Superconducting wire connection structure

Abstract

This superconducting wire connection structure comprises a first superconducting wire and a second superconducting wire. The first superconducting wire has a first end section in the longitudinal direction of the first superconducting wire. The second superconducting wire has a second end section in the longitudinal direction of the second superconducting wire. The first superconducting wire and the second superconducting wire each have a substrate, a middle layer disposed on the substrate, and a superconducting layer disposed on the middle layer. A connection part, which is a section of the superconducting wire connection structure where the superconducting layer located at the first end section and the superconducting layer located at the second end section are connected, has a first sandwiching member and a second sandwiching member. The superconducting layer at the first end section and the superconducting layer at the second end section are sandwiched by the first sandwiching member and the second sandwiching member. The thermal expansion rate of the first sandwiching member and the thermal expansion rate of the second sandwiching member are 0.95-1.05 times the thermal expansion rate of the substrate.

Description

[Technical Field]

[0001] This disclosure relates to a superconducting wire connection structure. This application claims priority under Japanese Patent Application No. 2021-203579, filed on 15 December 2021. All contents contained in said Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] International Publication No. 2016 / 129469 (Patent Document 1) describes a superconducting wire connection structure. The superconducting wire connection structure described in Patent Document 1 comprises a first superconducting wire, a second superconducting wire, and a bonding layer. Each of the first and second superconducting wires comprises a metal substrate, an intermediate layer, and a superconducting layer. The intermediate layer is disposed on the metal substrate. The superconducting layer is disposed on the intermediate layer. The first superconducting wire has a first end in the longitudinal direction of the first superconducting wire. The second superconducting wire has a second end in the longitudinal direction of the second superconducting wire.

[0003] In the superconducting wire connection structure described in Patent Document 1, the superconducting layer at the first end and the superconducting layer at the second end are superconductingly joined with a bonding layer in between. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2016 / 129469 [Overview of the project]

[0005] The superconducting wire connection structure of this disclosure comprises a first superconducting wire and a second superconducting wire. The first superconducting wire has a first end in the longitudinal direction of the first superconducting wire. The second superconducting wire has a second end in the longitudinal direction of the second superconducting wire. Each of the first and second superconducting wires has a base material, an intermediate layer disposed on the base material, and a superconducting layer disposed on the intermediate layer. The connection portion, which is the part of the superconducting wire connection structure where the superconducting layer at the first end and the superconducting layer at the second end are connected, has a first clamping member and a second clamping member. The superconducting layer at the first end and the superconducting layer at the second end are clamped by the first clamping member and the second clamping member. The thickness of the connection portion is 2 mm or less. The thermal expansion coefficients of the first clamping member and the second clamping member are between 0.95 and 1.05 times the thermal expansion coefficient of the base material. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a plan view of the superconducting wire connection structure 100. [Figure 2] Figure 2 is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] Figure 3 is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] Figure 4 is a diagram illustrating the manufacturing process of the superconducting wire connection structure 100. [Figure 5] Figure 5 is a cross-sectional view of the superconducting wire connection structure 100 according to the second modified example. [Figure 6] Figure 6 is a plan view of the superconducting wire connection structure 100 according to the third modified example. [Figure 7] Figure 7 is a cross-sectional view of section VII-VII in Figure 6. [Figure 8] Figure 8 is a cross-sectional view of the superconducting wire connection structure 100 according to the fourth modified example. [Figure 9] Figure 9 is a cross-sectional view of the superconducting wire connection structure 100 according to the fifth modified example. [Figure 10] Figure 10 is a cross-sectional view of the superconducting wire connection structure 100 according to the sixth modified example. [Modes for carrying out the invention]

[0007] [Issues this disclosure aims to address] In order to prevent damage to the connection portion of the superconducting wire connection structure described in Patent Document 1 (the portion where the superconducting layer at the first end and the superconducting layer at the second end are connected by a bonding layer), it is conceivable to sandwich the first end and the second end with a pair of plate members (hereinafter referred to as "first plate member" and "second plate member") and fasten the first plate member and the second plate member with screws.

[0008] However, in this case, screw holes must be formed in the first and second plate members, which increases the thickness of both the first and second plate members, resulting in reduced heat dissipation at the connection point. Poor heat dissipation at the connection point may cause the superconducting layer at the connection point to quench when the temperature at the connection point rises.

[0009] This disclosure has been made in view of the above-mentioned problems. More specifically, this disclosure provides a superconducting wire connection structure that can prevent damage at the connection while improving heat dissipation at the connection.

[0010] [Effects of this disclosure] The superconducting wire connection structure of this disclosure makes it possible to prevent damage at the connection point while improving heat dissipation at the connection point.

[0011] [Description of Embodiments in this Disclosure] First, embodiments of this disclosure will be listed and described.

