Superconducting Bi(sub 2)Sr(sub 2)Ca(sub 2)Cu(sub 3)O(sub x) closed-loop coils carrying persistent current at temperature above 77 K

摘要

We have succeeded for the first time in producing superconducting closed-loop coils that are made of Bi(sub 2)Sr(sub 2)Ca(sub 2)Cu(sub 3)O(sub x) tape and can be operated in a persistent current mode above 77 Kelvin. The persistent current density value has been deduced to be 600 A/cm(sup 2) at this temperature and the current is estimated to run for 10(sup 16) years. The persistent critical current density in our coils is about one order of magnitude smaller than the critical current value determined by a 1 (mu)V/cm criterion. The decay behaviour of the current in the coils is clearly separated in two regimes, an initial fast decay of the order of minutes followed by a slow logarithmic decay. In this paper, experimental results of the persistent current density as a function of temperature and applied magnetic field are also presented. (au)