NIOBIUM-ALUMINUM PRECURSOR WIRE, NIOBIUM-ALUMINUM PRECURSOR TWISTED WIRE, NIOBIUM-ALUMINUM SUPERCONDUCTING WIRE, AND NIOBIUM-ALUMINUM SUPERCONDUCTING TWISTED WIRE
20240428965 ยท 2024-12-26
Assignee
- National Institute For Materials Science (Ibaraki, JP)
- Japan Superconductivity Application Development Inc. (Kanagawa, JP)
Inventors
- Akihiro KIKUCHI (Tsukuba, JP)
- Yasuo IIJIMA (Tsukuba, JP)
- Masaru YAMAMOTO (Chuo, JP)
- Masatoshi KAWANO (Chuo, JP)
- Masato OTSUBO (Tokyo, JP)
Cpc classification
International classification
Abstract
The purpose of the present invention is to provide a niobium-aluminum precursor wire having properties such as expression of flexibility and ensuring a large single-wire length, as well as a twisted wire, a superconducting wire, and a superconducting twisted wire formed of the niobium-aluminum precursor wire. The present invention provides a niobium-aluminum precursor wire and a twisted wire using the same, the niobium-aluminum precursor wire including: a rod-like winding core (5) formed of a stabilized copper, or a stabilized copper and an unstabilized copper; a laminated body (3) that is wound around the winding core (5) and that is formed of an aluminum foil and a niobium foil laminated one on the other; and a covering body (1) that covers the circumference of the laminated body and that is formed of a stabilized copper, or a stabilized copper and an unstabilized copper. The volume ratio of the stabilized copper with respect to the unstabilized copper contained in the precursor wire is 0.5-2.0, and the volume ratios of the stabilized copper contained in the winding core (5) and the covering body (1) are within prescribed ranges. According to the present invention, a superconducting wire and a superconducting twisted wire are provided by thermally treating the precursor wire and the twisted wire.
Claims
1. A niobium-aluminum precursor wire comprising: a rod-shaped core that is formed of a copper stabilizer or that is formed of a copper stabilizer and a non-copper stabilizer; a lamination that is wound around the core and that has a structure of overlapping an aluminum foil and a niobium foil each other; and a covering body that covers a periphery of the lamination, wherein the covering body is formed of the copper stabilizer or is formed of the copper stabilizer and the non-copper stabilizer, wherein a volume ratio of the copper stabilizer to the non-copper stabilizer, contained in the niobium-aluminum precursor wire is 0.5 or more and 2.0 or less; and the niobium-aluminum precursor wire satisfying, with respect to a total volume of the volume of the copper stabilizer contained in the core and the volume of the copper stabilizer contained in the covering body, the following conditions: (1) a volume percentage of the copper stabilizer contained in the core is in a range of 30% to 70%; and (2) a volume percentage of the copper stabilizer contained in the covering body is in a range of 70% to 30%, wherein a total of the volume percentage of the copper stabilizer contained in the core and the volume percentage of the copper stabilizer contained in the covering body is 100%.
2. The niobium-aluminum precursor wire according to claim 1, wherein the volume ratio of the copper stabilizer to the non-copper stabilizer, contained in the precursor wire is 0.9 or more and 2.0 or less.
3. The niobium-aluminum precursor wire according to claim 1, comprising a layer formed of a substance exhibiting low reactivity to an aluminum and a copper, wherein the layer is between the core and the lamination.
4. The niobium-aluminum precursor wire according to claim 1, comprising a layer formed of a substance exhibiting low reactivity to an aluminum and a copper, wherein the layer is between the lamination and the covering body.
5. The niobium-aluminum precursor wire according to claim 1, having an outer diameter of 0.05 mm or less.
6. A niobium-aluminum precursor twisted wire, which is one first order twisted wire formed by carrying out an operation of bundling and twisting two or more niobium-aluminum precursor wires, wherein each of the two or more niobium-aluminum precursor wires is the niobium-aluminum precursor wire according to claim 1.
7. A niobium-aluminum precursor twisted wire, which is one second order twisted wire formed by carrying out, one time, an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein each of the two or more niobium-aluminum precursor twisted wires used in the bundling and twisting operation is the niobium-aluminum precursor twisted wire according to claim 6.