[0012] (1) A superconducting wire connection structure according to an embodiment includes a first superconducting wire and a second superconducting wire. The first superconducting wire has a first end portion in the longitudinal direction of the first superconducting wire. The second superconducting wire has a second end portion in the longitudinal direction of the second superconducting wire. Each of the first superconducting wire and the second superconducting wire includes a base material, an intermediate layer disposed on the base material, and a superconducting layer disposed on the intermediate layer. A connection portion, which is a part of the superconducting wire connection structure where the superconducting layer at the first end portion and the superconducting layer at the second end portion are connected, includes a first clamping member and a second clamping member. The superconducting layer at the first end portion and the superconducting layer at the second end portion are clamped between the first clamping member and the second clamping member. The thickness of the connection portion is 2 mm or less. The coefficient of thermal expansion of the first clamping member and the coefficient of thermal expansion of the second clamping member are 0.95 times or more and 1.05 times or less the coefficient of thermal expansion of the base material.

[0013] According to the superconducting wire connection structure of (1) above, it is possible to improve heat dissipation at the connection portion while preventing damage to the connection portion.

[0014] (2) In the superconducting wire connection structure of (1) above, the connection portion may further include a cover member. The first clamping member and the second clamping member may be covered by the cover member. The coefficient of thermal expansion of the cover member may be 0.95 times or more and 1.05 times or less the coefficient of thermal expansion of the base material.

[0015] According to the superconducting wire connection structure of (2) above, it is possible to improve the water resistance at the connection portion.

[0016] (3) The superconducting wire connection structure of (2) above may further include a third superconducting wire. The third superconducting wire may include a base material, an intermediate layer, and a superconducting layer. The superconducting layer of the third superconducting wire may be disposed to face the superconducting layer at the first end portion and the superconducting layer at the second end portion. The first clamping member and the second clamping member may clamp the first end portion, the second end portion, and the third superconducting wire.

[0017] (4) In the superconducting wire connection structure of (2) or (3) above, the thermal conductivity of the first clamping member, the thermal conductivity of the second clamping member, and the thermal conductivity of the cover member are 0.1 × 10 2 The temperature may be W / m·℃ or higher. The thickness of the first clamping member and the thickness of the second clamping member may be 0.2 mm or less.

[0018] According to the superconducting wire connection structure described in (4) above, it is possible to further improve heat dissipation at the connection point.

[0019] (5) In the superconducting wire connection structures described in (2) to (4) above, the thermal resistance of the connection part may be 16°C / W or higher.

[0020] According to the superconducting wire connection structure described in (5) above, it is possible to reduce the amount of heat generated at the connection point.

[0021] (6) In the superconducting wire connection structures described in (1) to (5) above, the c-axis direction of the crystal grains of the oxide superconductor constituting the superconducting layer may be aligned with the thickness direction of the superconducting layer. When a current of 200A flows through the superconducting wire connection structure, the current density in the c-axis direction of the superconducting layer at the connection is 50A / mm 2 The following is also acceptable.

[0022] According to the superconducting wire connection structure described in (6) above, it is possible to further improve heat dissipation at the connection point.

[0023] [Details of the embodiments of this disclosure] Next, details of embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals, and redundant descriptions will not be repeated.

[0024] (Configuration of the superconducting wire connection structure according to the embodiment) The superconducting wire connection structure according to the embodiment will be described below. The superconducting wire connection structure according to the embodiment will be referred to as superconducting wire connection structure 100.

[0025] Figure 1 is a plan view of the superconducting wire connection structure 100. Figure 2 is a cross-sectional view taken along line II-II in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 1. As shown in Figures 1 to 3, the superconducting wire connection structure 100 includes a first superconducting wire 10 and a second superconducting wire 20.

[0026] The first superconducting wire 10 comprises a base material 11, an intermediate layer 12, a superconducting layer 13, a protective layer 14, and a stabilizing layer 15.

[0027] The base material 11 is, for example, a tape made of stainless steel. A copper layer 11a and a nickel layer 11b are clad on the base material 11. The copper layer 11a is positioned on the base material 11, and the nickel layer 11b is positioned on the copper layer 11a. The copper layer 11a and the nickel layer 11b are crystal-oriented. However, the base material 11 is not limited to this. The base material 11 may be made of Hastelloy®. If the base material 11 is made of Hastelloy, the copper layer 11a and the nickel layer 11b are not clad.

[0028] The intermediate layer 12 is placed on the substrate 11. If the substrate 11 is a tape made of stainless steel, a copper layer 11a and a nickel layer 11b are interposed between the intermediate layer 12 and the substrate 11. The intermediate layer 12 is composed of, for example, layers of stabilized zirconia (YSZ), yttrium oxide (Y2O3), and cerium oxide (CeO2) being sequentially laminated. As described above, since the nickel layer 11b is crystal-oriented, the intermediate layer 12 on top of it is also crystal-oriented. The intermediate layer 12 is formed, for example, by magnetron sputtering. If the substrate 11 is Hastelloy or the like, the crystal-oriented intermediate layer 12 is formed, for example, by IBAD (Ion Beam Assisted Deposition).

