JPH0695469B2 - Superconducting wire connection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a superconducting wire connection structure used in a nuclear fusion toroidal magnet, a particle accelerator magnet, a superconducting power generator magnet, and the like.

"Prior Art" As one conventional method of connecting superconducting wires, the connecting methods shown in Figs. 5 and 6 are known.

In the conventional connection method shown in FIGS. 5 and 6, the ends of the superconducting wires 1 and 1 to be connected are butted, and a plurality of short pieces are put around the butted part so as to abut the superconducting wires 1 and 1. This is a method in which the connecting superconducting wires 2 are arranged, and a plurality of connecting superconducting wires 2 surround the ends of the superconducting wires 1 and 1, and a metal-based adhesive 3 is filled and fixed around them.

Further, the method shown in FIGS. 7 and 8 is known as another conventional example of the method of connecting superconducting wires.

The connecting method shown in FIG. 7 and FIG. 8 is used when connecting the superconducting wire 7 in which the superconducting filament 6 is arranged inside the stabilizing material 5 made of copper. Is removed by a required length to expose the superconducting filaments 6, and the exposed superconducting filaments 6 are knitted or tied together, and then the outer circumference thereof is covered with a copper tube (or a copper plate) 8 to surround the copper plate or the copper tube. This is a method in which a metal-based adhesive is filled inside for connection.

[Problems to be Solved by the Invention] The conventional connection method described with reference to FIGS. 5 and 6 is applicable to both alloy superconducting wires and compound superconducting wires. Since the superconducting conductors of the superconducting wires to be connected are not completely metal-bonded to each other but are connected via the metallic adhesive 3, there is a problem that heat is generated. In order to reduce this heat generation, it is necessary to lengthen the connecting superconducting wire 2 as much as possible to reduce the contact resistance, but this raises the material cost and the joining work also takes time.

On the other hand, in the conventional method described with reference to FIGS. 7 and 8, it is necessary to expose the superconducting filament 6 and perform a braiding operation, so that the superconducting filament can be processed into an alloy system. Although applicable to the superconducting wire, there is a problem that the superconducting filament after the heat treatment is brittle and cannot be applied to the connection of the compound superconducting wire which is difficult to process. When connecting an alloy-based superconducting wire having a workable superconducting filament, the braided portion is covered with the copper tube 8 after the superconducting filament 6 is braided. There is a problem that it is difficult to completely cover the exposed superconducting filament 6 due to the formation of a gap in.

The present invention has been made in view of the above problems, it is possible to connect a superconducting wire more easily than the conventional connecting method, less heat is generated at the connection portion, and the deterioration of the superconducting characteristics does not occur, and the compound-based superconducting It is an object of the present invention to provide a method for connecting wires or alloy-based superconducting wires at a lower cost than before.

"Means for Solving Problems" In order to solve the above problems, the present invention provides one or more base materials obtained by forming a superconducting fiber material, which becomes a superconducting fiber by heat treatment, inside a matrix. Using a ring-shaped joint connector consisting of, the ends of both superconducting wires to be connected are butted and covered with a joint connector, and the outer peripheral surface of the ends of the superconducting wires is brought into close contact with the inner peripheral surface of the joint connector to connect the superconducting wires. To connect.

"Operation" Insert the end of the superconducting wire into the annular joint connector,
By connecting the superconducting wire by contacting the entire inner surface of the joint connector with the end of the superconducting wire, the contact area of the connecting portion is made larger than in the prior art and heat generation in the connecting portion is reduced.
Since the contact area of the connecting portion can be increased as compared with the conventional one, the connecting portion can be made shorter than the conventional one, and the cost can be reduced. Further, the superconducting fiber produced by heat-treating the joint connector contacts both superconducting wires to connect them, and the superconducting wires are connected without causing heat generation.

