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

IInternal Mg diffusion technology (IMD) unfolds the expansive prospect of MgB2 superconducting wires. To the facilitate 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 performances 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 Je and layer Jc significantly, while shrinking wire diameter would further improve wires transport capability. The optimal Je and layer Jc of wire in 0.8 mm diameter reached 1.2×104 A/cm2 and 1.1×105 A/cm2 respectively at 4.2 K and 8 T, which contained C-coated B powder and was annealed at 650 ℃. These improved wires were eligible for magnets use in term of performances, integrity, length and uniformity.