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

Abstract

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°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.

arXiv comment14 pages, 21 figures

References in corpus (13)

• Nitrogen and argon doping of niobium for superconducting radio frequency cavities: a pathway to highly efficient accelerating structures
• Dependence of the residual surface resistance of superconducting RF cavities on the cooling dynamics around $T_{\mathrm{c}}$
• Superheating field of superconductors within Ginzburg-Landau theory
• Efficient expulsion of magnetic flux in superconducting RF cavities for high $Q_0$ applications
• Surface Superconductivity in Niobium for Superconducting RF Cavities
• Multilayer coating for higher accelerating fields in superconducting radio-frequency cavities: a review of theoretical aspects
• Muon spin rotation studies of electronic excitations and magnetism in the vortex cores of superconductors
• Radio-frequency electromagnetic field and vortex penetration in multilayered superconductors
• Strong Meissner screening change in superconducting radio frequency cavities due to mild baking
• Superconductors in realistic geometries: Geometric edge barrier versus pinning
• Flux pinning characteristics in cylindrical ingot niobium used in superconducting radio frequency cavity fabrication
• Muon spin rotation studies of niobium for superconducting RF applications
• Superheating in coated niobium

Cited by in corpus (12)

• Superfluid flow in disordered superconductors with Dynes pair-breaking scattering: depairing current, kinetic inductance, and superheating field
• Superheating fields of semi-infinite superconductors and layered superconductors in the diffusive limit: structural optimization based on the microscopic theory
• Effects of nonmagnetic impurities and subgap states on the kinetic inductance, complex conductivity, quality factor and depairing current density
• Critical Fields of Nb${}_3$Sn Prepared for Superconducting Cavities
• Depth-resolved measurements of the Meissner screening profile in surface-treated Nb
• A New High Parallel-Field Spectrometer at TRIUMF's $\beta$-NMR Facility
• Evidence for current suppression in superconductor-superconductor bilayers
• Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted $\beta$-emitter ${}^8$Li
• Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier
• Coaxial multi-mode cavities for fundamental SRF research in an unprecedented parameter space
• Depth-resolved Characterization of Meissner Screening Breakdown in Surface Treated Niobium
• Search for inhomogeneous Meissner screening in Nb induced by low-temperature surface treatments