JPH06104026A - Connection structure of superconductor - Google Patents

Abstract

PURPOSE:To provide a connection structure of a superconductor, which is in a compact form, and for which a.c. loss is reduced. CONSTITUTION:A disc-shape soldering plate 9 is provided on the end part of a superconductor 2 to be connected, and is inserted in a sleeve 4, the surface of which is coated with an oxide superconductor layer 6, while a solder 8 of lower melting point than the soldering plate 9, is injected from a solder filling port 7 provided on the sleeve 4, and a gap between the respective superconductors 2 and 2 in the sleeve 4 is thus filled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable-in-conduit type forced cooling using a connection structure with a superconducting conductor or a bus bar in a superconducting magnet device and a compound superconducting wire used for a coil for generating a high magnetic field. The present invention relates to a superconducting conductor connection structure.

[0002]

2. Description of the Related Art Conventionally, as a connection structure for a superconducting conductor such as a forced cooling coil, a superconducting conductor 2 formed by twisting a plurality of superconducting wires on a copper block 1 or the like is connected with solder as shown in FIG. A structure in which both copper blocks 1 and 1 are connected via a solder 3 has been adopted. In this type of connection structure, in order to reduce heat generation at the connection part,
It was necessary to increase the contact area between the superconducting conductor 2 and the copper block 1 or the copper block 1 and also the step area of the copper block 1.

On the other hand, a plurality of superconducting wires are twisted together and housed in a conduit made of a strength member such as stainless steel, and a refrigerant is forced to flow into the space between the superconducting wires and the space between the superconducting wires and the conduit. As shown in JP-A-57-171841, the connection structure of a cable-in-conduit type forced cooling superconducting conductor that performs cooling by superposing the parts to be connected and caulking them together, A structure in which a superconducting conductor is generated by heat treatment to form a connection structure of the superconducting conductors, and JP-A-61-66380 and JP-A-62-2
As disclosed in 9081 and Japanese Patent Laid-Open No. 1-177114,
The superconducting wires of heat-treated superconducting conductors are alternately superposed and brazed, or alternately superposed and soldered with the connecting member. The wire is divided and stored, and the wire is impregnated with solder.

[0004]

However, in a superconducting poloidal coil or the like for a fusion reactor, there are severe space restrictions, and it is necessary to design the connecting portion as compact as possible. Moreover, it is necessary to suppress the AC loss when the pulse excitation is performed. If the conventional structure in which copper blocks are connected by solder is adopted, not only is it difficult to make it compact, but moreover, heat generation due to AC loss increases, which may hinder stable excitation of the superconducting coil. large.

On the other hand, in the above-mentioned cable-in-conduit type forced cooling superconducting conductor connection structure, since the connection portions are overlapped and caulked before the heat treatment and then the heat treatment is performed, the connection point at the time of the connection processing is performed. There is no risk of deterioration or damage of superconducting characteristics. However, instead of inserting each other into a connecting structure such as a sleeve and crimping together with the sleeve, the superconducting fuel wires are simply superposed on each other and caulked, so that the connection is made strong. , The connection part is integrally restrained, and the connection part is fixed at several places in the longitudinal direction with a support so that the connection part does not move due to electromagnetic force etc., and a cooling flow path is secured between the connection part and the conduit. Otherwise, there is a disadvantage that the superconducting characteristics and cooling characteristics deteriorate. On the other hand, in the connection structure of the superconducting conductors that connect the superconducting wires after heat treatment, since the compound-based superconducting material, which is weak in strength, is used, not only there is the risk of deterioration and damage to the superconducting properties at the connection points. , Joule heat is generated at the connecting portion because a connecting member made of a dissimilar metal and a resistor such as a braze or a solder are interposed between the superconducting wires. Causing instability. Furthermore, in these connection structures, the connection part becomes huge, and there are problems in terms of error magnetic field and size limitation.

Therefore, a first object of the present invention is to provide a connection structure for a superconducting conductor which is compact and has reduced AC loss. A second object of the present invention is to provide a cable-in-conduit type forced cooling superconducting device which is small in size, has low resistance connection performance with little Joule heat generation, and does not cause deterioration of superconducting properties at the connection portion. It is to provide a connection structure of conductors.

[0007]

The present invention is based on the above-mentioned first aspect.
In order to achieve the above object, in a superconducting conductor connection structure in which a plurality of superconducting wires are twisted together, the ends of mutual superconducting conductors to be connected are formed of a low resistance material in a sleeve with a superconducting layer formed on the surface. It is configured to be filled with a superconducting material in a gap formed by the sleeve and the superconducting conductor.

