Superconducting wire connecting case and superconducting magnet

Abstract

To reduce generation of voids in a container for connecting a superconducting wire.SOLUTION: A container for connecting a superconducting wire includes a superconducting wire having a superconducting material, superconducting solder used for electrically joining two or more superconducting wires, a container having an outer wall and a bottom plate for holding the superconducting solder and the superconducting wire, and an inner wall at least partially integrated with the bottom plate so that a cavity is provided in the container.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to a superconducting wire splicing container and a superconducting magnet. [Background technology]

[0002] MRI (Magnetic Resonance Imaging) devices sometimes use superconducting magnets that use superconductors. To create a superconducting magnet, it is important to connect superconducting wires. When connecting superconducting wires, it is important to minimize power loss.

[0003] Here, in connecting superconducting wires, there is a method in which the superconducting wires are soldered using a superconducting solder that exhibits superconductivity at low temperatures, the soldered superconducting wires are enclosed in a container to create a superconducting wire connection container, and the superconducting wires are connected using the superconducting wire connection container.

[0004] However, when the superconducting solder is cooled and solidified in the container, voids may occur, and if voids are formed near the superconducting wire, the connection characteristics of the superconducting wire may deteriorate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 4,744,506 Summary of the Invention [Problem to be solved by the invention]

[0006] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to reduce the occurrence of voids in a superconducting wire splicing container. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems. [Means for solving the problem]

[0007] A superconducting wire connection container according to an embodiment comprises a superconducting wire having a superconducting material, superconducting solder used to electrically join two or more of the superconducting wires, a container having an outer wall and a bottom plate that hold the superconducting solder and the superconducting wires, and an inner wall at least partially integrated with the bottom plate so as to provide a cavity in the container. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a procedure for producing a superconducting wire connection container. [Figure 2] FIG. 2 is a diagram illustrating an example of a procedure for producing a superconducting wire connection container. [Figure 3] FIG. 3 is a diagram illustrating the background according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating the appearance of the superconducting wire connection container according to the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view illustrating the configuration of the superconducting wire connection container according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of the configuration of a superconducting wire connection container according to the second embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the configuration of a superconducting wire connection container according to the second embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of the configuration of a superconducting wire connection container according to the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of the configuration of a superconducting wire connection container according to the second embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a superconducting wire connection container according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) Hereinafter, embodiments of a superconducting wire (superconducting wire) connection container and a superconducting (superconducting) magnet will be described in detail with reference to the drawings. Note that in the embodiments, superconductivity and superconductivity are synonymous.

[0010] First, we will explain the connection of superconducting wires. For example, MRI (Magnetic Resonance Imaging) devices use superconducting magnets made of superconductors, and the connection between superconducting wires is important for creating superelectromagnets. When connecting superconducting wires, it is important to suppress power loss.

[0011] Here, one possible method for connecting superconducting wires is to solder them together using superconducting solder that exhibits superconductivity at low temperatures, and then enclose the soldered superconducting wire in a container to form a superconducting wire connection container. By connecting superconducting wires through this superconducting wire connection container, it is possible to create a superconducting magnet for, for example, an MRI.

[0012] Examples of procedures for producing a superconducting wire connection container are shown in Figures 1 and 2. Figure 1 shows an example of producing a superconducting wire connection container by a method in which a superconducting wire is immersed in concentrated nitric acid and then soldered to the filament, while Figure 2 shows an example of producing a superconducting wire connection container by a method in which a superconducting wire is tin-substituted and then soldered.

[0013] 1 shows an example of producing a superconducting wire connection container by a method of soldering a superconducting wire to a filament after immersing the wire in concentrated nitric acid. First, in step S1, a superconducting wire 9 typically includes a base material 1 containing copper or a copper compound, and a superconducting material 2 provided inside the base material 1. Examples of the superconducting material 2 include NbTi and Nb3Sn. When the superconducting wire 9 is immersed in concentrated nitric acid 10, the base material 1 made of copper or a copper compound dissolves, exposing the internal superconducting material 2 and forming a filament shape.

