论文标题
超导RF腔的电磁响应
Electromagnetic Response of Superconducting RF Cavities
论文作者
论文摘要
最近报道了在狭窄温度区域内的niobium srf空腔$ t_c \ simeq 9 \，\ mbox {K k} $在狭窄温度区域中的niobium srf腔的频率转移异常。我们开发了用于计算NB SRF腔的表面电流响应的方法，以及共鸣的频移和质量因子，作为基于温度，频率和混乱的功能，基于Keldysh的函数，基于Keldysh的表面功能，用于非平衡超导性的理论，与Maxwell的理论和边界条件以及响应功能和电子磁场的理论和边界条件相连。我们表明，异常对杂质疾病敏感。我们在频移异常的结果与NB的实验结果非常吻合，而在费米表面和非均匀的非磁性疾病上具有各向异性差距。我们还表明，在患有中间疾病的SRF腔中，质量因子作为杂质散射率的函数最大，$ \ hbar/τδ\ sim {\ cal o}（1）$，最大$ q $随着频率的增加而减小。
Recently reported anomalies in frequency shift of order $δf\sim 0.1 -10\,\mbox{kHz}$ for Niobium SRF cavities in a narrow temperature region near $T_c\simeq 9\,\mbox{K}$ are sensitive to the surface preparation and Nitrogen doping. We developed methods for calculating the surface current response of Nb SRF cavities, as well as the resonant frequency shift and quality factor, as functions of temperature, frequency and disorder based on the Keldysh formulation of the theory for nonequilibrium superconductivity coupled with Maxwell's theory and boundary conditions for the response functions and electromagnetic field. We show that the anomaly is sensitive to impurity disorder. Our results for the anomaly in the frequency shift are in good agreement with experimental results for Nb with an anisotropic gap on the Fermi surface and inhomogeneous non-magnetic disorder. We also show that the quality factor as a function of the impurity scattering rate is maximum for in SRF cavities with intermediate disorder, $\hbar/τΔ\sim{\cal O}(1)$ with the maximum $Q$ decreasing with increasing frequency.
