Improving superconducting properties of 100 m class MgB₂ wire with 18+1 filaments produced via internal Mg diffusion process

Internal Mg diffusion (IMD) technology reveals the expansive prospects of MgB 2 superconducting wires. To facilitate the practical application of IMD, a series of 100 m class MgB 2 wires with 18 + 1 filaments were prepared in this study. Based on the optical micrographs and performance analyses, the annealing temperature, B powder type and diameter of wires were refined. The results indicated that introducing C-coated B powder into wires would accelerate the diffusion of Mg melt and enhance the J e and layer J c significantly, while shrinking the wire diameter would further improve the wire transport capability. The optimal J e and layer J c of wire with an 0.8 mm diameter reached 1.2 × 10 4 and 1.1 × 10 5 A cm −2 , respectively at 4.2 K and 8 T, which contained C-coated B powder and was annealed at 650 °C. These improved wires were eligible for magnet use in terms of performances, integrity, length and uniformity.