The problem is to attain a joint for multi-core superconducting wires having a high critical current property. The joint for superconducting wires of the present invention has a first sintered body containing MgB.sub.2 configured to fix a plurality of superconducting wires, and a second sintered body containing MgB.sub.2 configured to joint the superconducting wires.

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.

The sheath (3) is a material, which includes an aluminium (Al) matrix, in which nanometric aluminium oxide particles (Al.sub.2O.sub.3) are homogenously dispersed, the content of Al.sub.2O.sub.3 is 0.25 to 5 vol. % and the balance is Al. It is preferred that Al.sub.2O.sub.3 originates from the surface layer present on Al powder used as feedstock material for consolidation. The superconductor based on magnesium diboride (MgB.sub.2) core (1) is fabricated by powder-in-tube or internal magnesium diffusion to boron technology, while the tube is the Al+Al.sub.2O.sub.3 composite, which is a product of powder metallurgy. A loose Al powder is pressed by cold isostatic pressing, and then the powder billet is degassed at elevated temperature and under vacuum, and then is hot extruded into a tube. A thin diffusion barrier (2) tube filled up with a mixture of Mg and B powders or Mg wire surrounded with B powder is placed into the Al+Al.sub.2O.sub.3 composite tube under inert gas or vacuum. Such composite unit is cold worked into a thin wire and then annealed at 625-655° C. for 8-90 min, what results in a formation superconducting MgB.sub.2 in a wire's core (1).

Proposed is a novel embedded structure for suppressing a disturbance in the cross sectional shape and a non-uniform deformation of a metal member arising in a precursor when producing an MgB2 multi-core wire material by a surface reduction process. This superconductive multi-core wire material precursor is characterized by having: soft Cu and Fe pure metals disposed in the center; mixed powder elements, each comprising as a sheath material a metal such as Fe or Nb having a barrier effect preventing a reaction between Mg and Cu, the mixed powder elements being disposed in a form that surrounds the periphery of the soft metal serving as the central material; and disposed around these, an outer shell layer produced from a harder metal than the central material and the sheath material.

A method of making a film comprising depositing magnesium and boron on a substrate; depositing a capping layer to form a capped film; and cooling the capped film so as to form a magnesium diboride film. The depositing may comprise tuning a ratio of the Mg to the B so as to tailor a resistivity of the magnesium diboride film anywhere in the range 10 μΩ*cm≤ρ≤500 mΩ*cm, and so as to form the magnesium diboride film comprising a superconductive film having a critical temperature greater than 10K or in a range 10K-40K. The magnesium diboride film can have an area greater than or equal to a circular area having a diameter of at least 4 inches; a thickness and sheet resistance varying by less than 10% over an entirety of the area; and a surface roughness less than 2 nm over the entirety of the area.

An object of the invention is to provide: an MgB.sub.2 superconducting thin-film wire that exhibits excellent J.sub.c characteristics even under a 20 K magnetic field; and a method for producing thereof. The MgB.sub.2 superconducting thin-film wire includes a long substrate and an MgB.sub.2 thin film formed on the long substrate. The MgB.sub.2 thin film has a microtexture such that MgB.sub.2 columnar crystal grains stand densely together on the surface of the long substrate, and has T.sub.c of 30 K or higher. In grain boundary regions of the MgB.sub.2 columnar crystal grains, a predetermined transition metal element is dispersed and segregated. The predetermined transition metal element is an element having a body-centered cubic lattice structure.

The present disclosure relates to DC transmission. Some embodiments may include a device for DC transmission comprising: a superconducting transmission line including a superconducting conductor element; and a cooling device for cooling an inner region of the transmission line with a fluid coolant to a temperature below a critical temperature of the superconducting conductor element. The superconducting transmission line may comprise a vacuum-insulated sleeve thermally isolating the inner region of the transmission line from a warmer outer surrounding area. The cooling device may comprise a feed device feeding coolant at an end region of the transmission line into the inner region of the transmission line. The transmission line may be free of internally arranged feed devices for feeding coolant at locations away from the end region.

A system and method for fabricating accelerator cavities comprises forming at least two half cavities and joining the half cavities with a longitudinal seal. The half cavities can comprise at least one of aluminum, copper, tin, and copper alloys. The half cavities can be coated with a superconductor or combination of materials configured to form a superconductor coating.

A system and method for fabricating accelerator cavities comprises forming at least two half cavities and joining the half cavities with a longitudinal seal. The half cavities can comprise at least one of aluminum, copper, tin, and copper alloys. The half cavities can be coated with a superconductor or combination of materials configured to form a superconductor coating.

The present invention addresses a problem of providing an MgB2 wire material having a small reversible bending radius, a superconducting coil using the same, and an MRI without lowering a critical current value and a critical current density of the MgB2 wire material to an extreme. To solve the problem, provided are a superconducting wire having a plurality of MgB2 strands and a first base metal, a superconducting coil using the same, and an MRI, the superconducting wire being characterized in that in a cross section orthogonal to a wire longitudinal direction, a center point of an area surrounded by the plurality of MgB2 strands and a center axis of a cross section of the superconducting wire are disposed in separated positions.