In order to achieve the above-mentioned second object of the present invention, a cable using a plurality of compound superconducting wires
In a superconducting conductor connection structure of in-conduit type forced cooling, the stranded wires of the compound type ultra-fine multi-core wire to be connected are divided and inserted into a connection sleeve made of low resistance material and compression molded. The bundled outer periphery is covered with a conduit, and then compression-molded to obtain the same shape as the conductor portion conduit, followed by heat treatment.

[0009]

In the first means, the inside of the sleeve is magnetically shielded, and the superconducting material filled in the gap formed by the superconducting conductor and the sleeve maintains the superconducting state. It is possible to suppress Joule heat generation. The AC loss (mainly eddy current loss) during pulse energization is much smaller than the conventional configuration because the sleeve, which is a good conductor, is magnetically shielded and is not affected by changes in the magnetic field. Will be things.

In the second means, a connecting sleeve having a low resistivity and a high thermal conductivity is used to connect the superconducting wires to each other, and the compression molding is divided into two stages, and finally the heat treatment is performed, so that a low heat generation is achieved. It has excellent heat removal characteristics, is mechanically strong, and has little wire movement due to electromagnetic force, so it is possible to suppress superconducting instability due to heat generation and to make a compact structure with little deterioration in superconducting characteristics. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a part of an embodiment of the present invention by cutting. In the figure, 2 is a superconducting conductor in which a plurality of superconducting wires are twisted together, and 4 is a sleeve. The sleeve 4 is made of a copper material, and has a cylindrical sleeve body 5 having an inner diameter larger than the diameter of the superconducting conductor 2, and a surface of the sleeve body 5 made of a Bi-based material or the like coated for magnetic shielding inside the sleeve. Oxide superconductor layer 6
And a solder filling port 7 provided at an intermediate portion of the sleeve 5. Reference numeral 8 is a low melting point solder injected and filled from the solder filling port 7.

Further, a disc-shaped solder plate 9 having a melting point higher than that of the low melting point solder 8 is provided inside the superconducting conductor 2 and between the end of the sleeve 4 and the superconducting conductor 2, and the low melting point solder 8 is provided. Is configured so as not to flow outside when being injected from the solder filling port 7. The sleeve 4 is provided with an air vent (not shown) for exhausting the internal air when the low melting point solder 8 is injected.

With the above configuration, the empirical magnetic field of the solder in the sleeve 4 can be suppressed to a low level, and the critical current of the solder can be increased. As a result, it is possible to configure a compact connection portion that does not generate Joule heat. Furthermore, when pulsed energization is performed, the eddy current loss that occurs in the connection portion due to the change in the magnetic field in the conventional configuration can be suppressed in this embodiment.

FIG. 2 is a front view showing a part of another embodiment of the present invention by cutting it. In the figure, 2 is a superconducting conductor and 10 is a sleeve. The sleeve 10 includes a sleeve body 5 formed of a copper material, a Bi-based oxide superconductor layer 6 coated on the surface of the sleeve body 5 for magnetic shielding in the sleeve, and the sleeve body 5 It is composed of a superconducting wire 11 which is made of NbTi or the like embedded in the above and acts so as to increase the effective sectional area of the solder. The superconducting wire 11 is formed by twisting a plurality of superconducting wires. The low melting point solder 8 is injected and filled into the sleeve main body 5 through a solder filling port (not shown), but the solder plate 9 is prevented from flowing out.
Is arranged and provided. The sleeve 10 is provided with an air vent (not shown) for exhausting the internal air when the solder 8 is injected.

With the above structure, the current flowing through the superconducting conductor 2 is transferred to the sleeve 10 via the solder.
It also flows into the superconducting wire 11 buried inside, and as a result, the critical current value at the connection can be increased.

FIG. 3 is a perspective view showing a part of another embodiment of the present invention, which is cut away. In the cable-in-conduit type forced cooling superconducting conductor connection structure of this embodiment, heat treatment is performed after the conductor is formed into a coil shape.
The target is a forced cooling coil manufactured by the Wind & React method.

In the figure, 12A and 12B are conductors to be connected, and the sub-cables 13A and 13B are provided in the respective conduits.
B is accommodated. The sub-cables 13A and 13B include a number of extra fine multi-core wires 14 composed of a compound-based superconducting member such as Nb ₃ Sn and a stabilizing material such as copper and a barrier material mainly for the purpose of diffusion and insulation. It is constructed by twisting each one and then twisting several more.

