Superconducting Joining Concept for Internal Magnesium Diffusion-Processed Magnesium Diboride Wires

A superconducting joint of unreacted monofilament internal magnesium diffusion-processed magnesium diboride (MgB₂) wires was fabricated by exploiting the phenomenon of magnesium diffusion into the boron layer inside the superconducting joint. Unprecedentedly, the joint was able to carry an almost identical transport current compared to the bare wire in a 2-7 T magnetic field at 20 K. The joint also exhibited very low joint resistance of 2.01 × 10^-13 Ω in self-field at 20 K. Among commercially available superconductors, this work is the first to successfully realize a superconducting joint that is capable of transferring current from one conductor to another without any notable degradation under strong magnetic fields. This work demonstrates great potential to apply MgB₂ in a range of practical applications, where superconducting joints are essential.