Persistent Current of Bi2223/Ag Closed Coil in 77 K

Closed superconducting coils made from Bi2223/Ag multi-filamentary tapes were successfully fabricated. By measuring the magnetic flux density at the center of the coil, we were able to observe the persistent current mode of superconducting closed coil in liquid nitrogen. The persistent current measured was 1.39 A and remained unchanging for more than 500 hours after several hours decay. It was estimated from the decay curve that the upper limit resistance of the closed-loop coil was in the order 10^-13 Omega of . Current-voltage characteristic was derived form the decay curve and different models were applied in fitting the experiment data..