JPH08102226A - Composite superconductive conductor - Google Patents

Abstract

PURPOSE: To try to reduce coupling loss by storing, in a stabilizing Cu, a plurality of superconductive element wires embedded in Pb-Sn solder to which a third element is added. CONSTITUTION: Pb (40-mx) weight%, Sn (60-nx) weight% (m is 0<m, n<1; m+n=1) and a third element xweight% are contained, and a solder 3 is obtained. Flux is applied to the surface of superconductive element wires 2 twisted in Rutherford type, etc., and the wall surface of a groove to which a stabilizing Cu material 4 is to be soldered. Next a plurality of superconductive element wires 2 are bundled and stored in the groove of the stabilizing Cu material 4, and a storage body is obtained. This storage body is soaked in a solder vessel filled with a molten solder 3, a plurality of superconductive element wires 2 in the storage body are embedded in the solder 3, then a cover material 6 made of Cu is attached to the surface of the solder 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite superconducting conductor in which a plurality of superconducting element wires are embedded in solder, and more particularly to a composite superconducting conductor using solder having a small coupling loss.

[0002]

2. Description of the Related Art Conventionally, as a superconducting conductor capable of carrying a large current, a plurality of superconducting element wires are bundled and a general eutectic solder such as Pb-60Sn solder (Pb is 60% by weight).
It is known that it is formed by being embedded in a solder (hereinafter, referred to as “w%”) mixed with Sn and housed in a conductor reinforcing material.

7 to 9 show cross-sectional structures of composite superconducting conductors produced by this method. The composite superconducting conductor 31 shown in FIG. 7 is a U-shaped stabilizing Cu that is a reinforcing material.
A plurality of twisted superconducting wires 32 housed inside the groove of the material 34 are embedded in a solder 33, and a lid member 36 made of Cu is mounted on the surface of the solder 33. A Nb-Ti filament or the like is used as the superconducting element wire 32 (Susumu Shimamoto et al., "LCT for Nuclear Fusion".
Development of Superconducting Magnet ”, Hitachi Review, Vol.71, pp21-2
8, 1989).

Further, the composite superconducting conductor 41 shown in FIG.
A superconducting cable 45 composed of a plurality of twisted superconducting wires 42 housed in the groove of a U-shaped stabilized Cu-Ni material 44 which is a reinforcing material is embedded in a solder 43. As the superconducting element wire 42, Nb-T in Cu is used.
The one with embedded i-filament is used.
Nagato et al., "Development of superconducting conductor for LHD helical coil", Proc. Of the 50th Low Temperature Engineering Superconductivity Society, pp86, 1993
reference). The composite superconducting conductor 31 shown in FIGS. 7 and 8
All of Nos. 41 to 41 are maintained in a superconducting state by being immersed in liquid helium.

On the other hand, the composite superconducting conductor 51 shown in FIG.
A "cable-in-conduit" type composite superconducting conductor, in which a plurality of stabilizing Cu materials 54a and 54b are arranged in a hollow tubular conduit 56 made of SuS (stainless steel material) and surrounded by these stabilizing Cu materials. The superconducting cable 55 stored in the enclosed space is embedded in the solder 53,
The superconducting cable 55 is maintained in a superconducting state by forcibly flowing supercritical helium into the groove 59 of the U-shaped stabilized Cu material 54a. As the strand of the superconducting cable 55, Nb3 Sn filament or the like is used (F. Hosono et al., "AC L
osses of the Toroidal Model Pancake (Hollow Conduc
tor Type) ", IEEE Trans. Applied Superconductivit
y, Vol.3, 1992, pp.535-538).

[0006]

However, in the above-mentioned conventional composite superconducting conductor in which superconducting element wires are bundled, a large coupling loss occurs due to the flow of a coupling current between the element wires. Coupling loss is generally proportional to the time constant τ, which indicates the rate at which the coupling current decays. The time constant τ is expressed by the following equation τ = μo / 2r (lp / 2π) 2 ... (1). In the above formula (1), μo represents the magnetic permeability of vacuum, r represents the resistance value of the coupling current path (hereinafter referred to as “equivalent resistance value”), and lp represents the twist pitch.