8. A niobium-aluminum precursor twisted wire, which is one third order twisted wire formed by carrying out, two times, an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein the niobium-aluminum precursor twisted wire of the one third order twisted wire manufactured by the bundling and twisting operation carried out for a second time is one manufactured by carrying out the operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein each of the two or more niobium-aluminum precursor twisted wires is one manufactured by the bundling and twisting operation carried out for a first time, and wherein each of two or more niobium-aluminum precursor twisted wires used in the bundling and twisting operation carried out for the first time is the niobium-aluminum precursor twisted wire according to claim 6.
9. A niobium-aluminum precursor twisted wire, which is an (n+1) order twisted wire formed by carrying out, n times (wherein the n is an integer 3 or more), an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires to form one twisted wire, wherein a niobium-aluminum precursor twisted wire manufactured by the bundling and twisting operation carried out at each time after a second time is one manufactured by carrying out the operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein each of the two or more niobium-aluminum precursor twisted wires is one manufactured by carrying out the bundling and twisting operation one before manufacturing the each of the two or more niobium-aluminum precursor twisted wires, and wherein each of two or more niobium-aluminum precursor twisted wires used in the bundling and twisting operation carried out for a first time is the niobium-aluminum precursor twisted wire according to claim 6.
10. A niobium-aluminum superconducting wire, comprising a superconducting phase imparted by heat-treating the niobium-aluminum precursor wire according to claim 1.
11. The niobium-aluminum superconducting wire according to claim 10, wherein the superconducting phase comprises a phase represented by Nb.sub.3Al.
12. A niobium-aluminum superconducting twisted wire, comprising a superconducting phase imparted by heat-treating the niobium-aluminum precursor twisted wire according to claim 6.
13. The niobium-aluminum superconducting twisted wire according to claim 12, wherein the superconducting phase comprises a phase represented by Nb.sub.3Al.
Description
BRIEF DESCRIPTION OF DRAWINGS
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DESCRIPTION OF THE EMBODIMENTS
[0098] Hereinafter, exemplary embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist thereof.
[0099] As described above, the niobium-aluminum precursor wire of an aspect of the present invention includes: a rod-shaped core that is formed of a copper stabilizer or that is formed of a copper stabilizer and a non-copper stabilizer; a lamination that is wound around the core and that has a structure of overlapping an aluminum foil and a niobium foil each other; and a covering body that covers a periphery of the lamination, wherein the covering body is formed of the copper stabilizer or is formed of the copper stabilizer and the non-copper stabilizer. In addition, in the above niobium-aluminum precursor wire, a volume ratio of the copper stabilizer to the non-copper stabilizer, contained therein is 0.5 or more and 2.0 or less, and the above niobium-aluminum precursor wire satisfies, with respect to a total volume of the volume of the copper stabilizer contained in the core and the volume of the copper stabilizer contained in the covering body, the following conditions: (1) a volume percentage of the copper stabilizer contained in the core is in a range of 30% to 70%; and (2) a volume percentage of the copper stabilizer contained in the covering body is in a range of 70% to 30%, (wherein a total of the volume percentage of the copper stabilizer contained in the core and the volume percentage of the copper stabilizer contained in the covering body is 100%).
[0100] In the present application, the term niobium-aluminum precursor wire means a niobium-aluminum (Nb.sub.3Al) wire that is only subjected to wire rod processing (specifically, wire drawing processing) and is not subjected to heat treatment. On the other hand, a superconducting wire manufactured by heat-treating the niobium-aluminum wire is referred to as a niobium-aluminum superconducting wire in the present application.
[0101] As understood from the facts that the niobium-aluminum precursor wire of an aspect of the present invention has a structure of including the following: a rod-shaped core that is formed of a copper stabilizer or that is formed of a copper stabilizer and a non-copper stabilizer; a lamination that is wound around the core and that has a structure of overlapping an aluminum foil and a niobium foil each other; and a covering body that covers a periphery of the lamination, wherein the covering body is formed of the copper stabilizer or is formed of the copper stabilizer and the non-copper stabilizer, the above niobium-aluminum precursor wire is a so-called monofilamentary wire.
