroscopy and secondary-ion mass spectrometry
• Implantation studies of low-energy positive muons in niobium thin films