Heat Treatment Study of Nb3Sn CICC

The design and fabrication of the model coil for the 40 T hybrid superconducting outsert has been completed at High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL). Wind-and-React method is adopted to ease subsequent handling and assembly and to protect the brittle material. The model coil which is made of Nb3Sn CICC will undergo a high temperature diffusion reaction according to the optimum heat treatment schedule for the Nb3Sn/RRP (R) superconducting strand. The facility specialized in the heat treatment of Nb3Sn superconducting coils has been established in CHMFL, and several kinds of monitoring instruments are equipped to monitor impurities in the argon gas during heat treatment. At present, the heat treatment of the model coil has been finished and the performance test results of the model coil meet our requirements. This paper mainly presents the introduction of the heat treatment facility, details of heat treatment process for the model coil, and some simulations of the states during heat treatment.