[0102] Both of the rod-shaped core that constitutes the above niobium-aluminum precursor wire and the covering body that covers the periphery of the lamination that has a structure of overlapping an aluminum foil and a niobium foil each other are formed of a copper stabilizer or formed of a copper stabilizer and a non-copper stabilizer. Both of the above rod-shaped core and the above covering body are preferably formed of a copper stabilizer.
[0103] The copper stabilizer is pure copper such as oxygen free copper, and is a stabilizing material. This is because in the case where a niobium-aluminum precursor wire is put to practical use as a superconducting wire, in the unlikely event that the superconducting state is broken, the niobium-aluminum precursor wire is required to have a composite structure in which a pure metal that is a material (this material is referred to as a stabilizing material) that has an excellent electric conductivity at extremely low temperatures served as a bypass route is necessarily composited as a material thereof, and as the pure metal, pure copper is preferable.
[0104] The non-copper stabilizer means a material other than the above copper stabilizer.
[0105] The rod-shaped core literally has a rod-like shape, and the shape of the core is not particularly limited as long as the objects of the present invention can be achieved.
[0106] The lamination that has a structure of overlapping an aluminum foil and a niobium foil each other means the thing which overlaps one aluminum foil and one niobium foil each other. Usually, the thickness of the aluminum foil is preferably 0.1 mm (i.e., 100 m), and the thickness of the niobium foil is preferably 0.03 mm (i.e., 30 m). However, the thicknesses are not particularly limited to these values as long as the objects of the present invention can be achieved, and it is more preferable as the thicknesses are thinner.
[0107] Also, usually, it is preferable that the aluminum foil and the niobium foil are laid to overlap each other so that the side in contact with the core is the aluminum foil. However, the order is not particularly limited to this order as long as the objects of the present invention can be achieved.
[0108] In order that the lamination having a structure of overlapping the aluminum foil and the niobium foil each other is wound around the rod-shaped core, it is only required that the lamination having a structure of overlapping the aluminum foil and the niobium foil each other is wound into a roll around the rod-shaped core.
[0109] The form of the covering body that covers the periphery of the lamination having a structure of overlapping an aluminum foil and a niobium foil each other is not particularly limited as long as the covering body is formed of the copper stabilizer or is formed of the copper stabilizer and the non-copper stabilizer, as described above. The form of the covering body is usually one copper tube.
[0110] In the niobium-aluminum precursor wire, the volume ratio of the copper stabilizer to the non-copper stabilizer, contained therein is 0.5 or more and 2.0 or less. When the lower limit is set to 0.5 or more, the proportion of the copper stabilizer in the ultra-fine niobium-aluminum superconducting wire increases in the case where an ultra-fine (specifically, 50 m or less) niobium-aluminum wire is processed into a superconducting wire, and thus a situation in which the wire rod is burnt out in the unlikely event that the superconducting state is broken and quenching occurs is preferably avoided. From such a point of view; the lower limit of the volume ratio of the copper stabilizer to the non-copper stabilizer is set to preferably 0.9 or more, and more preferably 1.0 or more. When the upper limit is set to 2.0 or less, a situation in which for the reason that the proportion of the copper stabilizer in the ultra-fine niobium-aluminum superconducting wire is too large, the proportion of superconductivity is relatively small and the superconducting effect is weakened can be preferably avoided.
[0111] The above niobium-aluminum precursor wire satisfies, with respect to a total volume of the volume of the copper stabilizer contained in the core and the volume of the copper stabilizer contained in the covering body, the following conditions: (1) a volume percentage of the copper stabilizer contained in the core is in a range of 30% to 70%, and (2) a volume percentage of the copper stabilizer contained in the covering body is in a range of 70% to 30%. Here, a total of the volume percentage of the copper stabilizer contained in the core and the volume percentage of the copper stabilizer contained in the covering body is 100%.
