Local Measurement of Current Density by Magneto-Optical Current   Reconstruction in Normally and Overpressure Processed Bi-2223 Tapes
  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. 
S. Patnaik, D.M. Feldmann, A. Polyanskii, Y. Yuan, J. Jiang, X.Y. Cai,   E.E. Hellstrom, D.C. Larbalestier and Y. Huang