Detection of Critical Current Distribution of YBCO-Coated Conductors Using Permanent Magnet Method

We developed a non-destructive and contactless system for measuring the critical current (I_c) in YBa₂Cu₃O_7-δ (YBCO)-coated conductors by using a permanent magnet (Sm₂Co₁₇). This I_c measurement method is based on the repulsive force (F_r) between the magnet and the shielding current in high-temperature superconductor-coated conductors. We measured F_r using a high-resolution load sensor and found that accurate F_r could be determined without the effect of thick copper film on the YBCO thin film and Hastelloy tape of the substrate. We can determine I_c from F_r0, which is the maximum repulsive force determined from an extrapolated value of the F_r vs. L curve for L = 0 mm, described in our previous paper. We show that the permanent magnet method can be used to determine the longitudinal I_c distribution and large-scale defects in YBCO-coated conductors. In addition, it turned out from this experiment that the permanent magnet method was effective to rapidly measure the longitudinal I_c distribution of long-scale coated conductors.