Characterization of 2G HTS Tape-to-Tape Joints Through Non-Contact Trapped Field Measurements

Previous reports (Yang et al., 2022, 2024) have shown that 2G HTS tapes can be joined together with silver nanoparticle slurries through resistive Joule heating at moderate compression pressures (<5 MPa). These reports demonstrate significant improvements in specific joint resistance uniformity (82–272 nΩ × cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) and critical current retention percentage (97–100%) at high heating rates of approximately 30 °C/min. Nevertheless, it was shown that defects such as CuO phase and/or voids at the AgNPs/Cu interface may still affect the superconducting properties during assembly, pressing, and heating. In this study, we propose a new method to non-contactly characterize the location of these defects through trapped field distribution, thus allowing further improvement of process parameters. The field cooled (FC) scheme is used to obtain the trapped field distribution profile. In addition, the superconducting current distribution in the 2G HTS tape is calculated through the corresponding mathematical formula (based on electromagnetism). A detailed analysis of the microstructure and compositional distribution (e.g., porosity and oxidation) at the tape-to-tape joint boundary will be discussed in conjunction with superconducting properties characterized by trapped field measurement and traditional I-V methods.