"Embodiment" FIGS. 1 and 2 are for explaining one embodiment of the present invention. The superconducting wire 10 shown in FIG. 1 is a superconducting fiber material 11 which becomes a superconducting fiber by heat treatment. It has a structure in which a large number of are provided inside a stabilizing material 12 made of copper or the like. The superconducting wire 10 used in this embodiment is
It has a structure in which Nb fibers are dispersed and mixed inside the matrix made of copper, and it is manufactured by using the in-situ method of drawing the in-situ rod manufactured by melting Cu-Nb alloy of the required components. is there. The superconducting wire of this example
As described below, 10 is completed as a superconducting wire by forming Sn plating and then performing diffusion heat treatment to diffuse Sn to form Nb ₃ Sn superconducting fibers inside.

To connect the superconducting wires 10 and 10, a tubular joint connector having an inner diameter slightly larger than the diameter of the superconducting wire 10.
The end portions of the superconducting wires 10 and 10 are inserted into 13, and the inner peripheral surface of the joint connector 13 is brought into contact with the outer peripheral surfaces of the end portions of the superconducting wires 10 and 10. Next, press the joint connector 13 against the superconducting wire 10 using a crimping jig,
Crim the 10,10 ends.

When the ingot 14 shown in FIG. 3 (a) is manufactured by melting the required component Cu—Nb alloy, the joint connector 13 is obtained by processing the ingot 14.
The ingot 14 has a structure in which dendrites 16 of Nb are dispersed in a base 15 made of copper. By subjecting the ingot 14 to wire drawing, as shown in FIG. 3 (b), It is possible to obtain an in-situ rod 19 in which a large number of fibers 18 made of Nb are closely arranged in the base 17.
A tubular joint connector 13 is manufactured by making a hole in the center of an in-situ rod 19 having a required length.

After connecting the superconducting wires 10 and 10 by using the joint connector 13, Sn plating is applied to the surface of the joint connector 13 to form a Sn layer, and the superconducting wires 10 and 10 are subjected to diffusion heat treatment to have Nb ₃ Sn inside. Generate a superconducting conductor. The diffusion heat treatment is a treatment of heating at 700 to 800 ° C. for 20 to 100 hours.

By performing the heat treatment, Sn diffuses into the Nb fibers 18 inside the joint connector 13 and reacts, Nb ₃ Sn is generated, and the joint connector 13 becomes a superconducting conductor. In order to heat the joint connector 13 and the superconducting wires 10 and 10 at a high temperature for a long time by the diffusion heat treatment, copper atoms are diffused between the contact surfaces of the joint connector 13 and the superconducting wire 10, and the inner circumference of the joint connector 13 is increased. The surface and the outer peripheral surfaces of the superconducting wires 10 and 10 are molecularly bonded and welded,
Bonding strength is improved.

When the joint connector 13 is used for joining as described above, since the joint connector 13 itself is a superconductor, the problem of heat generation in the joint connector 13 does not occur, and moreover, the joint connector 13 does not have a problem of heat generation by diffusion heat treatment. Since the peripheral surface and the outer peripheral surfaces of the superconducting wires 10 and 10 are welded together, the resistance of the joint surface is small and the heat generation is smaller than in the conventional case. Further, as compared with the conventional method shown in FIG. 6 in which the superconducting wire for connection is adhered to the outer peripheral side of the end portion of the superconducting wire, the joint connector 13 and the superconducting wire
Since the contact area with 0 is also large, the joint connector 13 can be made shorter than the conventional superconducting wire for connection, and there is an effect that it can be connected at low cost.

By the way, in the case of connecting the compound-based superconducting wire after the diffusion heat treatment with the joint connector 13, when the joint connector 13 is crimped to the end of the superconducting wire, the brittle superconductor is damaged. Bond with a system adhesive. Joint connector used in this case 13
Is used after forming Sn plating on the surface and subjecting it to diffusion heat treatment to generate superconducting fibers inside, and not performing diffusion heat treatment after joining.

When the metal-based adhesive is used for bonding in this way, the metal-based adhesive may become a heat generating portion, but the joint connector 13
Since the inner peripheral surface of 1 and the outer peripheral surfaces of the superconducting wires 10 and 10 are in full contact with each other, the contact area is much larger than that of the conventional structure shown in FIG. 6, and the heat generation at the bonded portion is reduced.