[0112] When the volume percentage of the copper stabilizer contained in the core located at the center of the above niobium-aluminum precursor wire and the volume percentage of the copper stabilizer contained in the covering body located at the outer periphery of the above niobium-aluminum precursor wire are both set in the above ranges, the mechanical characteristics of the entire niobium-aluminum precursor wire can be balanced, which is a composite of metals such as niobium, aluminum, and copper that have different hardnesses, elongations, and mechanical properties such as work hardening rate and plastic working limit. Therefore, according to the above niobium-aluminum precursor wire, the final wire diameter (specifically, outer diameter) after wire drawing processing can be set to 50 m or less, and further a single wire length of 1,000 m or more can be secured.
[0113] Setting the volume percentage of the copper stabilizer contained in the core located at the center to 30% or more is desirable because the mechanical characteristics of the entire niobium-aluminum precursor wire can be balanced. The copper stabilizer in the center is derived from the core used when an aluminum foil and a niobium foil are wound to overlap each other, but setting the volume percentage of the copper stabilizer in the center to 30% or more is desirable, also from the point of view that the problem that the diameter of the core becomes thinner due to the small amount of copper stabilizer and thus working properties significantly reduce can be preferably avoided.
[0114] Also, setting the volume percentage of the copper stabilizer contained in the core located at the center to 70% or less is desirable because the mechanical characteristics of the entire niobium-aluminum precursor wire can be balanced. Specifically, the above setting is desirable because the situation that the copper sheath is easily torn and peeled off during wire drawing processing, which is a cause to induce wire breakage can be avoided. This is because setting the volume percentage of the copper stabilizer in the center to 70% or less means that the volume percentage of the copper stabilizer at the outer periphery is greater than 30%, thereby meaning that a sufficient thickness of the covering body (namely, the thickness of the copper sheath) that is formed of the copper stabilizer or that is formed of the copper stabilizer and the non-copper stabilizer, which is located at the outer periphery of the niobium-aluminum precursor wire can be secured and the problem that the copper sheath has a thinner thickness and is easily torn can be desirably avoided.
[0115] The niobium-aluminum precursor wire of an aspect of the present invention includes a layer (this layer is also referred to as a diffusion barrier layer in the present application) formed of a substance exhibiting low reactivity to aluminum between the above core and/or the above covering body and the above lamination.
[0116] When a niobium-aluminum superconducting wire is manufactured by heat-treating the above niobium-aluminum precursor wire, aluminum of the aluminum foil constituting the above lamination reacts with copper of the above core and/or the above covering body in contact with the aluminum foil, and this may affect the characteristics of the entire niobium-aluminum superconducting wire depending on the reaction amount thereof, and thus the diffusion barrier layer is preferable in terms that such a situation can be prevented.
[0117] Hence, the diffusion barrier layer is not particularly limited as long as the objects of the present invention can be achieved if the substance exhibits low reactivity to aluminum and copper to the extent that does not affect the characteristics of the entire niobium-aluminum superconducting wire when a niobium-aluminum superconducting wire is manufactured by heat treatment the above niobium-aluminum precursor wire. Specific examples thereof include niobium and tantalum.
[0118] The diffusion barrier layer between the above core and the above lamination and the diffusion barrier layer between the above lamination and the above covering body may be formed of the same material or formed of the different materials as long as the materials are substances exhibiting low reactivity to aluminum and copper.
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[0120] The niobium-aluminum precursor twisted wire of an aspect of the present invention is one first order twisted wire formed by carrying out an operation of bundling and twisting two or more niobium-aluminum precursor wires described above as an aspect of the present invention. A cross-sectional view of the first order twisted wire is illustrated in
[0121] As illustrated in
[0122] On the other hand, as illustrated in
[0123] When a niobium-aluminum precursor wire of a conventional multifilamentary wire is bent, the strain applied to the center becomes extremely large because the individual filaments adhere to each other and are integrated as a whole and the neutral axis of bending is at the center of the entire multifilamentary wire, as seen in the conceptual diagram illustrating the bending mechanism in
[0124] On the other hand, when the niobium-aluminum precursor twisted wire of an aspect of the present invention is bent, even in the case where several tens of niobium-aluminum precursor wires, which are monofilamentary wires, are bundled and twisted to form a niobium-aluminum precursor twisted wire having a large diameter (in other words, an assembly of niobium-aluminum precursor wires), as seen in the conceptual diagram illustrating the bending mechanism in
[0125] The niobium-aluminum precursor twisted wire of an aspect of the present invention is also a niobium-aluminum precursor twisted wire formed, as one second order twisted wire, by carrying out, one time, an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires. Here, the niobium-aluminum precursor twisted wire used in the above bundling and twisting operation, namely the bundling and twisting operation carried out for the first time is the niobium-aluminum precursor twisted wire (i.e., first order twisted wire) described above as an aspect of the present invention.