[0029] The superconducting layer 13 is located on the intermediate layer 12. The superconducting layer 13 is formed of REBCO. REBCO is REBaCu3O y(RE represents rare earth elements). Rare earth elements include, for example, yttrium (Y), praseodymium (Pr), neodymium (Nd), samarium (Sm), eurobium (Eu), gadollium (Gd), holmium (Ho), and ytterbium (Yb). The superconducting layer 13 is formed, for example, by PLD (Pulsed Laser Deposition). The superconducting layer 13 may also be formed by MOD (Metal Organic Deposition).

[0030] As described above, since the intermediate layer 12 is crystal-oriented, the superconducting layer 13 above it is also crystal-oriented. More specifically, the c-axis of the REBCO crystal grains constituting the superconducting layer 13 is aligned with the thickness direction of the superconducting layer 13.

[0031] The protective layer 14 is located on the superconducting layer 13. The protective layer 14 is made of silver (Ag). The protective layer 14 may also be made of a silver alloy. The protective layer 14 is formed, for example, by sputtering.

[0032] The stabilizing layer 15 is located on the protective layer 14. The stabilizing layer 15 is also located on the surface of the substrate 11 opposite to the intermediate layer 12, on the side surface of the substrate 11, on the side surface of the intermediate layer 12, on the side surface of the superconducting layer 13, and on the side surface of the protective layer 14. The stabilizing layer 15 is made of copper. The stabilizing layer 15 may be made of a copper alloy. The stabilizing layer 15 is formed, for example, by a plating method.

[0033] The first superconducting wire 10 has a first end 10a. The first end 10a is the end of the first superconducting wire 10 in the longitudinal direction. At the first end 10a, the protective layer 14 and the stabilizing layer 15 have been removed. That is, at the first end 10a, the superconducting layer 13 is exposed.

[0034] The second superconducting wire 20 comprises a base material 21, an intermediate layer 22, a superconducting layer 23, a protective layer 24, and a stabilizing layer 25.

[0035] The base material 21 is, for example, a tape made of stainless steel. A copper layer 21a and a nickel layer 21b are clad on the base material 21. The copper layer 21a is positioned on the base material 21, and the nickel layer 21b is positioned on the copper layer 21a. The copper layer 21a and the nickel layer 21b are crystal-oriented. However, the base material 21 is not limited to this. The base material 21 may be made of Hastelloy. If the base material 21 is made of Hastelloy, the copper layer 21a and the nickel layer 21b are not clad.

[0036] The intermediate layer 22 is placed on the base material 21. If the base material 21 is a tape made of stainless steel, a copper layer 21a and a nickel layer 21b are interposed between the intermediate layer 22 and the base material 21. The intermediate layer 22 is constructed, for example, by sequentially laminating a layer of stabilized zirconia, a layer of yttrium oxide, and a layer of cerium oxide.

[0037] As described above, since the nickel layer 21b is crystal-oriented, the intermediate layer 22 above it is also crystal-oriented. The intermediate layer 22 is formed, for example, by magnetron sputtering. If the substrate 21 is Hastelloy or the like, the crystal-oriented intermediate layer 22 is formed, for example, by IBAD.

[0038] The superconducting layer 23 is located on the intermediate layer 22. The superconducting layer 23 is formed of REBCO. The superconducting layer 23 is formed of, for example, PLD. The superconducting layer 23 may also be formed of MOD. As described above, since the intermediate layer 22 is crystal-oriented, the superconducting layer 23 above it is also crystal-oriented. More specifically, the c-axis direction of the crystal grains of the REBCO constituting the superconducting layer 23 is aligned with the thickness direction of the superconducting layer 23.

[0039] The protective layer 24 is located on the superconducting layer 23. The protective layer 24 is made of silver. The protective layer 24 may also be made of a silver alloy. The protective layer 24 is formed, for example, by sputtering.

[0040] The stabilizing layer 25 is located on the protective layer 24. The stabilizing layer 25 is also located on the surface of the substrate 21 opposite to the intermediate layer 22, on the side surface of the substrate 21, on the side surface of the intermediate layer 22, on the side surface of the superconducting layer 23, and on the side surface of the protective layer 24. The stabilizing layer 25 is made of copper. The stabilizing layer 25 may be made of a copper alloy. The stabilizing layer 25 is formed, for example, by a plating method.

