Repairing Locally Defective Coated Conductors by Adhering a Thin Superconducting Patch

•The thin superconducting (SC) patch was fabricated by separating the metal substrate from the high Tc superconductor (HTS) coated conductor after cutting the both sides of the tape using scissors. An SC patch 20 mm in length was soldered on the defect using In-Bi solder.•It was found that by applying SC patches on the defective area in a conductor, the overall Ic of the conductor can obtain 90% or more of the Ic of a defect-free conductor tape.•The Ic values of HTS tapes with SC patches were measured in liquid nitrogen after single and double bending tests at various diameters with SC patches. It was found that there was no damage when the HTS tapes with SC patches were wound on a bobbin having a diameter of 50 mm or more. 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.