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[0127] The niobium-aluminum precursor twisted wire of an aspect of the present invention is also a niobium-aluminum precursor twisted wire formed as one third order twisted wire by carrying out, two times, an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein the niobium-aluminum precursor twisted wire of the one third order twisted wire manufactured by the bundling and twisting operation carried out for the second time is manufactured by carrying out an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein each of the two or more niobium-aluminum precursor twisted wires is one manufactured by the bundling and twisting operation carried out for the first time Here, each of two or more niobium-aluminum precursor twisted wires used in the bundling and twisting operation carried out for the first time is the niobium-aluminum precursor twisted wire (i.e., first order twisted wire) described above as an aspect of the present invention.
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[0129] The niobium-aluminum precursor twisted wire of an aspect of the present invention is also a niobium-aluminum precursor twisted wire, which is an (n+1) order twisted wire formed by carrying out, n times (wherein the n is an integer 3 or more), an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires to form one twisted wire, wherein a niobium-aluminum precursor twisted wire manufactured by the bundling and twisting operation carried out at each time after a second time is one manufactured by carrying out the above operation of bundling and twisting two or more niobium-aluminum precursor twisted wires, wherein each of the two or more niobium-aluminum precursor twisted wires is one manufactured by carrying out the bundling and twisting operation one before manufacturing the each of the two or more niobium-aluminum precursor twisted wires. Here, each of two or more niobium-aluminum precursor twisted wires used in the bundling and twisting operation carried out for the first time is the niobium-aluminum precursor twisted wire (i.e., first order twisted wire) described above as an aspect of the present invention. As such, a high order twisted wire of a fourth or more order twisted wire can be, if necessary, manufactured by repeatedly carrying out an operation of bundling and twisting two or more niobium-aluminum precursor twisted wires to form one twisted wire.
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[0131] The niobium-aluminum superconducting wire of an aspect of the present invention has a superconducting phase imparted by heat-treating the niobium-aluminum precursor wire described above as an aspect of the present invention. It is preferable that the superconducting phase includes a phase represented by Nb.sub.3Al. For the above heat treatment, a known heat treatment process that is adopted when a niobium-aluminum precursor wire is converted into a superconducting wire has only to be applied. Specifically, for example, the niobium-aluminum precursor wire has only to be maintained at any temperature less than the melting point of pure copper (1,085 C.) for several minutes to several hundred hours in a vacuum (10.sup.2 Pa or less) or in an atmosphere of non-oxidizing inert gas (argon gas, nitrogen gas, or the like), and cooled in the furnace.
[0132] The niobium-aluminum superconducting twisted wire of an aspect of the present invention has a superconducting phase imparted by heat-treating the niobium-aluminum precursor twisted wire described above as an aspect of the present invention. It is preferable that the superconducting phase includes a phase represented by NB.sub.3Al. For the above heat treatment, a known heat treatment process that is adopted when a niobium-aluminum precursor wire is converted into a superconducting wire has only to be applied. Specifically, for example, the niobium-aluminum precursor wire has only to be maintained at any temperature less than the melting point of pure copper (1,085 C.) for several minutes to several hundred hours in a vacuum (10.sup.2 Pa or less) or in an atmosphere of non-oxidizing inert gas (argon gas, nitrogen gas, or the like), and cooled in the furnace.
[0133] Conditions that are not specified in the present application are not particularly limited as long as the objects of the present invention can be achieved.
EXAMPLES
[0134] Next, embodiments of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the embodiments of the present invention are not limited to the following examples as long as the gist thereof is not exceeded.
