HIE-ISOLDE超导谐振器BCS材料参数的确定
Determination of the BCS material parameters of the HIE-ISOLDE superconducting resonator
摘要:
利用Mattis-Barclay理论对实验结果进行拟合,研究了HIE-ISOLDE四分之一波谐振器(QWR)上Nb薄膜涂层的超导材料参数。指出BCS理论中材料参数的拟合估计量之间存在很强的相关性,并提出了通过同时拟合表面电阻和有效穿透深度来消除相关性的方法。与以前的研究不同,在拟合中没有假设文献值。由于表面电阻和穿透深度对相干长度和平均自由程的依赖性相似,因此这种拟合不能消除这两个参数之间的相关性。由SQUID磁强计测量的上临界场显示出对RF结果的互补约束,并且这允许确定所有的材料参数。
英文摘要:
Superconducting material parameters of the Nb film coating on the Quarter-Wave Resonator (QWR) for the HIE-ISOLDE project were studied by fitting experimental results with the Mattis-Bardeen theory. We pointed out a strong correlation among fitted estimators of material parameters in the BCS theory, and proposed a procedure to remove the correlation by simultaneously fitting the surface resistance and effective penetration depth. Unlike previous studies, no literature values were assumed in the fitting. As surface resistance and penetration depth had a similar dependence on coherence length and mean free path, the correlation between these two parameters could not be eliminated by this fitting. The upper critical field measured by SQUID magnetometry showed complementary constraint to the RF result, and this allowed all the material parameters to be determined.
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