FIG. 4 shows a joint connector 20 of the second embodiment of the present invention. The joint connector 20 of the present embodiment is composed of two semi-cylindrical base materials 21, 21.

The base material 21 has an internal structure equivalent to that of the joint connector 13 used in the above-described embodiment, and has a structure in which the superconducting fiber material is dispersed inside the Cu base.

The base materials 21, 21 cover the end portions of the superconducting wires 10, 10 to be connected and are bonded to the superconducting wires 10, 10 in a tubular shape to connect the superconducting wires 10, 10.

By the way, when the joint connector 13 having the above structure is used for connecting the Nb ₃ Ge-based superconducting wire, the superconducting wire is subjected to diffusion heat treatment by Ge plating instead of Sn plating, and the structure is applied using the superconducting wire. Good. Further, it goes without saying that the connection method using the joint connector 13 can be applied to the connection to the alloy-based superconducting wire. Joint connector
13 may have a rectangular tube shape.

"Production Example 1" A cylindrical in-situ ingot of Cu-40% Nb with a diameter of 50 mm manufactured by the in-situ method was formed with a shaft hole with a diameter of 20 mm, and in this shaft hole, an oxygen-free copper rod covered with a Ta pipe was formed. Inserted. Subsequently, swaging, intermediate annealing and wire drawing were performed to obtain a wire rod having a diameter of 1 mm and a length of about 0.5 km.

A Sn plating layer having a thickness of 30 μm was formed on the surface of this wire by electroplating. The thickness of the Sn plating layer is determined so that the tin concentration in the entire wire is about 16% by weight when Sn is diffused inside the wire by a diffusion heat treatment as described later. Is.

The length of the wire is about 0.5 km, but when manufacturing a coil obtained by winding a wire having a total length of 2 km, it is necessary to connect four wires.

Therefore, the wires are connected using the joint connector having the structure shown in FIGS. 1 and 2. In order to manufacture this joint connector, first, a Cu-40% Nb indie ingot with a diameter of 50 mm manufactured by the in-situ method is used.
Diameter reduced to mm, cut to the required length, diameter 3.5 mm in the center
A shaft hole of is formed by a drill. Next, the diameter of this tube is reduced to an outer diameter of 2 mm and an inner diameter of 1.2 mm, and a total length of 40 mm is cut to obtain a joint connector. A 70 μm thick Sn plating layer was formed on the surface of this joint connector.

Next, butt the ends of the four wires together, pass the joint connector so that the joint connectors contact each other at a length of 20 mm, and crush the ends of the joint connector with a crimping jig to connect the wires. did. Prior to connection, the surface of each wire is covered with a glass yarn braided layer for insulation treatment.

Next, the wire material connected as described above was subjected to a heat treatment of heating at 200 ° C. for 50 hours to diffuse and eliminate Sn in the Sn plating layer, and then coiled.

Then, the coil was subjected to diffusion heat treatment by heating it to 550 ° C. for 100 hours to manufacture an Nb ₃ Sn superconducting coil. After immersing the superconducting coil in liquid helium, a current of 100 A is applied and a magnetic field of 5 T (tesla) of the backup coil is applied to the superconducting coil.
A magnetic field of T was generated. At this time, no heat generation was observed at the connection portion, and the normal superconducting state was maintained.

[Example 2] An ultra-fine multi-core Nb ₃ Sn superconducting wire with stabilized copper was manufactured by an internal plating method, and a heat treatment was performed at a wire diameter of 1.4 mm for heating at 800 ° C for 50 hours to complete the Nb ₃ Sn superconducting wire. .

Next, a joint connector used to wind the coil by connecting two superconducting wires was produced.

The joint connector is manufactured by the in-situ method. After reducing the diameter of an in-situ ingot with a diameter of 50 mm to a diameter of 3 mm, forming a Sn plating layer with a thickness of 100 μm on the surface, cutting it to a length of 30 mm and a diameter of 1.5 mm in the center part. Shaft holes were formed, and further diffusion heat treatment was performed at 575 ° C for 100 hours to complete the process.