Manufacture of Niobium-Aluminum Precursor Wire and Evaluation of its Characteristics
[0135] The examples for the manufacture of niobium-aluminum precursor wires are illustrated in Examples 1 to 14. The examples of Examples 5 to 7 and Examples 11 to 14 correspond to the examples for the manufacture of niobium-aluminum precursor wires, which are illustrated as an aspect of the present invention, so-called Examples. And the other examples correspond to the examples for the manufacture of niobium-aluminum precursor wires, which do not belong to the aspects of the present invention, so-called Comparative Examples.
Example 1
[0136] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 2.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.1 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having an outer diameter after final wire drawing processing (this outer diameter is referred to as a final wire diameter in the present application) of 0.05 mm and a single wire length of 126 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 0.5. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 7.5% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 92.5%.
Example 2
[0137] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 2.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 14.0 mm and an inner diameter of 10.1 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.183 mm and a single wire length of 566 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 4.1% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 95.9%.
Example 3
[0138] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 3.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.1 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 455 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 0.6. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 15.4% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 84.6%.
Example 4
[0139] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 3.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 14.0 mm and an inner diameter of 10.1 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.067 mm and a single wire length of 233 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.1. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 8.7% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 91.3%.
Example 5
[0140] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 5.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.1 mm, and s subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 2063 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 33.7% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 66.3%.
[0141] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 6
[0142] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 6.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a NB.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.6 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1313 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 48.0% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 52.0%.
[0143] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 7
[0144] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 7.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 11.2 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1466 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 65.5% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 34.5%.
[0145] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 8
[0146] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 6.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 14.0 mm and an inner diameter of 10.1 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.07 mm and a single wire length of 134 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 2.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 72.3% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 27.7%.
Example 9
[0147] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 9.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 14.0 mm and an inner diameter of 13.0 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.12 mm and a single wire length of 30 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.2. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 75.0% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper contained in the pure copper tube (namely, outer sheath) located at the outer periphery was as low as 25.0%. Since the pure copper outer sheath was so thin, the copper frequently was torn and thus peeled off on the way of the processing.
Example 10
[0148] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 10.0 mm in the following manners; winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 14.0 mm and an inner diameter of 13.6 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.2 mm and a single wire length of 10 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.3. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 90.1% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper contained in the pure copper tube (namely, outer sheath) located at the outer periphery was as quite low as 9.9%. Therefore, the pure copper outer sheath was far thinner than in Example 9, and the copper peeled off and the wire breakage occurred at a high level on the way of the processing.
Example 11
[0149] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 4.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.8 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 2015 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 0.5. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 31.6% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 68.4%.
[0150] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 12
[0151] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 5.0 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 10.8 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1957 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 0.7. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 41.9% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 58.1%.
[0152] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 13
[0153] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 5.2 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 9.4 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1650 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely, non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 1.5. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 30.1% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of the pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 69.9%.
[0154] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
Example 14
[0155] A lamination was manufactured by winding a pure niobium foil having 0.1 mm thickness and a pure aluminum foil having 0.03 mm thickness around a pure copper core having a diameter of 5.5 mm in the following manners: winding only the pure niobium foil around the core with the required number of turns at the winding start, thereby forming an inner diffusion barrier layer; then winding the pure niobium foil and the pure aluminum foil to overlap each other, and forming a Nb.sub.3Al phase in the case where the reaction of the pure niobium foil and the pure aluminum foil occurs; and again winding only the pure niobium foil with the required number of turns at the winding end, thereby forming an outer diffusion barrier layer. The manufactured lamination was inserted into a pure copper tube having an outer diameter of 12.3 mm and an inner diameter of 9.0 mm, and subjected to cold extrusion processing, and drawing processing by means of a carbide die and a diamond die, thereby obtaining a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1750 m. The volume ratio of the pure copper (namely, copper stabilizer) to the non-pure copper (namely; non-copper stabilizer) in the obtained niobium-aluminum precursor wire was 2.0. And the volume percentage of the pure copper (namely, copper stabilizer) in the above core located in the center was 30.1% with respect to the total volume of the pure copper in the above core and the pure copper (namely, copper stabilizer) in the pure copper tube. In other words, the proportion of pure copper (namely, copper stabilizer) in the pure copper tube located at the outer periphery was 69.9%.
