JPH0634362B2 - Superconducting wire joining method - Google Patents

Description

The present invention relates to a method for joining superconducting wires, and more particularly to a superconducting wire formed by embedding a plurality of superconducting filaments in a stabilizing material. To join
The present invention relates to a preferable superconducting wire joining method.

[Background of the Invention]

In recent years, superconducting wires have come to be used in devices such as coils of nuclear fusion devices that require a large current to flow.

However, there is a limit to the length of the superconducting wire and it is necessary to connect a superconducting wire of a predetermined length before use. However, in the conventionally known connection methods (brazing method, pressure welding method, welding method, etc.), the electrical resistance of the connection portion is large and the amount of heat generated during energization is large, which makes it difficult to adopt.

In order to improve this, there is a superconducting wire connecting method proposed in Japanese Patent Laid-Open No. 59-16207.

According to this method, as shown in FIG. 17, the superconducting filaments 2 and 2'exposed by removing the stabilizing material of the connecting portions of the superconducting wires 1 and 1'to be connected are overlapped with each other and connected. The superconducting filaments 2 and 2'that are housed in the working tube 10 and pressed through the connecting tube 10 are pressed and joined to each other.

However, in this joining method, the superconducting wire 1 and the superconducting filament 2 of 1 ', which are to be connected to each other,
Since 2'and 2'contact only the outer overlapping portions, it is difficult to secure a high critical current value.

Also, the superconductor filaments 2 and 2'on the side of contact
Has a drawback that when it is pressed through the connecting tube 10, it is bent inside the superconducting wire and is bent almost to the center position, so that the bending workability is high and it is easy to break, and the superconducting property is deteriorated. .

In addition, in Japanese Patent Application No. 59-191611, which is being applied for, as shown in FIG. 10, the superconducting filaments 2 and 2'at the tips of the superconducting wires 1 and 1'to be joined are made to face each other as shown in FIG. After intersecting with each other, the copper ring 3 shown in FIG. 12 was set as shown in FIG. 13 and crimped as shown in FIG.

However, in this method, the first line in the AA cross section of FIG.
As shown in FIG. 5, the superconductor filaments 2 and 2'can be densely crimped, but in the BB cross section, the superconductor filament 2 cannot be made dense as shown in FIG.

For this reason, the high critical current value that can be secured in a low magnetic field is difficult to secure a high critical current value in a high magnetic field because the superconductor filament 2'is liable to sway.

[Object of the Invention]

An object of the present invention is to provide a superconducting wire joint capable of ensuring a high critical current value even in a high magnetic field by increasing the density of the superconductor filament and preventing the superconducting filament from moving during energization.

[Outline of Invention]

The feature of the present invention is to increase the density of both sides of the superconducting filament's weighted portion, that is, the non-weighted portion of the superconductor filament, so that a sleeve is set on the non-weighted portion of the superconductor filament and crimped. By so doing, it is possible to increase the density and prevent the fluctuation of the superconductor filament during energization, thereby ensuring a high critical current value even in a high magnetic field.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS.

In the figure, reference numerals 1 and 1'represent superconducting wires to be joined.

As shown in FIG. 10, the superconducting filaments 2 and 2'are prepared by immersing the tips of the superconducting wires 1 and 1'in concentrated nitric acid.
Copper is removed as a stabilizing material.

After this, the superconducting wires 1 and 1'to be joined are faced to each other as shown in Fig. 11 and overlapped so as to intersect with each other, and then the outer diameter φ6.0 mm, inner diameter φ3.5 mm, and length 14 mm of Fig. 12 are obtained. Copper ring 3 and Fig. 5 according to the present invention. Outer diameter φ3.4m
Sleeves 4 and 4'having a diameter of m, an inner diameter of 2.4 mm and a length of 5 mm are set as shown in FIG. 1 and crimped as shown in FIG.

As a result, the superconductor filaments 2 and 2'has a high density even at the non-overlapping portions because of the sleeve 4 as shown in FIG.

As a result, according to this embodiment, even when the superconductor filaments 2 and 2'do not overlap with each other (2 mm or less) during the energization, the superconducting filaments 2 and 2'do not sway, and a high critical current value can be secured even in a high magnetic field.

The sleeves 5 and 5'shown in FIG. 5 are chamfered 6 on the inner surface side of the ends, and since the edges of the sleeves have no corners, the corners directly contact the superconductor filaments 2 and 2'when crimping, causing disconnection. Can be prevented.

FIG. 7 shows that when the copper at the tips of the superconducting wires 1 and 1'is removed with concentrated nitric acid, the time of immersion in concentrated nitric acid is shortened and the stabilized copper is not completely removed, but the diameter φ2. The core having a diameter of about 1.0 mm is left for the superconducting wires 1 and 1'of 3 mm.

The tips of the cores 7 and 7'are bent. After this, above 7,
Superconducting wires 1 and 1'having a core 7'are opposed to each other. At this time, the tips of the cores 7 and 7'are bent in opposite directions so that they do not interfere with each other when pressed.