[0041] The second superconducting wire 20 has a second end 20a. The second end 20a is the end of the second superconducting wire 20 in the longitudinal direction. At the second end 20a, the protective layer 24 and the stabilizing layer 25 have been removed. That is, at the second end 20a, the superconducting layer 23 is exposed.

[0042] The first superconducting wire 10 and the second superconducting wire 20 are arranged, for example, so that their first end 10a and second end 20a are adjacent to each other.

[0043] The superconducting layer 13 at the first end 10a is connected to the superconducting layer 23 at the second end 20a. This connection is made, for example, using a third superconducting wire 30 and a bonding layer 40. The third superconducting wire 30 has a base material 31, an intermediate layer 32, and a superconducting layer 33.

[0044] The base material 31 is, for example, a tape formed of stainless steel. A copper layer 31a and a nickel layer 31b are clad on the base material 31. The copper layer 31a is positioned on the base material 31, and the nickel layer 31b is positioned on the copper layer 31a. The copper layer 31a and the nickel layer 31b are crystal-oriented. However, the base material 31 is not limited to this. The base material 31 may be formed of Hastelloy. If the base material 31 is formed of Hastelloy, the copper layer 31a and the nickel layer 31b are not clad.

[0045] The intermediate layer 32 is placed on the base material 31. If the base material 31 is a tape made of stainless steel, a copper layer 31a and a nickel layer 31b are interposed between the intermediate layer 32 and the base material 31. The intermediate layer 32 is constructed, for example, by sequentially laminating a layer of stabilized zirconia, a layer of yttrium oxide, and a layer of cerium oxide.

[0046] As described above, since the nickel layer 31b is crystal-oriented, the intermediate layer 32 above it is also crystal-oriented. The intermediate layer 32 is formed, for example, by magnetron sputtering. If the substrate 31 is Hastelloy or the like, the crystal-oriented intermediate layer 32 is formed, for example, by IBAD.

[0047] The superconducting layer 33 is located on the intermediate layer 32. The superconducting layer 33 is formed of REBCO. The superconducting layer 33 is formed of, for example, PLD. The superconducting layer 33 may also be formed of MOD. As described above, the intermediate layer 32 is crystal-oriented, so the superconducting layer 33 above it is also crystal-oriented. More specifically, the c-axis direction of the crystal grains of the REBCO constituting the superconducting layer 33 is aligned with the thickness direction of the superconducting layer 33.

[0048] The third superconducting wire 30 is arranged such that the superconducting layer 33 faces the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a. The junction layer 40 is positioned between the superconducting layer 33 and the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a.

[0049] The bonding layer 40 is formed of REBCO. The c-axis direction of the crystal grains of the REBCO constituting the bonding layer 40 is aligned with the c-axis direction of the REBCO constituting the superconducting layer 13 at the first end 10a, the c-axis direction of the REBCO constituting the superconducting layer 23 at the second end 20a, and the c-axis direction of the REBCO constituting the superconducting layer 33. Therefore, the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a are superconductingly bonded by the third superconducting wire 30 (superconducting layer 33) and the bonding layer 40.

[0050] The portion of the superconducting wire connection structure 100 where the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a are connected is defined as the connection portion 50. The connection portion 50 includes a first clamping member 51, a second clamping member 52, and a cover member 53. However, the connection portion 50 does not necessarily have a cover member 53. Furthermore, the connection portion 50 may also have a bonding layer 40.

[0051] The first clamping member 51 and the second clamping member 52 are sheet-like members. The first clamping member 51 and the second clamping member 52 clamp the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a and the third superconducting wire 30. The first clamping member 51 and the second clamping member 52 are fixed to each other, for example, by welding. The first clamping member 51 and the second clamping member 52 may also be fixed to each other by soldering.

[0052] The cover member 53 is a sheet-like material. The cover member 53 covers the first clamping member 51 and the second clamping member 52. More specifically, the cover member 53 has a first portion 53a and a second portion 53b. The cover member 53 is folded over so that the first portion 53a and the second portion 53b face each other. The first clamping member 51 and the second clamping member 52 are positioned between the first portion 53a and the second portion 53b. The first portion 53a is fixed to the second portion 53b, for example, by soldering. This seals the inside of the cover member 53.

[0053] The thickness of the connecting portion 50 is denoted as thickness T. Thickness T is 2 mm or less. Thickness T may be 1.8 mm or less or 1.5 mm or less. Thickness T is, for example, 60 μm or more or 100 μm or more. The thermal expansion coefficients of the first clamping member 51, the second clamping member 52, and the cover member 53 are 0.95 times or more and 1.05 times or less than the thermal expansion coefficients of the base material 11, the base material 21, and the base material 31. It is preferable that the constituent materials of the first clamping member 51, the second clamping member 52, and the cover member 53 are the same as the constituent materials of the base material 11, the base material 21, and the base material 31. In the example shown in Figure 2, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, the third superconducting wire 30, the bonding layer 40, the first clamping member 51, the second clamping member 52, and the cover member 53 are laminated is thickness T.

