JP2008234957A - Connecting method of thin-film superconductive wire and its connection structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method and a connection structure which easily connects a thin-film superconductive wire even at such an actual site as inside a manhole, without jeopardizing various characteristics required of its connecting part for use in a practical equipment. <P>SOLUTION: At least two of first thin-film superconductive wires each with a superconductive layer (1), a metal protection layer (1), and a stabilized metal layer formed on a substrate (1) with a part peeled of each stabilized metal layer in the vicinity of a connecting end ready for connection, and at least one second thin-film superconductive wire with a superconductive layer (2), and a metal protection layer (2) formed on a substrate (2), are prepared in the connection method of the thin-film superconductive wires. The connecting ends of the first thin-film superconductive wires are arranged in opposition, the metal protection layer (2) of the second thin-film superconductive wire and the metal protection layer (1) of the first thin-film superconductive wire with the stabilized metal layer peeled off and exposed are arranged in opposition, and the metal protection layer (1) of the first thin-film superconductive wire and the metal protection layer (2) of the second thin-film superconductive wire are connected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for connecting a thin film superconducting wire used in superconducting equipment such as a superconducting power cable, a superconducting magnet, a superconducting energy storage device, a superconducting transformer, a superconducting fault current limiter, and an MRI apparatus, and a connecting structure thereof.

  The thin film superconducting wire used in superconducting equipment has an oxide superconducting layer that allows current to flow in a superconducting state on an intermediate layer such as cerium oxide on a metal substrate such as Hastelloy or Ni alloy. A metal protective layer with a water-blocking function to prevent the phenomenon that the performance deteriorates by reacting with the oxide superconducting layer, and the current is bypassed to prevent the superconducting layer from burning when an excessive current flows in the superconducting layer. A metal stabilization layer is formed.

  As an example of a method for connecting the thin film superconducting wires, a stabilized silver layer is formed on an oxide superconducting layer to which silver is added on a tape-like substrate as shown in Patent Document 1. A method has been proposed in which the surfaces of the plurality of oxide superconductors on the side of the stabilized silver layer are opposed to each other and the stabilized silver layers are connected to each other via solder.

  Further, in the connection method disclosed in Patent Document 2, at the end portions of two thin film superconducting wires to be connected, the oxide superconducting layer at the end portions is removed to expose a part of the substrate, and each oxide superconductor Oxide superconducting layers for connection for connecting exposed oxide substrates to each other and connecting each oxide superconducting layer so as to straddle the bonded portions of the substrates, the exposed portions, and the oxide superconducting layers. And a method of forming a surface protective layer on the oxide superconducting layer and the connecting oxide superconducting layer has been proposed.

  Furthermore, in the method of Patent Document 3, the superconducting thin film surfaces of two superconducting thin films on which a superconducting thin film is formed are brought into contact with each other so that parts of the superconducting thin film surfaces are in contact with each other. There has been proposed a connection method in which the superconducting thin film of the same kind as the superconducting thin film is deposited on the thin film surface following the portion in contact with the superconducting thin film after the position is adjusted so that the crystal orientations thereof substantially coincide.

JP 2000-133067 A JP 2001-319750 A JP 2005-63695 A

However, in Patent Document 1, since the silver layer is very thin, if tensile stress or bending stress is applied to the two connected superconducting wires, peeling occurs between the silver layer and the superconducting layer, or the silver layer is There was a problem of mechanical weakness. In addition, when a current close to the critical current of the wire flows, heat is generated due to the connection resistance between the two wires, causing superconducting breakdown from the connection portion, causing a problem that the connection portion is burned.

  In Patent Document 2, although the mechanical strength is sufficient, the oxide superconducting layer for connection is formed by the CVD method. Therefore, in order to form the oxide superconducting layer having the same crystal orientation, the CVD method is first used. An expensive and large-sized film forming apparatus is required. In addition, when connecting on the site such as a manhole for connecting a superconducting cable, for example, it is necessary to bring the equipment into a narrow space, and the film formation time requires a long time of several hours. Since it takes about 1000 hours to connect the books, it is an unrealistic way to connect one cable.

  In Patent Document 3, an RF sputtering method is used as a method for depositing a superconducting thin film on a connection portion. However, when performing the RF sputtering method, it is necessary to put the connection portion in a vacuum chamber and perform sputtering in a vacuum state. There is also a need for expensive and large equipment. Further, the film formation takes time similarly to the CVD of Patent Document 2, and is not a technique that can be easily connected on site.

  The present invention has been made in view of the above points, and does not impair various characteristics required for a connection portion of a thin film superconducting wire used in practical equipment, and can be easily connected even in a field environment such as a manhole. And it aims at providing a connection structure.

