JPH09167705A - Current-carrying lead for oxide superconductive coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide current-currying leads of an oxide superconductive coil, which are superior in strength and electric conductivity by constituting additive which an oxide generated by internal oxidation dispersively strengthens with gold alloy added to silver. SOLUTION: The oxide superconductive coil 101 is generated by winding a band-shaped superconductive wire 102 in a spiral form, and battledore-like current-carrying leads 103a and 103b are connected to both ends so that they are erected. Gold alloy is used for the conductive leads 103a and 103b. The composition is Ag-0.026at% Mg-0.01at% Ni, for example and it is connected and fixed to the oxide superconductive coil 101 by using silver solder. The oxide superconductive coil 101 to which the current carrying leads 103a and 103b are connected executes a partial melting/slow cooling/heating processing at the maximum temperature of 885 deg.C. In the process, the current-carrying leads 103a and 103b are distributively strengthened by means of the internal oxidation of additive with the heat processing, and strength improves. Thus, the current-carrying leads superior in strength and electric conductivity can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-carrying lead that connects a power source and a superconducting coil when supplying a current to an oxide superconducting coil.

[0002]

2. Description of the Related Art In a superconducting magnet, for example, an oxide superconducting coil or the like is used as its coil and is installed in a cooling atmosphere. The oxide superconducting coil and a power source installed in a room temperature atmosphere are operated via a current-carrying lead (installed in a cryogenic atmosphere) provided upright on the oxide superconducting coil.

FIG. 6 is a perspective view showing the structure of a current-carrying lead of a conventional oxide superconducting coil. Oxide superconducting coil 2
01 is formed by spirally winding a band-shaped superconducting wire rod having an oxide as a constituent element, and on top of it, current-carrying leads 202a and 202b for supplying a current to the coil, a measurement voltage terminal 203a, 203b, 203c, 2
03d is erected. A refrigerant is passed through the central pipe 204. Pure silver is used as the material of the current-carrying leads 202 to ensure the necessary conductivity.

[0004]

However, as described above, when physically soft pure silver is used for the current-carrying lead, since the strength is not sufficient, deformation may occur due to electromagnetic force,
May cause breakage. Further, when a metal having a strength other than pure silver is used, even if the strength is secured, the electrical conductivity is deteriorated, and the increase in resistivity increases heat generation during energization. Therefore, it cannot be used as a conducting lead.

Therefore, an object of the present invention is to provide a current-carrying lead of an oxide superconducting coil which is excellent in strength and electric conductivity.

[0006]

In order to achieve the above-mentioned object, the present invention provides an oxide superconducting coil for supplying current to an oxide superconducting coil formed by concentrically winding an oxide superconducting wire. In the energization lead connected to
It is composed of a silver alloy in which an additive that disperses and strengthens the oxide generated by internal oxidation is added to silver.

According to this structure, the current-carrying lead using the silver alloy can improve the lack of strength, which is a drawback of pure silver, without impairing the electrical conductivity. The composition of this silver alloy is Ag-Mg-Ni, Ag-Mg, Ag-Ni, A
It can be either g-Mg-Zr. According to this structure, the mechanical strength can be improved while ensuring the electrical conductivity, and the silver alloy suitable for the current-carrying lead can be obtained.

In this case, it is desirable that the silver alloy contains 0.01 to 1.5 at% of additives other than Ag. According to this configuration, the additive amount is 0.01 to 1.5 at%.
The mechanical strength can be improved several times when selected in the range.

[0009]

1 is a perspective view showing an embodiment of a current-carrying lead of an oxide superconducting coil according to the present invention. As shown in FIG. 1, the oxide superconducting coil 101 is
Made by winding a band-shaped superconducting wire 102 in a spiral shape,
At both ends thereof, a battledore-shaped energizing leads 103a and 103b are provided.
Are connected to stand upright.

The superconducting wire 102 contains Bi (bismuth): Sr (strontium): Ca (calcium):
The superconductor powder having a composition ratio of Cu (copper) = 2: 2: 1: 2 is dissolved in a solution, and the solution is applied to a metal tape. The oxide superconducting coil 101 is manufactured by using this as a single pancake coil having an inner diameter of 15 mm, an outer diameter of 50 mm, a total number of turns of 70, and a total length of wire rod of 7 m.

A silver alloy is used for the current-carrying leads 103a and 103b. The composition is, for example, Ag (silver)-
0.026 at% Mg (magnesium) -0.01 at
% Ni (nickel), which is connected and fixed to the oxide superconducting coil 101 using silver solder. Oxide superconducting coil 10 in which current-carrying leads 103a and 103b are connected
No. 1 is partially melted and gradually cooled at a maximum temperature of 885 ° C.
In this process, the current-carrying leads 103a and 103b are heat-treated to be dispersed and strengthened by internal oxidation of the additive, and the strength is improved.

