The present invention is intended to increase the critical current density of a wire rod having a shape with good symmetry such as a round wire or a square wire by making use of mechanical milling method. The production method of the present invention for the MgB.sub.2 superconducting wire rod comprises a mixing process of preparing a powder by adding a solid organic compound to a magnesium powder and a boron powder and then applying an impact to the powder to prepare a mixture of the powder in which boron particles are dispersed inside magnesium particles, a filling process of filling a metal tube with the mixture, an elongation process of elongating the metal tube filled with the mixture and a heat treatment process of heat-treating the metal tube to synthesize MgB.sub.2.

A superconducting wire according to one embodiment of the present disclosure includes: a substrate having a first surface and a second surface; a superconducting layer having a third surface and a fourth surface; and respective coating layers. The second surface is opposite to the first surface. The fourth surface is opposite to the third surface. The superconducting layer is disposed on the substrate such that the third surface faces the second surface. The respective coating layers are disposed on the first surface and the fourth surface. Adhesion strength between the substrate and the coating layer disposed on the first surface is lower than adhesion strength between the superconducting layer and the coating layer disposed on the fourth surface.

A precursor for Nb.sub.3Sn single-core superconducting wire includes a Sn-based wire rod, a first Cu-based tube covering an outer circumferential surface of the Sn-based wire rod, an Nb-based tube covering an outer surface of the first Cu-based tube, and a second Cu-based tube covering an outer surface of the Nb-based tube. The Sn-based wire rod contains a matrix phase and at least one kind of hard phases that is harder than the matrix phase. In a cross section parallel to a longitudinal direction of the precursor for Nb.sub.3Sn single-core superconducting wire, a maximum dimension of the hard phases in a width direction perpendicular to the longitudinal direction is 50% or less of a minimum dimension in the width direction of the Sn-based wire rod and/or is equal to or smaller than a minimum thickness in the width direction of the Nb-based tube.

A superconducting coil device includes a vacuum vessel, a superconducting coil located inside the vacuum vessel, a heat shield surrounding the superconducting coil within the vacuum vessel, and an electric current introduction line for introducing an electric current into the superconducting coil. The electric current introduction line includes an outer current lead part located outside of the heat shield, within the vacuum vessel, and thermally coupled to the heat shield, and an inner current lead part located inside of the heat shield and connecting the outer current lead part to the superconducting coil. The outer current lead part includes a main body serving as an electric current path to the superconducting coil, an insulation layer that covers the main body, and a heat shield layer that covers the insulation layer and has a lower emissivity than the insulation layer.

A conductor assembly for transmitting power includes a former that defines a shape, a superconductor material disposed around the former, and a thermally insulating jacket (TIJ) disposed around and spaced apart from the superconductor material. An outer surface of the superconductor material and an inner surface of the TIJ can define an annulus through which a coolant can flow. The conductor assembly can also include an external layer, disposed around an outside surface of the TIJ, to provide structural support to the conductor assembly. The conductor assembly can also include an electrical insulation layer disposed around the outside surface of the TIJ or around the superconductor material.

A method of producing polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y (Y-358) whereby powders of yttrium (III) oxide, a barium (II) salt, and copper (II) oxide are pelletized, calcined at 850 to 950° C. for 8 to 16 hours, ball milled under controlled conditions, pelletized again and sintered in an oxygen atmosphere at 900 to 1000° C. for up to 72 hours. The polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y thus produced is in the form of elongated crystals having an average length of 2 to 10 μm and an average width of 1 to 2 μm, and embedded with spherical nanoparticles of yttrium deficient Y.sub.3Ba.sub.5Cu.sub.8O.sub.y having an average diameter of 5 to 20 nm. The spherical nanoparticles are present as agglomerates having flower-like morphology with an average particles size of 30 to 60 nm. The ball milled polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y prepared under controlled conditions shows significant enhancement of superconducting and flux pinning properties.

To provide a superconducting magnet apparatus with a structure which can prevent an increase in apparatus size even when a number of connection portions serving to connect superconducting wires is great. The superconducting magnet apparatus includes a first wiring-holding portion (tubular body (12)) extending from a bobbin (6) in an axial direction of a superconducting coil (1) and a second wiring-holding portion (joint plate (13)) which is provided on a same side in the axial direction as the tubular body (12), extends in a direction intersecting with the axial direction, and has a greater diameter than that of the bobbin (6) and the tubular body (12). Superconducting wires (7a to 11a) which extend from the superconducting coil (1) and connect to one another are spirally wound on the tubular body (12) and fastened to a groove (13a) formed on the joint plate (13).

The purpose of the present invention is to provide a method for causing sufficient deformation in precursor particles even when a soft high-purity metal is used for an outer layer material in mechanical milling, and manufacturing an MgB.sub.2 superconducting wire. A method for manufacturing an MgB.sub.2 superconducting wire in which an MgB.sub.2 filament is covered by an outer layer material, the method comprising: subjecting magnesium powder and boron powder to a shock that is insufficient for MgB.sub.2 to be clearly produced, and producing precursor particles in which boron particles are dispersed inside a magnesium matrix; filling a metal tub with the precursor particles; processing the metal tube filled with precursor particles to form a wire; and heat-treating the wire to synthesize the MgB.sub.2; wherein the method is characterized in that a portion of the wire-drawing step includes swaging.

One example includes a superconducting current control system. The system includes an inductive coupler comprising a load inductor and a control inductor. The inductive coupler can be configured to inductively provide a control current from the control inductor to a superconducting circuit device based on a load current being provided through the load inductor. The system also includes a current control element comprising a superconducting quantum interference device (SQUID) array comprising a plurality of SQUIDs. The current control element can be coupled to the inductive coupler to control an amplitude of the load current through the load inductor, and thus to control an amplitude of the control current to the superconducting circuit device.

The invention relates to a superconducting electrical switch. The switch comprises two parallel branches of superconducting material in a loop, and a magnetic field generator which generates a time-varying magnetic field through the loop in a direction generally parallel to the axis of the loop. The magnetic field generator is selectively activated and de-activated to switch the electrical switch between a low-resistance state and a higher-resistance state. In the low-resistance state, there is no magnetic field through the loop and transport current flows through the loop. In the higher-resistance state, a magnetic field through the loop induces a screening current such that the sum of the transport current and the screening current is substantially equal to the critical current or is greater than the critical current of the superconducting material. The switch may be used in, for example, a rectifier or fault current limiter.