The first aspect of the thin-film superconducting wire connection method according to the first aspect of the present invention is that a part of the stabilizing metal layer in the vicinity of the connection end to be connected is peeled off and the superconducting layer (1) is disposed above the substrate (1). At least two first thin film superconducting wires on which a metal protective layer (1) and a stabilizing metal layer are formed, and a superconducting layer (2) and a metal protective layer (2) are formed above the substrate (2). Preparing at least one second thin film superconducting wire comprising:
Disposing the connection end of the first thin film superconducting wire oppositely,
The metal protective layer (2) of the second thin film superconducting wire and the metal protective layer (1) exposed by peeling off the stabilizing metal layer of the first thin film superconducting wire are opposed to each other.
A method for connecting a thin film superconducting wire, wherein the metal protective layer (1) of the first thin film superconducting wire and the metal protective layer (2) of the second thin film superconducting wire are connected.

  In each thin film superconducting wire, an intermediate layer may be provided between the substrate and the superconducting layer. According to this aspect, the metal stabilization layer that bypasses the current to prevent the superconducting layer from burning out when an excessive current flows through the superconducting layer is connected, while maintaining the strength of the connection portion, Even when a current exceeding the critical current flows, the thin film superconducting wire capable of flowing a stable current without burning the wire is made possible.

The second aspect of the thin film superconducting wire connection method according to the first invention is:
The second thin film superconducting wire having a melting point equal to or lower than the melting point of the first low melting point metal used for bonding the metal protective layer (1) and the stabilizing metal layer when preparing the first thin film superconducting wire. The metal protective layer (1) and the metal protective layer (2) are connected using a low-melting-point metal of the thin film superconducting wire.
According to this aspect, the electrical and mechanical connection of the connecting portion can be reliably performed while maintaining the electrical and mechanical connection between the metal protective layer forming the thin film superconducting wire and the stabilizing metal layer.

The third aspect of the method for connecting thin film superconducting wires according to the first invention is:
The stabilizing metal layer (1) of each of the at least two first thin film superconducting wires to be connected is connected via a joint, and the stabilizing metal layer is connected using the second low melting point metal. The thin film superconducting wire connecting method is characterized in that:
According to this aspect, the electrical and mechanical connection of the connection part is reliably performed while maintaining the electrical and mechanical connection of the metal protective layer and the stabilizing metal layer forming the thin film superconducting wire and the connection part. Can do.

The 4th aspect of the connection method of the thin film superconducting wire which is 1st invention is as follows.
The thin-film superconducting wire connection method is characterized in that at least two of the stabilizing metal layers are joined to each other by at least two joints with a highly conductive metal tape.
Note that the same tape as the stabilizing metal layer may be used as the highly conductive metal tape.

  According to this aspect, the length for peeling the stabilizing metal layer in the vicinity of the connection end can be shortened, and the work can be easily performed. In addition, when connecting two thin film superconducting wires having different thicknesses of the stabilizing metal layer, the thickness of the stabilizing metal layer at the connecting portion is not uniform, and a thin stabilizing metal layer and a thick stabilizing metal layer are I can do it. At this time, the current flowing through the stabilizing metal layer is restricted by the thin stabilizing metal layer to exceed the critical current, and the stabilization becomes insufficient when viewed from the thin film superconducting wire having the thick stabilizing metal layer. Therefore, if the connection part is covered with a thick stabilizing metal layer, the characteristic of the connection part is not restricted, and therefore a tape having a thickness suitable for the connection part can be used.

The fifth aspect of the method for connecting thin film superconducting wires according to the first invention is:
A method of connecting thin film superconducting wires, characterized in that a nonmagnetic material or an extremely low magnetic material is used for the substrate (2) of the second thin film superconducting wire.
According to this aspect, the AC loss of the second thin film superconducting wire portion can be reduced.

The first aspect of the connection structure of the thin film superconducting wire of the second invention is:
A superconducting layer (1), a metal protective layer (1), and a stabilizing metal layer are formed above the substrate (1) from which a part of the stabilizing metal layer near the connection end has been peeled off. A thin film superconducting wire,
At least one second thin film superconducting wire having a superconducting layer (2) and a metal protective layer (2) formed above the substrate (2);
A connecting portion formed by connecting the metal protective layer of the first thin film superconducting wire and the second thin film superconducting wire; and a member covering an outer surface of the second thin film superconducting wire on the opposite side to the connecting portion. A joint formed by
The connection end of the first thin film superconducting wire is disposed oppositely, and the metal protective layer (2) of the second thin film superconducting wire and the stabilizing metal layer of the first thin film superconducting wire are peeled off. The exposed metal protective layer (1) is disposed oppositely, the first thin film superconducting wire and the second thin film superconducting wire are connected via the connecting portion, and the second thin film superconducting wire A thin film superconducting wire connection structure in which a member covering an outer surface is connected via at least one joint.

