Development and Performance of the First Nb_3Sn Thin-Film Cavity via Bronze Process

Low-temperature synthesis of Nb_3Sn thin-film cavity is of great significance in the field of superconducting radio frequency (SRF). The bronze process can grow only stable Nb_3Sn phase at 700 ℃, so it is considered to be the most promising process for low-temperature synthesis of Nb_3Sn thin-film cavity. We successfully fabricated the worldwide first Nb_3Sn thin-film cavity by bronze process. We technically solved the key problems of precursor preparation, characterized and analyzed the uniformity of the Nb_3Sn film, and tested the performance of the cut-out samples and the whole cavity of the Nb_3Sn 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_3Sn by bronze process has the great potential to more practical copper-based Nb_3Sn thin-film cavity, which is expected to achieve a substantial improvement in the performance of SRF cavity and comprehensive engineering applications.