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

Abstract

Internal Mg diffusion (IMD) technology reveals the expansive prospects of MgB2 superconducting wires. To facilitate the practical application of IMD, a series of 100 m class MgB2 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 × 104 and 1.1 × 105 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.