Development And Performance Research Of Practical Iron-based Superconducting High Field Insert Coil

Iron-based superconductor(IBS)was newly discovered superconducting material in 2008.Its highest critical temperature is 55 K,according to the classification of superconducting material,belongs to high-temperature superconducting material,and has been widely concerned and studied by research groups around the world in recent years.The Institute of Electrical Engineering,Chinese Academy of Sciences(IEECAS)is leading the world in the preparation of iron-based superconducting tape,and successfully prepared 100 meters of iron-based superconducting tape in 2017,providing conditions for the practical research of IBS.This study relied on the condition of large diameter water-cooled magnet in the CHFML,the research of iron-based superconducting high field insert coil was carried out to explore the performance of iron-based superconducting long tape.This paper mainly carried out the following research works:Property measurement of iron-based superconducting tape:The micro structure of before and after heat treatment iron-based superconducting tape was characterized,and the effect of heat treatment process on the distribution of core wires was explored and analyzed.The mechanical parameters were obtained by stretching the before and after heat treatment iron-based superconducting tape using standard stretching method.The current carrying capacity of iron-based superconducting tape at 4.2 K was experimentally measured in the background field of water-cooled magnet.The study of mechanical and electrical properties of iron-based superconducting tape provides basic data for the design of insert coil.Simulation analysis of quench characteristics and AC loss characteristics for iron-based superconducting tape:The thermal conductivity of iron-based superconducting tape from 4.2 K to 300 K was measured by PPMS.By combining the thermal-electrical coupling equation and H equation,which have been widely used in superconductor simulation in recent years,with the E-J constitutive relation of superconductor,two two-dimensional axial symmetry models are established to analyze the quench and AC loss characteristics of iron-based superconducting tape.The quench propagation process of iron-based superconducting tape was studied,and the quench parameters of iron-based superconducting tape at 4.2 K are measured.The effects of core wire number,magnetic field amplitude,magnetic field frequency and core wire spacing on the AC loss of iron-based superconducting tape were investigated,which provided a reference direction for the optimization of the preparation process of iron-based superconducting tape.Design and analysis of iron-based superconducting high field insert coil:Based on the parameters of three hundred-meter iron-based superconducting tapes,the whole design of iron-based superconducting high field insert coil was carried out,including the electromagnetic design and structural design of the insert coil;The mechanical characteristics of the whole development process of the insert coil were analyzed and checked,including the winding pretension of the double pancake coil,the thermal stress during the cooling process,and the joint action of the electromagnetic force and thermal stress in process of the coil charge experiment.The development and experimental research of iron-based superconducting high field insert coil:Starting from the preliminary work,the full-scale model coil is developed.Some key technological problems in the development of the insert coil are explored and solved,and the coil optimization is carried out.The joint technology of insert coil is explored,different types of iron-based superconducting tape joints were fabricated,and the resistance and mechanical strength of the joints were measured.The iron-based superconducting insert coil was developed and the test system for the coil was set up.The excitation experiment is carried out under the background field of water-cooled magnet,and the test experiment achieved the design goal.The insert coil successfully generated a central magnetic field strength more than 1 T at a high background magnetic field of 20 T.