Superconducting Joint Structures For Bi-2212 Wires Using a Powder-in-Tube Technique

Bi-2212/Ag superconducting wires are being considered as key conductor candidates for the development of high-field magnets. This work focuses on the design and testing of various joint structures for multifilamentary Bi-2212 wires using powder-in-tube techniques. The joints are made between the unreacted wires and subsequently heat treated with the wires. The microstructure and transport properties of different joint architectures including step joints, scarf joints and etched joints have been explored. The performance of etched-joints are found to be very sensitive to the etching parameters including etching time, making it difficult to develop a reliable jointing process. Scarf joints and step joints can carry higher currents (320 A and 475 A in self-field at 4 K) than the etched joints (225 A in self-field at 4 K) as a result of connecting a larger area of the exposed filaments without damaging the filaments.