JPH05182536A - Superconductor and stabilizing member used therein - Google Patents

Abstract

PURPOSE:To improve the operational stability of a superconductor without damaging the intrinsic low-resistivity of high-purity aluminum in a magnetic field by forming a layer made of metal whose electric resistance is higher than that of high-purity copper between the high-purity aluminum and the high-purity copper so as to form a stability member in a compound layer. CONSTITUTION:In a superconductor which comprises superconductive wire 1 and also high- purity aluminum 3 and high-purity copper 6 both composing a stabilizing member united with one another via solder 7 as a metallic adhesive, a layer made of metal 4 whose electric resistance is higher than that of the high-purity copper 6 is interposed between the high-purity aluminum 3 and the high-purity copper 6 so that the stabilizing member may be formed in a compound layer. For example, into the oxygen free copper 6 (a copper purity of 99.996%) the followings are inserted: a superconductive twisted wire 2 prepared by intertwisting the superconductive wires 1 each comprising a number of niobium-titanium alloy group superconductive filaments embedded in oxygen free copper having its purity of 99.996%, and a compound member 5 comprising the high-purity aluminum 3 coated with a copper member 4 made of a copper-10% of nickel alloy. Then their respective component members are united with one another via the solder 7. This can substantially reduce the resistivity of the high-purity aluminum in a magnetic field so as to improve the operational stability of the aluminum stabilizing superconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-current superconducting conductor having high stability in a magnetic field and a stabilizing material used therefor, and more particularly to improvement of an aluminum stabilizing material.

[0002]

2. Description of the Related Art A high magnetic field, large capacity magnet used in a nuclear fusion device or an energy storage device is generally constructed by using a superconducting conductor. As the superconducting conductor, a large number of immersion cooling type conductors that are immersed in a coolant such as liquid helium for cooling, and so-called hollow type conductors in which a coolant passage is formed in the conductor have been proposed.

Since a large-capacity superconducting conductor has a large capacity, in consideration of safety when the superconducting state is broken, a superconducting material which becomes a superconducting state at extremely low temperature is embedded in a metal such as copper as a filament. A multi-core type superconducting wire is used in combination with a large amount of stabilizing materials such as high-purity aluminum and high-purity copper.

The reason for using high-purity aluminum having a purity of 99.99% or more as a stabilizing material is that high-purity copper, such as oxygen-free copper, has an electric resistance at an extremely low temperature, that is, at a liquid helium temperature of 4.2K. Since it is / 10, stability of 10 times that of copper can be achieved with the same cross-sectional area. From another point of view, by using high-purity aluminum instead of copper, the cross-sectional area of the stabilizing material can be reduced to 1/10, and the superconducting conductor and eventually the superconducting magnet can be made compact. Is.

However, since high-purity aluminum has a low mechanical strength, when it is used as a magnet, a conductor having a high mechanical strength such as high-purity copper and a metallic adhesive such as solder are used as a conductor that withstands the electromagnetic force. It is generally used integrally.

In this case, since aluminum is difficult to solder, a method is used in which aluminum is coated with copper in advance, and this is integrated with the superconducting wire and copper as a strength member by soldering.

As the copper coated on the high-purity aluminum and the copper as the strength member, the same high-purity material as aluminum is used in order to improve electrical and thermal stability.

In general, the electric resistance of a composite of two kinds of metals is satisfied by a composite rule and can be obtained by the following formula.

1 / R = 1 / R ₁ + 1 / R ₂ Here, R ₁ and R ₂ are resistances of two kinds of metals, respectively, and R is a composite resistance.

This equation is expressed by the specific resistance ρ in each magnetic field,
Substituting ρ ₁ , ρ ₂ and cross-sectional areas A, A ₁ , A ₂ , it is expressed by A / ρ = (A ₁ + A ₂ ) / ρ = A ₁ / ρ ₁ + A ₂ / ρ ₂ .

5 tesla (T) of the composite material in which the cross-sectional area ratio of high-purity aluminum and high-purity copper is 0.8: 0.2.
When the specific resistance (ρ) in the magnetic field is calculated using the above-mentioned compounding rule, the value of aluminum: A ₁ = 0.8, ρ ₁ = 2.5 × 10 ⁻⁹ Ω · cm The value of copper: A ₂ = Substituting 0.2 and ρ ₂ = 4.0 × 10 ⁻⁸ Ω · cm, ρ = 3.1 × 10 ⁻⁹ Ω · cm is obtained.

