Simple model for the RF field amplitude dependence of the trapped flux sensitivity in superconducting RF cavities

Abstract

The improvement of the performance of RF superconducting cavities has recently motivated a considerable research effort in order to elucidate the effect of trapped magnetic flux on the surface resistance $R_s$. In this paper we show that by introducing a non-linear pinning force in the Gittleman-Rosenblum equations for the RF power dissipation due to a trapped magnetic flux in a superconductor, we can empirically describe the linear dependence on the RF field amplitude $B_{rf0}$ of the additional surface resistance $R_{fl}$. We also show that the proportionality between the RF-field dependent and independent terms $R_{fl}^1$ and $R_{fl}^0$, and the frequency dependence of $R_{fl}^1$ follow naturally from this approach.

References in corpus (6)

• Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG
• Dynamics of vortex penetration, jumpwise instabilities and nonlinear surface resistance of type-II superconductors in strong rf fields
• Microwave response of thin niobium films under perpendicular static magnetic fields
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Cited by in corpus (5)

• 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
• Impact of geometry on the magnetic flux trapping of superconducting accelerating cavities
• Vortex Dynamics and Dissipation Under High-amplitude Microwave Drive
• Fluxon-induced losses in niobium thin-film cavities revisited