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The main goal of the model coil is to demonstrate the feasibility of 'Insulation-Wind-React' manufacturing process and to confirm the feasibility of the superconducting outsert design. The model coil was wound with Cable-in-Conduit Conductor (CICC) using restacked-rod process (RRP) strand, and cooled with forced-flow supercritical helium with inlet temperature of 4.5 K. The test of the model coil in the 7.5 T background field has been completed, and the test program included cool-down, full DC characterization before and after cyclic loading, AC losses, and so on. The test results have confirmed the characterization of the conductor and the mechanical performance of the model coil, and validated the 40 T hybrid magnet superconducting outsert design.

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 Nb 3 Sn CICC will undergo a high temperature diffusion reaction according to the optimum heat treatment schedule for the Nb 3 Sn/RRP superconducting strand. The facility specialized in the heat treatment of Nb 3 Sn 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.

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