Tan Teng, Wolak M A, Xi X X, Tajima T, Civale L
Department of Physics, Temple University, Philadelphia, 19122, Pennsylvania, USA.
Los Alamos National Laboratory, Los Alamos, 87545, New Mexico, USA.
Sci Rep. 2016 Oct 24;6:35879. doi: 10.1038/srep35879.
Bulk niobium Superconducting Radio-Frequency cavities are a leading accelerator technology. Their performance is limited by the cavity loss and maximum acceleration gradient, which are negatively affected by vortex penetration into the superconductor when the peak magnetic field at the cavity wall surface exceeds the vortex penetration field (H). It has been proposed that coating the inner wall of an SRF cavity with superconducting thin films increases H. In this work, we utilized Nb ellipsoid to simulate an inverse SRF cavity and investigate the effect of coating it with magnesium diboride layer on the vortex penetration field. A significant enhancement of H was observed. At 2.8 K, H increased from 2100 Oe for an uncoated Nb ellipsoid to 2700 Oe for a Nb ellipsoid coated with ~200 nm thick MgB thin film. This finding creates a new route towards achieving higher acceleration gradient in SRF cavity accelerator beyond the theoretical limit of bulk Nb.
块状铌超导射频腔是一种领先的加速器技术。其性能受到腔损耗和最大加速梯度的限制，当腔壁表面的峰值磁场超过涡旋穿透场（H）时，涡旋渗透到超导体中会对其产生负面影响。有人提出，在超导射频腔的内壁涂上超导薄膜会增加H。在这项工作中，我们利用铌椭球体模拟反超导射频腔，并研究用二硼化镁层涂覆它对涡旋穿透场的影响。观察到H有显著增强。在2.8K时，H从未涂覆的铌椭球体的2100奥斯特增加到涂覆了约200纳米厚二硼化镁薄膜的铌椭球体的2700奥斯特。这一发现为在超导射频腔加速器中实现高于块状铌理论极限的更高加速梯度开辟了一条新途径。