Therefore, the specific resistance as a composite material of high-purity aluminum coated with high-purity copper is 3.1 × 10 ^-9 Ω.
・ It is considered that cm at 5T contributes to the stability of the superconductor. However, when high-purity aluminum and high-purity copper were compounded so that the cross-sectional area ratio was 0.8: 0.2 and the specific resistance was measured at 4.2K and 5T, it was 6 × 10 ^-9 Ω.
The value is cm, which is higher than the value calculated by the compound rule. Therefore, the specific resistance of the composite material of high-purity aluminum and high-purity copper is lower than what is expected to be practically useful.

[0013]

As described above, the composite material of high-purity aluminum and high-purity copper shows a value higher than the specific resistance expected by the compound law in a magnetic field at extremely low temperature, and thus the stability is improved. Will contribute less. Therefore, it has been desired to establish a method for utilizing the small specific resistance value of high-purity aluminum in a magnetic field, which is inherently combined with high-purity copper that is a mechanical strength member.

There is no clear answer at present as to why the composite material of high-purity aluminum and high-purity copper exhibits a specific resistance value which does not meet the compounding rule, but it is considered to be due to a certain Hall effect. ..

The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to stabilize the high-purity aluminum without compromising the low specific resistance of the high-purity aluminum in the original magnetic field even when it is compounded. It is to provide a superconducting conductor having excellent properties.

[0016]

In order to achieve the above object, in the present invention, when high-purity aluminum and high-purity copper are used in combination as a stabilizer, the electric resistance between them is higher than that of high-purity copper. It is designed to be composited through a metal layer.

In this case, as the metal having a higher electric resistance than that of high-purity copper, a metal having a specific resistance of 1 × 10 ⁻⁷ Ω · cm or more at an extremely low temperature where a superconducting conductor is used is desirable. It is desirable that the increase rate of electrical resistance in the same shows a tendency similar to that of high-purity aluminum, for example, copper-nickel alloy, copper-manganese alloy, copper-tin alloy, deoxidized copper, silver alloy, nickel alloy, zinc alloy, etc. Is used. This metal is used by being coated directly on high-purity aluminum as a stabilizing material. Therefore, when the high-purity aluminum is a composite material of high-purity copper, the metal is used by being interposed between the high-purity aluminum and the high-purity copper. In addition, since the composite resistance of the metal alloy with the aluminum having a high purity decreases as the amount of the metal alloy decreases, it is desirable to make the layer as thin as possible.

[0018]

Since the stabilizing material for a superconducting conductor according to the present invention has the structure as described above, a superconducting conductor using the stabilizer has a high resistance metal layer serving as a resistor, and a high effect due to a certain Hall effect. It is possible to significantly reduce the specific resistance as compared with a superconducting conductor using a high-purity aluminum material only coated with pure copper.

[0019]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, the superconducting conductor according to the embodiment has a twisted wire 2 formed by twisting a superconducting wire 1 in which a large number of niobium-titanium superconducting filaments are embedded in oxygen-free copper having a purity of 99.996%. And a composite material 5 obtained by coating high-purity aluminum 3 with a copper material 4 made of a copper-10% nickel alloy, oxygen-free copper 6 serving as a mechanical strength member and a stabilizing material (purity 99.996%) , And each component is integrated with solder 7. In this case, the composite material 5 is processed as follows.

For example, copper-1 having an outer diameter of 42 mm and an inner diameter of 36 mm
Outer diameter 35mm, purity 99.99 in 0% nickel alloy tube
A 9% or more high-purity aluminum rod is inserted, and a heat treatment is applied to the middle of the rod by a co-drawing method to draw a rectangular section of, for example, 4 mm × 8 mm.

The composite material 5 manufactured in this manner is inserted into the oxygen-free copper 6 together with the twisted wire 2, and the constituent materials are combined and integrated with the solder 7.