[0156] It has been confirmed that according to this example, which is an embodiment of the present invention, a niobium-aluminum precursor wire having a final wire diameter of 0.05 mm and a single wire length of 1,000 m or more can be obtained.
[0157] Table 1 summarizes the respective numerical values of the diameters of the pure copper cores (namely, copper cores), the inner and outer diameters of the pure copper tubes (namely, copper tubes), the volume percentages of the copper (namely, division rates of the copper) in the center and at the outer periphery; the volume ratios of the pure copper to the non-pure copper (namely, (pure copper/non-pure copper) ratio), the final wire diameters, and the single wire lengths in Examples 1 to 14.
TABLE-US-00001 TABLE 1 Division rate Copper Copper tube of copper (pure Single core Inner Outer Outer copper/non- Final wire wire Diameter diameter diameter Center periphery pure copper) diameter length Example (mm) (mm) (mm) (%) (%) ratio (mm) (m) Example 1 2.0 10.1 12.3 7.5 92.5 0.5 0.05 126 Example 2 2.0 10.1 14.0 4.1 95.9 1.0 0.183 566 Example 3 3.0 10.1 12.3 15.4 84.6 0.6 0.05 455 Example 4 3.0 10.1 14.0 8.7 91.3 1.1 0.067 233 Example 5 5.0 10.1 12.3 33.7 66.3 1.0 0.05 2063 Example 6 6.0 10.6 12.3 48.0 52.0 1.0 0.05 1313 Example 7 7.0 11.2 12.3 65.5 34.5 1.0 0.05 1466 Example 8 6.0 10.1 14.0 27.7 72.3 2.0 0.07 134 Example 9 9.0 13.0 14.0 75.0 25.0 1.2 0.12 30 Example 10 10.0 13.6 14.0 90.1 9.9 1.3 0.2 10 Example 11 4.0 10.8 12.3 31.6 68.4 0.5 0.05 2015 Example 12 5.0 10.8 12.3 41.9 58.1 0.7 0.05 1957 Example 13 5.2 9.4 12.3 30.1 69.9 1.5 0.05 1650 Example 14 5.5 9.0 12.3 30.1 69.9 2.0 0.05 1750
[0158]
[0159] As illustrated in
[0160] On the other hand, it has also been confirmed that in any of the niobium-aluminum precursor wires described in Examples 1 to 4 and Examples 8 to 10, which do not belong to the aspects of the present invention, both securing an ultra-fine final wire diameter of 0.05 mm and securing a long single wire length of 1,000 m or more are not satisfied.
[0161] Consequently, it has been confirmed that according to the niobium-aluminum precursor wire of the present invention, in addition to securing a long single wire length of 1,000 m or more, an ultra-fine final wire diameter of 0.05 mm (50 m) thinner than a human hair can be also secured, and thus the niobium-aluminum precursor wire of the present invention can exert bendability (so-called flexibility) and insulation treatment and coiling can be realized by handling similar to that of a niobium-titanium alloy wire even in the case where electromagnets are manufactured by using a niobium-aluminum (Nb.sub.3Al) superconducting wire.
Manufacture of Niobium-Aluminum Superconducting Wire and Evaluation of its Characteristics
Example 15
[0162] Regarding a niobium-aluminum precursor wire obtained in Example 5 of the Examples, wherein the niobium-aluminum precursor wire is an ultra-fine monofilamentary wire (i.e., element wire) and has a final wire diameter of 0.05 mm and a single wire length of 2063 m. one part thereof was cut out, and maintained at 800 C. for 10 hours in a high vacuum of 10.sup.3 Pa or less so that a diffusion reaction occurs to generate a Nb.sub.3Al phase of a superconducting phase at the portion of the niobium/aluminum lamination, thereby manufacturing (i.e., producing) a niobium-aluminum superconducting wire. An external magnetic field of up to 18 T (tesla) was applied to this niobium-aluminum superconducting wire in liquid helium, and the superconducting transport current value that enables to pass the current with zero resistance was measured.
