Heat Treatment for Nb₃Sn Coils of CFETR CSMC

A heat treatment system for superconducting coil had been built at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) for the central solenoid model coil (CSMC) for the China Fusion Engineering Test Reactor (CFETR). The CSMC is composed of Nb₃Sn and NbTi hybrid superconducting coils. As Nb₃Sn is a brittle material, the technology of “wind and react” has been used to manufacture Nb₃Sn coil. During the heat treatment process, various measuring instruments have been used to monitor the heat treatment parameters (e.g., temperature, pressure, impurity gas content). The heat treatment of the inner coil and the outer coil of CSMC has been completed. The evolution temperature and temperature uniformity meet the technical requirements of CSMC heat treatment. The performance of the witness sample meets the recommended value. The measurement results of the coil deformation meet the requirements of the Nb₃Sn coil design. Here, the manufacture, measurements, and test results are presented, providing a solid basis for the heat treatment of large size superconducting coils.