Superconducting wire, superconducting coil, and superconducting device

Abstract

To provide a superconducting wire capable of realizing a low electrical resistance and a high mechanical strength.SOLUTION: A superconducting wire includes: a first wire; a second wire adjacent to the first wire; a joint layer electrically connecting the first and second wires; and a member connecting the joint layer with at least one of the first and second superconducting wires. The member has a melting point from 900°C and 1100°C inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a superconducting wire, a superconducting coil, and a superconducting device. [Background technology]

[0002] For example, nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems use superconducting coils to generate strong magnetic fields. Superconducting coils are formed by winding superconducting wire around a bobbin.

[0003] To increase the length of superconducting wires, for example, multiple superconducting wires are connected together. For example, the ends of two superconducting wires are connected using a connection structure. The connection structure for connecting superconducting wires is required to have low electrical resistance and high mechanical strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-195469 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a superconducting wire that can achieve a high critical current and high connection strength. [Means for solving the problem]

[0006] According to an embodiment, a superconducting wire is provided which has a first wire, a second wire adjacent to the first wire, a connection layer electrically connecting the first wire and the second wire, and a member connecting the connection layer and at least one of the first wire and the second wire, wherein the melting point of the member is 900°C or higher and 1100°C or lower. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a superconducting wire according to a first embodiment. [Figure 2] FIG. 3 is a schematic cross-sectional view showing an example of a method for measuring the connection strength of the superconducting wire according to the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of a first modified example of the superconducting wire according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of a second modified example of the superconducting wire according to the first embodiment. [Figure 5] FIG. 4 is a schematic cross-sectional view of a third modified example of the superconducting wire according to the first embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view of a fourth modified example of the superconducting wire according to the first embodiment. [Figure 7] FIG. 4 is a schematic cross-sectional view showing another example of the method for measuring the connection strength of the superconducting wire according to the first embodiment. [Figure 8] FIG. 10 is a schematic cross-sectional view of a fifth modified example of the superconducting wire according to the first embodiment. [Figure 9] FIG. 10 is a schematic cross-sectional view of a sixth modified example of the superconducting wire according to the first embodiment. [Figure 10] FIG. 4 is a schematic cross-sectional view showing yet another example of the method for measuring the connection strength of the superconducting wire according to the first embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view of a seventh modified example of the superconducting wire according to the first embodiment. [Figure 12] FIG. 4 is a schematic perspective view of a superconducting coil according to a second embodiment. [Figure 13] FIG. 4 is a schematic cross-sectional view of a superconducting coil according to a second embodiment. [Figure 14] FIG. 10 is a block diagram of a superconducting device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are designated by the same reference numerals throughout the drawings, and duplicate descriptions will be omitted. Each drawing is a schematic diagram for explaining and facilitating understanding of the embodiments, and the shapes, dimensions, ratios, etc. may differ from those of an actual device. However, these may be appropriately modified in design, taking into consideration the following description and known techniques.

[0009] In this specification, the "particle size" of a particle or the like refers to the major axis of the particle unless otherwise specified. The major axis of a particle is the maximum length between any two points on the periphery of the particle. The minor axis of a particle is the length of a line segment that passes through the midpoint of the line segment corresponding to the major axis, is perpendicular to the line segment, and has the periphery of the particle as both ends. The aspect ratio of a particle is the ratio of the major axis to the minor axis of the particle (major axis / minor axis). The major and minor axes of a particle can be determined, for example, by image analysis using a scanning electron microscope (SEM).

[0010] [First embodiment] According to the first embodiment, a superconducting wire is provided which has a first wire, a second wire adjacent to the first wire, a connection layer electrically connecting the first wire and the second wire, and a member connecting the connection layer and at least one of the first wire and the second wire, wherein the melting point of the member is 900°C or higher and 1100°C or lower.

[0011] 1 is a schematic cross-sectional view of a superconducting wire according to the first embodiment. A superconducting wire 200 of the first embodiment is formed by connecting two superconducting wires (a first wire 210 and a second wire 220) to each other, for example, to form a long superconducting wire.

[0012] Here, a first direction D1 that intersects with the direction from the first wire rod 210 toward the connection layer 221 and runs along the first wire rod 210 is defined as the X-axis direction. A second direction D2 from the first wire rod 210 toward the connection layer 221 is defined as the Z-axis direction. A direction perpendicular to the Z-axis direction is defined as the X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction.

[0013] Superconducting wire 200 includes first wire 210, second wire 220, connection layer 221, and member 222.

[0014] The member 222 connects the connection layer 221 to at least one of the first wire 210 and the second wire 220.

[0015] 1, member 222 contacts a part of the lower surface of connection layer 221 having an interface with first wire rod 210, a part of first wire rod 210, and a part of second wire rod 220. As a result, connection layer 221, first wire rod 210, and second wire rod 220 are physically connected via member 222. By providing member 222 so as to connect connection layer 221 to first wire rod 210 and second wire rod 220, the connection strength of superconducting wire 200 can be improved, which is preferable.

[0016] The member 222 is made of, for example, a metal, and includes at least one selected from the group consisting of Ag, Cu, Au, and Ge.

[0017] The melting point of the member 222 is not less than 900° C. and not more than 1100° C. The heat treatment under pressure when producing the superconducting wire 200 of this embodiment is performed at, for example, not less than 700° C. and not more than 850° C. The temperature of this heat treatment is not less than 70% of the melting point of the member 222, and the member 222 can be easily softened during the heat treatment.

[0018] By setting the melting point of the component 222 to 900°C or higher, it is possible to prevent the generation of regions where no particles are present, which would otherwise occur if the molten component 222 pushes out the particles that make up the connection layer 221 during heat treatment under pressure. This makes it possible to obtain a sufficient current path in the connection layer 221. Furthermore, in the connection layer 221 of this embodiment, the heat treatment is performed with the constituent particles in contact with each other, causing a reaction between the particles, thereby achieving high superconductivity with a sufficient current path. Therefore, by setting the heat treatment temperature to be somewhat higher than the melting point of the component 222, it is possible to prevent the molten component 222 from entering between the particles before the particles react with each other.

[0019] Furthermore, by setting the temperature to 1100°C or less, the temperature of the heat treatment can be set to 70% or more of the melting point of component 222, so that component 222 can be sufficiently softened during the heat treatment, and component 222 can contribute to the connection of each wire.

[0020] Other configurations of the superconducting wire according to the embodiment will be described below.

[0021] (First wire) The first wire 210 includes a first superconducting layer 210a and a first substrate 210b. The first superconducting layer 210a is provided on the first substrate 210b.

[0022] The first wire 210 is electrically connected to the second wire 220 via the connection layer 221. This allows current to flow between the first wire 210 and the second wire 220 via the connection layer 221.

[0023] The first substrate 210b is made of, for example, a metal, such as a nickel alloy or a copper alloy.

[0024] The first substrate 210b is, for example, a nickel-chromium-molybdenum alloy.

[0025] The first superconducting layer 210a is, for example, an oxide superconducting layer. The first superconducting layer 210a includes, for example, a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The first superconducting layer 210a includes, for example, at least one rare earth element (RE) selected from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0026] The first superconducting layer 210a is, for example, (RE)Ba2Cu3O δ (RE is a rare earth element, 6≦δ≦7) The first superconducting layer 210a has a chemical composition expressed as follows. δ (6≦δ≦7), YBa2Cu3O δ (6≦δ≦7), or EuBa2Cu3O δ It has a chemical composition expressed as (6≦δ≦7). The first superconducting layer 210a is, for example, a rare earth oxide superconductor.

[0027] The first superconducting layer 210a includes, for example, a single crystal having a perovskite structure.

[0028] (Second wire) The second wire 220 is disposed adjacent to the first wire 210 .

