Magnetic Flux Dynamics in Horizontally Cooled Superconducting Cavities

Abstract

Previous studies on magnetic flux expulsion as a function of cooling details have been performed for superconducting niobium cavities with the cavity beam axis placed parallel respect to the helium cooling flow, and findings showed that for sufficient cooling thermogradients all magnetic flux could be expelled and very low residual resistance could be achieved. In this paper we investigate the flux trapping and its impact on radio frequency surface resistance when the resonators are positioned perpendicularly to the helium cooling flow, which is representative of how superconducting radio-frequency (SRF) cavities are cooled in an accelerator. We also extend the studies to different directions of applied magnetic field surrounding the resonator. Results show that in the cavity horizontal configuration there is a different impact of the various field components on the final surface resistance, and that several parameters have to be considered to understand flux dynamics. A newly discovered phenomenon of concentration of flux lines at the cavity top leading to cavity equator temperature rise is presented.

References in corpus (3)

• Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG
• Dependence of the residual surface resistance of superconducting RF cavities on the cooling dynamics around $T_{\mathrm{c}}$
• Nitrogen-Doped 9-Cell Cavity Performance in a Test Cryomodule for LCLS-II

Cited by in corpus (8)

• Efficient expulsion of magnetic flux in superconducting RF cavities for high $Q_0$ applications
• Effect of interstitial impurities on the field dependent microwave surface resistance of niobium
• Flux expulsion in niobium superconducting radio-frequency cavities of different purity and essential contributions to the flux sensitivity
• Flux trapping in superconducting accelerating cavities during cooling down with a spatial temperature gradient
• Nonlinear Dynamics and Dissipation of a Curvilinear Vortex Driven by a Strong Time-Dependent Meissner Current
• Impact of geometry on the magnetic flux trapping of superconducting accelerating cavities
• Demagnetization of a Complete Superconducting Radiofrequency Cryomodule: Theory and Practice
• Improved high-gradient performance for medium-velocity superconducting half-wave resonators: Surface preparation and trapped flux mitigation