Development and Performance of the First Nb$_3$Sn Thin-Film Cavity via Bronze Process
Ming Lu1, Didi Luo1, Feng Pan1, Chunlong Li1, Shichun Huang1, Ziqin Yang1, Andong Wu1, Qingwei Chu1, Tongtong Zhu1,2, Shuai Wu1,2, Teng Tan1, and Hao Guo1,3*
1Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China 2School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China 3School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
Abstract：Low-temperature synthesis of Nb$_3$Sn thin-film cavity is of great significance in the field of superconducting radio frequency (SRF). The bronze process can grow only stable Nb$_3$Sn phase at 700 ℃, so it is considered to be the most promising process for low-temperature synthesis of Nb$_3$Sn thin-film cavity. We successfully fabricated the worldwide first Nb$_3$Sn thin-film cavity by bronze process. We technically solved the key problems of precursor preparation, characterized and analyzed the uniformity of the Nb$_3$Sn film, and tested the performance of the cut-out samples and the whole cavity of the Nb$_3$Sn film. It is obtained that the $Q_0$ value of the cavity at 4.2 K is about $1.2\times10^{9}$, which is greater than the performance of the bulk-niobium cavity under the same conditions. This result means that the preparation of Nb$_3$Sn by bronze process has the great potential to more practical copper-based Nb$_3$Sn thin-film cavity, which is expected to achieve a substantial improvement in the performance of SRF cavity and comprehensive engineering applications.
2022, Vol. 39 