[0029] The second wire 220 includes a second superconducting layer 220a and a second substrate 220b. The second superconducting layer 220a is provided on the second substrate 220b.

[0030] The second substrate 220b, like the first substrate 210b, is, for example, a metal, and may comprise the same material as the first substrate 210b or a different material.

[0031] The second superconducting layer 220a is, for example, an oxide superconducting layer similar to the first superconducting layer 210a, and may comprise the same material or a different material.

[0032] (connection layer) The connection layer 221 contacts at least a part of the first wire 210 and at least a part of the second wire 220, and electrically connects the first wire 210 and the second wire 220 together.

[0033] The connection layer 221 is connected to at least one of the first wire rod 210 and the second wire rod 220 via the member 222. For example, the member 222 connects a side surface, which is a surface intersecting a first direction from the first wire rod 210 to the second wire rod 220, to a lower surface of the connection layer 221 having an interface with the first wire rod 210. Here, the first direction is, for example, the X-axis direction. By using the member 222 to connect the exposed side surface of the first wire rod 210 and the exposed lower surface of the connection layer 221, it is possible to suppress peeling of particles constituting the connection layer 221 from the first wire rod 210 due to penetration of the member 222 into the connection layer 221. This makes it possible to suppress degradation of the conduction path.

[0034] The connection layer 221 is, for example, a group of single-crystal or polycrystalline particles containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The connection layer 221 is, for example, composed of a group of single-crystal or polycrystalline particles containing at least one rare earth element (RE) selected from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0035] The connection layer 221 is, for example, (RE)Ba2Cu3O δ (RE is a rare earth element, 6≦δ≦7) and is composed of a group of single crystal or polycrystalline particles having a chemical composition. δ(6≦δ≦7), YBa2Cu3O δ (6≦δ≦7), or EuBa2Cu3O δ The connection layer 221 is made up of a group of single crystal or polycrystalline particles having a chemical composition expressed as (6≦δ≦7). The connection layer 221 is made up of, for example, a group of single crystal or polycrystalline particles of a rare earth oxide superconductor.

[0036] The average particle size of these particles is 500 nm or more and 30 μm or less, preferably 1 μm or more and 10 μm or less. When the average particle size of these particles is 500 nm or more, sufficient crystallinity can be obtained, thereby achieving high superconducting properties. Furthermore, when the average particle size is 30 μm or less, the film thickness of the connection layer 221 can be controlled so as not to be too thick. This reduces resistive portions such as voids present in the connection layer 221, thereby enabling the resistance of the superconducting wire 200 to be reduced. Additionally, when the average particle size is 30 μm or less, the contact area between the connection layer 221 and the first wire 210 and the contact area between the connection layer 221 and the second wire 220 can be sufficiently increased, thereby increasing the connection strength of the superconducting wire 200.

[0037] The aspect ratio of these particle groups is 1.5 or more and 50 or less, preferably 3 or more and 10 or less. When the aspect ratio of these particle groups is 1.5 or more, connection layer 221 can have superconducting properties. Furthermore, when the aspect ratio of the particle groups is 50 or less, the packing density of connection layer 221 can be sufficiently increased, and the film thickness of connection layer 221 can be controlled so as not to be too thick. Furthermore, the contact area between connection layer 221 and first wire 210 and the contact area between connection layer 221 and second wire 220 can be sufficiently increased, and the connection strength of superconducting wire 200 can be increased.

[0038] The porosity of the connection layer 221 is 10% or more and 70% or less, preferably 20% or more and 50% or less. When the porosity of the connection layer 221 is 10% or more, it becomes easier for the component to penetrate into the first region, thereby increasing the connection strength, and when it is 70% or less, it is possible to ensure a sufficient amount of particles in the connection layer 221, thereby preventing a decrease in critical current due to a lack of current paths.

[0039] Here, a method for producing a superconducting wire according to the embodiment shown in FIG. 1 will be described.

[0040] First, prepare the first wire 210 and the second wire 220. If each superconducting layer has a protective layer (mainly a Cu layer and an Ag layer) that prevents the superconducting layers from reacting with moisture in the air, this layer is removed by, for example, wet etching to expose the respective superconducting layers 210a and 220a.

[0041] Thereafter, the first wire rod 210 and the second wire rod 220 are arranged with the superconducting layers of the first wire rod 210 and the second wire rod 220 facing in the same direction, and with at least a portion of the first wire rod 210 and the second wire rod 220 in contact with the member 222. Here, the member 222 is obtained by using, for example, a metal sheet. The member 222 used preferably has a thickness of 0.001 mm or more and 1 mm or less. When the thickness of the member 222 is 0.001 mm or more, sufficient strength of the superconducting wire rod 200 can be obtained. When the thickness is 1 mm or less, heat during heat treatment can sufficiently reach the inside of the member 222, and the member 222 can be easily softened, so that the first wire rod 210 and the second wire rod 220 can be connected by the member 222.

[0042] Next, single-crystal or polycrystalline particles of the rare earth oxide superconductor described above in the section (Connection Layer) are mixed with a solution mainly composed of an organic compound containing the same metal element in a ratio of 5:1 to 1:3 depending on the average particle size of the particles to obtain a mixture for the connection layer. The mixture obtained as described above is cast to a required thickness on the first wire 210 and the second wire 220. Thereafter, the mixture is dried and fired in oxygen at 700°C to 850°C to form the connection layer 221 on the first wire 210 and the second wire 220.

[0043] In this manner, a structure for obtaining superconducting wire 200 in FIG. 1 is obtained.

[0044] Next, pressure is applied by placing a weight on the overlapping portion of the connection layer 221 and each wire in the structure obtained above. For example, a jig for applying pressure can be prepared and used to clamp the wires. When a jig is used, the jig may be removed after connection, or may remain attached. Removing the jig makes it easier to wind the coil, so it is preferable to remove it.

[0045] Next, heat treatment is performed under pressure, for example, in an argon atmosphere containing 100 ppm to 1500 ppm of oxygen at a temperature of 700°C to 850°C, and then in oxygen at a temperature of 300°C to 600°C.

[0046] The heat treatment softens the member 222, resulting in the member 222 shown in FIG.

[0047] In this manner, superconducting wire 200 in FIG. 1 is obtained.

[0048] The critical current of the superconducting wire according to this embodiment can be measured, for example, as follows.

[0049] <Method for measuring critical current> The critical current is the maximum current value that can flow with zero electrical resistance, and can be measured using the four-terminal measurement method. Terminals are attached to the connected superconducting wire 200, and measurements are performed in liquid nitrogen. As the voltage increases with increasing resistance, the current value at which the voltage begins to increase is taken as the critical current.

[0050] The connection strength of the superconducting wire according to this embodiment can be evaluated, for example, in accordance with Japanese Industrial Standard JIS K 6849 (1994) "Test method for tensile bond strength (method for measuring by applying a tensile load perpendicular to the bonding surface)." Specific measurement methods for the example in Fig. 1 will be explained using Fig. 2. Fig. 2 is a schematic cross-sectional view showing a method for measuring the connection strength of the example superconducting wire in Fig. 1.

[0051] <Method for measuring the connection strength of the superconducting wire in Figure 1> (fixing of superconducting wire) 2, one side of double-sided adhesive tape 240 is adhered to first substrate 210b or second substrate 220b, and the other side of double-sided adhesive tape 240 is adhered to base 250, thereby fixing superconducting wire 200 to base 250. At this time, the dimensions of double-sided adhesive tape 240 used to fix base 250 and the substrate of one of the wires are such that the width is the same as the length of the wire, and the length is such that the strength is sufficient to prevent peeling between base 250 and the substrate during measurement of the connection strength.