[0014] Subsequently, in step S2, an operation is performed to twist together the two filaments with the exposed portions of the superconducting material 2. Specifically, the filament-shaped superconducting material 2a in the superconducting wire 9a made of the base material 1a and the superconducting material 2a and the filament-shaped superconducting material 2b in the superconducting wire 9b made of the base material 1b and the superconducting material 2b are twisted together, thereby connecting the superconducting wire 9a and the superconducting wire 9b.

[0015] Subsequently, in step S3, the superconducting wire 9a and the superconducting wire 9b are placed in the container 3. The container 3 is typically made of a conductive material such as copper.

[0016] Subsequently, in step S4, two or more superconducting wires, i.e., superconducting wires 9a and 9b, are electrically joined by superconducting solder 4. Superconducting solder 4 is a solder that exhibits superconductivity at low temperatures. As an example, superconducting wires 9a and 9b are soldered together by superconducting solder 4 that is in a liquid state at high temperatures (exhibiting a superconducting state at low temperatures), and superconducting solder 4 solidifies at low temperatures, thereby electrically joining superconducting wires 9a and 9b by superconducting solder 4. For example, at a low temperature after further cooling, such as to the temperature of liquid helium, superconducting solder 4 becomes superconducting, so that the electrical resistance at the connection between superconducting wires 9a and 9b becomes zero, thereby suppressing power loss.

[0017] FIG. 2 shows an example of producing a superconducting wire connection container by a method of soldering a filament after tin-substitution of a superconducting wire 9. First, in step S1, the superconducting wire 9 typically includes a base material 1 containing copper or a copper compound, and a superconducting material provided inside the base material 1. Examples of the superconducting material include NbTi and Nb3Sn. When the superconducting wire 9 is immersed in molten tin 11, as in step S2, the base material 1 made of copper or a copper compound dissolves and the superconducting material 2 is exposed. At this time, the surface of the superconducting material 2 is coated with tin, thereby providing tin plating. This operation is performed for each of the two superconducting wires.

[0018] Subsequently, in step S3, the tin-plated superconducting wire 9a and the superconducting wire 9b are placed in the container 3. The container 3 is typically made of a conductive material such as copper.

[0019] Subsequently, in step S4, two or more superconducting wires, i.e., superconducting wires 9a and 9b, are electrically joined by superconducting solder 4. Specifically, the superconducting solder 4 is, for example, a solder that exhibits superconductivity at low temperatures. As an example, the superconducting wires 9a and 9b are soldered together by the superconducting solder 4 that is in a liquid state at high temperatures (exhibiting a superconducting state at low temperatures), and the superconducting solder 4 solidifies at low temperatures, thereby electrically joining the superconducting wires 9a and 9b by the superconducting solder 4. At low temperatures after further cooling, such as to the temperature of liquid helium, the superconducting solder 4 becomes superconducting, so that the electrical resistance at the connection between the superconducting wires 9a and 9b becomes zero, thereby suppressing power loss.

[0020] As described above, as a method for producing a superconducting wire connection container for connecting superconducting wires, a case where a superconducting wire connection container is produced by a method of soldering a filament after immersing it in concentrated nitric acid, and a case where a superconducting wire connection container is produced by a method of soldering a superconducting wire after tin substitution have been described. However, the embodiments are not limited to these, and in the embodiments, superconducting wire connection may be performed by crimping bonding, solid-state bonding, or the like.

[0021] Here, crimping refers to a method of joining multiple superconducting wires by crimping. In the case of crimping, first, the processes of steps S1 and S2 in FIG. 1 are performed in the same manner. In the case of crimping, in step S3, superconducting wire 9a and superconducting wire 9b are inserted into a metal sleeve. In step S4, pressure is applied to the metal sleeve, and superconducting wire 9a and superconducting wire 9b are crimped and joined. Finally, the vicinity of the entrance of the metal sleeve is soldered.

