Design And Research Of High Temperature Superconducting Of CFETR CS Magnet

In order to achieve high-confinement mode operation,the CFETR central solenoidal magnet requires the highest magnetic field to 17.5 T.The common LTS materials can no longer meet the design requirements.So the HTS/LTS hybrid magnet made by Bi-2212 and Nb3Sn is proposed.The superconducting joints are the important components for connecting the electrical and the cooling circuits of the magnet.This paper focuses on the design and analysis of the superconducting joint for the Bi-2212 CICC.The main contents include:(1)Based on the requirements for different types of joint in different locations of CFETR CS magnet,the HTS sub-cable butt joint and the HTS lap type joint were designed.The sub-cable butt joint can be used in the inner of CS coil,which need to undo the last stage of the cable and the ends of the sub-cable are connected by the silver insert.The lap type joint can be used to connect the coil termination to the the busbar in the feeder system,and the conductor terminals can be directly connected via the saddle copper sole by indium soldering.(2)Using COMSOL to build the finite element model,the resistance of the HTS sub-cable butt joint and the lap type joint were analyzed.The theoretical analysis method was used to calculate the AC loss of the lap type joint.The improved THEA code was used to simulate the temperature rise characteristics of the butt joint and the lap type joint under the steady-state current operational condition.(3)The design and manufacture of the Bi-2212 round wire butt joint samples have been completed,the joint was connected by the sliver sleeve,and the sleeve region was compressed and sintered.The critical current of the samples were measured at the liquid helium temperature,and the voltage-current characteristic of the butt joint,the Bi-2212 wire and the silver sleeve were compared.(4)The preliminary design of the large-caliber background field magnet for the HTS joint test platform was carried out.The current time constant was analyzed by theoretical analysis method.The important parameters including the sharing t temperature and hot spot temperature of the superconducting strand were simulated by Gandalf.