Fabrication and transport properties of MgB/sub 2/ mono-core wire and solenoid coil

Round 100 m long class MgB/sub 2/ mono-core wires with Fe/Cu composite sheaths were successfully fabricated using an in situ PIT method. The J/sub c/ of the round MgB/sub 2//(Fe/Cu) wires reached 380 A/mm/sup 2/ at 4.2 K and 6 T, and exceeded 2500 A/mm/sup 2/ at 3 T. High areal reduction of the MgB/sub 2/ core was found to be effective in improving the transport properties of the MgB/sub 2/ wires. Using a 58 m long MgB/sub 2//(Fe/Cu) wire, we made a solenoid coil with 495 turns and tested it in liquid helium. The dimensions of the MgB/sub 2/ coil were 30 mm in inner diameter, 48 mm in outer diameter, and 50 mm in height. The I/sub c/ of the coil reached 214 A, which corresponds to a J/sub coil/=238 A/mm/sup 2/ and a core-J/sub c/=1420 A/mm/sup 2/. The coil generated a magnetic field at a center of B/sub o/=2.05 T and a maximum magnetic field of B/sub m/=2.17 T.