[0022] 1 is also performed in the case of solid-state bonding. In the case of solid-state bonding, the superconducting wire 9a and the superconducting wire 9b are inserted into a compression jig in step S3. In step S4, the compression jig is pressurized and heated, and the superconducting wire 9a and the superconducting wire 9b are solid-state bonded.

[0023] Next, the background of the embodiment will be described.

[0024] Up to this point, the creation of a container for connecting superconducting wires has been described. However, when the superconducting solder 4 in a liquid state in step S4 is cooled and solidified in the container 3, voids or gaps may occur.

[0025] This point will be explained with reference to FIG. 3. FIG. 3 is a diagram showing the structure of a container 3, which is a superconducting wire splicing container according to a comparative example. The container 3 has an outer wall 21 and a bottom plate 22, and holds a superconducting material 2 and superconducting solder 4. The superconducting solder 4 is a solder that has superconducting properties at low temperatures. When the superconducting solder is cooled and solidified inside the container, voids 20 may occur. If voids 20 occur near the superconducting material 2, the connection characteristics of the superconducting wire may deteriorate. Therefore, it is desirable to control the occurrence of voids 20 so that they do not occur near the superconducting material 2.

[0026] In view of this background, a superconducting wire connection container according to an embodiment includes a superconducting wire having a superconducting material 2, a superconducting solder 4 used to electrically join two or more superconducting wires, and a container 3 having an outer wall 21 and a bottom plate 22 that hold the superconducting solder 4 and the superconducting wires, and the container 3 includes an inner wall at least partially integrated with the bottom plate 22 so as to provide a cavity. Specifically, the container 3 includes an inner wall at least partially integrated with the bottom plate 22 so as to provide a cavity from the bottom plate portion.

[0027] Here, by providing a cavity from the bottom plate of the vessel 3, a difference in cooling rate occurs between the inner wall and the outer wall, making it possible to control the occurrence of voids. This point will be described later. In addition, by providing a cavity, the vessel 3 can be structured to be efficiently cooled, for example, when it is incorporated and operated as part of a superconducting magnet.

[0028] The configuration according to the first embodiment will be described in detail with reference to Fig. 4 and Fig. 5. Fig. 4 is an external view of the superconducting wire connection container according to the first embodiment, and Fig. 5 is a cross-sectional view of the superconducting wire connection container according to the first embodiment.

[0029] As shown in FIGS. 4 and 5 , a superconducting wire splicing container according to an embodiment includes superconducting wires 9a, 9b having superconducting materials 2a, 2b, a superconducting solder 4 used to electrically join the two or more superconducting wires 9a, 9b, and a container 3 having an outer wall 21 and a bottom plate 22 for holding the superconducting solder 4 and the superconducting wires 9a, 9b. The superconducting wires 9a, 9b include base materials 1a, 1b containing copper or a copper compound, and superconducting materials 2a, 2b provided inside the base materials 1a, 1b. The superconducting solder 4 is, for example, a solder that exhibits superconductivity at low temperatures. The superconducting wire splicing container according to an embodiment is used to splice superconducting wires included in the superconducting coil of a superconducting magnet, for example.

[0030] Here, a cavity 5 is provided from the bottom plate portion of the container 3, and the container 3 has an inner wall 31 at least partly integrated with the bottom plate 22. Note that the superconducting wire splicing container according to the embodiment includes, in addition to the container 3, superconducting wires 9a and 9b placed in the container 3 and superconducting solder 4 filled in the container 3.

[0031] The inner wall 31 may also be made of a conductive material to enhance thermal conductivity.

[0032] Next, the effects obtained by using the superconducting wire splicing container according to the embodiment will be described. The container 3 according to the embodiment has a cavity 5, so that the cooling rate can be made different between the inner wall 31 and the outer wall 21. As an example, the inner wall 31 and the outer wall 21 can be designed so that the cooling rate near the inner wall 31 is higher than the cooling rate near the outer wall 21.