The sub-cables 13A and 13B are respectively inserted into connection sleeves 15 made of a low resistance material such as copper or pure aluminum and then caulked. Here, the connection sleeve 15 has an outer periphery coated with an oxide film or an electric insulation material for electrical insulation, so that heat generation due to AC loss between the connection portions is reduced. Further, the respective connection points (that is, the positions of the connection sleeves 15) are appropriately displaced in the longitudinal direction to prevent the size of the entire outer circumference from enlarging at the connection points.

The connecting portion 16 connected as described above is
Bundled and covered with two divided conduits 17A and 17B,
And conductors 12A, 12 that should be connected to each other to maintain airtightness
The conduits 17A and 17B are welded to the respective B conduits. The connection portion thus covered with the conduit is compression-molded to have a predetermined size and then heat-treated to form a superconducting conductor. Since there is a gap between the conduit and the sub cables 13A and 13B housed inside,
The refrigerant flows through this gap.

According to the above structure, in the connection structure of the cable-in-conduit type forced cooling superconducting conductor,
Reduces Joule heat generation when energizing the connection of superconducting wires.
Moreover, in order to improve heat exchange with helium which is a refrigerant around the superconducting wire, the connection sleeve 15 having a low resistivity and a high thermal conductivity is used. In addition, it is possible to mechanically and firmly connect by compression molding. Since the connecting portion 16 is bundled and welded to the outer periphery of the conduits 17A and 17B and further compression-molded, the connecting portion 16 is integrally and restrained in the conduit, and the ultrafine multi-core wire 14 moves due to electromagnetic force to cause superconducting instability. Does not occur. In addition, connect sleeve 15 to 9
By using high-purity aluminum with a purity of 9.999% or more, and selecting the size and shape so that the final processing degree of the connecting sleeve 15 by compression molding of the conduit after connection is 20% or less, or 90% or more , Fig. 4 (30th
The low resistivity can be maintained, as shown in the "Cryogenic Engineering Research Conference", B1-3, pp.20 (1983)).
The Joule heat can be reduced.

[0021]

As described above, according to the present invention, it is possible to provide a more compact superconducting conductor connecting structure without causing Joule heat generation and eddy current loss. Further, it is possible to provide a connection structure for a cable-in-conduit type forced cooling superconducting conductor which is small in size, has low resistance connection performance with little Joule heat generation, and does not cause deterioration of superconducting properties at the connection portion.

[Brief description of drawings]

FIG. 1 is a front view showing a cutaway part of an embodiment of the present invention.

FIG. 2 is a front view showing a part of another embodiment of the present invention by cutting.

FIG. 3 is a perspective view showing a part of another embodiment of the present invention, which is cut away.

FIG. 4 is a curve diagram showing the relationship between the cold workability and the specific resistance of high-purity aluminum for explaining the operation of still another embodiment of the present invention.

FIG. 5 is a front view showing a connection configuration of a conventional superconductor.

[Explanation of symbols]

2 ... Superconducting conductor, 4, 10 ... Sleeve, 5 ... Sleeve body, 6 ... Oxide superconducting layer, 7 ... Solder filling port, 8 ... Low melting point solder, 9 ... Solder plate, 11 ... Superconducting wire, 12A, 12B
… Conductor, 13A, 13B… Sub cable, 14… Extra fine multi-core wire,
15 ... Connection sleeve, 16 ... Connection part, 17A, 17B ... Conduit.

Claims (2)

[Claims] 1. In a superconducting conductor connection structure comprising a plurality of superconducting wires twisted together, the ends of the superconducting conductors to be connected are placed in a sleeve formed of a low resistance material and having a superconducting layer formed on the surface thereof. A structure for connecting a superconducting conductor, wherein the superconducting conductor is inserted and a gap formed between the sleeve and the superconducting conductor is filled with a material having a superconducting property. 2. In a connection structure of a cable-in-conduit type forced cooling superconducting conductor using a plurality of compound superconducting wires, the twisted wires of the compound extra fine multi-core wires to be connected are divided into low resistance materials. A cable characterized by being inserted into a connection sleeve, compression-molded, covering the outer periphery of a bundle of these multiple connection parts with a conduit, then further compression-molded into the same shape as the conductor part conduit, and heat-treated.・ In-conduit type forced-cooling superconducting conductor connection structure.