Since the tips of the cores 7 and 7'are bent and pressed to the opposite side, there is little interference at the time of pressing.

Then, as in FIGS. 1 and 2, the copper ring 3 and the sleeves 4 and 4'are set and pressed. FIG. 9 shows a cross section of the end portion after crimping. The cross section has a sleeve 4'and a core 7'in addition to the superconductor filament 2 ', the superconductor filament 2'can further increase the density, and the fluctuations of the superconductor filaments 2 and 2'can be reduced. It is possible to secure a higher critical current value in a high magnetic field.

The cores 8 and 8'in FIG. 8 are prepared by dissolving the stabilizing material with concentrated nitric acid.
A core having a diameter of about 1.0 mm like 7, 7'in FIG. 7 is prepared.

Next, the tip of the superconducting wires 1 and 1'is immersed in concentrated nitric acid to a shallow depth, and the stabilized copper at the tips of the cores 7 and 7'is completely melted to produce cores 8 and 8 '.

After this, superconducting wires 1 and 1'having cores 8 and 8 '
Press and face each other, and stack them so that they intersect.
In this case, since the cores 8 and 8'are short, it is easy to intersect without causing interference.

After that, as shown in FIGS. 1 and 2, the copper rings 3, 3'sleeves 4, 4'are set and crimped to obtain the same effect as that of the superconducting wire having the cores 7, 7 '.

9 in FIG. 2 is a brazed member which is applied to the end of the joint after the ring is crimped so as to increase the strength of the joint.

With the conventional brazing method or cold pressure welding method, a superconducting joint cannot be obtained and a resistance of about 1 × 10 ⁻⁸ Ω is exhibited, but with the method of the present invention, a superconducting state can be secured and a high critical current value of the joint portion. Can be secured.

FIG. 18 compares the ring crimping method without the sleeve, the ring crimping method with the sleeve and the ring crimping method with the core and the sleeve.

When the magnetic field strength is 2T, the critical current value of 1500A is used without the sleeve and with the ring crimping method, but is 1900 with the "with sleeve" or "ring crimping method with both core and sleeve" respectively.
A, improve to 2200A.

At magnetic field strength of 6T, 500A is 1200 each
A, improve to 1800A.

As described above, in the ring crimping method, the critical current at the joint is remarkably improved when the sleeve or the core is inserted.

〔The invention's effect〕

According to the present invention, not only the superconductor filaments to be joined can be joined in a high density state, but also the density of the non-overlapping ends of the superconductor filaments can be increased, and as a result, the superconductor filaments that are being energized can be increased. 2,2 '
It is possible to reduce the fluctuation of the magnetic field and secure a high critical current value of the junction even in a high magnetic field.

[Brief description of drawings]

FIG. 1 shows a state in which a superconducting filament of the present invention is entangled with a copper ring and a sleeve set, FIG. 2 shows a state in which the set ring is crimped, and FIGS.
Sections AA and BB in FIG. 5, FIG. 5 is a side view of a sleeve for closely bonding superconductor filaments, FIG. 6 is a side view of a sleeve whose inner surface is chamfered, and FIG. 7 is concentrated nitric acid. Fig. 8 is a side view of the superconducting wire in which the stabilizing material is removed by using
Figure is a side view of a short-core superconducting wire in which the stabilizing material at the tip of the core is melted, and Figure 9 is an end cross-section when a ring is crimped using a superconductor filament with a core at the tip as in 7 or 8. Fig. 10 is a side view of the superconducting wire in which the stabilizing material at the tip of the superconducting wire is removed with concentrated nitric acid, and Fig. 11 is the first view.
The superconducting wires shown in Fig. 0 are opposed to each other, and the superconducting filaments are overlapped so as to intersect with each other. Fig. 12 is a ring to be crimped to join the superconducting wires, and Fig. 13 is overlapping so as to intersect the superconducting filaments. The ring is set, FIG. 14 is the state where the rings are crimped and joined,
5, FIG. 16 is a cross section taken along line AA and BB in FIG. 14, and FIG.
The figure is a conventionally known joining method of JP-A-59-16207, and FIG. 18 is data for explaining the effect of the present invention. 1, 1 '... superconducting wire, 2, 2' ... superconducting filament, 3 ... copper ring, 4, 4'and 5, 5 '... sleeve, 6 ... sleeve 5, 5' part,
7,7 'and 8,8' ... Stabilizer copper adhering cores.

Claims (2)

[Claims] 1. A stabilizing material at an end portion of a superconducting wire to be joined is removed with concentrated nitric acid or the like, and superconductor filaments are made bare and overlap each other so as to face each other and then crimped with a ring. In the legal method, a method of joining superconducting wires, characterized in that a sleeve is put in the end portions of the superconducting wires which are not overlapped and crimped. 2. The method according to claim 1, wherein a sleeve is used in which the corners of the sleeve end are chamfered so as not to disconnect the filament to the superconductor during crimping. Method.