[0052] Next, one side of another double-sided adhesive tape 240 is adhered to at least a portion of the superconducting layer of the wire that is not fixed to the base 250 (in FIG. 2, the second superconducting layer 220a of the second wire 220). At this time, the dimensions of the double-sided adhesive tape 240 used to fix the superconducting layer of the other wire to the tensioning device 260 are set so that the width is the same as that of the wire, and the length is set to a length that ensures strength that prevents peeling between the base 250 and the superconducting layer during measurement of the connection strength. In addition, the double-sided adhesive tape 240 used to fix the latter tensioning device 260 and the wire is provided at a position a certain distance from the end of the connection layer 221. For example, the length can be 1 mm or more and 40 mm or less, preferably 5 mm or more and 20 mm or less.

[0053] Any double-sided adhesive tape 240 may be used as long as it has sufficient adhesive strength to withstand this measurement, and for example, carbon tape for SEM observation may be used.

[0054] When measuring the connection strength of the superconducting wire in the example of FIG. 2, the double-sided adhesive tape 240 having the above-mentioned determined dimensions is used for each measurement.

[0055] (Measurement using a tension device) The pulling device 260 is operated in a direction away from the wire (second wire 220 in FIG. 2 ) fixed to the pulling device 260 via the double-sided adhesive tape 240. At this time, the speed of the pulling device 260 is kept constant, and the superconducting wire 200 is pulled at, for example, a speed of 100 μm to 5 mm per second, preferably a speed of 500 μm to 1 mm per second. By setting the speed of the pulling device 260 to 100 μm to 5 mm per second, the measurement time can be shortened within a range that suppresses measurement errors due to the wires easily peeling from each other. For example, the distance traveled by the pulling device 260 until the wire is completely peeled from the connection layer can be measured as the connection strength.

[0056] The above method can be used to evaluate the connection strength between the first wire or the second wire and the connection layer.

[0057] The porosity of connection layer 221 of superconducting wire 200 can be measured as follows after the above-described connection strength test.

[0058] <Method for measuring the porosity of the connecting layer> First, the connection portion including the connection layer 221 is embedded in, for example, an epoxy resin, and because there is a concern that peeling may occur at the end of the connection, the center of the firmly connected connection portion is cut using a diamond saw or the like. At this time, if, for example, a member 222 is present between the connection layer 221 and the first wire rod 210 in a modified example described later, the cross section of the connection layer 221 for measuring the porosity of the connection layer 221 is located at a position that avoids this member 222. Furthermore, when measuring a member 222 that has penetrated the connection layer 221 as in a modified example described later, the actual measurement of the porosity of the connection layer 221 is performed after measuring the member 222.

[0059] Next, the cut surface is polished with waterproof paper and a buff, after which a conductive coating is applied and the observation position is determined using an SEM. Ion milling is then performed at the determined observation position, and after the conductive coating is applied, SEM observation is performed.

[0060] Depending on the average particle size of the powder used, if the average particle size is 2-3 μm, SEM images of three cross sections are taken at a magnification of approximately 2500x. The cross section of the connecting layer 221 is then processed at a position that divides the long side of the approximately rectangular shape of the connecting layer 221 into four equal parts when viewed in plan, to obtain three cross sections. The larger the average particle size, the lower the magnification of the SEM image taken, and the smaller the average particle size, the higher the magnification. The SEM images are binarized using ImageJ, for example, to separate the particles and voids, and then the areas of each are calculated. The porosity of each cross section is calculated from the ratio of these areas. The porosity obtained for each cross section is then averaged to obtain the desired porosity of the connecting layer.

[0061] Modified examples of the superconducting wire according to the first embodiment will be described below.

[0062] FIG. 3 is a schematic cross-sectional view of a first modified example of the superconducting wire according to the first embodiment.

[0063] In Figure 3, member 222 has, in addition to member 222a located between first wire 210 and second wire 220, member 222b covering the exposed portion of connection layer 221 except for the interface with first wire 210 and second wire 220.

[0064] Member 222b contacts at least a part of first superconducting layer 210a and at least a part of second superconducting layer 220a, thereby improving the connection strength between connection layer 221 and first wire 210 and between connection layer 221 and second wire 220, thereby improving the connection strength of superconducting wire 200.

[0065] When the surface of the connection layer 221 facing the lower surface having the interface with each wire is defined as the upper surface, and the surface of the connection layer 221 located between the upper and lower surfaces of the connection layer 221 is defined as the side surface, the member 222b does not need to be in contact with the entire upper surface or the entire side surface of the connection layer 221.

[0066] The member 222b may be provided so as to connect at least one of the first wire material 210 and the second wire material 220 to the connection layer 221. For example, there may be an area where part of the side surface of the connection layer 221 is not covered. Also, there may be a minute gap between the member 222b and the connection layer 221. It is preferable that the member 222b contacts substantially the entire top surface and side surface of the connection layer 221.

[0067] Superconducting wire 200 in Fig. 3 can be produced as follows: Here, parts that overlap with the method for producing superconducting wire 200 in Fig. 1 will be omitted.

[0068] First, after performing the method for fabricating a structure for obtaining superconducting wire 200 shown in Fig. 1 described above, member 222b is placed so as to be in contact with connection layer 221. Thereafter, the structure described above is subjected to heat treatment under pressure, thereby obtaining superconducting wire 200 shown in Fig. 3.

[0069] The critical current, connection strength, and porosity of the connection layer of the obtained superconducting wire 200 of Figure 3 can be measured in the same manner as described above in <Method for measuring critical current>, <Method for measuring connection strength of superconducting wire in Figure 1>, and <Method for measuring porosity of connection layer>.

[0070] FIG. 4 is a schematic cross-sectional view of a second modified example of the superconducting wire according to the first embodiment.

[0071] 4, component 222 is also present inside connection layer 221. Region 223 is a portion where part of component 222 is present inside connection layer 221, and is formed, for example, when part of component 222 penetrates connection layer 221. This is because connection layer 221 is made up of a group of particles, and part of component 222 penetrates into voids present between the particle groups, thereby forming region 223. This can improve the connection strength of superconducting wire 200, so it is preferable that part of component 222 is present inside connection layer 221 in region 223.

[0072] In FIG. 4, the member 222 covers a part of the surface of the first base material 210b and a part of the surface of the second base material 220b.

[0073] Superconducting wire 200 in FIG. 4 can be fabricated in the same manner as the above-described method for fabricating superconducting wire 200 in FIG.

[0074] In FIG. 4, the member 222 is softened by the heat treatment, and the member 222 penetrates into the connection layer 221, and a region 223 is formed.

[0075] The region 223 may include at least one of a first region 224 located between the connection layer 221 and the first wire 210 and a second region 225 located between the connection layer 221 and the second wire 220. In this case, the first region 224 and the second region 225 satisfy at least one of a first condition that the first region 224 is located within a range of 5 μm to 1 mm from the end of the first wire 210 in the first direction D1 and a second condition that the second region 225 is located within a range of 5 μm to 1 mm from the end of the second wire 220 in the first direction D1. Preferably, the first and second conditions are satisfied. That is, it is preferable that the first region 224 is located within a range of 5 μm to 1 mm from the end of the first wire 210 and that the second region 225 is located within a range of 5 μm to 1 mm from the end of the second wire 220. This can improve the connection strength of the superconducting wire 200.

[0076] Preferably, at least one of the first condition and the second condition is satisfied, and member 222 present in first region 224 contacts first wire 210, or member 222 present in second region 225 contacts second wire 220. This can improve the connection strength of superconducting wire 200.

[0077] Region 223 is also preferably present in second direction D2 within a range of 5 μm to 1 mm from the interface between first wire 210 or second wire 220 and connecting layer 221. This can improve the connection strength of superconducting wire 200.