Oxygen-free copper in the superconducting conductor, copper-10%
The cross-sectional area ratio of nickel alloy and high-purity aluminum is set to 0.
The ratio was 66: 0.07: 0.27, and this was immersed in 4.2K liquid helium, and the specific resistance at 5T was measured. As a result, it was 5 × 10 ^-9 Ω · cm. On the other hand, the conductor (almost the same cross-sectional area ratio) of the conventional stabilizing material that only uses oxygen-free copper as the covering material is 15 × 10 ⁻⁹ Ω · cm, which is three times that of the stabilizing material of this embodiment. The resistance value of This value was about 4.5 times as large as 3.35 × 10 ⁻⁹ Ω · cm calculated by the compound rule.

FIG. 2 shows another example of a superconducting conductor. A plurality of superconducting wires 1 are twisted around a composite material 5, which are inserted into oxygen-free copper 6 and integrated with solder 7. It is a thing.

FIG. 3 shows another example of the aluminum stabilizing material, in which an oxygen-free copper layer 8 is formed on the outer periphery of the composite material 5 shown in FIG. Similar to the composite material 5 shown above, this composite material can be manufactured by the friendship method or the like. Even if the superconducting conductor as shown in FIG. 1 or FIG. is there.

FIG. 4 shows another example of a superconducting conductor. A plurality of superconducting wire rods 1 are twisted around a composite material 5, which are inserted into an oxygen-free copper 6 and integrated by a braid 7. However, the difference from the case of FIG. 2 is that a lid member made of oxygen-free copper 6 is used as in FIG.

[0027]

As described above, according to the present invention, a layer of metal having a higher electric resistance than that of high-purity copper is interposed between high-purity aluminum and high-purity copper as a stabilizer to form a composite. Further, there is an effect that the specific resistance in the magnetic field can be significantly reduced and the stability of the aluminum-stabilized superconducting conductor can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a superconducting conductor according to the present invention.

FIG. 2 is a sectional view showing another example of a superconducting conductor according to the present invention.

FIG. 3 is a sectional view showing another example of the aluminum stabilizing material according to the present invention.

FIG. 4 is a view of a fireplace showing another example of the superconducting conductor according to the present invention.

[Explanation of symbols]

 1 Superconducting Wire 2 Superconducting Stranded Wire 3 High Purity Aluminum 4 Copper-Nickel Alloy Layer as Metal 5 Composite Material as Aluminum Stabilizer 6 Oxygen Free Copper 7 Solder as Metallic Adhesive 8 Oxygen Free Copper Layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoichi Suzuki 3550 Kidayo-cho, Tsuchiura-shi, Ibaraki Hitachi Cable Co., Ltd. Tsuchiura factory (72) Inventor Yasuhiro Yuzawa 3550 Kida-yomachi, Tsuchiura-shi, Ibaraki Hitachi Cable Ltd. Tsuchiura factory

Claims (5)

[Claims] 1. A superconducting conductor obtained by integrating a superconducting wire with high-purity aluminum and high-purity copper as a stabilizing material with a metallic adhesive, wherein the high-purity aluminum and high-purity copper have the high-purity level between them. A superconducting conductor comprising a metal layer having a higher electrical resistance than copper interposed. 2. The superconducting conductor according to claim 1, wherein the high-purity aluminum is coated on the outer periphery thereof with a metal material having a higher electric resistance than that of the high-purity copper. 3. The superconducting conductor according to claim 1, wherein the high-purity aluminum is one whose outer periphery is sequentially coated with a metal having a higher electric resistance than the high-purity copper and high-purity copper. 4. A stabilizing material for use in a superconducting conductor obtained by integrating a superconducting wire with high-purity aluminum and high-purity copper as a stabilizing material with a metallic adhesive, wherein the outer periphery of said high-purity aluminum is used. A stabilizing material for a superconducting conductor, comprising a metal layer having a higher electric resistance than the high-purity copper. 5. A stabilizing material for use in a superconducting conductor obtained by integrating a superconducting wire with high-purity aluminum and high-purity copper as a stabilizing material with a metallic adhesive, the stabilizing material being provided on the outer periphery of the high-purity aluminum. A stabilizing material for a superconducting conductor, wherein a metal layer having a higher electric resistance than the high-purity copper and a high-purity copper layer are sequentially provided.