Medium-temperature furnace baking of 1.3 GHz 9-cell superconducting cavities at IHEP
Feisi He, Weimin Pan, Peng Sha, Jiyuan Zhai, Zhenghui Mi, Xuwen Dai, Song Jin, Zhanjun Zhang, Chao Dong, Baiqi Liu, Hui Zhao, Rui Ge, Jianbing Zhao, Zhihui Mu, Lei Du, Liangrui Sun, Liang Zhang, Conglai Yang, Xiaobing Zheng
Abstract
Abstract Recently, heat treatment in the range of 250 °C–500 °C has been attempted with the aim of improving the quality factor ( Q ) of superconducting radio-frequency (SRF) cavities worldwide. Herein, medium-temperature (mid-T) furnace baking experiments were conducted at the Institute of High Energy Physics to obtain higher Q values. First, 1.3 GHz 1-cell cavities received mid-T furnace baking at different temperatures, resulting in not only the improvement of Q but also an anti- Q -slope behavior. Furthermore, mid-T furnace baking was applied to six 1.3 GHz 9-cell cavities, all of which indicated higher Q and anti- Q -slope behavior. The average Q was 3.8 × 10 10 at 16 MV m −1 . The maximum gradients of the 9-cell cavities were 22.7–26.5 MV m −1 . Finally, the mid-T furnace baked 1.3 GHz 9-cell cavities were welded with helium vessel, with no degradation in the vertical tests. In addition, the mid-T furnace baking process was simplified in comparison with European X-ray Free Electron Laser and Linear Coherent Light Source because of the cancellation of light electro-polishing. This simplification is beneficial in the mass production of SRF cavities with high Q , which are widely adopted in free electron lasers and high-energy colliders.