Frequency dependence of trapped flux sensitivity in SRF cavities
arXiv:1711.05902 · doi:10.1063/1.5016525
Abstract
In this letter, we present the frequency dependence of the vortex surface resistance of bulk niobium accelerating cavities as a function of different state-of-the-art surface treatments. Higher flux surface resistance per amount of trapped magnetic field - sensitivity - is observed for higher frequencies, in agreement with our theoretical model. Higher sensitivity is observed for N-doped cavities, which possess an intermediate value of electron mean-free-path, compared to 120 C and EP/BCP cavities. Experimental results from our study showed that the sensitivity has a non-monotonic trend as a function of the mean-free-path, including at frequencies other than 1.3 GHz, and that the vortex response to the rf field can be tuned from the pinning regime to flux-flow regime by manipulating the frequency and/or the mean-free-path of the resonator, as reported in our previous studies. The frequency dependence of the trapped flux sensitivity to the amplitude of the accelerating gradient is also highlighted.
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- Vortex Dynamics and Dissipation Under High-amplitude Microwave Drive
- Simple model for the RF field amplitude dependence of the trapped flux sensitivity in superconducting RF cavities
- Measurements of the amplitude-dependent microwave surface resistance of an Au/Nb bilayer
- Fluxon-induced losses in niobium thin-film cavities revisited
- Quantifying Trapped Magnetic Vortex Losses in Niobium Resonators at mK Temperatures
- Improved high-gradient performance for medium-velocity superconducting half-wave resonators: Surface preparation and trapped flux mitigation
- Dissipation by surface states in superconducting RF cavities