[0078] The upper limit of the range from the end of the first wire 210 or the end of the second wire 220 where the first region 224 or the second region 225 can be present is preferably 200 μm or less. When the first region 224 or the second region 225 is present 5 μm or more from the end of the first wire 210 or the end 220 of the second wire 200, the connection strength of the superconducting wire 200 can be increased. Furthermore, when the first region 224 or the second region 225 is present within a range of 1 mm or less from the end of the first wire 210 or the end 220 of the second wire 200, the component 222 can be prevented from pushing aside particles constituting the connection layer 221 and penetrating in the first direction. This makes it possible to obtain a sufficient connection area and ensure a sufficient current path, thereby preventing a decrease in critical current. Here, the connection area refers to the contact area between the first wire 210 or the second wire 220 and the connection layer 221 when a current passes between the wires via the connection layer 221.

[0079] Therefore, in order to increase the connection strength of the superconducting wire 200 and to achieve a higher critical current by obtaining a sufficient connection area, it is preferable that the range from the end of the first wire 210 or the end of the second wire 220 in which the first region 224 or the second region 225 may exist is 5 μm or more and 1 mm or less.

[0080] The critical current, connection strength, and porosity of the connection layer of the obtained superconducting wire 200 in Fig. 4 can be measured in the same manner as the methods described above in <Method for measuring critical current>, <Method for measuring connection strength of superconducting wire in Fig. 1>, and <Method for measuring porosity of connection layer>. However, when measuring the length of member 222 in the first direction in which it penetrates connection layer 221, this is done before measuring the porosity of connection layer 221.

[0081] Here, a method for measuring the length of the member 222 in the first direction that penetrates into the connection layer 221 will be described.

[0082] <Method for measuring distance along first direction of penetration into connection layer of component> When the member 222 has the first region 224 as shown in Figure 4, the desired distance can be measured by measuring the member 222 remaining on the first superconducting layer 210a of the first wire 210 after the connecting layer 221 is peeled from, for example, the first wire 210.

[0083] First, after performing the <Method for measuring the connection strength of the superconducting wire in FIG. 1>, the connection layer 221 and, for example, the first wire 210 are peeled off.

[0084] Thereafter, a mapping image of elements derived from the components of the member 222 is captured by EDX (Energy Dispersive X-ray Spectroscopy) on the surface of the first superconducting layer 210a of the first wire 210. This makes it possible to measure the penetration distance of the member 222 into the connection layer 221 in the first direction D1.

[0085] To perform EDX imaging, first, the region on the surface of the first superconducting layer 210a where the connecting layer 221 existed before the separation of the connecting layer 221 from the first wire 210 is divided into five equal parts along a third direction D3 that intersects with the first direction D1 and is parallel to this surface. The third direction is, for example, the Y-axis direction that intersects with the X-axis and runs along the surface of the first superconducting layer 210a. The two end regions of the five equal parts divided along the Y-axis are excluded from the EDX imaging range. In other words, the three central regions of the five equal parts divided along the third direction D3 are used as the EDX imaging range. The EDX imaging magnification is set so that the component 222 with the longest penetration distance along the first direction D1 is within the field of view in each imaging range. For each EDX image obtained in this way, the average length in the third direction of the components 222 present on the surface of the first superconducting layer 210a is calculated. The average penetration length described above is determined, for example, by measuring the penetration length of the member 222 at positions that divide each width of each EDX image along the third direction D3 into six equal parts. By averaging these five lengths obtained from each of the three EDX images, i.e., a total of 15 lengths, the length along the first direction D1 that the member 222 penetrates into the connecting layer 221 can be determined.

[0086] FIG. 5 is a schematic cross-sectional view of a third modified example of the superconducting wire according to the first embodiment.

[0087] In Figure 5, the member 222 has a first member 222a located between the first wire 210 and the second wire 220, as well as a second member 222b covering the exposed portion of the connection layer 221 except for the interface between the first wire 210 and the second wire 220.

[0088] In FIG. 5, the second member 222b is also present inside the connection layer 221, and a region 223 is present.

[0089] Superconducting wire 200 in FIG. 5 can be fabricated in the same manner as the above-described method for fabricating superconducting wire 200 in FIG.

[0090] The critical current, connection strength, and porosity of the connection layer of the obtained superconducting wire 200 of Figure 5 can be measured in the same manner as described above in <Method for measuring critical current>, <Method for measuring connection strength of superconducting wire in Figure 1>, <Method for measuring distance along the first direction of penetration of component into connection layer>, and <Method for measuring porosity of connection layer>.

[0091] 5, second member 222b may penetrate into connecting layer 221 along second direction D2, thereby providing second member 222b with region 223. This region preferably exists in a range of 5 μm to 1 mm from the surface of connecting layer 221 in second direction D2. The region can be confirmed by observing a cross section of connecting layer 221 in a plane intersecting the XY plane formed by the X and Y axes, for example, in the ZX plane.

[0092] FIG. 6 is a schematic cross-sectional view of a fourth modified example of the superconducting wire according to the first embodiment.

[0093] In FIG. 6, first superconducting layer 210a and second superconducting layer 220a face each other, and connecting layer 221 is provided so as to be located between first superconducting layer 210a and second superconducting layer 220a.

[0094] In this case, the superconducting layers of first wire 210 and second wire 220 are disposed facing each other, and connection layer 221 is sandwiched between them, thereby providing a structure that protects connection layer 221. This means that, for example, when superconducting wire 200 of Fig. 6 is wound around a coil, connection layer 221 of superconducting wire 200 wound in the nth turn is protected from contact with superconducting wire 200 wound in the n+1th turn, thereby suppressing wear of connection layer 221.

[0095] The member 222 connects the connection layer 221 to at least one of the first wire 210 and the second wire 220. In FIG.

[0096] The member 222 penetrates the connection layer 221 and forms a region 223 that exists in a range of 5 μm to 1 mm from the end of the first wire 210.

[0097] Superconducting wire 200 in FIG. 6 can be produced as follows.

[0098] First, first base material 210b is placed so that at least a portion thereof is in contact with member 222. Then, connection layer 221 is applied to at least a portion of second superconducting layer 220a. Then, connection layer 221 is placed so that at least a portion of first superconducting layer 210a faces at least a portion of the surface of connection layer 221 opposite to the surface in contact with second superconducting layer 220a. In other words, connection layer 221 is located between first superconducting layer 210a and second superconducting layer 220a.

[0099] This provides a structure for obtaining superconducting wire 200 in Fig. 6. Thereafter, the above-described pressing method and heat treatment are performed to obtain superconducting wire 200 in Fig. 6.

[0100] The critical current and porosity of the connecting layer in the obtained superconducting wire 200 of Figure 6 can be measured in the same manner as described above in <Method for measuring critical current>, <Method for measuring the distance along the first direction of penetration of the component into the connecting layer>, and <Method for measuring the porosity of the connecting layer>.

[0101] A method for measuring the connection strength in Fig. 6 will be described with reference to Fig. 7. Fig. 7 is a schematic cross-sectional view showing a method for measuring the connection strength in the example of the superconducting wire in Fig. 6.

[0102] <Method for measuring the connection strength of superconducting wires in Figure 6> In Fig. 7, similar to the method described in <Method for measuring the connection strength of superconducting wires in Fig. 1>, the substrate of one wire is fixed to base 250 via double-sided adhesive tape 240. Then, the substrate of the other wire is fixed to tensioning device 260 via double-sided adhesive tape 240. The dimensions of double-sided adhesive tape 240 used here are similar to those described in <Method for measuring the connection strength of superconducting wires in Fig. 1>. In the case of Fig. 7, double-sided adhesive tape 240 is provided at a certain distance from the end of member 222, and this distance is similar to the distance described in <Method for measuring the connection strength of superconducting wires in Fig. 1>.