The composition of the silver alloy used for the current-carrying leads 103a and 103b is Ag-Mg-Ni and Ag-Mg-Ni.
A combination of Mg, Ag-Ni, and Ag-Mg-Zr (Zr: zirconium) can also be used. Here, the optimum conditions of the conducting leads 103a and 103b will be examined. Since the stress for deforming pure silver is 40 MPa, the required strength cannot be obtained without alloying. Therefore,
The following examinations are necessary.

FIG. 2 is a characteristic diagram showing the dependence of the mechanical strength of an Ag-Mg-Ni alloy on the added concentration. The vertical axis represents the stress by which the base material is deformed (yield stress), and the horizontal axis represents the addition amount of the additive. The characteristics shown here indicate the results of a tensile test in which a silver alloy base material was formed into a tape, and a strain gauge was attached to the tape. The mechanical strength is improved depending on the amount of the additive added, but when the addition amount exceeds 1.5 at%, the mechanical strength is not significantly improved.

FIG. 3 is a characteristic diagram showing the electrical conductivity of the cryogenic portion (77K). As is clear from the figure, the electrical conductivity decreases as the amount of the additive added increases, but 1.5
It can be said that the addition of up to at% is a sufficient practical level. From these, it can be said that the optimum addition amount is from 0.01 at% where the mechanical strength exceeds 80 MPa to 1.5 at% at which the mechanical strength does not increase so much.

FIG. 4 is a perspective view showing another embodiment of the present invention. A plurality of oxide superconducting coils 101a, 101b, 101c, 101d having the configuration shown in FIG. 1 are arranged coaxially in the vertical direction, and the coils are connected by inter-coil conducting leads 104, and the lowest conducting leads 105 are provided.
The (power supply side) has a shape in which the length of the energization lead 103 is extended. With this configuration, the same effect as in the case of FIG. 1 can be obtained.

[0016]

EXAMPLES The present inventors conducted experiments on the current-carrying leads 101a and 101b in the configuration of FIG. Here, the size of the energizing lead is 15 mm in width and 0.3 in thickness.
mm, length 70 mm, and this was energized in 4.2K, 12T. As a result, the calorific value of the lead is 1.2 for pure silver.
.About.1.3 times, the mechanical strength was improved to 2 to 3 times, and the lead was not deformed or broken after the measurement.

Further, the present inventors have found that Ag-0.05 at.
% Mg material was also examined by the same method and conditions as above, but in this case as well, no deformation or breakage was observed in the current-carrying lead. Furthermore, the present inventors have found that Ag-0.
Also for 022 at% Mg-0.015 at% Zr,
The same method and conditions as described above were examined, but in this case as well, no deformation or breakage was observed in the current-carrying lead.

Furthermore, the present inventors have found that Ag-0.05 at.
% Ni material was also examined by the same method and conditions as above, but in this case as well, no deformation or breakage was observed in the current-carrying lead. The present invention can be applied not only to the current-carrying leads shown in FIGS. 1 and 4 but also to the sample holder shown in FIG. This sample holder has two current leads 106a, 106b arranged in parallel,
In addition to fixing the upper portions of the current leads 106a and 106b, the current leads 106a and 10b are supported by the disc-shaped flange 107 having the shaft body 107a and the shaft body 107a.
Each of the supporters 108a and 108b for fixing 6b in the middle is provided.

In such a structure, the current lead 10
The silver alloy according to the present invention can be used for 6a and 106b. The effect obtained from this is as described above.

[0020]

As is apparent from the above, according to the present invention, since the silver alloy is used as the material of the current-carrying lead, the lack of strength, which is the defect of pure silver, is improved without impairing the electrical conductivity. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a current-carrying lead of an oxide superconducting coil according to the present invention.

FIG. 2 is a characteristic diagram showing the addition concentration dependence of the mechanical strength of the silver alloy Ag—Mg—Ni used in the present invention.

FIG. 3 is a characteristic diagram showing electric conductivity of a cryogenic portion (77K).

FIG. 4 is a perspective view showing another embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of a sample holder showing an application example of the present invention.

FIG. 6 is a perspective view showing a configuration of a current-carrying lead of a conventional oxide superconducting coil.

[Explanation of symbols]

 101 oxide superconducting coil 102 superconducting wire 103a, 103b, 105 energizing lead 104 energizing lead between coils

Claims (3)

[Claims] 1. An oxide produced by internal oxidation in a current-carrying lead connected to an oxide superconducting coil for supplying current to the oxide superconducting coil formed by concentrically winding an oxide superconducting wire. A current-carrying lead of an oxide superconducting coil, characterized in that the current-carrying lead is composed of a silver alloy in which a dispersion-strengthening additive is added to silver. 2. The silver alloy is Ag-Mg-Ni, Ag-
The current-carrying lead for an oxide superconducting coil according to claim 1, which is one of Mg, Ag-Ni, and Ag-Mg-Zr. 3. The silver alloy contains 0.0% or more of additives other than Ag.
The current-carrying lead of the oxide superconducting coil according to claim 2, characterized in that it is 1 to 1.5 at%.