[0033] It is known that there is a negative correlation between the cooling rate when the superconducting solder 4 is cooled and solidified and the number of voids that occur. In other words, when the superconducting solder 4 is cooled and solidified rapidly, fewer voids occur compared to when the superconducting solder 4 is cooled and solidified slowly. Also, the probability of voids occurring is lower in places where the superconducting solder 4 is cooled and solidified rapidly compared to when the superconducting solder 4 is cooled and solidified slowly. This makes it possible to control the occurrence of voids.

[0034] As an example, the superconducting wire splicing container according to the embodiment can vary the temperature drop rate during cooling depending on the location by varying the wall structure depending on the location. As an example, the temperature drop rate can be varied by differentiating the thickness of the inner wall 31 from the thickness of the outer wall 21. As another example, the material of the inner wall 31 can be different from the material of the outer wall 21, thereby making the thermal conductivity different, and thereby making the temperature drop rate during cooling different.

[0035] Here, the superconducting wires 9a and 9b are provided in a location where the rate of temperature decrease during cooling is fast.

[0036] As an example, if the cooling rate near the inner wall 31 is designed to be higher than the cooling rate near the outer wall 21, the probability of voids occurring near the inner wall 31 will be lower than the probability of voids occurring near the outer wall 21. Therefore, the superconducting wires 9a and 9b are provided near the inner wall 31, where the temperature decreases faster during cooling. In this case, if the superconducting wires 9a and 9b are arranged near the inner wall 31, the probability of voids occurring will be lower in the region 81 where the superconducting wires 9a and 9b are arranged than in other regions. As a result, the probability of voids occurring in the region where the superconducting wires 9a and 9b are arranged can be lower than the probability of voids occurring in other regions, and the connection characteristics of the superconducting wire can be improved.

[0037] Conversely to the above case, when the cooling rate near the inner wall 31 is designed to be slower than the cooling rate near the outer wall 21, the probability of void generation near the inner wall 31 becomes higher than the probability of void generation near the outer wall 21. In this case, the superconducting wires 9a and 9b are provided near the outer wall 21, where the temperature decreases faster during cooling. Even in this case, the probability of void generation in the region where the superconducting wires 9a and 9b are arranged can be reduced compared to the probability of void generation in other regions, thereby improving the connection characteristics of the superconducting wire.

[0038] Returning to the explanation of the embodiment, another effect obtained by using the superconducting wire splicing container according to the embodiment is that the container 3 according to the embodiment has a cavity 5 in its center, thereby improving cooling efficiency. Specifically, the region near the inner wall 31 can be cooled in a shorter time than if the cavity 5 were not present. The superconducting wire splicing container according to the embodiment is used by cooling it to a temperature at which the superconducting solder 4 becomes superconducting, and the cooling of the container 3 at this time can be made more efficient. Note that by forming the inner wall 31 from a conductive material, the thermal conductivity of the inner wall 31 can be increased, and the cooling rate of the container 3 can be further improved.

[0039] The embodiment is not limited to the above example. As an example, the cooling rate can be controlled by controlling the diameter 32 of the cavity 5. Specifically, by widening the diameter 32 of the cavity 5, the contact surface area with the air or the heat conduction zone near the inner wall 31 can be increased, thereby increasing the cooling rate. This allows the location of void concentration to be shifted to a location other than near the inner wall 31. This makes it possible to control the occurrence of voids. Furthermore, by changing the size and shape of the cavity 5 and the thickness, angle, and shape of the inner wall 31, the cooling rate near the inner wall 31 can be controlled, and the probability of void occurrence can be controlled based on this. Furthermore, the cross-sectional shape of the cavity 5 (inner wall 31) may be various shapes, such as a circle, an ellipse, a triangle, a rectangle, or a polygon. Furthermore, the cross-sectional shapes of the outer wall 21 and the bottom plate 22 may also be various shapes, such as a circle, an ellipse, a triangle, a rectangle, or a polygon.

