When bending a superconducting cable of a stack conductor structure in which a plurality of layers of tape wires are stacked, a twisting process is performed for the superconducting cable immediately before a bending portion of the superconducting cable.

A connection structure of a superconducting layer according to an embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer provided between the first superconducting layer and the second superconducting layer and including a first substance containing a rare earth element, barium, copper, and oxygen and a second substance containing a metal element, in which a first region per unit area at a first interface between the first superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the first superconducting layer are in contact with each other, and a second region per unit area at a second interface between the second superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the second superconducting layer are in contact with each other.

A connection structure of a superconducting layer according to an embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer provided between the first superconducting layer and the second superconducting layer and including a first substance containing a rare earth element, barium, copper, and oxygen and a second substance containing a metal element, in which a first region per unit area at a first interface between the first superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the first superconducting layer are in contact with each other, and a second region per unit area at a second interface between the second superconducting layer and the connection layer is 1% or more and 50% or less where the second substance and the second superconducting layer are in contact with each other.

An oxide superconducting wire includes: a superconducting laminate comprising a substrate and an oxide superconducting layer; and a stabilization layer made of copper plating formed around the superconducting laminate. A thickness d of the stabilization layer is in the range of 10 to 40 μm. A ratio Ra/d of the thickness d of the stabilization layer and an arithmetic mean roughness Ra of an outer surface of the stabilization layer is in the range of 0.005 to 0.03. An intermediate layer is arranged between the substrate and the oxide superconducting layer. When a tensile test of pulling the oxide superconducting wire in a longitudinal direction within a stress range of 180 to 600 MPa in liquid nitrogen is performed, a ratio of a critical current when a repeated pulling number reaches 100,000 times and an initial critical current measured before the tensile test is 0.99 or more.

An oxide superconducting wire includes: a superconducting laminate comprising a substrate and an oxide superconducting layer; and a stabilization layer made of copper plating formed around the superconducting laminate. A thickness d of the stabilization layer is in the range of 10 to 40 μm. A ratio Ra/d of the thickness d of the stabilization layer and an arithmetic mean roughness Ra of an outer surface of the stabilization layer is in the range of 0.005 to 0.03. An intermediate layer is arranged between the substrate and the oxide superconducting layer. When a tensile test of pulling the oxide superconducting wire in a longitudinal direction within a stress range of 180 to 600 MPa in liquid nitrogen is performed, a ratio of a critical current when a repeated pulling number reaches 100,000 times and an initial critical current measured before the tensile test is 0.99 or more.

A superconducting wire includes a substrate and a superconducting material layer. The substrate includes a first main surface and a second main surface opposite to the first main surface. The superconducting material layer is disposed on the first main surface. Along at least a part of the superconducting wire in a direction in which the superconducting wire extends, the superconducting material layer is disposed to cover a side surface of the substrate in a width direction of the substrate and cover at least a part of the second main surface. A thickness of the superconducting material layer located on the first main surface varies along the width direction. A maximum thickness of the superconducting material layer located on the second main surface is smaller than a maximum thickness of the superconducting material layer located on the first main surface.

A superconducting wire includes a substrate and a superconducting material layer. The substrate includes a first main surface and a second main surface opposite to the first main surface. The superconducting material layer is disposed on the first main surface. Along at least a part of the superconducting wire in a direction in which the superconducting wire extends, the superconducting material layer is disposed to cover a side surface of the substrate in a width direction of the substrate and cover at least a part of the second main surface. A thickness of the superconducting material layer located on the first main surface varies along the width direction. A maximum thickness of the superconducting material layer located on the second main surface is smaller than a maximum thickness of the superconducting material layer located on the first main surface.

A method of fabricating a superconducting wire includes forming a buffer layer on the substrate, the buffer layer including an Al.sub.2O.sub.3 layer, the Al.sub.2O.sub.3 layer being formed by reactive magnetron sputtering in which first oxygen gas as reactant gas and a sputtering target made of aluminium metal are used, the Al.sub.2O.sub.3 layer being formed while being supplied the first oxygen gas at a first concentration, the first concentration being a concentration of the first oxygen gas at which an emission intensity of Al in plasma near a surface of the sputtering target is not less than 25% and not more than 80% of a first reference value, the first reference value being the emission intensity of Al at which the concentration of the first oxygen gas is zero; and forming a superconducting layer above the buffer layer.

A method of fabricating a superconducting wire includes forming a buffer layer on the substrate, the buffer layer including an Al.sub.2O.sub.3 layer, the Al.sub.2O.sub.3 layer being formed by reactive magnetron sputtering in which first oxygen gas as reactant gas and a sputtering target made of aluminium metal are used, the Al.sub.2O.sub.3 layer being formed while being supplied the first oxygen gas at a first concentration, the first concentration being a concentration of the first oxygen gas at which an emission intensity of Al in plasma near a surface of the sputtering target is not less than 25% and not more than 80% of a first reference value, the first reference value being the emission intensity of Al at which the concentration of the first oxygen gas is zero; and forming a superconducting layer above the buffer layer.

An oxide superconducting wire includes a superconducting laminate including an oxide superconducting layer disposed, either directly or indirectly, on a substrate, and a stabilization layer which is a Cu plating layer covering an outer periphery of the superconducting laminate. An average crystal grain size of the Cu plating layer is 3.30 μm or more and equal to or less than a thickness of the Cu plating layer.