  According to this aspect, the metal stabilization layer that bypasses the current to prevent the superconducting layer from burning out when an excessive current flows through the superconducting layer is connected, while maintaining the strength of the connection portion, Even when a current exceeding the critical current flows, the wire rod does not burn, and a stable current can flow.

The second aspect of the connection structure of the thin film superconducting wire of the second invention is:
The member covering the outer surface of the second thin film superconducting wire is made of the stabilizing metal layer of the first thin film superconducting wire, and the stabilizing metal layers are directly connected to each other. A connection structure for a thin film superconducting wire according to claim 6.
According to this aspect, connection can be performed without increasing the number of parts.

The third aspect of the connection structure of the thin film superconducting wire of the second invention is:
A member covering the outer surface of the second thin film superconducting wire is made of a highly conductive metal tape, and the highly conductive metal tape and the stabilizing metal layer are connected to each other. A connection structure of lines.

  According to this aspect, the length for peeling the stabilizing metal layer in the vicinity of the connection end can be shortened, and the work can be easily performed. In addition, when connecting two thin film superconducting wires having different thicknesses of the stabilizing metal layer, the thickness of the stabilizing metal layer at the connecting portion is not uniform, and a thin stabilizing metal layer and a thick stabilizing metal layer are I can do it. At this time, the current flowing through the stabilizing metal layer is restricted by the thin stabilizing metal layer to exceed the critical current, and the stabilization becomes insufficient when viewed from the thin film superconducting wire having the thick stabilizing metal layer. Therefore, if the connection part is covered with a thick stabilizing metal layer, the characteristic of the connection part is not restricted, and therefore a tape having a thickness suitable for the connection part can be used.

  According to the present invention, the electrical and mechanical connection of the connecting portion can be reliably performed while maintaining the electrical and mechanical connection between the metal protective layer forming the thin film superconducting wire and the stabilizing metal layer. Furthermore, by using the stabilizing metal layer already formed on the thin film superconducting wire as the connecting portion, it is possible to flow a current stably up to the critical current of the wire, and it is possible to easily connect. In addition, by forming the connection portion with the thin metal protective layer facing the connection portion, the connection can be performed with a low connection resistance, so that a current can flow stably.

  A preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  FIG. 1 is a schematic diagram of a process for explaining a first embodiment of connection of a thin film superconducting wire of the present invention. FIG. 1A shows a step of removing the stabilizing metal layer 15 at the end in the longitudinal direction of the first thin film superconducting wire 10, and FIG. 1B shows a space between the two first thin film superconducting wires 10. The step of connecting the second thin film superconducting wire 20, FIG. 1C is a schematic diagram of the step of joining the stabilizing metal layers 15 of the first thin film superconducting wire 10.

  A first thin film superconducting wire 10 in which an intermediate layer (1) 12, a superconducting layer (1) 13, a metal protective layer (1) 14 and a stabilizing metal layer 15 are sequentially formed on a substrate (1) 11; A second thin film superconducting wire 20 in which an intermediate layer (2) 22, a superconducting layer (2) 23, and a metal protective layer (2) 24 are sequentially formed on a substrate (2) 21 is prepared. At this time, the intermediate layer (1) 12 and the intermediate layer (2) 22 may not be formed depending on the types of the substrate (1) 11 and the substrate (2) 21. For example, when the substrate (1) 11 and the substrate (2) 21 are made of Ni alloy or the like, the intermediate layer (1) is used to prevent Ni from diffusing into the superconducting layer (1) 13 and the superconducting layer (2) 23. ) 12 and the intermediate layer (2) 22 are required. When the substrate (1) 11 and the substrate (2) 21 are made of an Ag alloy or the like, the intermediate layer (1) 12 and the intermediate layer (2) 22 are It may not be formed.

  The stabilizing metal layer 15 of the first thin film superconducting wire 10 is formed to be longer than the length of the substrate (1) 11, the intermediate layer (1) 12, the superconducting layer (1) 13, and the metal protective layer (1) 14. It extends outside the end surface 17 which is a cross-sectional portion of the portion 16. The stabilizing metal layer 15 of the first thin film superconducting wire 10 is peeled off as shown in FIG. As shown in FIG. 1C, the length of peeling the stabilizing metal layer 15 covers the second thin film superconducting wire 20 having a length D in the longitudinal direction so that the stabilizing metal layers 15 can be joined to each other. I just need it. At this time, the length D of the second thin film superconductor 20 is preferably 20 mm ≦ D ≦ 300 mm, more preferably 30 mm ≦ D ≦ 100 mm. As a method of peeling the stabilization metal layer 15, a gap between the stabilization metal layer 15 and the metal protective layer (1) 14 has a melting point lower than the melting point of the stabilization metal layer 15 and the melting point of the metal protection layer (1) 14. In the case where the first low melting point metal A is bonded, a method of melting the low melting point metal A by applying heat may be used.