[0040] Furthermore, the embodiment is not limited to the above example, and the cooling efficiency near the inner wall 31 may be further improved by filling the cavity 5 with a thermal conduction band.

[0041] 4 and 5, the superconducting wires are connected by immersing the superconducting wires in concentrated nitric acid and then joining them with superconducting solder 4 as shown in Fig. 1, and by using tin plating as shown in Fig. 2. However, the method for connecting the superconducting wires is not limited to this, and the superconducting wires may be connected by, for example, pressure bonding or solid-state bonding.

[0042] As described above, in the first embodiment, the superconducting wire connecting container includes a superconducting wire having a superconducting material 2, superconducting solder 4 used to electrically join two or more superconducting wires, and a container 3 having an outer wall 21 and a bottom plate 22 that hold the superconducting solder 4 and the superconducting wire, and the container 3 includes an inner wall at least partially integrated with the bottom plate 22 so that a cavity 5 is formed extending from the bottom plate portion of the container 3. By forming the cavity 5 extending from the bottom plate portion of the container 3, it is possible to prevent the generation of voids. In addition, it is possible to improve the cooling efficiency of the container 3.

[0043] (Second embodiment) The embodiment is not limited to the above-mentioned example. In the second embodiment, the case where the shape of the inner wall 31 is changed in various ways will be described.

[0044] As an example, as shown in FIG. 6 , a superconducting wire splicing container according to the second embodiment includes superconducting wires 9 a, 9 b, superconducting solder 4 used to electrically join two or more superconducting wires 9 a, 9 b, and a container 3 having an outer wall 21 and a bottom plate 22 that hold the superconducting solder 4 and the superconducting wires 9 a, 9 b. Here, a cavity 5 is provided from the bottom plate portion of the container 3, and the container 3 includes an inner wall 40 at least partially integrated with the bottom plate 22. The thickness of a region 41 in an upper portion of the inner wall 40 (a portion away from the bottom plate 22) is made thicker than that of a portion of the inner wall 40 closer to the bottom plate 22. That is, the thickness of the inner wall 40 varies depending on the height measured from the bottom plate 22. As a result, the cooling rate of the inner wall 40 near the bottom plate 22 is faster than the cooling rate of the inner wall 40 near the upper portion of the inner wall 40. Therefore, for example, the probability of voids occurring near the region 82 is reduced, and by arranging the superconducting wire in this vicinity, the influence of voids can be reduced.

[0045] 7 , a superconducting wire connecting container according to the embodiment includes superconducting wires 9a, 9b, superconducting solder 4 used to electrically connect two or more superconducting wires 9a, 9b, an outer wall 21 and a bottom plate 22 that hold the superconducting solder 4 and the superconducting wires 9a, 9b, and a container 3 having inner walls 50a, 50b and a wall 51. Here, a cavity 5 is provided from the bottom plate portion of the container 3, and the upper part of the cavity 5 is closed by the wall 51. In other words, the wall 51 connecting the inner walls 50a, 50b to each other is provided on the side of the inner walls 50a, 50b opposite to the bottom plate 22. As a result, the cooling rate of the inner walls 50a, 50b near the bottom plate 22 is faster than the cooling rate of the inner walls 50a, 50b near the upper parts of the inner walls 50a, 50b. Therefore, for example, the probability of voids occurring near the region 83 is reduced, and by arranging the superconducting wire in this vicinity, the influence of voids can be reduced.

[0046] 8, a superconducting wire splicing container according to an embodiment includes superconducting wires 9a, 9b, superconducting solder 4 used to electrically join two or more superconducting wires 9a, 9b, and a container 3 having an outer wall 21 and a bottom plate 22 for holding the superconducting solder 4 and the superconducting wires 9a, 9b, and inner walls 60, 61 disposed at an angle to the bottom plate. As a result, the cooling rate near regions 84 and 85, for example, is higher than the cooling rate in other locations. Therefore, the probability of voids occurring near regions 84 and 85 is reduced, and the influence of voids can be reduced by arranging superconducting wires in these vicinity.