Manufacture of Niobium-Aluminum Precursor Twisted Wire and Superconducting Twisted Wire and Evaluation of Their Characteristics
Example 16
[0163] Regarding a niobium-aluminum precursor wire obtained in Example 5 of the Examples, wherein the niobium-aluminum precursor wire is an ultra-fine monofilamentary wire (i.e., element wire) and has a final wire diameter of 0.05 mm and a single wire length of 2063 m, one part thereof was used to prepare 19 monofilamentary wires, and by bundling and twisting the 19 monofilamentary wires, one niobium-aluminum precursor twisted wire (i.e., first order twisted wire) was manufactured (i.e., produced).
Example 17
[0164] Regarding a niobium-aluminum precursor wire obtained in Example 5 of the Examples, wherein the niobium-aluminum precursor wire is an ultra-fine monofilamentary wire (i.e., element wire) and has a final wire diameter of 0.05 mm and a single wire length of 2063 m. one part thereof was used to prepare 7 monofilamentary wires, and by bundling and twisting the 7 monofilamentary wires, one niobium-aluminum precursor twisted wire (i.e., first order twisted wire) was manufactured. In this way, 7 of these niobium-aluminum precursor twisted wires (i.e., 7 first order twisted wires) were prepared. And it has been confirmed that by bundling and twisting the 7 niobium-aluminum precursor twisted wires (i.e., 7 first order twisted wires) to form one niobium-aluminum precursor twisted wire, a second order twisted wire was manufactured.
[0165] It has also been confirmed (not illustrated) that even in the case of a niobium-aluminum precursor twisted wire processed into a second or higher order twisted wire, by carrying out, as is in the case with the first order niobium-aluminum precursor twisted wire, the process of maintaining the second or higher order niobium-aluminum twisted wire at 800 C. for 10 hours in a high vacuum of 10.sup.3 Pa or less so that a diffusion reaction occurs to generate a Nb.sub.3Al phase of a superconducting phase at the portion of the niobium/aluminum lamination, the second or higher order niobium-aluminum twisted wire (namely, niobium-aluminum superconducting twisted wire) exhibiting superconducting characteristics and no damage due to the bundling and twisting processing can be manufactured.
[0166] It has also been found that by bundling and twisting the required number of twisted wires in this manner, a niobium-aluminum twisted wire (namely, niobium-aluminum superconducting twisted wire) capable of extremely easily and freely increasing the current capacity to the desired current capacity can be manufactured (i.e., produced).
[0167] It has also been found that even in any case of niobium-aluminum precursor twisted wires or niobium-aluminum superconducting twisted wires having a NB.sub.3 Al phase of a superconducting phase generated by heat-treating the niobium-aluminum precursor twisted wires, the individual niobium-aluminum precursor wires or the individual niobium-aluminum superconducting wires, which are ultra-fine monofilamentary wires having a final wire diameter of 0.05 mm or less, do not adhere to each other, so that the monofilamentary wires (i.e., niobium-aluminum precursor wires or niobium-aluminum superconducting wires) can smoothly slide locally inside the twisted wire (i.e., niobium-aluminum precursor twisted wire or niobium-aluminum superconducting twisted wire) when being bent, thereby relieving the strain.
Industrial Applicability
[0168] The present invention is highly expected to be used and applied to various superconducting application instruments, such as medical MRI, NMR spectrometers, linear motor cars, high-energy particle accelerators, nuclear fusion reactors, superconducting motors, and superconducting generators. Therefore, the present invention can be used in a wide variety of industries (for example, medical instrument industry, electrical/communication instrument industry, transportation industry, and energy industry).
[0169] REFERENCE SIGNS LIST [0170] 1 Copper tube (, which is formed of copper stabilizer or copper stabilizer and non-copper stabilizer) [0171] 2, 4 Diffusion barrier layer (, which is formed of niobium, tantalum, or the like) [0172] 3 Lamination (, which is formed of niobium/aluminum) [0173] 5 Core (, which is formed of copper stabilizer or copper stabilizer and non-copper stabilizer)