Effects of local variations in critical current density on the performance of long Bi-2223 tapes

A vital requirement for commercial application of Bi-2223 tapes is that the high critical current densities currently obtainable in short or intermediate lengths can be maintained when piece-lengths are scaled up by more than an order of magnitude. In this paper the effects of statistical variations in local I-V characteristics on the critical current of long superconducting tapes are investigated computationally. The local I-V characteristic is parameterized by the standard power law parameters I-c and index n. Analytic solutions and simulated data are presented for a number of statistical distributions in local I-V parameters, including Gaussian, Weibull and polynomial distributions. The study concludes that for typical parameters, given local statistical variations in I-c, there should be no significant loss in performance as tape lengths are scaled up by factors of 10 to 100.