Local Measurement of Current Density by Magneto-Optical Current Reconstruction in Normally and Overpressure Processed Bi-2223 Tapes

TL;DR

This study uses magneto-optical techniques to analyze local current densities in Bi-2223 tapes, revealing significant improvements in current uniformity and maximum local current density through overpressure processing.

Contribution

It introduces a detailed local measurement method for current density in Bi-2223 tapes and demonstrates how overpressure processing enhances current distribution and maximum current density.

Findings

Overpressure processing increases Jc from 40 to 48 kA/cm^2.

Current distribution becomes more uniform after overpressure treatment.

Maximum local current density reaches nearly 300 kA/cm^2 after processing.

Abstract

Magneto-optical current reconstruction has been used for detailed analysis of the local critical current density (Jc) variation in monocore Bi-2223 tapes. We find, even in high quality tapes with bulk transport Jc ~ 40 kA/cm^2 (77K, 0T), that there exist local regions which possess current densities of more than 200 kA/cm^2. Overpressure processing at 148 bar significantly improved Jc to 48 kA/cm^2 by improving the connectivity. For the overpressure-processed sample we find that the current distribution is more uniform and that the maximum local current density at 77 K is increased almost to 300 kA/cm^2.