Repairing Locally Defective Coated Conductors by Adhering a Thin Superconducting Patch

Abstract Defects are frequently introduced during the fabrication process of long-length coated conductors and typically have a critical current (Ic) that is lower than the average Ic of the conductor. If the Ic of a defective area can be increased to a value similar to the average conductor Ic, the applicability of long-length high-Tc superconducting (HTS) tape with defects can be improved. We have proposed a method for effectively repairing locally defective or damaged HTS tape using a superconducting (SC) patch, which was prepared by separating the metal substrate from the HTS coated conductor by interface delamination. The SC patch has high engineering critical current density with a simple structure of stabilizing layer / superconducting layer / stabilizing layer. Attaching a SC patch repairs local defects in a conductor by enabling the defective area to exhibit a comparatively higher Ic. The average Ic value of the defect-free HTS tape was about 160 A, while the Ic value of HTS tape including defective areas was about 105 A, but was increased to a level of 150 A when SC patches were applied. It was found that, by applying SC patches on the defective area in a conductor, the overall Ic of the conductor can reach at least 90% of the Ic value produced by a defect-free conductor. Further, no damage was found when the HTS tapes with SC patches were wound on a bobbin with a diameter of at least 50 mm.