JP2003086039A - Al-STABILIZED SUPERCONDUCTIVE WIRE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-stabilized superconductive wire having higher stability at a collapse of superconductivity by improving the cooling effect of an Al stabilizer. SOLUTION: In an Al-stabilized superconductive wire that includes a superconductive conductor 1 combined with an Al stabilization material 3 through a solder layer 2, the Al stabilization material 3 includes an Al material 4 that has Cu-alloy coating layers 6a and 6b formed on its surfaces and that is placed around the superconductive conductor 1 with gaps 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-stabilized superconducting wire, and more particularly to an Al-stabilized superconducting wire which has improved stability during superconducting collapse by improving cooling efficiency.
l Stabilized superconducting wire.

[0002]

2. Description of the Related Art In a superconducting conductor which is cooled to a critical temperature or lower with a refrigerant such as liquid helium and the like and is heated to a critical temperature or higher due to thermal or mechanical disturbance, the superconducting state is broken and the normal conducting state is reached. May be burned out by Joule heat generation.

Therefore, normally, in a superconducting conductor,
When heat is generated, the heat is quickly removed, and a stabilizing material for suppressing the heat generation by bypassing the current is combined. Stabilizers need to have low electrical resistance, good heat capacity and thermal conductivity, as well as a composition suitable for cooling, and in many cases,
Cu or Al is used as a constituent material.

Comparing Al and Cu as stabilizers,
In terms of electrical resistance at low temperatures, Al is advantageous in that it is at a level ten times lower than Cu, while Cu is
Is advantageous in that it has remarkably excellent mechanical strength when compared with low-strength Al, which is difficult to process in combination with a superconducting conductor.

Due to these characteristics, Cu is generally used in combination with a superconducting material to form a superconducting conductor,
On the other hand, Al is usually combined with a superconducting conductor by some means in order to improve stabilization. As a superconducting wire material embodying these structures, Al and Cu are used.
It is known that a stabilizer of Al is soldered onto a superconducting core wire that is a composite of.

Specifically, a superconducting wire rod has been proposed in which an Al material coated with a Cu alloy is used as a stabilizing material in order to prevent the soldering inhibition due to the formation of an oxide film on the surface of the Al material. In this proposal, the reason for using Cu alloy instead of pure Cu for the Cu coating material is to suppress the current flow due to the Hall effect in the Cu coating material and improve the stability.

That is, when pure Cu is used as the coating material, when a current flows in a magnetic field in the vertical direction, a voltage due to the Hall effect is generated in the direction perpendicular to the magnetic field, and the Hall current based on this voltage flows through the Cu coating. Since it becomes easier and the electric resistance increases due to the so-called compound rule, a Cu alloy having a high electric resistance is used to suppress this.

As an example of the superconducting wire having the above-mentioned structure, Japanese Patent Laid-Open No. 8-50826 can be cited. To this end, a plurality of Al-stabilizers having a fan-shaped cross section coated with CuNi alloy are arranged on the outer periphery of a core wire made of an NbTi alloy-based superconducting material, and the Al stabilizers are tightly joined by soldering. Superconducting wire is shown,
The characteristics are excellent in current density and stability, and low AC loss.

[0009]

However, according to the conventional Al-stabilized superconducting wire material disclosed in the above publication, the Al-stabilized material is in close contact with the superconducting core wire and is in a state of being mutually bonded. Therefore, the cooling by the refrigerant is limited to one surface of the fan-shaped Al stabilizing material. Therefore, since the cooling area cannot be large, the cooling is insufficient, and the Al stabilizing material functions when the superconducting state collapses. There is a risk of disappearing.

Therefore, an object of the present invention is to provide an Al-stabilized superconducting wire having improved stability during superconducting collapse by improving the cooling efficiency of the Al-stabilizing material.

[0011]

In order to achieve the above-mentioned object, the present invention provides an Al-stabilized superconducting wire which is constructed by integrally composing an Al-stabilizing material on a superconducting core wire through a solder layer. An Al-stabilized superconducting wire is provided, in which the Al-stabilizing material is formed by arranging an Al material having a Cu alloy coating layer formed on the surface thereof with a space around the superconducting core wire. To do.

It is preferable that the Al material has a quadrangular cross-sectional shape and does not have a Cu alloy coating layer on an appropriate surface other than the surface to be joined to the superconducting core wire by soldering. In this case, the exposed portion is formed in the Al material forming the stabilizing material, and this portion comes into direct contact with the refrigerant, so that the cooling efficiency is further improved.

As a specific construction for this purpose, a Cu alloy coating layer is not provided on the surfaces other than the surface of the Al material having a quadrangular cross section in contact with the solder layer and the surface opposite to the solder layer. In addition, a configuration in which the Cu alloy coating layer is not provided on all surfaces other than the surface in contact with the solder layer is conceivable.

In the case of the former constitution, a high cooling efficiency for the Al stabilizing material can be obtained, and the effect of protecting the Al material by the Cu alloy coating layer can be expected, while the latter constitution is adopted. In this case, the exposed area of the Al material is maximized, so that higher cooling efficiency is established.

Further, as a result of the above-described two configurations, the coating layer of the Cu alloy is divided in the circumferential cross section of the Al material constituting the stabilizing material, so that the electrical resistance is increased by the Hall effect. Can be eliminated more strictly, and the effect of improving stability can also be obtained.

In the present invention, the stabilizing material is preferably formed on the superconducting core wire by spiral winding of an Al material. In this case, the number of Al materials may be single or plural. Specifically, a predetermined number of Al materials in which a coating layer of a Cu alloy is formed on a predetermined surface of an Al material having a quadrangular cross section are prepared, and the Al material is spirally wound on the solder layer.

