Structural Analysis And Performance Research Of Large-Bore CICC High Temperature Superconducting Magnet And Its Conductors

Strong magnetic field can regulate and control matter,and provide a platform for fundamental research of various disciplines.At present,hybrid magnet is the most effective way to generate magnetic field above 40 T.Hybrid magnet is usually composed of a water-cooled resistive insert magnet and a low temperature superconductor(LTS)Cable-in-Conduit Conductors(CICC)outsert magnet.However,LTS cannot meet the requirements of developing higher field magnet as the limitation of low upper critical field.High temperature superconductor(HTS)with higher upper critical field is the inevitable choice to development higher-field superconducting magnet.In addition to providing higher central field strength in the future,the bore and radial dimension of superconducting magnet tend to be larger,the design of CICC superconducting magnet with large bore will be a tendency in developing higher-field hybrid magnet.This dissertation focuses on the design and study of HTS CICC conductor and large-bore CICC superconducting magnet,properties of various practical HTS have been studied;two conductor structures based on REBa2Cu3O7-x(REBCO)tape are studied,analyzed and optimized;the preliminary design scheme of high temperature superconducting magnet is given based on the optimized TSTC CICC conductor,and the mechanical performance of this magnet is studied.First,the mechanical and electromagnetic performance of Bi2Sr2CaCu2O8-x(Bi2212),(Bi,Pb)2Sr2Ca2Cu3O10-x(Bi2223),REBa2Cu3O7-x(REBCO)and iron-based superconductor are compared in detail to explored the application prospect of these superconductors in high field.The advantages of REBCO and iron-based superconductor are analyzed,however,the performance of iron-based superconductor in high field needs further study.Second,coils wound by Ba122 iron-based superconductor tape are made to verify the feasibility of the application of iron-based superconductor in high field.The critical current and overcurrent capacity of the coil was tested under 30 T after the improvement of heat treatment and winding process,the disadvantages of iron-based superconductor in high field are analyzed.Next,two conductor structures based on REBCO tape are proposed.The relationship between CORC cable winding parameters and the strain of REBCO tape is introduced in brief.The relationship between the critical current of CORC cable and the diameter of the central former,the winding angle of REBCO tape,the width of REBCO tape and the thickness of the copper stabilizer layer in REBCO tape are studied.Based on the experimental results,the expression of the relationship between the critical current of CORC cable and its winding parameters is derived,and a better structural design scheme of CORC cable is proposed.In addition,a TSTC CICC conductor which can be used in high field magnets is designed based on the concept of TSTC conductor.Large transverse electromagnetic load is generated when TSTC CICC conductor is excitated in high field.The critical tensile stress in the thickness direction of REBCO tape and the critical compressive stress in the width direction of REBCO tape are small,which are greatly affected by transverse load.In this dissertation,the study on the relationship between the angle of REBCO stacking,the thickness of cable jacket,load intensity,different types of REBCO tapes and the stress/strain of REBCO tape under ransverse electromagnetic load is carried out,which provides a basis for the optimization of TSTC CICC conductor structure and the selection of REBCO tape,besides,the feasibility of TSTC CICC conductor application in high field is verified.At last,the preliminary design scheme of high temperature superconducting magnet is given based on the structure of TSTC CICC conductor.In order to study the mechanical performance of TSTC CICC superconducting magnet in high field,a hybrid magnet consisting of water-cooled resistive magnet,TSTC CICC superconducting magnet and Nb3Sn CICC superconducting magnet is designed and its electromagnetic performance were analyzed.The mechanical performance of outsert superconducting magnet in normal operation is analyzed,the mechanical strength of conductor jacket is analyzed and checked by ITER structural design criterion.The fatigue life of the conductor jacket under cyclic excitation is evaluated.The electromagnetic force generated by symmetry axis or magnetic center offset and the torque generated by angular misalignment of symmetry axes between the outsert superconducting magnet and the insert water-cooled resistive magnet is calculated.