Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: Stability theory, disorder, and laminates

Abstract

Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-Tc materials such as Nb${}_3$Sn, NbN, and MgB${}_2$. Indeed, beyond the so-called superheating field $H_{sh}$, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for $H_{sh}$, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB${}_2$? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.

22 pages, 17 figures

References in corpus (5)

• Dendritic flux avalanches and nonlocal electrodynamics in thin superconducting films
• Superheating field of superconductors within Ginzburg-Landau theory
• 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
• Dynamics of superconducting vortices driven by oscillatory forces in the plastic flow regime

Cited by in corpus (15)

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• Quasiparticle spectroscopy, transport, and magnetic properties of Nb films used in superconducting transmon qubits
• A generalized phenomenological model for the magnetic field penetration and magnetization hysteresis loops of a type-II superconductor
• 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
• Critical fields of superconductors with magnetic impurities
• The nontrivial effects of annealing on superconducting properties of Nb single crystals
• Ac losses in field-cooled type I superconducting cavities
• Depth-resolved Characterization of Meissner Screening Breakdown in Surface Treated Niobium
• Quasiparticle spectroscopy in technologically-relevant niobium using London penetration depth measurements
• A Time-Dependent Ginzburg-Landau Framework for Sample-Specific Simulation of Superconductors for SRF Applications
• Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity
• Vortex nucleation barriers and stable fractional vortices near boundaries in multicomponent superconductors