  Next, it arrange | positions so that the end surface 17 of the at least 2 1st thin film superconducting wire 10 may oppose, and the stabilization metal layer 15 may come to an upper surface. Further, as shown in FIG. 1B, the metal protective layer (1) 14 of the first thin film superconducting wire 10 and the metal protective layer (2) 24 of the second thin film superconducting wire 20 face each other. The first thin film superconducting wire 10 and the second thin film superconducting wire 20 are connected to form a connection portion 18 in which the first thin film superconducting wire 10 and the second thin film superconducting wire 20 are in contact with each other. The connection method of the connecting portion 18 is such that when the first low melting point metal A is used for bonding the stabilizing metal layer 15 and the metal protective layer (1) 14, The connection may be made using the second low melting point metal B having the same or lower melting point. When the distance m in the length direction of the connecting portion 18 is increased, the connection resistance tends to be small, and a preferable small connection resistance is 30 mm or more. However, the tendency to decrease the connection resistance is small at 50 mm or more, and at 100 mm or more. I found it almost unchanged. Therefore, the distance m of the connecting portion 18 is preferably 30 to 100 mm, more preferably 30 to 50 mm.

  And as shown in FIG.1 (c), the stabilization metal layer 15 and the board | substrate (2) 21 of the 2nd thin film superconducting wire 20 are joined, Furthermore, the stabilization metal layer 15 is joined, and the junction part 19 is joined. Form. The method for joining the stabilizing metal layer 15 and the substrate (2) 21 and the method for joining the joint portion 19 are the same as those for the connection portion 18 and have a melting point at a temperature equal to or lower than that of the first low melting point metal A. Bonding may be performed using the low-melting-point metal B of 2. At this time, the length L1 in the longitudinal direction of the stabilizing metal layer 15 bonded on the substrate (2) 21 is expressed by D / 2 ≦ L1 ≦ D expressed in relation to the length D of the second thin film superconducting wire 20. Is within the range. Preferably, it is 50 mm or longer than D / 2. In FIG. 1, the gap distance n is provided between the first thin film superconducting wires 10, but it is not necessary to leave a gap by setting n = 0.

  FIG. 2 is a schematic diagram of a process for explaining a second embodiment of connection of the thin film superconducting wire of the present invention. FIG. 2A is a schematic diagram of a process of peeling the stabilizing metal layer 15 at the end 16 in the longitudinal direction of the first thin film superconducting wire 10. FIG. 2B is a schematic diagram of a process of connecting the second thin film superconducting wire 20 between the two first thin film superconducting wires 10. FIG. 2C is a schematic diagram of a process of joining the stabilizing metal layers 15 across the substrate (2) 21 of the second thin film superconducting wire 20 with the highly conductive metal tape 25.

  A first thin film superconducting wire 10 and a second thin film superconducting wire 20 having the same configuration as in the first embodiment are prepared. The stabilizing metal layer 15 of the first thin film superconducting wire 10 includes a substrate (1) 11, an intermediate layer (1) 12, a superconducting layer (1) 13, and a metal protective layer (1) 14 as shown in FIG. The stabilizing metal layer 15 is peeled off from the end portion 16 by the exposed length L2, and the metal protective layer (1) 14 is exposed. As a method of exposing the metal protective layer (1) 14, the space between the stabilized metal layer 15 and the metal protective layer (1) 14 is lower than the melting point of the stabilized metal layer 15 and the melting point of the metal protective layer (1) 14. In the case where the first low melting point metal A having a melting point is bonded, a method of melting the low melting point metal A by applying heat may be used. At this time, the length of L2 is preferably m ≦ L2 ≦ m + 50 mm.

  Next, it arrange | positions so that the end surface 17 of the at least 2 1st thin film superconducting wire 10 may oppose, and the stabilization metal layer 15 may come to an upper surface. Further, as shown in FIG. 2B, the metal protective layer (1) 14 of the first thin film superconducting wire 10 and the metal protective layer (2) 24 of the second thin film superconducting wire 20 face each other. The first thin film superconducting wire 10 and the second thin film superconducting wire 20 are connected to form a connection portion 18 in which the first thin film superconducting wire 10 and the second thin film superconducting wire 20 are in contact with each other. The joining method of the connection portion 18 is equivalent to the first low melting point metal A when the first low melting point metal A is used for joining the stabilizing metal layer 15 and the metal protective layer (1) 14. Alternatively, the connection may be performed using the second low melting point metal B having a low melting point. When the distance m in the length direction of the connecting portion 18 is increased, the connection resistance tends to be small, and a preferable small connection resistance is 30 mm or more. However, the tendency to decrease the connection resistance is small at 50 mm or more, and at 100 mm or more. I found it almost unchanged. Therefore, the distance m of the connecting portion 18 is preferably 30 to 100 mm, more preferably 30 to 50 mm. In addition, the exposure length L2 should just be longer than the distance m of the connection part 18. FIG.

