The Study of Induction Brazing for Vertical Stability Coil Copper Conductor

The vertical stability coil will be used in China Fusion Engineering Test Reactor (CFETR) to improve its control capability on plasma. In view of the severe operation environment and high reliable requirement, it is a challenge for the coil to keep reliability during the whole lifetime, considering the prominent advantages of induction brazing, which is proposed for the coil joint connection. According to the electromagnetic-thermal coupling theory, the induction brazing simulation is carried out under different induction coil parameters. And a set of relatively reasonable induction coil parameter is obtained based on the average temperature and standard deviation of copper sample. In order to verify the brazing performance of the determined induction coil, the brazing experiment is launched with different joint structures and the brazing inspection is performed subsequently. Although it seems some joint design have the advantage of minimizing the damage on the outer magnesium oxide insulation layer, while they fail to satisfy the strength requirement. Based on the lessons, a new joint with thin external sleeve is designed and a series of performance tests are employed. It indicates that there is no large temperature gradient in the joint radial direction and the joint strength is prominently improved.