[0103] Fig. 8 is a schematic cross-sectional view of a fifth modified example of the superconducting wire according to the first embodiment. In Fig. 8, the member 222 has a third member 222c and a fourth member 222d.

[0104] The third member 222c and the fourth member 222d connect the connection layer 221 to at least one of the first wire 210 and the second wire 220.

[0105] 8, fourth member 222d contacts the other side surface of connecting layer 221, which is different from the side surface that contacts third member 222c. Since fourth member 222d covers the other side surface of connecting layer 221, wear of connecting layer 221 due to contact with other superconducting wire 200 can be further suppressed compared to FIG.

[0106] Superconducting wire 200 in FIG. 8 can be produced as follows.

[0107] First, first base material 210b is placed so that at least a portion thereof is in contact with third member 222c. Then, connection layer 221 is applied to at least a portion of second superconducting layer 220a. Then, first superconducting layer 210a is placed so that at least a portion thereof faces at least a portion of the surface of connection layer 221 opposite to the surface in contact with second superconducting layer 220a. Then, second base material 220b is placed so that at least a portion thereof is in contact with fourth member 222d. At this time, different materials can be used for member 222 in contact with first base material 210b and member 222 in contact with second base material 220b, or the same material can be used.

[0108] This provides a structure for obtaining superconducting wire 200 in Fig. 8. Thereafter, the above-described pressing method and heat treatment are performed to obtain superconducting wire 200 in Fig. 8.

[0109] The critical current and the porosity of the connection layer of the obtained superconducting wire 200 in Fig. 8 can be measured in the same manner as the methods described above in <Method for measuring critical current>, <Method for measuring distance along first direction of penetration of member into connection layer>, and <Method for measuring porosity of connection layer>. Furthermore, the connection strength of the superconducting wire 200 in Fig. 8 can be measured in the same manner as the method described above in <Method for measuring connection strength of superconducting wire in Fig. 6>.

[0110] 9 is a schematic cross-sectional view of a sixth modified example of the superconducting wire according to the first embodiment. In FIG.

[0111] The third wire 230 includes a third superconducting layer 230a and a third substrate 230b. The third superconducting layer 230a is provided on the third substrate 230b. The third superconducting layer 230a and the third substrate 230b may be made of the same material as the first superconducting layer 210a and the first substrate 230b, respectively, or may be made of a different material.

[0112] Third superconducting layer 230a is provided to face first superconducting layer 210a and second superconducting layer 220a. Providing third wire 230 can reduce energy loss of superconducting wire 200. This is because when a current flows from first wire 210 to second wire 220, the current can pass through third superconducting layer 230a, which has a lower resistance.

[0113] The member 222 is provided to connect the connection layer 221 to at least one of the first wire rod 210 and the second wire rod 220. In Fig. 9, the member 222 is provided to cover the surface exposed to the outside of the third wire rod 230 and the side surface of the connection layer, but for example, the member 222 may be located between the first wire rod 210 and the second wire rod. In this case, the member 222 is located between the first wire rod 210 and the second wire rod, and is provided to connect the connection layer 221 to at least one of the first wire rod 210 and the second wire rod 220.

[0114] The member 222 has a region 223 that penetrates into the connecting layer 221, and the region 223 exists in a range of 5 μm to 1 mm from the end of the connecting layer 221 in the first direction D1 from the first wire 210 to the second wire 220.

[0115] Superconducting wire 200 in FIG. 9 can be produced as follows.

[0116] First, the third superconducting layer 230a is molded to a required thickness, dried, and then fired in oxygen at 700°C to 850°C to obtain the connection layer 221. Next, the first wire 210 and the second wire 220 are arranged so that the superconducting layers face the same direction. Thereafter, the third wire 230 on which the connection layer 221 is formed is arranged so that the first superconducting layer 210a and the second superconducting layer 220a face the third superconducting layer 230a with the connection layer 221 interposed therebetween. Then, the member 222 is placed so as to be in contact with the third base material 230b.

[0117] This provides a structure for obtaining superconducting wire 200 in Fig. 9. Thereafter, the above-described pressing method and heat treatment are performed to obtain superconducting wire 200 in Fig. 9.

[0118] The critical current and porosity of the connecting layer in the obtained superconducting wire 200 of Figure 9 can be measured in the same manner as described above in <Method for measuring critical current>, <Method for measuring the distance along the first direction of penetration of the component into the connecting layer>, and <Method for measuring the porosity of the connecting layer>.

[0119] A method for measuring the connection strength in Fig. 9 will be described with reference to Fig. 10. Fig. 10 is a schematic cross-sectional view showing a method for measuring the connection strength in the example of the superconducting wire in Fig. 9.

[0120] <Method for measuring the connection strength of superconducting wires in Figure 9> 10, first, a case will be described in which third base material 230b is covered with member 222 and the position of third base material 230b cannot be determined. In this case, as shown in FIG. 10, member 222 covering third base material 230b is fixed to base 250 via double-sided adhesive tape 240. The first or second base material is fixed to tension device 260 in the same manner as described in <Method for measuring connection strength of superconducting wire in FIG. 6>.

[0121] 10, a case will be described in which third base material 230b is not completely covered with member 222 and the position of third base material 230b is distinguishable. In this case, double-sided adhesive tape 240 is used with dimensions similar to those described in <Method for measuring connection strength of superconducting wire in FIG. 1>, and third base material 230b is fixed to base 250. The first or second base material is fixed to tension device 260 in the same manner as in <Method for measuring connection strength of superconducting wire in FIG. 6>.

[0122] In the example of FIG. 10, tensioning device 260 may be fixed to either the first or second substrate, or to both the first and second substrates.

[0123] Superconducting wire 200 is fixed to base 250 and tensioning device 260 using double-sided adhesive tape 240, and then the connection strength of superconducting wire 200 is measured using tensioning device 260.

[0124] The above method can be used to evaluate the connection strength between the first wire, the second wire, or the third wire and the connection layer.

[0125] FIG. 11 is a schematic cross-sectional view of a seventh modified example of the superconducting wire according to the first embodiment.

[0126] The member 222 has a fifth member 222e and a sixth member 222f. The member 222e is provided so as to cover the lower surface of the connection layer 221 in FIG.

[0127] The sixth member 222f is provided so as to cover the surface of the third wire 230 exposed to the outside and the side surface of the connection layer 221.

[0128] Third wire 230 is preferably covered with member 222, which can improve the connection strength of superconducting wire 200.

[0129] Superconducting wire 200 in FIG. 11 can be produced as follows.

[0130] After obtaining the structure for obtaining superconducting wire 200 in FIG. 9 as described above, member 222 is arranged so as to contact at least a portion of first wire 210 and at least a portion of second wire 220.

[0131] This provides a structure for obtaining superconducting wire 200 in Fig. 11. Thereafter, the above-described pressing method and heat treatment are performed to obtain superconducting wire 200 in Fig. 11.

[0132] The critical current, connection strength, and porosity of the connection layer of the obtained superconducting wire 200 of Figure 11 can be measured in the same manner as described above in <Method for measuring critical current>, <Method for measuring connection strength of superconducting wire in Figure 9>, <Method for measuring distance along the first direction of penetration of component into connection layer>, and <Method for measuring porosity of connection layer>.

[0133] The superconducting wire according to the first embodiment includes a first wire, a second wire adjacent to the first wire, a connection layer electrically connecting the first wire and the second wire, and a member connecting the connection layer and at least one of the first wire and the second wire, the melting point of the member being 900° C. or higher and 1100° C. or lower. This makes it possible to realize a superconducting wire having a high critical current and connection strength.

[0134] [Second embodiment] The superconducting coil of the second embodiment includes the superconducting wire of the first embodiment. Hereinafter, some of the description that overlaps with the first embodiment may be omitted.