The equivalent resistance value r is a value determined by the contact resistance between the wires, the contact area, or the resistance value of the intervening material. Taking the composite superconducting conductor shown in FIG. 8 as an example,
Since Cu, Cu-Ni, and Pb-Sn solder are interposed between the superconducting element wires, the equivalent resistance value r (unit: Ωm) is
The following formula

[Equation 1] Is represented by

In the above formula (2), lCu (unit: m) is the length of the Cu portion in the coupling current path, and 1CuNi (unit: m).
m) is the length of the Cu-Ni portion in the coupling current path,
PbSn (unit: m) is the length of the solder part in the coupling current path, and ρCu (unit: Ωm) is C at 4.2K.
The specific resistance of u, ρCuNi (unit: Ωm) is the specific resistance of Cu-Ni at 4.2K, and ρPbSn (unit: Ωm) is 4.
The specific resistance of the solder at 2K is shown.

From the above equations (1) and (2), when a solder having a small specific resistance value of about 0.6 × 10 −9 Ωm is used like the conventional composite superconducting conductor, the equivalent resistance value is Becomes smaller and the time constant τ decreases, so that the coupling loss increases. In particular, the coupling loss becomes large when pulse energization or AC energization is performed. If this coupling loss becomes larger than a certain value, the possibility of quenching the superconducting coil formed by winding the composite superconducting conductor increases.

Therefore, an object of the present invention is to provide a composite superconducting conductor having a small coupling loss.

[0011]

In order to solve the above problems, a composite superconducting conductor according to a first aspect of the present invention stabilizes a plurality of superconducting element wires embedded in solder.
In the composite superconducting conductor housed in u, the solder is formed by adding a third element to Pb-Sn solder.

In the above, as the third element, S
Either b or In may be added.
Is α, the weight ratio of the third element is x percent, and m and n are 0 <m <1,0 <n <1, m + n = 1.
When the real number is
x) percent Pb, a weight ratio (60−nx) percent Sn, and a weight ratio x percent α. Further, the third element may be Sb, and the weight ratio x% of the third element may be set to a value within the range of 0 <x ≦ 10.
n, and the weight ratio x percent of the third element is 0 <x
You may make it the value within the range of <= 15.

The composite superconducting conductor according to the second aspect of the present invention is a composite superconducting conductor in which a plurality of superconducting element wires embedded in solder are housed in stabilized Cu. It is configured by adding a third element and a fourth element to Pb-Sn solder.

In the above, the third element may be Sb and the fourth element may be In. Further, the third element is α, the weight ratio of the third element is y percent, the fourth element is β, the weight ratio of the fourth element is z percent, and x = y + z. , M,
When n is a real number such that 0 <m <1, 0 <n <1, m + n = 1, the solder has a weight ratio (40-mx) percent Pb and a weight ratio (60-nx) percent Sn.
And a weight ratio y percentage α and a weight ratio z percentage β. Alternatively, the third
Element is Sb, the fourth element is In, the weight ratio y percent of the third element is a value within the range of 0 <y ≦ 10, and the weight ratio z percent of the fourth element is May be set to a value within the range of 0 <z ≦ 15.

[0015]

According to the present invention having the above structure, as a solder in which a superconducting element wire is embedded in a composite superconducting conductor, a solder obtained by adding a third element to Pb-Sn solder instead of the conventional Pb-Sn solder. Or, since the solder in which the third element and the fourth element are added to Pb-Sn solder is used, the specific resistance at 4.2K becomes large. As a result, the equivalent resistance value increases and the time constant of the coupling loss decreases,
The coupling loss of the composite superconducting conductor is reduced.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional structure of a composite superconducting conductor which is a first embodiment of the present invention. As shown in FIG. 1, this composite superconducting conductor 1 has a U-shaped stabilized Cu material 4
A plurality of superconducting wires 2 housed inside are embedded in solder 3, and a lid member 6 made of Cu is mounted on the surface of the solder 3.

