High critical current of Cu-sheathed MgB2 wire at 20 K

For large-scale electric power applications of MgB2 wire, especially at AC environments, development of nonmagnetic sheath material is essential. In this study, Cu-sheathed MgB2 wire was fabricated using the powder-in-tube method and ultra-fine Mg and B precursor prepared by high-energy ball milling. Lowering the annealing temperature and shortening the annealing time effectively limit the reaction between Mg and Cu. Critical current density of the wire annealed at 700 degrees C for 5 minutes is 4.3 x 10(4) A/cm(2) at 20 K and self-field. Adding excess Mg in precursor further enhances critical current to 250 A at 20 K and self-field. These results demonstrate the potential of Cu-sheathed MgB2 wires for large-scale applications.