[0135] Fig. 12 is a schematic perspective view of a superconducting coil according to the second embodiment, and Fig. 13 is a schematic cross-sectional view of the superconducting coil according to the second embodiment.

[0136] The superconducting coil 700 of the second embodiment is used as a coil for generating a magnetic field in superconducting equipment such as NMR, MRI, heavy particle beam therapy equipment, or superconducting magnetic levitation trains.

[0137] Superconducting coil 700 includes a bobbin 110, a first insulating plate 111a, a second insulating plate 111b, and a winding portion 112. Winding portion 112 includes superconducting wire 120 and inter-wire layers .

[0138] FIG. 12 shows a state in which the first insulating plate 111a and the second insulating plate 111b are removed.

[0139] The reel 110 is made of, for example, fiber-reinforced plastic. The superconducting wire 120 is, for example, tape-shaped. The superconducting wire 120 is wound around the reel 110 in a concentric, so-called pancake shape around a winding center C, as shown in FIG.

[0140] Inter-wire layer 130 has a function of fixing superconducting wire 120. Inter-wire layer 130 has a function of preventing superconducting wire 120 from being damaged by vibration during use of the superconducting device or by friction between wires.

[0141] The first insulating plate 111a and the second insulating plate 111b are formed of, for example, fiber-reinforced plastic. The first insulating plate 111a and the second insulating plate 111b have the function of insulating the winding portion 112 from the outside. The winding portion 112 is located between the first insulating plate 111a and the second insulating plate 111b.

[0142] The superconducting wire 120 is the superconducting wire of the first embodiment.

[0143] As described above, according to the second embodiment, by using superconducting wires having a high critical current and connection strength, a superconducting coil with improved characteristics can be realized.

[0144] [Third embodiment] The superconducting device of the third embodiment is a superconducting device equipped with the superconducting coil of the second embodiment. Hereinafter, some of the description overlapping with the first and second embodiments will be omitted.

[0145] 14 is a block diagram of a superconducting device according to a third embodiment. The superconducting device according to the third embodiment is a heavy ion beam therapy device 800. The heavy ion beam therapy device 800 is an example of a superconducting device.

[0146] The heavy ion beam therapy device 800 includes an injection system 50 , a synchrotron accelerator 52 , a beam transport system 54 , an irradiation system 56 , and a control system 58 .

[0147] The injection system 50 has a function of generating, for example, carbon ions to be used in therapy and pre-accelerating the ions to be injected into the synchrotron accelerator 52. The injection system 50 has, for example, an ion generation source and a linear accelerator.

[0148] The synchrotron accelerator 52 has a function of accelerating the carbon ion beam injected from the injection system 50 to an energy level suitable for treatment. The synchrotron accelerator 52 uses the superconducting coil 700 of the second embodiment.

[0149] The beam transport system 54 has a function of transporting the carbon ion beam injected from the synchrotron accelerator 52 to the irradiation system 56. The beam transport system 54 has, for example, a bending electromagnet.

[0150] The irradiation system 56 has a function of irradiating a patient, who is an irradiation target, with the carbon ion beam injected from the beam transport system 54. The irradiation system 56 has, for example, a rotating gantry that enables the carbon ion beam to be irradiated from any direction. The rotating gantry uses the superconducting coil 700 of the second embodiment.

[0151] The control system 58 controls the injection system 50, the synchrotron accelerator 52, the beam transport system 54, and the irradiation system 56. The control system 58 is, for example, a computer.

[0152] The heavy ion beam therapy device 800 of the third embodiment uses the superconducting coil 700 of the second embodiment in the synchrotron accelerator 52 and the rotating gantry, thereby realizing the heavy ion beam therapy device 800 with excellent characteristics.

[0153] In the third embodiment, a heavy ion beam therapy device 800 has been described as an example of a superconducting device, but the superconducting device may also be a nuclear magnetic resonance device (NMR), a magnetic resonance imaging device (MRI), or a superconducting magnetic levitation railway vehicle.

[0154] [Example] Example 1 GdBa2Cu3O δThree wires with a protective layer (oxide superconducting layer) formed on them were prepared. Two were 4 mm wide and 50 mm long, and one was 12 mm wide and 10 mm long. The protective layer at the tip of the two long, thin wires was removed by 15 mm, and the protective layer on the entire surface of the short, thick wire was removed by wet etching using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer (corresponding to the superconducting layers of the first and second wires, and the third wire).

[0155] Next, Gd2O3, BaCO3, and CuO powders were prepared, weighed appropriately, and then thoroughly mixed. The mixed powder was heat-treated at 900°C to obtain a calcined body. The calcined body was then pulverized, and the obtained powder was compression-molded to produce a green compact. The obtained green compact was sintered at 960°C to obtain GdBa2Cu3O δ An oxide superconductor with a composition of (6≦δ≦7) was produced. The obtained oxide superconductor was wet-pulverized and then heat-treated at 470°C in an oxygen atmosphere to obtain GdBa2Cu3O4 with an average particle size of 5.9 μm. δ Powders consisting of single-crystal or polycrystalline particles with (6≦δ≦7) were obtained.

[0156] The resulting powder was mixed with a solution whose main component was an organic compound containing the same metal element as the powder in a weight ratio of 2:1, and the mixture was applied to the superconductor of the third wire. After drying at 150°C, it was fired in oxygen at 800°C.

[0157] A 10mm square 50μm thick Ag sheet was placed on a pressure jig, and the first and second wires were placed on top of the Ag sheet with the superconducting layers facing up. A third wire was placed on top of the superconducting layers of the first and second wires with the connecting layer facing down, and another 10mm square 50μm thick Ag sheet was placed on top of that. The whole assembly was screwed in place with a torque of 4N·m and heat-treated at 820°C in argon containing 500ppm oxygen, and then at 450°C in oxygen.

[0158] The connection sample was removed from the furnace, removed from the pressure jig, and attached with a terminal. The connection sample was then immersed in liquid nitrogen to measure the critical current. Another connection sample prepared in the same way was used for the connection strength evaluation, and then for the porosity evaluation.

[0159] <Method for measuring critical current> The critical current of the fabricated superconducting wire was measured by a four-probe measurement method after removing it from the pressure jig. Terminals were attached to the connected superconducting wire, and measurements were performed in liquid nitrogen. Since the voltage increases as the resistance increases, the current value at which the voltage began to increase was taken as the critical current. The obtained critical currents are shown in Tables 1 and 2. Note that the critical currents shown in Tables 1 and 2 are expressed as a multiple of Comparative Example 1, with the value for Comparative Example 1 being set as 1.

[0160] <Method for measuring the connection strength of superconducting wire> The connection strength of the superconducting wire was evaluated in accordance with the Japanese Industrial Standard JIS K 6849 (1994) "Test method for tensile bond strength (method of measuring by applying a tensile load perpendicular to the adhesive surface)." For the measurement, first, the entire member covering the third substrate was fixed to the base using double-sided adhesive tape.

[0161] Next, the first substrate and the tensioning device were fixed together using double-sided adhesive tape. The dimensions of the double-sided adhesive tape 240 used here were 4 mm wide, the same as the first wire, and its length was long enough to ensure sufficient strength to prevent separation between the base and the first substrate during measurement of the connection strength. Carbon tape for SEM observation was used as the double-sided adhesive tape.

[0162] Thereafter, the pulling device was operated in a direction away from the first wire fixed to the pulling device via double-sided adhesive tape. The speed of the pulling device was kept constant, and the superconducting wire was pulled at a speed of 700 μm per second. The distance traveled by the pulling device until the wire completely peeled off from the connection layer was measured as the connection strength. The obtained connection strengths are shown in Tables 1 and 2. Note that the connection strengths shown in Tables 1 and 2 are values ​​that indicate how many times the value of Comparative Example 1 is, with the value of Comparative Example 1 being set as 1 as the reference.