[0054] The thickness of the first clamping member 51, the second clamping member 52, and the cover member 53 is preferably 0.2 mm or less. The thickness of the first clamping member 51, the second clamping member 52, and the cover member 53 may be 150 μm (0.15 mm) or less. The thickness of the first clamping member 51, the second clamping member 52, and the cover member 53 is, for example, 30 μm or more or 50 μm or more. The thermal conductivity of the first clamping member 51, the second clamping member 52, and the cover member 53 is 0.1 × 10⁻⁶. 2 It is preferable that the thermal conductivity is 0.3 × 10⁻⁶. The thermal conductivity of the first clamping member 51, the second clamping member 52, and the cover member 53 is 0.3 × 10⁻⁶. 2 W / m·℃ or higher or 0.5 × 10 2 It may be above W / m·℃.

[0055] The thermal resistance of the connecting portion 50 is, for example, 16°C / W or more. The thermal resistance of the connecting portion 50 is measured in accordance with the JEDEC standard (JESD51-2A). To measure the thermal resistance of the connecting portion 50, the connecting portion 50 is separated from the superconducting wire connection structure 100. In this case, the lengths of the first superconducting wire 10 and the second superconducting wire 20 extending from the connecting portion 50 are set to 100 mm or less. Depending on the constituent material of the connecting portion 50, the thermal resistance of the connecting portion 50 may be 18°C / W or more, or 20°C / W or more.

[0056] When a current of 200 A flows through the superconducting wire connection structure 100, the current density in the c-axis direction of the superconducting layer in the connecting portion 50 is 50 A / mm 2 or less, which is preferable. The current density in the c-axis direction of the superconducting layer in the connecting portion 50 is obtained by dividing the current flowing through the superconducting wire connection structure 100 by the bonding area between the superconducting layer 13 at the first end 10a and the bonding layer 40 (or the bonding area between the superconducting layer 23 at the second end 20a and the bonding layer 40). When a current of 200 A flows through the superconducting wire connection structure 100, the current density in the c-axis direction of the superconducting layer in the connecting portion 50 is 45 A / mm 2 or less. When a current of 200 A flows through the superconducting wire connection structure 100, the current density in the c-axis direction of the superconducting layer in the connecting portion 50 is, for example, 10 A / mm 2 or more.

[0057] (Method for Manufacturing Superconducting Wire Connection Structure According to Embodiment) A method for manufacturing the superconducting wire connection structure 100 will be described below.

[0058] FIG. 4 is a manufacturing process diagram of the superconducting wire connection structure 100. As shown in FIG. 4, the method for manufacturing the superconducting wire connection structure 100 includes a preparation step S1, a microcrystalline layer forming step S2, a connecting step S3, an oxygen introducing step S4, and a cover member attaching step S5.

[0059] In the preparation step S1, a first superconducting wire 10, a second superconducting wire 20, and a third superconducting wire 30 are prepared.

[0060] In the microcrystalline layer formation step S2, a microcrystalline layer is formed on the superconducting layer 33. The microcrystalline layer may be placed on the superconducting layer 13 at the first end 10a and on the superconducting layer 23 at the second end 20a, instead of on the superconducting layer 33. The microcrystalline layer is formed from a polycrystalline REBCO.

[0061] In forming the microcrystalline layer, firstly, an organic compound film is formed on the superconducting layer 33, for example, by a spin coating method. This organic compound film contains the constituent elements of REBCO. Secondly, the organic compound film is calcined. This calcination process transforms the organic compound film into a precursor of REBCO. Hereinafter, the calcined organic compound film will be referred to as the calcined film. Thirdly, after calcination, the calcined film is heat-treated. This decomposes the carbides contained in the calcined film, forming a microcrystalline layer containing microcrystals of REBCO.

[0062] In connection step S3, the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a are connected to the superconducting layer 33 using a microcrystalline layer. In connection step S3, firstly, the first superconducting wire 10 and the second superconducting wire are arranged so that the first end 10a and the second end 20a are adjacent to each other, and the third superconducting wire 30 is arranged so that the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a face each other with a microcrystalline layer in between.

[0063] Secondly, the first end 10a, the second end 20a, and the third superconducting wire 30 are clamped by the first clamping member 51 and the second clamping member 52. With the first end 10a, the second end 20a, and the third superconducting wire 30 clamped by the first clamping member 51 and the second clamping member 52, the first clamping member 51 and the second clamping member 52 are fixed to each other by welding or the like. Thirdly, heating and pressurizing are applied to the superconducting layer 13 at the first end 10a, the superconducting layer 23 at the second end 20a, the superconducting layer 33, and the microcrystalline layer via the first clamping member 51 and the second clamping member 52. As a result, the microcrystals of REBCO contained in the microcrystalline layer undergo oriented crystallization (epitaxial growth from the superconducting layer 13 at the first end 10a, the superconducting layer 23 at the second end 20a, and the superconducting layer 33), forming the bonding layer 40.