  Then, as shown in FIG. 2 (c), the highly conductive metal tape 25 is joined between the stabilizing metal layers 15 across the substrate (2) 21 of the second thin film superconducting wire 20. The highly conductive metal tape 25 and the substrate (2) 21 of the second thin film superconducting wire 20 are joined, and each stabilizing metal layer 15 is further joined to form two joints 19. The method for joining the stabilizing metal layer 15 and the substrate (2) 21 and the method for joining the joint portion 19 are the same as those for the connection portion 18 and have a melting point at a temperature equal to or lower than that of the first low melting point metal A. Bonding may be performed using the low-melting-point metal B of 2. At this time, the highly conductive metal tape 25 may be the same tape as the stabilizing metal layer 15. In FIG. 2, the gap distance n is provided between the first thin film superconducting wires 10, but it is not necessary to leave a gap with n = 0.

  FIG. 3 is a schematic diagram for explaining an embodiment of the connection structure of the thin film superconducting wire of the present invention. FIG. 3A is a schematic diagram of a connection structure of thin film superconducting wires formed when n = 0 in the thin film superconducting wire connecting method shown in FIG. FIG. 3B is a schematic diagram of a connection structure of thin film superconducting wires formed when n = 0 in the thin film superconducting wire connecting method shown in FIG. FIG. 3C shows a thin film superconducting wire in the case where the junction 19 is formed not on the second thin film superconducting wire 20 but on the first thin film superconducting wire 10 in the thin film superconducting wire connecting method shown in FIG. It is a schematic diagram of the connection structure. Similarly, FIG. 3D shows a connection method of the thin film superconducting wire shown in FIG. 1, in which the junction 19 is formed not on the second thin film superconducting wire 20 but on the first thin film superconducting wire 10 and n = It is a schematic diagram of the connection structure of the thin film superconducting wire formed when it is set to 0. According to the connection method of the thin film superconducting wire shown in FIG. 3C and FIG. 3D, the stabilizing metal layer 15 may be joined at one place, and one stabilizing metal layer 15 is once a metal protective layer (1). It is not necessary to perform joining again after peeling off from 14, and the work becomes easier. Furthermore, since the junction 19 is formed not on the second thin film superconducting wire 20 but on the first thin film superconducting wire 10, the thickness of the connecting portion of the thin film superconducting wire can be reduced.

  In FIG. 1 and FIG. 2, a gap distance n is provided between the first thin film superconducting wires 10, but this case is particularly suitable when connecting thin film superconducting wires used in superconducting power cables. FIG. 4 is a schematic structure of a general superconducting cable. A cable core at the center of the superconducting cable 31 is formed by winding a tape-shaped thin film superconducting wire 33 around a metal (for example, copper) former 32 in a spiral shape, and an electric insulating layer 34 (material is paper or semi-synthetic). Paper) and then a protective layer 35 (eg made of conductive paper or copper braided wire). The cable core is a flexible metal (for example, stainless steel or aluminum) double insulation tube, that is, an insulation material disposed between the inner tube 36 and the outer tube 38 and between the inner tube 36 and the outer tube 38. It is housed in a double heat insulation pipe made of 37. Thus, in a structure such as a superconducting power cable, the thin film superconducting wire 33 is wound around the metal former 32. Therefore, when the metallic formers 32 are connected by welding or the like when connecting the cables, if there is no gap distance n between the thin film superconducting wires 33 and the thin film superconducting wires 33 are present immediately above the connecting portion, the metal The performance of the thin film superconducting wire 33 deteriorates due to the influence of heat caused by welding between the formers 32.

  However, if a gap distance n is provided between the first thin film superconducting wires 10 as shown in FIGS. 1C, 2C, and 3D, the welding between the metal formers 32 is completed. After that, by newly connecting the second thin film superconducting wire 20, the first thin film superconducting wire 10 and the second thin film superconducting wire 20 are not affected by heat due to welding between the metal formers 32. The cable core in the superconducting cable 31 can be connected without degrading the performance. Thus, in order not to be affected by heat due to welding or the like, the gap distance n is preferably 200 mm to 600 mm.