[0163] <Method for measuring the porosity of the connecting layer> First, the connection part including the connection layer was embedded in epoxy resin, and because there was a concern about peeling at the end of the connection, the center of the firmly connected connection part was cut with a diamond saw. At this time, the cross section of the connection layer for measuring the porosity of the connection layer was taken at a location that avoided the members existing between the connection layer and the first wire or the second wire.

[0164] Next, the cut surface was polished with waterproof paper and a buff, after which a conductive coating was applied and the observation position determined using an SEM. Ion milling was performed at the determined observation position, and after applying a conductive coating, SEM observation was performed.

[0165] SEM images were taken at three cross sections at approximately 2500x magnification. The cross section of the connecting layer was cut at a position that divided the long side of the approximately rectangular shape into four equal parts when viewed in plan, yielding three cross sections. The SEM images were binarized using ImageJ to separate the particles and voids, and the area of ​​each was calculated. The porosity of each cross section was calculated from the ratio of these areas. The porosity obtained for each cross section was averaged to obtain the desired porosity of the connecting layer. The porosity of the resulting connecting layer is shown in Tables 1 and 2.

[0166] <Method for measuring distance along first direction of penetration into connection layer of component> The distance was determined by measuring the member remaining on the first superconducting layer of the first wire after the connection layer and the first wire were separated.

[0167] First, after the <Method for measuring the connection strength of superconducting wire> is performed, the connection layer and the first wire are peeled off.

[0168] Then, a mapping image of elements derived from the components of the first superconducting layer of the first wire was taken by EDX, which allowed us to measure the penetration distance of the component into the connecting layer in the first direction.

[0169] To perform EDX imaging, the area on the surface of the first superconducting layer where the connecting layer existed before the separation of the connecting layer and the first wire was first divided into five equal parts along a third direction that intersects with the first direction and is parallel to this surface. Of the five equal parts divided along the third direction, the two end areas were excluded from the area to be imaged by EDX. The EDX imaging magnification was set to a range in each imaging range that would allow the component with the longest penetration distance along the first direction to be included in the field of view.

[0170] For each EDX image obtained in this way, the average length in the third direction of the members present on the surface of the first superconducting layer was calculated. The average penetration length described above was determined by measuring the length of penetration of the members at positions that divided each width of each EDX image along the third direction into six equal parts. The five lengths obtained for each of the three EDX images, i.e., a total of 15 lengths, were averaged to determine the length along the first direction in which the members penetrated into the connecting layer. The obtained lengths along the first direction in which the members penetrated into the connecting layer are shown in Tables 1 and 2.

[0171] Example 2 GdBa2Cu3O with an average particle size of 2.2 μm δ A powder consisting of single-crystal or polycrystalline particles (6≦δ≦7) was used, and the same connection sample as in Example 1 was prepared and evaluated in the same manner, except that the mixing ratio of the powder to a solution whose main component was an organic compound containing the same metal element as the obtained powder was changed to 1:1 due to the change in particle size.

[0172] Example 3 A connection sample similar to that in Example 1 was prepared, except that an Ag sheet with a thickness of 20 μm was used, and the same evaluation was carried out.

[0173] Example 4 A connection sample similar to that in Example 1 was prepared, except that only one Ag sheet was provided below the first and second wires, and the same evaluation was carried out.

[0174] Example 5 The powder described in Example 1 was mixed with a solution mainly composed of an organic compound containing the same metal element as the obtained powder in a weight ratio of 2:1, and the mixture was applied to an Ag sheet instead of the third wire, dried at 150° C., and then fired in oxygen at 800° C. A connection sample similar to that in Example 1 was prepared and evaluated in the same manner, except that the connection layer side of the obtained Ag sheet was placed on the superconducting layers of the first and second wires and no other Ag sheets were used.

[0175] Example 6 Only the first and second wires from which the protective layer described in Example 1 had been peeled were used, and a powder and solution were mixed and applied to one of them in a weight ratio of 2:1, then dried at 150°C and fired in oxygen at 800°C. A connection sample similar to that in Example 1 was prepared, except that the two wires were placed opposite each other, and similar evaluations were performed.

[0176] Example 7 A connection sample similar to that in Example 1 was prepared, except that a Cu sheet was used instead of an Ag sheet, and the same evaluation was carried out.

[0177] Example 8 A connection sample similar to that in Example 1 was prepared, except that an Au sheet was used instead of an Ag sheet, and the same evaluation was carried out.

[0178] Example 9 A connection sample similar to that in Example 1 was prepared, except that a Ge sheet was used instead of an Ag sheet, and the same evaluation was carried out.

[0179] Example 10 GdBa2Cu3O with an average particle size of 1.7 μm δ A connection sample similar to that in Example 1 was prepared and evaluated in the same manner, except that a powder consisting of single-crystal or polycrystalline particles (6≦δ≦7) was used (the mixing ratio of powder to solution was changed to 1:1 due to the change in particle size).

[0180] Example 11 GdBa2Cu3O with an average particle size of 8.6 μm δA connection sample similar to that in Example 1 was prepared and evaluated in the same manner, except that a powder consisting of single-crystal or polycrystalline particles (6≦δ≦7) was used (the mixing ratio of powder to solution was changed to 1:2 due to the change in particle size).

[0181] Example 12 GdBa2Cu3O with an average particle size of 1.3 μm δ A connection sample similar to that in Example 1 was prepared and evaluated in the same manner, except that a powder consisting of single-crystal or polycrystalline particles (6≦δ≦7) was used (the mixing ratio of powder to solution was changed to 1:1 due to the change in particle size).

[0182] Example 13 GdBa2Cu3O with an average particle size of 11.0 μm δ A connection sample similar to that in Example 1 was prepared and evaluated in the same manner, except that a powder consisting of single-crystal or polycrystalline particles (6≦δ≦7) was used (the mixing ratio of powder to solution was changed to 1:2 due to the change in particle size).

[0183] (Comparative Example 1) A connection sample similar to that in Example 1 was prepared without the Ag sheet, and the same evaluation was carried out.

[0184] (Comparative Example 2) A connection sample similar to that in Example 2 was prepared without the Ag sheet, and the same evaluation was carried out.

[0185] (Comparative Example 3) A connection sample similar to that in Example 1 was prepared without the Ag sheet, and after firing, the entire connection was sealed with solder at a temperature of 300° C., and the same evaluation was carried out.

[0186] Comparative Example 4 A connection sample similar to that in Example 1 was prepared without the Ag sheet, and after firing, the entire connection portion was fixed by pressure bonding with an Ag sheet at room temperature, and the same evaluation was carried out.

[0187] (Comparative Example 5) A connection sample similar to that in Example 1 was prepared, except that an Al sheet was used instead of an Ag sheet, and the same evaluation was carried out.

[0188] (Comparative Example 6) A connection sample similar to that in Example 1 was prepared, except that a Pt sheet was used instead of an Ag sheet, and the same evaluation was carried out.

[0189] Tables 1 and 2 show the results of the critical current, connection strength, porosity, and length along the first direction in which the member penetrates into the connection layer for all examples and comparative examples.

[0190] [Table 1] [Table 2]

[0191] In contrast to Comparative Examples 1 to 4, in which the connection began to peel off when the wires were removed from the pressure jig, Examples 1 to 6, in which an Ag sheet was installed, all showed improved critical current and connection strength characteristics. In particular, in Example 2, which used powder with a small particle size, although the porosity of the connection layer was low, the contact area between the particles and between the particles and the superconducting layer of the wire increased, improving the contact area of ​​the wire and resulting in a high critical current.