[0064] During the heating process S3, oxygen is released from the superconducting layer 13 at the first end 10a, the superconducting layer 23 and 33 at the second end 20a, and the bonding layer 40. Therefore, in the oxygen introduction process S4, oxygen is introduced into the superconducting layer 13 at the first end 10a, the superconducting layer 23 and 33 at the second end 20a, and the bonding layer 40 by heating and holding the connection in an oxygen-containing atmosphere.

[0065] In the cover member attachment process S5, the cover member 53 is attached. The cover member 53 is folded back so that the first clamping member 51 and the second clamping member 52 are sandwiched between the first part 53a and the second part 53b, and is attached by soldering the first part 53a to the second part 53b. As a result, the superconducting wire connection structure 100 with the structure shown in Figures 1 to 3 is manufactured.

[0066] (Effects of the superconducting wire connection structure according to the embodiment) The effects of the superconducting wire connection structure 100 are explained below.

[0067] In the superconducting wire connection structure 100, the greater the thickness (thickness T) of the connection portion 50, the better the mechanical strength of the connection portion 50, but the worse the heat dissipation of the connection portion 50. However, in the superconducting wire connection structure 100, the thickness T is set to 2 mm or less, so the heat dissipation of the connection portion 50 is improved. As a result of the improved heat dissipation of the connection portion 50 in the superconducting wire connection structure 100, even if the connection portion 50 generates heat, quenching is less likely to occur in the superconducting layer 13 at the first end 10a, the superconducting layer 23 at the second end 20a, the superconducting layer 33, and the bonding layer 40.

[0068] Damage to the connection portion 50 is caused by thermal stress resulting from the difference in thermal expansion coefficients between the base materials 11, 21, and 31 and the first clamping member 51, the second clamping member 52, and the cover member 53. In the superconducting wire connection structure 100, the thermal expansion coefficients of the first clamping member 51, the second clamping member 52, and the cover member 53 are between 0.95 and 1.05 times the thermal expansion coefficients of the base material 11, the base material 21, and the base material 31.

[0069] As a result, the first clamping member 51, the second clamping member 52, and the cover member 53 expand and contract similarly with the thermal expansion and contraction of the base material 11, base material 21, and base material 31, making it difficult for the above-mentioned thermal stress to occur. In this way, the superconducting wire connection structure 100 makes it possible to suppress damage at the connection portion 50 even when the thickness T is reduced.

[0070] In the superconducting wire connection structure 100, the inside of the cover member 53 is sealed, and the intrusion of moisture into the inside of the cover member 53 is suppressed. Therefore, with the superconducting wire connection structure 100, the deterioration of the superconducting properties of the superconducting layer 13 at the first end 10a, the superconducting layer 23 at the second end 20a, the superconducting layer 33, and the bonding layer 40 due to moisture is suppressed.

[0071] The thickness of the first clamping member 51, the thickness of the second clamping member 52, and the thickness of the cover member 53 are 0.2 mm or less, and the thermal conductivity of the first clamping member 51, the thermal conductivity of the second clamping member 52, and the thermal conductivity of the cover member 53 is 0.1 × 10⁻⁶.2 If the thermal resistance of the connection part 50 is 16°C / W or higher, the heat dissipation performance of the connection part 50 is further improved.

[0072] Generally, from the viewpoint of making the connection portion 50 compact, it is preferable to reduce the junction area between the superconducting layer 13 at the first end 10a and the bonding layer 40 (or the junction area between the superconducting layer 23 at the second end 20a and the bonding layer 40), that is, to increase the current density in the c-axis direction of the superconducting layer in the connection portion 50. On the other hand, if the current density in the c-axis direction of the superconducting layer in the connection portion 50 is reduced, the amount of heat generated in the connection portion 50 will be reduced.

[0073] Therefore, when a current of 200A flows through the superconducting wire connection structure 100, the current density in the c-axis direction of the connection part 50 is 50A / mm². 2 In the following cases, the reduction in heat generation at the connection portion 50 makes it less likely for quenching to occur in the superconducting layer 13 at the first end 10a, the superconducting layer 23 at the second end 20a, the superconducting layer 33, and the bonding layer 40.

[0074] (First variation) In the example above, the cover member 53 is made of a single member, but the cover member 53 may be made of two members (hereinafter referred to as the "first member" and the "second member"). In this case, the first member and the second member constituting the cover member 53 are fixed to each other by soldering or the like while sandwiching the first clamping member 51 and the second clamping member 52.

