Field limit and nano-scale surface topography of superconducting radio-frequency cavity made of extreme type II superconductor

Abstract

The field limit of superconducting radio-frequency cavity made of type II superconductor with a large Ginzburg-Landau parameter is studied with taking effects of nano-scale surface topography into account. If the surface is ideally flat, the field limit is imposed by the superheating field. On the surface of cavity, however, nano-defects almost continuously distribute and suppress the superheating field everywhere. The field limit is imposed by an effective superheating field given by the product of the superheating field for ideal flat surface and a suppression factor that contains effects of nano-defects. A nano-defect is modeled by a triangular groove with a depth smaller than the penetration depth. An analytical formula for the suppression factor of bulk and multilayer superconductors are derived in the framework of the London theory. As an immediate application, the suppression factor of the dirty Nb processed by the electropolishing is evaluated by using results of surface topographic study. The estimated field limit is consistent with the present record field of nitrogen-doped Nb cavities. Suppression factors of surfaces of other bulk and multilayer superconductors, and those after various surface processing technologies can also be evaluated by using the formula.

17 pages, 6 figures

References in corpus (5)

• Dynamics of vortex penetration, jumpwise instabilities and nonlinear surface resistance of type-II superconductors in strong rf fields
• Temperature dependence of the superheating field for superconductors in the high-k London limit
• Effect of Impurities on the Superheating field of Type II superconductors
• Reply to "Comment on the 'Decrease of the surface resistance in superconducting niobium resonator cavities by the microwave field'"
• Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

Cited by in corpus (13)

• Superfluid flow in disordered superconductors with Dynes pair-breaking scattering: depairing current, kinetic inductance, and superheating field
• Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: Stability theory, disorder, and laminates
• Superheating fields of semi-infinite superconductors and layered superconductors in the diffusive limit: structural optimization based on the microscopic theory
• Flux trapping in superconducting accelerating cavities during cooling down with a spatial temperature gradient
• Dissipative conductivity of a dirty superconductor with Dynes subgap states under a dc bias current up to the depairing current density
• Simulation of Non-linear SRF losses derived from characteristic topography of etched and electropolished niobium surfaces
• Superheating in coated niobium
• Analysis of RF losses and material characterization of samples removed from a Nb3Sn-coated superconducting RF cavity
• Impact of border defects on the magnetic flux penetration in superconducting films
• Tuning critical field, critical current, and diode effect of narrow thin-film superconductors through engineering inhomogeneous Pearl length
• Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity
• Electropolishing-Induced Topographic Defects in Niobium: Insights and Implications for Superconducting Radio Frequency Applications
• Streamline controlled rectification of supercurrent in thin-film asymmetric weak links