Modeling voltage distribution and current limit in Ag/Bi2Sr2Can−1CunO2n+4

Abstract

Limitations on the critical current density in Bi2Sr2CaCu2O8 films grown on MgO(001) by metalorganic deposition Current and voltage distributions in Ag/Bi 2 Sr 2 Ca nϪ1 Cu n O 2nϩ4 ͑BSCCO͒ composites are calculated from an analytical model that is based on interfacial resistivity and geometric parameters. The model was verified by measuring the voltage distribution along Ag/Bi 2 Sr 2 Ca 2 Cu 3 O 10 bars that were fabricated by sinter forging between 400-845°C and 5-10 MPa. The results show that the solutions depend on a single dimensionless parameter, L, where L is the length of the interface and is associated with resistivity of the Ag ͑ s ͒, interfacial resistivity ͑ i ͒ between the Ag and the BSCCO, and thickness of the Ag ͑d s ͒. The voltage drop across the interface is proportional to ( i s /d s ͒ 1/2 . The model was extended for powder-in-tube tapes to examine the effects of cracking on critical current density.

Magneto-optical studies of current distributions in high-Tcsuperconductors

“…It has been shown that this effect can play an important role in determining the transport properties of the composite conductors (Gurevich et al 1993, Suenaga 1995, Welp et al 1995a. A distributed resistance model predicts that a characteristic current-transfer length, λ tr , governs the current flow around the barriers in the silver sheath (Fang et al 1996a and1996b). A magneto-optical study by Peterson et al (1997) yields an experimental value of λ tr of 0.56 mm at 77 K. This suggests that for a conductor with a crack spacing closer than λ tr , a current will flow in the silver sheath along the entire conductor length.…”

Current sharing between superconducting film and normal metal

“…The model is then used to determine the effectiveness of a "surround stabilizer". Section 2 of this paper introduces a planar model of voltage distribution in the stabilizer, which is a twodimensional generalization of the one-dimensional model that has been in use for some time [7,8,9,10,11,12,13]. In Section 3 we compare the effectiveness of two different types of stabilizers -"one-sided stabilizer" [1] and "surround stabilizer" [2,3].…”

Effect of core inhomogeneity on strain tolerance of Bi-2223 composite conductors

“…We observed that the tapes with the lower I c also exhibit lower strain tolerance. Previous studies, however, suggested that for a given conductor geometry, strain tolerance should decrease with increasing I c [18,19]. This apparent contradiction is resolved by considering an explanation that accounts for the fact that the flow of supercurrent is concentrated near the Ag/BSCCO interface, which also experiences the highest strains.…”