[0075] (Second variation) Figure 5 is a cross-sectional view of the superconducting wire connection structure 100 according to a second modified example. Figure 5 shows a cross-section at the position corresponding to II-II in Figure 1. As shown in Figure 5, the base material 11 at the first end 10a and the base material 21 at the second end 20a may form the second clamping member 52. In this case, the intermediate layer 12 and superconducting layer 13 at the first end 10a and the intermediate layer 22 and superconducting layer 23 at the second end 20a are partially removed, and the first clamping member 51 is fixed to the base material 11 and base material 21 by welding or the like. In the example shown in Figure 5, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, the third superconducting wire 30, the joining layer 40, the first clamping member 51, and the cover member 53 are laminated is thickness T. In this case as well, since the thickness T is set to 2 mm or less, the heat dissipation of the connection part 50 is improved, and the thermal expansion coefficient of the first clamping member 51, the second clamping member 52 ( Base material 11, Because the thermal expansion coefficients of the base material 21 and the cover member 53 are set to be between 0.95 and 1.05 times the thermal expansion coefficients of the base material 11, base material 21, and base material 31, damage to the connection part 50 due to thermal stress can be suppressed.

[0076] Although not shown in the diagram, the base material 31 may also be the first clamping member 51. In this case, the intermediate layer 32 and the superconducting layer 33 are partially removed, and the second clamping member 52 is fixed to the base material 31 by welding or the like.

[0077] (Third variation) Figure 6 is a plan view of the superconducting wire connection structure 100 according to the third modified example. Figure 7 is a cross-sectional view taken between VII-VII in Figure 6. As shown in Figures 6 and 7, the first superconducting wire 10 and the second superconducting wire 20 may be arranged in a stacked manner such that the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a face each other with a bonding layer 40 in between. In this case, the third superconducting wire 30 is not used in the superconducting wire connection structure 100. Thus, the connection configuration of the first superconducting wire 10 and the second superconducting wire 20 is not limited to the examples shown in Figures 1 to 3. In the example shown in Figure 7, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, the bonding layer 40, the first clamping member 51, the second clamping member 52, and the cover member 53 are stacked is thickness T. In this case as well, since the thickness T is set to 2 mm or less, the heat dissipation of the connection part 50 is improved, and since the thermal expansion coefficients of the first clamping member 51, the second clamping member 52, and the cover member 53 are set to be between 0.95 and 1.05 times the thermal expansion coefficients of the base material 11 and the base material 21, damage to the connection part 50 due to thermal stress can be suppressed.

[0078] (Fourth variation) Figure 8 is a cross-sectional view of the superconducting wire connection structure 100 according to the fourth modified example. Figure 8 shows a cross-section at the position corresponding to VII-VII in Figure 6. As shown in Figure 8, in the superconducting wire connection structure 100, the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a may be arranged to overlap and face each other with a bonding layer 40 in between, and the third superconducting wire 30 and the cover member 53 may not be used. In the example shown in Figure 8, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, the bonding layer 40, the first clamping member 51 and the second clamping member 52 are laminated is thickness T. In this case as well, since the thickness T is set to 2 mm or less, the heat dissipation of the connection part 50 is improved, and since the thermal expansion coefficients of the first clamping member 51 and the second clamping member 52 are set to be between 0.95 and 1.05 times the thermal expansion coefficients of the base material 11 and the base material 21, damage to the connection part 50 due to thermal stress can be suppressed.

[0079] (Fifth variation) Figure 9 is a cross-sectional view of the superconducting wire connection structure 100 according to the fifth modified example. Figure 9 shows a cross-section at the position corresponding to VII-VII in Figure 6. As shown in Figure 9, the superconducting wire connection structure 100 does not necessarily have a third superconducting wire 30, and the first superconducting wire 10 and the second superconducting wire 20 may be arranged on top of each other such that the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a face each other with a bonding layer 40 in between.

[0080] Furthermore, in the superconducting wire connection structure 100, the base material 11 may be the second clamping member 52, and the base material 21 may be the first clamping member 51. In this case, the intermediate layer 12 and superconducting layer 13 at the first end 10a and the intermediate layer 22 and superconducting layer 23 at the second end 20a are partially removed, and the base material 11 and base material 21 are fixed to each other by welding or the like. In the example shown in Figure 9, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, the joining layer 40, the first clamping member 51, the second clamping member 52, and the cover member 53 are laminated is thickness T. In this case as well, since the thickness T is set to 2 mm or less, the heat dissipation of the connection portion 50 is improved, and the first clamping member 51 (base material 2 1) Thermal expansion coefficient, second clamping member 52 (base material) 11 Since the thermal expansion coefficients of the base material 11 and the cover member 53 are set to be between 0.95 and 1.05 times the thermal expansion coefficients of the base material 11 and the base material 21, damage to the connection part 50 due to thermal stress can be suppressed.