If the gap distance n = 0 and no gap between the first thin film superconducting wires 10 is required as shown in FIGS. 3 (a), (b) and (d), it can be made of a metal such as a superconducting power cable. This is effective not for the purpose of winding the first thin film superconducting wire 10 around the outer periphery of the former, but for connecting only the thin film superconducting wire 10 alone. An example is when connecting a coil using a superconducting wire, such as a superconducting magnet. In such a case, the end faces 17 of the first thin film superconducting wire 10 are brought into contact with each other, the end faces 17 are joined together, and the second thin film superconducting wire 20 is joined together to reduce the thickness. It is possible to realize a connection structure having a connection resistance and a mechanical strength that is as strong as a wire. At this time, as the joining method of the end faces 17, the joining is performed using the second low melting point metal B having a melting point equal to or lower than that of the first low melting point metal A, as in the connection method of the connecting portion 18. It is good to do.
Below, the connection method of the thin film superconducting wire of this invention is demonstrated in detail by an Example.

  As the first thin film superconducting wire 10 to be connected, Hastelloy (registered trademark: the same applies hereinafter) (nickel-iron alloy) is rolled onto a substrate (1) 11 having a width of 10 mm and a thickness of 0.1 mm. An intermediate layer (1) 12 of YSZ (yttrium stabilized zirconia) 0.5 μm is formed by ion beam assisted sputtering, and further YBCO (yttrium-barium-copper-oxygen) oxide 1 μm is formed thereon by plasma laser deposition. The superconducting layer (1) 13 was formed by laminating. In order to prevent the superconducting layer (1) 13 from being deteriorated, a metal protective layer (1) 14 is formed on the superconducting layer (1) 13 by applying 5 μm of silver by a vacuum vapor deposition method. The first thin film superconducting wire 10 was manufactured by bonding a copper tape having a thickness of 0.1 mm with metal A to form a stabilized metal layer 15 made of copper. The first thin film superconducting wire 10 was put in liquid nitrogen and the critical current was measured to be 200 A. Further, as a resistance against overcurrent, a current of 700 A was passed for 2 seconds, but deterioration such as burnout and reduction of critical current occurred. There was no at all. Moreover, when the tensile test of this superconducting wire was conducted at room temperature, the wire broke at 1000 MPa.

  First, as a connection procedure of the thin film superconducting wires, the end portions 16 of the two first thin film superconducting wires 10 to be connected are 50 mm from the center point where the two first thin film superconducting wires 10 are brought together. Cut long. Each of the first thin film superconducting wires 10 is heated by soldering the stabilizing metal layer 15 to melt and peel off the low melting point metal A between the stabilizing metal layer 15 and the metal protective layer (1) 14. 16 to 100 mm, the substrate (1) 11, the intermediate layer (1) 12, the superconducting layer (1) 13, and the metal protective layer (1) 14 are separated into the superconducting wire side and the stabilizing metal layer 15 side. The part on the superconducting wire side consisting of the substrate (1) 11, the intermediate layer (1) 12, the superconducting layer (1) 13, and the metal protective layer (1) 14 after being separated is cut at a part 30 mm from the end 16. Thus, the end portions 16 of the two first thin film superconducting wires 10 can be set substantially at the center position of the longitudinal length L1 of the stabilizing metal layer 15 bonded onto the substrate (2) 21.

  At this time, L1 is a superconducting wire side composed of the substrate (1) 11, the intermediate layer (1) 12, the superconducting layer (1) 13, and the metal protective layer (1) 14 to the position of 100 mm from the end portion 16 and the stabilizing metal layer. It is almost equal to the length of the stabilizing metal layer 15 when separated to the 15 side. Then, the two first thin film superconducting wires 10 were arranged to face each other with the end faces 17 in contact with each other. Next, a second thin film superconducting wire 20 having a length D = 100 mm comprising a substrate (2) 21, an intermediate layer (2) 22, a superconducting layer (2) 23, and a metal protective layer (2) 24 is prepared. This is because the first thin film superconducting wire 10 previously wound around the superconducting device is prepared to be long, 100 mm from the end portion is cut, and the first thin film superconducting wire 10 is further stabilized. It is also possible to use one with the metal layer 15 peeled off.

