Nanoscale Nonlinear Radio Frequency Properties of Bulk Nb : Origins of Extrinsic Nonlinear Effects

Abstract

The performance of Niobium-based Superconducting Radio Frequency (SRF) particle accelerator cavities can be sensitive to localized defects that give rise to quenches at high accelerating gradients. In order to identify these material defects on bulk Nb surfaces at their operating frequency and temperature, a wide bandwidth microwave microscope with localized and strong RF magnetic fields is developed by integrating a magnetic write head into the near-field microwave microscope to enable mapping of the local electrodynamic response in the multi-GHz frequency regime at cryogenic temperatures. This magnetic writer demonstrates a localized and strong RF magnetic field on bulk Nb surface with $B_{surface}$ > 102 mT and sub-micron resolution. By measuring the nonlinear response of the superconductor, nonlinearity coming from the nano-scale weak link Josephson junctions due to the contaminated surface in the cavity fabrication process is demonstrated.

10 pages, 13 figures

References in corpus (2)

• Dynamics of vortex penetration, jumpwise instabilities and nonlinear surface resistance of type-II superconductors in strong rf fields
• Microwave Nonlinearities of an Isolated Long YBa_2Cu_3O_(7-d) Bi-crystal Grain Boundary

Cited by in corpus (10)

• Efficient expulsion of magnetic flux in superconducting RF cavities for high $Q_0$ applications
• Time-dependent Ginzburg-Landau treatment of RF Magnetic Vortices in Superconductors: Vortex-Semiloops in a Spatially Nonuniform Magnetic Field
• High Frequency Nonlinear Response of Superconducting Cavity-Grade Nb surfaces
• Imaging the paramagnetic nonlinear Meissner effect in nodal gap superconductor
• Microscopic Examination of SRF-quality Nb Films through Local Nonlinear Microwave Response
• Microwave Microscope Studies of Trapped Vortex Dynamics in Superconductors
• Local Whole-Device Scanning of Distortion in Superconducting Microwave Resonators
• Relaxation of Microwave Nonlinearity in a Cuprate Superconducting Resonator
• Localized High Frequency Electrodynamic Behavior of Optimally-doped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ Single Crystal films
• Microscopic Investigation of rf Vortex Nucleation in Nb3Sn Films Using a Near-Field Magnetic Microwave Microscope