Qualification activities of the spliced joint for CFETR

The CFETR toroidal field (TF) is designed to generate 14.5 T peak magnetic field when the operation current is 95.6 kA. To minimize the heat load of the joints to the cryogenic system, the internal joints are required to have resistance below 0.3 nil. 2 trial Nb3Sn spliced joints were successfully manufactured and tested in 2021. Through the test, the feasibility of the spliced joint design was verified. The trial joints obtained sufficiently low resistance, so we can consider omitting the step of removing chromium coating to avoid a large amount of harmful waste liquid and gases generated in the process. 2 full-size joint samples using a CFETR TF middle field (MF) CICC were built, one without chromium coating and one with, and studied the effect of chromium coating on resistance through simulation analysis and experiments.