Electromagnetic Analysis Of Nb₃Sn Superconducting Magnet

With the continuous development and application of superconductingtechnology，the increasing need for superconducting materials of high criticalcurrent debsity.Nb₃Sn superconducting magnet which takes intermetalliccompounds as substrate has special significance. The conductor is made by it，whose critical performance are superior to NbTi conductors，is the preferredmaterial of future fusion reactor’s superconducting magnet.For the first domestic fusion reactor with large Nb₃Sn CICC superconductingmagnet，the magnet are analyzed in this article by three parts.First，we made theelectromagnetic analysis of the Nb₃Sn superconducting maganet. The calculationformulas of Helical coils magnetic field was deduced which based on In an axiallysymmetric magnetic field analysis，The detailed magnetic field distribution is givenand the electromagnetic force distribution during the maximum magnetic field iscalculated.We calculated the coil inductance by flux method，energy method andclassical formula method and gave a consistent calculated values in order toprovide evidence for the follow-up magnet quench study.Then the magnet’s AC losswas analysed.We focused on considering the coupling loss betweensuperconducting strands and various sub cable. Based on the theoreticalcalculation，we calculated the energy deposition of this loss in conductors whichcompared with the conductor’s stability margin and proved the conductor stability.Finally, the superconducting magnet quench process, detection and protectioncircuit were studied.Based on the three-dimensional quench propagation model，weanalysed the quench propagation velocity and gave the quench resistance，temperature and current change curve.The active power method for quenchdetection is selected， then we protected the magnet by the discharge energyresistance.Using the MATLAB software to complete the simulation of the quenchdetection protection circuit to prove the correctness of theoretical calculation andmethod.The Nb₃Sn magnet electromagnetic analysis and inductance parameters’sdetermination, AC loss and magnet quench analysis and calculation as well as thequench detection and protection scheme design which provided a basis for the stable operation of the superconducting magnet.