Study On AC Loss Of Hybrid Superconductor

With the rapid development of advanced sciences such as the controlled thermonuclear reaction and high energy accelerator,the superconducting technology applications get more attention.The traditional cooling mode by liquid helium is gradually replaced by the cooling mode by refrigerator due to its large and complex refrigeration system and high cost for maintenance.By the reason of the cooling rate of refrigerator is not as good as immersion cooling,a superconductor with higher stability needs to be developed.By another superconductor recombination,not only the stability of the superconductor is improved,but also the current density increased.Hybrid method is an effective mean to improve the stability of the superconductor before a new superconducting material is developed or discovered and has an important application prospect.In this thesis,through parallel hybrid superconductor physical structure and the E-J properties of superconductors,the parallel model of current distribution of hybrid superconductor is established.The current distribution simulation calculation is applied on software,and at last,the correctness of the parallel current model is verified by an experiment.In the experiment,the mechanism of AC loss in superconductor is analyzed,and by considering the current distribution situation,the simulation and calculation on hybrid superconductor based on the AC loss model of Bean and Schonborg are implemented.Because the two superconducting tape is relatively close,the coupling loss caused by the magnetic field generated by the other superconducting strip electric current is taken into account.The experiment uses the four leads method to measure the AC loss of hybrid superconductor.According to the experimental results:in the total operation of the same current,YB,YYB and YYYB three kinds of hybrid superconductor,the AC loss of YYYB hybrid superconductor is minimum,and the AC loss of YB hybrid superconductor is maximum.It is theoretically explained that the reason is that due to the larger current in BSCCO hybrid superconductor and the higher AC loss density than YBCO,on the same condition,the YYYB combination hybrid superconductor has the minimum AC loss while the YB combination hybrid superconductor has the maximum AC loss.The experimental results are compared with the simulation results,and the two are in good agreement.This thesis studied the quench propagation velocity of high temperature/high temperature hybrid superconductor and puts forward the advantage of high temperature/high temperature hybrid superconductor:The BSCCO/YBCO hybrid superconductor quench propagation velocity is situated between the velocity of BSCCO superconductor and YBCO superconductor.Compared with Y series superconductor,there is a markble decline on quench propagation velocity of the BSCCO/YBCO hybrid superconductor,which avoids the problem of quench propagation range expanding caused by rapid loss of quench propagation velocity.The quench propagation velocity of BSCCO/YBCO hybrid superconductor is higher than it of Bi series superconductor,which resolves the permanent damage of local overheating on Bi series superconductors caused by the slow transmission of quench propagation.