In the present invention, examples of the superconducting material forming the superconducting core wire include NbTi and Nb ₃ S.
n or Nb ₃ Al can be used, and there are no particular restrictions on the type. Further, these superconducting materials are usually compounded with a matrix such as Cu or CuNi to form a superconducting core.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of an Al-stabilized superconducting wire according to the present invention will be described. In FIG. 1, reference numeral 1 is a superconducting core wire formed by combining a superconducting material such as NbTi and a matrix such as Cu, 2 is a solder layer formed on the superconducting core wire 1, and 3 is a solder layer formed on the solder layer 2. Another Al stabilizing material is shown, which is formed by spirally winding a plurality of Al materials 4 with an interval 5 therebetween.

The Al material 4 has a quadrangular (flat) cross section, and a surface 4a contacting the solder layer 2 and a surface 4b located on the opposite side of the solder layer 2 are covered with a Cu alloy by a clad. Layers 6a and 6b are formed, and surface 4a
The upper coating layer 6 a is integrally joined to the superconducting core wire 1 via the solder layer 2.

According to the Al-stabilized superconducting wire according to the above embodiment, the Al material 4 constituting the Al-stabilized material 3 is
Since the space 5 is arranged around the superconducting core wire 1, the refrigerant such as helium enters the space 5, and therefore the cooling efficiency for the Al stabilizing material 3 is significantly improved as compared with the conventional case. be able to.

The extent of increasing the contact area of the Al stabilizing material 3 with the refrigerant by forming the gap 5 can be as high as 30% or more. Therefore, the gap 5 is It is extremely important in improving the characteristics of the Al-stabilized superconducting wire.

Moreover, in this embodiment, Al
Cu alloy coating layer 6a only on surfaces 4a and 4b of material 4
Since the surfaces 4c and 4b are formed, the surfaces 4c and 4d of the other Al material come into direct contact with the refrigerant, and therefore, the effect of improving the cooling efficiency can be expected.

It is also advantageous that the coating layer of Cu alloy is divided by the surfaces 4c and 4d in the circumferential direction of the Al material 4, and as a result, the current generation due to the Hall effect can be prevented more strictly. Therefore, it is possible to highly eliminate the phenomenon of increased resistance due to the compound rule.

FIG. 2 shows another embodiment of the Al-stabilized superconducting wire according to the present invention. The difference from FIG. 1 is that the Cu alloy coating layer 6b on the surface 4b of the Al material 4 in FIG. 1 is removed, and the contact area with the refrigerant is increased by maximizing the exposed area of the Al material 4. However, the cooling efficiency is further improved. In the case of this embodiment, it goes without saying that the effect of preventing the resistance increase due to the compound rule can be obtained.

In the above two kinds of Al-stabilized superconducting wire rods, an example in which a coating layer of a Cu alloy is formed only on the surfaces 4a and 4b of the Al material 4 or only on 4a has been described. , In FIG. 1, 4c or 4d
It is also possible to additionally form a Cu alloy coating layer on any of the surfaces, or to form a Cu alloy coating layer on all of the surfaces 4a to 4d.

FIG. 3 is an example in which the Al-stabilized superconducting wire according to the present invention is applied to a cable-in-conduit type superconducting conductor, and a plurality of Al-stabilized superconducting wires 7 shown in FIG. 1 or 2 are used. Is an example in which these aggregates are twisted together and the aggregate is housed in a conduit 8 such as SUS.

Al stabilizing material 3 in each superconducting wire 7.
However, it exhibits excellent heat dissipation and current bypassing, backed by high cooling efficiency when superconducting collapses, enabling the construction of a cable-in-conduit type Al-stabilized superconducting conductor with excellent stability. .

[0028]

As described above, the Al according to the present invention
According to the stabilized superconducting wire, the Al stabilizing material is formed by arranging the Al material on the surface of which the Cu alloy coating layer is formed at predetermined intervals around the superconducting core wire. The Al stabilizing material is efficiently cooled by the refrigerant that has entered the space, and therefore, it is possible to provide the Al stabilizing superconducting wire having excellent stability during superconducting collapse.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an Al-stabilized superconducting wire according to the present invention.

FIG. 2 is an explanatory view showing another embodiment of an Al-stabilized superconducting wire according to the present invention.

FIG. 3 is an explanatory diagram showing a configuration example of a cable-in-conduit type superconducting conductor using the Al-stabilized superconducting wire of FIG. 1 or 2.

[Explanation of symbols]

1 Superconducting core 2 Solder layer 3 Al stabilizer 4 Al material 4a-4d surface 5 intervals 6a, 6b Cu alloy coating layer 7 Al stabilized superconducting wire 8 conduits

Claims (5)

[Claims] 1. An Al-stabilized superconducting wire constituted by integrally combining an Al stabilizer with a solder layer on a superconducting core wire, wherein the Al stabilizer forms a Cu alloy coating layer on the surface. 2. An Al-stabilized superconducting wire rod, characterized in that it is constituted by arranging the above-mentioned Al material at intervals around the superconducting core wire. 2. The Al material has a quadrangular cross-sectional shape, and has a structure in which the Cu alloy coating layer is not provided on an appropriate surface other than the surface in contact with the solder layer. 1. An Al-stabilized superconducting wire according to item 1. 3. The C-based Al material is provided on a surface other than a surface in contact with the solder layer and a surface located on the opposite side of the solder layer.
3. The Al-stabilized superconducting wire according to claim 2, which has a structure not having a coating layer of u alloy. 4. The Al-stabilized superconducting material according to claim 2, wherein the Al material does not have a coating layer of the Cu alloy on all surfaces other than the surface in contact with the solder layer. wire. 5. The Al-stabilized superconducting wire according to claim 1, wherein the Al-stabilizing material is formed by spirally winding the Al material around the superconducting core wire.