[0192] In Example 3, in which a thin Ag sheet was used, Ag easily penetrated into the connection layer, further improving the connection strength.

[0193] On the other hand, in Comparative Example 3, in which the connection was sealed with solder, the powder in the connection layer and the superconducting layer of the wire rod deteriorated due to heat, and although the connection strength was high, the critical current was low. Similarly, in Comparative Example 4, in which the connection was fixed by pressure bonding with an Ag sheet at room temperature, the structure in the connection layer collapsed under pressure, and the connection between the particles in the connection layer and the superconducting layer of the wire rod peeled off, and although the connection strength was high, the critical current was low.

[0194] It can be seen that the critical current and connection strength characteristics are also high in Examples 7 to 9, in which Cu, Au, and Ge, each with a melting point of 900° C. to 1100° C., are used instead of the Ag sheet.

[0195] On the other hand, in Comparative Example 5, which used an Al sheet with a melting point of less than 900°C, the Al reacted with the GdBCO material in the intervening layer, resulting in high connection strength, but a low critical current. In Comparative Example 6, which used a Pt sheet with a melting point of more than 1100°C, the Pt sheet did not soften, resulting in low connection strength.

[0196] In Examples 10 and 11, where the porosity is between 10% and 70%, the critical current and connection strength characteristics are high, but it can be seen that the characteristics are also sufficiently high in Example 12, where the porosity is less than 10%, and Example 13, where the porosity is more than 70%.

[0197] Furthermore, in Comparative Example 5, in which an Al sheet with a melting point of 660°C was used instead of an Ag sheet, the melting of the member proceeded too far, and it was found that the penetration distance of the member into the connection layer was greater than in Example 1. This shows that in Comparative Example 5, the member pushed aside the particles that make up the connection layer, making it impossible to obtain a sufficient connection area, and the current path was insufficient, resulting in a smaller critical current than in Example 1.

[0198] In addition, in Comparative Example 6, in which a Pt sheet with a melting point of 1769°C was used instead of the Ag sheet, the member was not melted sufficiently and did not penetrate into the connection layer. This shows that Comparative Example 6 has lower connection strength as a superconducting wire than Example 1.

[0199] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0200] The invention according to the embodiment will be described below.

[0201] [1] a first wire; a second wire rod adjacent to the first wire rod; a connection layer that electrically connects the first wire and the second wire; a member that connects the connection layer to at least one of the first wire rod and the second wire rod, The melting point of the member is 900°C or higher and 1100°C or lower.

[0202] [2] The superconducting wire according to [1], wherein the connection layer has a porosity of 10% or more and 70% or less.

[0203] [3] the member includes at least one of a first region existing between the connection layer and the first wire and a second region existing between the connection layer and the second wire, the first region and the second region satisfy at least one of a first condition and a second condition, The first condition is that the first region intersects with a direction from the first wire toward the connection layer and exists in a range of 5 μm to 1 mm from an end of the first wire in a first direction along the first wire, The superconducting wire according to [1] or [2], wherein the second condition is that the second region is present in a range of 5 μm or more and 1 mm or less from the end of the second wire along the first direction.

[0204] [4] The superconducting wire according to [1] or [2], wherein the member intersects with the direction from the first wire toward the connection layer and is present in a range of 5 μm to 1 mm from the end of the connection layer in a first direction along the first wire.

[0205] [5] The superconducting wire according to any one of [1] to [4], wherein the member comprises at least one selected from the group consisting of Ag, Cu, Au, and Ge.

[0206] [6] Further having a third wire, the connection layer is located between the first wire and the third wire and between the second wire and the third wire, The superconducting wire according to any one of [1] to [5], wherein the connecting layer electrically connects the first wire and the third wire, and the second wire and the third wire.

[0207] [7] The superconducting wire according to [6], wherein the connection layer has a porosity of 10% or more and 70% or less.

[0208] [8] the member includes at least one of a first region existing between the connection layer and the first wire and a second region existing between the connection layer and the second wire, the first region and the second region satisfy at least one of a third condition and a fourth condition, The third condition is that the first region exists in a range of 5 μm to 1 mm from an end of the first wire rod along a first direction from the first wire rod to the second wire rod, The fourth condition is that the second region is present in a range of 5 μm to 1 mm from the end of the second wire along the first direction.

[0209] [9] A superconducting wire according to any one of [6] to [8], wherein the member intersects with the direction from the first wire toward the connection layer and is present in a range of 5 μm to 1 mm from the end of the connection layer in a first direction along the first wire.

[0210]

[10] The superconducting wire according to any one of [6] to [9], wherein the member comprises at least one selected from the group consisting of Ag, Cu, Au, and Ge.

[0211]

[11] A superconducting coil comprising the superconducting wire according to any one of [1] to

[10] .

[0212]

[12]

[11] A superconducting device comprising the superconducting coil according to

[11] . [Explanation of symbols]

[0213] 200...superconducting wire, 210...first wire, 210a...first superconducting layer, 210b...first substrate, 220...second wire, 220a...second superconducting layer, 220b...second substrate, 221...connecting layer, 222...member, 222a-222f...first member to sixth member, 223...region, 224...first region, 225...second region, 230...third wire, 230a...third superconducting layer, 230b...third substrate, 240...double-sided adhesive tape, 250...base, 260...tensioning device, 700...superconducting coil, 800...heavy ion beam therapy device.

Claims

1. a first wire; a second wire rod adjacent to the first wire rod; a connection layer that electrically connects the first wire and the second wire; a member that connects the connection layer to at least one of the first wire rod and the second wire rod, The melting point of the member is 900°C or higher and 1100°C or lower.

2. 2. The superconducting wire according to claim 1, wherein the connection layer has a porosity of 10% or more and 70% or less.

3. the member includes at least one of a first region existing between the connection layer and the first wire and a second region existing between the connection layer and the second wire, the first region and the second region satisfy at least one of a first condition and a second condition, The first condition is that the first region intersects with a direction from the first wire toward the connection layer and exists in a range of 5 μm to 1 mm from an end of the first wire in a first direction along the first wire, 2. The superconducting wire according to claim 1, wherein the second condition is that the second region is present in a range of 5 μm to 1 mm from an end of the second wire along the first direction.

4. 2. The superconducting wire according to claim 1, wherein the member intersects the direction from the first wire toward the connection layer and is present in a range of 5 μm to 1 mm from the end of the connection layer in a first direction along the first wire.

5. 2. The superconducting wire according to claim 1, wherein the member comprises at least one selected from the group consisting of Ag, Cu, Au, and Ge.

6. Further comprising a third wire; the connection layer is located between the first wire and the third wire and between the second wire and the third wire, 2. The superconducting wire according to claim 1, wherein the connection layer electrically connects the first wire and the third wire, and the second wire and the third wire.

7. 7. The superconducting wire according to claim 6, wherein the connection layer has a porosity of 10% or more and 70% or less.

8. the member includes at least one of a first region existing between the connection layer and the first wire and a second region existing between the connection layer and the second wire, the first region and the second region satisfy at least one of a third condition and a fourth condition, The third condition is that the first region exists in a range of 5 μm to 1 mm from an end of the first wire rod along a first direction from the first wire rod to the second wire rod, 7. The superconducting wire according to claim 6, wherein the fourth condition is that the second region is present in a range of 5 μm to 1 mm from an end of the second wire along the first direction.

9. The superconducting wire according to claim 6, wherein the member intersects the direction from the first wire toward the connection layer and is present in a range of 5 μm to 1 mm from the end of the connection layer in a first direction along the first wire.

10. 7. The superconducting wire according to claim 6, wherein the member comprises at least one selected from the group consisting of Ag, Cu, Au, and Ge.

11. A superconducting coil comprising the superconducting wire according to claim 1.

12. A superconducting device comprising the superconducting coil according to claim 11.

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