Oxide superconducting wire, solenoid coil, magnetic field generating apparatus, and process for production of oxide superconducting wire

Abstract

The cross section of a wire is round and is composed of several units, each consisting of tape-like superconductors laminated in an approximately rhombic shape, which are arranged such that they form a hexagon as a whole. Oxide superconducting tape wires each consisting of a plurality of oxide superconducting filaments are arranged in rotational symmetry to a core. The oxide superconducting filaments have the cross section such that the average thickness is 3 to 20 μm and the average aspect ratio is larger than 2 and smaller than 10. A step of arranging the oxide superconducting tape-like wires in rotational symmetry is accomplished when the multi-core tape-like wires are packed in a third metal pipe which becomes a metal sheath later. Since the multi-core tape wires having oxide superconducting filaments are arranged in rotational symmetry, the oxide superconductor in the oxide superconducting filaments permits its c axis to orient in various directions. This makes it possible to prevent the critical current from decreasing irrespective of the direction in which the magnetic field is applied and to increase the critical current density (Jc) because the oxide superconducting filament has an optimal size. The oxide superconductor should be a bismuth-based oxide superconductor, preferably be the one which has a composition of Bi 2 Sr 2 Ca 1 Cu 2 O x .

1 . An oxide superconducting wire which is characterized in that the wire has an approximately round cross section perpendicular to its lengthwise direction, the cross section is composed of several units, each unit being composed of a plurality of elements in the form of tape-like oxide superconductors which are laminated stepwise on top of each other in the direction perpendicular to the lengthwise direction at an angle of about 60 degrees with respect to the element surface within said cross section, said unit having an approximately rhombic shape within said cross section, said cross section having at least three different units which are arranged such that adjacent units have a rotational symmetry at about 120 degrees with respect to the direction of tape lamination and at least one side of a unit of rhombic shape is in contact with an adjacent unit.