  The metal protective layer (1) 14 of the first thin film superconducting wire 10 connected to the metal protective layer (2) 24 of the second thin film superconducting wire 20 is disposed so as to overlap each other by 50 mm, and bismuth and tin are mainly used. The low melting point metal B having a melting point of 150 ° C. or lower is connected using solder to form the connection portion 18. For the back side of the second thin film superconducting wire 20 on which the superconducting layer (2) 23 of the substrate (2) 21 is not attached, the oxide layer on the back side surface of the substrate (2) 21 is formed after the connection portion 18 is formed or in advance. It is necessary to remove the solder chemically or mechanically or to form a silver layer on which solder can be easily put by sputtering or the like in advance so that the solder can be put on. In the state where the first thin film superconducting wire 10 and the second thin film superconducting wire 20 are connected by the connecting portion 18, the stabilized metal layer 15 that has been peeled off first is returned to the original state, thereby stabilizing both. Since the metal layer 15 has a length L1 of 100 mm, which is substantially equal to the length D of the second thin film superconducting wire 20, the stabilized metal layers 15 overlap each other by about 100 mm, that is, the joint 19 The length of the joint is about 100 mm, and is a portion where the stabilized metal layer 15 peeled off and the substrate of the second thin film superconducting wire 20 are overlapped with the stabilizing metal layer 15 of the two thin film superconducting wires 10. The thin film superconducting wire 10 is connected by joining all 19 with solder made of low melting point metal B without any gap.

  The characteristics of the thin film superconducting wire having this connection structure were evaluated. As a result, the current at which a voltage of 1 μV / cm is generated by passing a current is 198 A, which is 2 A lower than 200 A, which is the critical current of the original wire (thin film superconducting wire 10), and is comparable to the thin film superconducting wire 10. It had current-carrying characteristics. Further, when the connection resistance was measured, it was suppressed to a very small value of 0.1 μΩ. Furthermore, although a short current of 700 A for 2 seconds was passed at a liquid nitrogen temperature, there was no significant heat generation in the connection structure portion, and the wire rod could withstand the excessive current without burning. After that, the wire rod was returned to room temperature and a tensile test was performed. As a result of the tensile test, the connection structure portion itself was not broken at all at a portion away from the connection structure portion at 1120 MPa, and no mechanical deformation or cracking occurred. It was confirmed.

  As the first thin film superconducting wire 10 to be connected, a Ni-5% W alloy (nickel-5% tungsten alloy) was used as the substrate (1) 11. Unlike the Hastelloy of Example 1, this substrate (1) 11 is a magnetic material, and it is observed that when an alternating current is applied, the alternating current loss is about three times larger than Hastelloy due to the influence of magnetism. It is also mechanically weak and breaks at about 300 MPa. An intermediate layer (1) 12 made of CeO (ceria oxide) is formed by 1.0 μm on the substrate (1) 11 by an electron beam method, and a YBCO oxide is further formed thereon by a CVD method (chemical vapor deposition method). Superconductive layer (1) 13 was formed by laminating 1 μm. This method can be made faster than the method of forming the intermediate layer (1) 12 / superconducting layer (1) 13 by IBAD-PLD on the Hastelloy substrate (1) 11, and the thin film superconducting wire This is a manufacturing method that reduces costs. Connection using the first thin film superconducting wire 10 was performed.

  In the second embodiment, the two first thin film superconducting wires 10 are arranged at positions where the end portions 16 are separated from each other by 200 mm. First, the outermost metal stabilization layer 15 was peeled off by 50 mm from the end portion 16 and cut off to leave the metal protective layer (1) 14 exposed. Next, a second thin film superconducting wire 20 for connection is prepared. Here, a substrate (2) 21 made of nonmagnetic Hastelloy is used, and the critical current is higher than that of the first thin film superconducting wire 10 and is long. A thin film superconducting wire having a thickness of 260 mm was prepared. The metal protective layer (1) 14 of the first thin film superconducting wire 10 connected to the metal protective layer (2) 24 of the second thin film superconducting wire 20 is disposed so as to overlap each other by 30 mm, and bismuth and tin are mainly used. Solder connection using a low melting point metal B having a melting point of 150 ° C. or less was performed. Next, a highly conductive metal tape 25 made of the same copper as the first and second thin film superconducting wires having a thickness of 400 mm and a thickness of 0.1 mm is prepared, and the stabilized metal layer of the first thin film superconducting wire 10 is prepared. 15 were bonded to the first and second thin film superconducting wires 10 and 20 with solder over the entire length of 400 mm so as to overlap each other by 50 mm as the joint portion 19.

  As a result of evaluating the characteristics of the thin film superconducting wire having this connection structure portion in the same manner as the thin film superconducting wire having the connection structure of Example 1, the current that generates a voltage of 1 μV / cm when the current flows is the original wire It was 98% of the critical current of (thin film superconducting wire 10), and the connection resistance was also 0.1 μΩ. Withstands a short-time overcurrent of 700 A 2 seconds at a liquid nitrogen temperature. As a result of the tensile test, it breaks first in the portion other than the connection structure portion as in Example 1, and the connection structure portion of the thin film superconducting wire itself is broken. Was confirmed to be mechanically strong. Moreover, when the AC loss of the thin film superconducting wire was measured, the AC loss of the connection structure portion was 1/3 lower than the thin film superconducting wire of the Ni-5% W substrate because the substrate was non-magnetic. I was able to suppress it.