In order to connect the two Nb ₃ Sn superconducting wires, the ends of the two superconducting wires are inserted into the joint connector, the ends of the superconducting wires are butted, and fixed by soldering. Then, a superconducting coil was manufactured.

The completed superconducting coil was immersed in liquid helium, and a magnetic field of 5T was generated independently by applying a current of 400A. Furthermore, by arranging a backup coil outside it, 10T
Succeeded in generating a magnetic field. At that time, heat generation and voltage generation did not occur at the connection portion.

"Effects of the Invention" As described above, the present invention uses an annular joint connector in which a superconducting fiber material is arranged in a base, and the inner peripheral surface of the joint connector is covered with the outer peripheral surface of the end portion of the superconducting wire to be connected. It is possible to reduce the contact resistance by increasing the contact area between the superconducting wire and the joint connector as compared with the conventional method in which the superconducting wire for connection is longitudinally connected in order to connect and connect the superconducting wire. It is possible to eliminate heat generation at the connecting portion. Further, since the contact resistance is small, the connecting portion can be made shorter than the conventional one, and there is an effect that the connection can be made at low cost. Furthermore, when heat treatment is performed on the superconducting wire and the joint connector, the inner peripheral surface of the joint connector and the outer peripheral surface of the superconducting wire are intermolecularly bonded, so that the bonding strength is improved, the contact resistance is reduced, and heat generation can be suppressed. effective. Furthermore, when the joint connector is adhered to the superconducting wire, heat may be generated at the adhering portion. However, compared with the conventional method in which the connecting superconducting wire is connected vertically, the superconducting wire and the joint connector are Since the contact area is large, there is an effect that heat generation at the adhesive portion can be reduced.

[Brief description of drawings]

1 to 3 are for explaining one embodiment of the present invention. FIG. 1 is a vertical sectional view of a connecting portion using a joint connector, and FIG. 2 is a transverse sectional view of the connecting portion. 3 (a) is a sectional view of an ingot, FIG. 3 (b) is a sectional view of an in-situ rod, FIG. 4 is a sectional view showing a split joint connector, and FIG. 5 is a conventional connecting structure. Fig. 6 is a longitudinal sectional view showing an example, Fig. 6 is a transverse sectional view of a conventional example shown in Fig. 5, and Figs. 7 and 8 are for explaining other conventional examples. Fig. 7 shows a superconducting filament. FIG. 8 is a cross-sectional view showing a state in which they are piled up, and FIG. 8 is a cross-sectional view showing a state in which the connecting portion is covered with a copper pipe. 10 …… Superconducting wire, 11 …… Superconducting fiber material 12 …… Stabilizer, 13,20 …… Joint connector.

Claims (4)

[Claims] 1. A method of connecting a compound-based superconducting wire or an alloy-based superconducting wire, which is heat-treated to produce a superconducting conductor, wherein a superconducting fiber material to be a superconducting fiber is formed inside the base by heat-treating. Using an annular joint connector composed of one or more base materials
A method for connecting superconducting wires, characterized in that the ends of each superconducting wire to be connected are butted and covered with a joint connector, and the outer peripheral surface of the end of the superconducting wire is brought into close contact with the inner peripheral surface of the joint connector to connect the superconducting wires. . 2. A joint connector for connecting a superconducting wire, wherein a superconducting conductor is arranged inside a stabilizing material, is fixed to the superconducting wire with a metallic adhesive. How to connect superconducting wires. 3. When connecting a superconducting wire in which a superconducting material to be a superconducting conductor is arranged inside a stabilizing material by heat treatment, the joint connector is crimped to the superconducting wire before the heat treatment to connect the superconducting wire. The method of connecting a superconducting wire according to claim 1, wherein 4. A method for connecting a superconducting wire according to claim 1, wherein a joint connector configured by joining two half-cylindrical bodies is used.