Superconducting Bi2Sr2Ca2Cu3Ox closed-loop coils carrying persistent current at temperatures above 77 K

We have succeeded in producing superconducting closed-loop coils from Bi2Sr2Ca2Cu3Ox tape. These coils can be operated in a persistent current mode even at temperatures above the boiling point of liquid nitrogen. The persistent current density value has been deduced to be 600 A/cm(2) at 77 K and the current has been estimated to run for 10(16) years. The persistent critical current density in our coils was about one order of magnitude smaller than the critical current density value determined by a 1 mu V/cm criterion. The decay behaviour of the current in the coils was clearly separated in two regimes, an initial fast decay of the order of minutes followed by a slow logarithmic-like decay. In this paper, experimental results of the persistent current density as a function of temperature and applied magnetic field are also presented.