  The composition of the superconducting material of the first thin film superconducting wire 10 and the second thin film superconducting wire 20 is RE-barium-copper-oxygen (RE is Y, Nd, Sm, Eu, Gd, Dy, Ho, Er , One atom selected from Yb) may be used.

It is a schematic diagram of the process explaining 1st Embodiment of the connection method of the thin film superconducting wire of this invention. It is a schematic diagram of the process explaining 2nd Embodiment of the connection method of the thin film superconducting wire of this invention. It is a schematic diagram explaining embodiment of the connection structure of the thin film superconducting wire of this invention. It is a schematic diagram explaining the schematic structure of a general superconducting cable.

Explanation of symbols

10 First thin film superconducting wire 11 Substrate (1)
12 Middle layer (1)
13 Superconducting layer (1)
14 Metal protective layer (1)
15 Stabilized metal layer 16 End 17 End face 18 Connection 19 Joint 20 Second thin film superconducting wire 21 Substrate (2)
22 Middle layer (2)
23 Superconducting layer (2)
24 Metal protective layer (2)
25: Conductive metal tape 31: Superconducting cable 32: Former 33: Thin film superconducting wire 34: Electrical insulating layer 35: Protective layer 36: Inner tube 37: Heat insulating material 38: Outer tube

Claims (8)

At least two of the superconducting layer (1), the metal protective layer (1), and the stabilizing metal layer are formed above the substrate (1) from which a part of the stabilizing metal layer near the connection end to be connected is peeled off. Preparing a first thin film superconducting wire and at least one second thin film superconducting wire having a superconducting layer (2) and a metal protective layer (2) formed above the substrate (2);
Disposing the connection end of the first thin film superconducting wire oppositely,
The metal protective layer (2) of the second thin film superconducting wire and the metal protective layer (1) exposed by peeling off the stabilizing metal layer of the first thin film superconducting wire are opposed to each other.
A method for connecting a thin film superconducting wire, comprising connecting the metal protective layer (1) of the first thin film superconducting wire and the metal protective layer (2) of the second thin film superconducting wire.   The second thin film superconducting wire having a melting point equal to or lower than the melting point of the first low melting point metal used for bonding the metal protective layer (1) and the stabilizing metal layer when preparing the first thin film superconducting wire. The method for connecting a thin film superconducting wire according to claim 1, wherein the metal protective layer (1) and the metal protective layer (2) are connected using a low melting point metal.   The stabilizing metal layer (1) of each of the at least two first thin film superconducting wires to be connected is connected via a joint, and the stabilizing metal layer is connected using the second low melting point metal. The thin film superconducting wire connection method according to claim 1, wherein the thin film superconducting wire is connected.   The method for connecting a thin film superconducting wire according to any one of claims 1 to 3, wherein at least two of the stabilizing metal layers are joined to each other by a highly conductive metal tape through a joint portion.   The thin film superconducting wire connection method according to any one of claims 1 to 4, wherein a nonmagnetic material or an extremely low magnetic material is used for the substrate (2) of the second thin film superconducting wire. A superconducting layer (1), a metal protective layer (1), and a stabilizing metal layer are formed above the substrate (1) from which a part of the stabilizing metal layer near the connection end has been peeled off. A thin film superconducting wire,
At least one second thin film superconducting wire having a superconducting layer (2) and a metal protective layer (2) formed above the substrate (2);
A connecting portion formed by connecting the metal protective layer of the first thin film superconducting wire and the second thin film superconducting wire; and a member covering an outer surface of the second thin film superconducting wire on the opposite side to the connecting portion. A joint formed by
The connection end of the first thin film superconducting wire is disposed oppositely, and the metal protective layer (2) of the second thin film superconducting wire and the stabilizing metal layer of the first thin film superconducting wire are peeled off. The exposed metal protective layer (1) is disposed oppositely, the first thin film superconducting wire and the second thin film superconducting wire are connected via the connecting portion, and the second thin film superconducting wire A connection structure for a thin film superconducting wire, wherein members covering an outer surface are connected via the joint.   The member covering the outer surface of the second thin film superconducting wire is made of the stabilizing metal layer of the first thin film superconducting wire, and the stabilizing metal layers are connected to each other. Item 7. A connection structure for a thin film superconducting wire according to Item 6.   The member covering the outer surface of the second thin film superconducting wire is made of a highly conductive metal tape, and the highly conductive metal tape and the stabilizing metal layer are connected to each other. 7. A connection structure for a thin film superconducting wire according to 6.

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