Reel-To-Reel Critical Current Measurement of REBCO Coated Conductors

Two reel-to-reel critical current (I-c) measurement systems for REBCO coated conductors (CCs) have been developed at the University of Houston. The first reel-to-reel system is based on the traditional four-probe method with a background field (up to 5 T) perpendicular to the tape surface. At present, in-field critical current of HTS tapes is measured typically over short samples cut from the ends of long tapes. Continuous in-field current transport testing of long tapes is done only at field lower than 1 T. Previously we found that I-c at low temperature in high fields, which is important for magnet applications, is strongly related to the I-c at 77 K, 3 T (perpendicular to tape) while not as much to 77 K, self-field I-c. Hence, we established a reel-to-reel system for measurement of I-c of CCs at 77 K, (B perpendicular to tape) so that in-field performance of long tapes can be qualified over their entire length and variations in in-field performance at lower temperatures can be accurately determined. The second reel-to-reel system uses a scanning Hall probe microscope (SHPM) and is for two-dimensional critical current density mapping and characterization of multi-filamentary CCs. Critical current distributions in both non-striated and 12-filament laser-striated long CCs have been mapped using this method. A novel iterative data analysis technique that was recently developed has been applied to the analysis of multi-filamentary CCs using the SHPM system.