[0081] (Sixth variation) Figure 10 is a cross-sectional view of the superconducting wire connection structure 100 according to the sixth modified example. The cross-section at the position corresponding to VII-VII in Figure 6 is shown in Figure 10. As shown in Figure 10, in the superconducting wire connection structure 100, the first superconducting wire 10 and the second superconducting wire 20 may be arranged on top of each other such that the superconducting layer 13 at the first end 10a and the superconducting layer 23 at the second end 20a face each other with a bonding layer 40 in between. In addition, in the superconducting wire connection structure 100, the base material 11 may be the second clamping member 52 and the base material 21 may be the first clamping member 51, and the base material 11 and the base material 21 may be fixed to each other. Furthermore, the superconducting wire connection structure 100 does not have to have the third superconducting wire 30 and the cover member 53. In the example shown in Figure 10, the maximum thickness of the portion where the first superconducting wire 10, the second superconducting wire 20, and the bonding layer 40 are laminated is thickness T. In this case as well, since the thickness T is set to 2 mm or less, the heat dissipation of the connection portion 50 is improved, and the first clamping member 51 (base material) 2 1) The coefficient of thermal expansion of the second clamping member 52 (base material) 1 1) Since the thermal expansion coefficient of the material is set to be between 0.95 and 1.05 times the thermal expansion coefficient of the base material 11 and the base material 21, damage to the connection part 50 due to thermal stress can be suppressed.

[0082] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and all modifications within the meaning and scope of equivalents of the claims are intended to be included. [Explanation of Symbols]

[0083] 10 First superconducting wire, 10a First end, 11 Base material, 11a Copper layer, 11b Nickel layer, 12 Intermediate layer, 13 Superconducting layer, 14 Protective layer, 15 Stabilizing layer, 20 Second superconducting wire, 20a Second end, 21 Base material, 21a Copper layer, 21b Nickel layer, 22 Intermediate layer, 23 Superconducting layer, 24 Protective layer, 25 Stabilizing layer, 30 Third superconducting wire, 31 Base material, 31a Copper layer, 31b Nickel layer, 32 Intermediate layer, 33 Superconducting layer, 40 Bonding layer, 50 Connection part, 51 First clamping member, 52 Second clamping member, 53 Cover member, 53a First part, 53b Second part, 100 Superconducting wire connection structure, S1 Preparation process, S2 Microcrystalline layer formation process, S3 Connection process, S4 oxygen introduction process, S5 cover member mounting process, T thickness.

Claims

1. A superconducting wire connection structure, First superconducting wire and, It comprises a second superconducting wire, The first superconducting wire has a first end in the longitudinal direction of the first superconducting wire, The second superconducting wire has a second end in the longitudinal direction of the second superconducting wire, Each of the first superconducting wire and the second superconducting wire comprises a base material, an intermediate layer disposed on the base material, and a superconducting layer disposed on the intermediate layer. The connecting portion of the superconducting wire connecting structure, which is the part where the superconducting layer at the first end and the superconducting layer at the second end are connected, has a first clamping member that includes at least a part of the base material located at the first end and a second clamping member that includes at least a part of the base material located at the second end. The superconducting layer at the first end and the superconducting layer at the second end are held between the first clamping member and the second clamping member. The thickness of the aforementioned connection portion is 2 mm or less. A superconducting wire connection structure wherein the thermal expansion coefficients of the first clamping member and the second clamping member are 0.95 times or more and 1.05 times or less the thermal expansion coefficient of the base material.

2. The aforementioned connection portion further includes a cover member, The first clamping member and the second clamping member are covered by the cover member, The superconducting wire connection structure according to claim 1, wherein the thermal expansion coefficient of the cover member is 0.95 times or more and 1.05 times or less than the thermal expansion coefficient of the base material.

3. The thermal conductivity of the first clamping member, the thermal conductivity of the second clamping member, and the thermal conductivity of the cover member is 0.1 × 10⁻⁶. ２ It is above W / m·℃, The superconducting wire connection structure according to claim 2, wherein the thickness of the first clamping member and the thickness of the second clamping member are 0.2 mm or less.

4. The superconducting wire connection structure according to claim 2, wherein the thermal resistance of the connection portion is 16°C / W or more.

5. The c-axis direction of the crystal grains of the oxide superconductor constituting the superconducting layer is aligned with the thickness direction of the superconducting layer. When a current of 200 A flows through the superconducting wire connection structure, the current density of the superconducting layer in the connection portion in the c-axis direction is 50 A / mm². ２ The superconducting wire connection structure according to any one of claims 1 to 4, as follows:

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