[0047] As another embodiment, as shown in FIG. 9 , a superconducting wire splicing container according to the embodiment includes superconducting wires 9a, 9b, superconducting solder 4 used to electrically join two or more superconducting wires 9a, 9b, and a container 3 having an outer wall 21, a bottom plate 22, and an inner wall 31 that hold the superconducting solder 4 and the superconducting wires 9a, 9b. A thermal conductor 70 for cooling is further provided. This allows the cooling rate near region 86 to be higher than the cooling rate in other locations. Therefore, the probability of voids occurring near region 86 is reduced, and the influence of voids can be reduced by arranging superconducting wires in this vicinity.

[0048] 7 in which the upper part of the cavity 5 is closed by the wall 51, as shown in FIG. 10, for example, the lower part of the cavity 5 may be closed by a bottom plate 71, and the bottom plate 71 and the bottom plate 22 may constitute the bottom plate of the superconducting wire splicing container. In this case, the bottom plate is formed inside the inner walls 50a, 50b and includes a portion that closes the lower part of the cavity 5. That is, the superconducting wire splicing container according to the embodiment includes a container 3 having superconducting wires 9a, 9b, superconducting solder 4 used to electrically join two or more superconducting wires 9a, 9b, outer wall 21 and bottom plate 22 that hold the superconducting solder 4 and the superconducting wires 9a, 9b, and a bottom plate 71 formed inside the inner walls 50a, 50b and that closes the lower part of the cavity 5. In this embodiment, the area of ​​the bottom plate can be designed to be large, and the superconducting wire splicing container can be cooled efficiently.

[0049] According to at least one of the embodiments described above, it is possible to reduce the occurrence of voids in the superconducting wire connection container.

[0050] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments 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, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0051] 1 Base material 2. Superconducting materials 3 containers 4. Superconducting solder 5 cavities 9 Superconducting wire 21 Exterior Wall 22 Bottom plate 31 Inner wall

Claims

1. a superconducting wire having a superconducting material; a superconducting solder used to electrically join two or more of the superconducting wires; a container having an outer wall and a bottom plate for holding the superconducting solder and the superconducting wire; A superconducting wire splicing container comprising an inner wall at least partially integrated with the bottom plate so as to provide a cavity in the container.

2. 2. The superconducting wire connection container according to claim 1, wherein said inner wall is made of a conductive material.

3. 2. The superconducting wire splicing container according to claim 1, wherein the wall structure is made different depending on the location, thereby making the rate of temperature decrease during cooling different depending on the location.

4. 2. The superconducting wire splicing container according to claim 1, wherein the thickness of said inner wall is different from the thickness of said outer wall.

5. 4. The superconducting wire splicing container according to claim 3, wherein the superconducting wire is provided in a location where the rate of temperature decrease is fast.

6. 2. The superconducting wire splicing container according to claim 1, wherein the thickness of said inner wall varies depending on the height measured from said bottom plate.

7. 2. The superconducting wire connection container according to claim 1, wherein a wall connecting said inner walls is provided on the inner walls on the opposite side to said bottom plate.

8. 2. The superconducting wire splicing container according to claim 1, further comprising a heat conductor for cooling.

9. 2. The superconducting wire splicing container according to claim 1, wherein the superconducting wire includes a base material containing copper or a copper compound, and the superconducting material provided inside the base material.

10. 2. The superconducting wire connection container according to claim 1, wherein said bottom plate is a portion formed inside said inner wall and includes a portion that closes a lower portion of said cavity.

11. 2. A superconducting magnet in which superconducting wires contained in a superconducting coil are connected using the superconducting wire connecting container according to claim 1.

Images