The solder 3 is formed by adding a third element to Pb-Sn solder (hereinafter, this solder 3 is referred to as "third element-added solder"). As the solder 3, for example, 37.5w% Pb and 57.5w% S are used.
37.5% P which is a solder consisting of n and 5w% Sb
b-57.5% Sn-5% Sb solder and 37.5w%
37.5% Pb-57.5% Sn-5% I which is a solder consisting of Pb, 57.5w% Sn and 5w% In.
n solder is preferred.

The superconducting element wire 2 is made of a known superconducting material, and for example, a Nb-Ti filament or the like is suitable.

A procedure for manufacturing the composite superconducting conductor 1 will be described. First, the superconducting wire 2 twisted in a Rutherford type, etc.
Flux is applied to the inner surface of the groove and the inner wall surface of the groove for soldering the stabilized Cu material 4. Next, a plurality of superconducting element wires 2 are bundled and housed in the groove of the stabilized Cu material 4 (hereinafter referred to as "housing body"). Next, store this container 230
A plurality of superconducting element wires 2 in the container are embedded in the solder 3 by passing through a solder bath filled with the solder 3 which has been heated and melted. Finally, the lid member 6 made of Cu is mounted on the surface of the solder 3.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 shows a cross-sectional structure of a composite superconducting conductor which is a second embodiment of the present invention. As shown in FIG. 2, this composite superconducting conductor 11 has a U-shaped stabilizing C
Multiple superconducting cables 1 housed in u-Ni material 14
5 is embedded in the solder 13 and is configured.

The solder 13 is a third element-added solder made by adding a third element to Pb-Sn solder. The solder 13 is, for example, 37.5% Pb-57.5% Sn-5% Sb, which is a solder composed of 37.5 w% Pb, 57.5 w% Sn, and 5 w% Sb.
37.5% Pb- which is a solder or a solder consisting of 37.5 w% Pb, 57.5 w% Sn and 5 w% In.
57.5% Sn-5% In solder is preferred.

The superconducting element wire 12 is made of a known superconducting material, and is preferably made of, for example, Cu in which an Nb-Ti filament is embedded.

A procedure for manufacturing the composite superconducting conductor 11 will be described. First, a plurality of superconducting wires 12 are twisted to produce a superconducting cable 15. Next, flux is applied to the surface of the superconducting cable 15 and the inner wall surface of the groove of the stabilizing Cu—Ni material 14 to be soldered. Next, stabilized Cu-Ni material 1
A plurality of superconducting cables 15 are housed in the groove 4 to produce a housing. Next, the plurality of superconducting cables 15 in the storage body are soldered to each other by passing the storage body through a solder bath filled with the melted solder 13 heated to 230 ° C.
Buried inside.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a cross-sectional structure of a composite superconducting conductor which is a third embodiment of the present invention. Figure 3 (A)
As shown in FIG. 2, the composite superconducting conductor 21 is a “cable-in-conduit” type composite superconducting conductor, and
Hollow tubular conduit 26 made of (stainless steel)
Twelve U-shaped stabilizing Cu materials 24a and two stabilizing Cu materials 24b are arranged inside, and the superconducting cable 25 housed in the space surrounded by these stabilizing Cu materials is solder 23. The superconducting cable 25 is buried in the U-shaped stabilizing Cu material 24a, and the superconducting cable 25 is maintained in a superconducting state by forcibly flowing supercritical helium into the groove 29.

As shown in FIG. 3 (B), the superconducting cable 25 includes a plurality of superconducting element wires 22 formed of a superconducting material such as Nb3Sn and a covering 27 made of, for example, a Cu--Sn alloy. Is coated with.

Since the composite superconducting conductor 21 uses the stainless steel material as the conduit material, the mechanical strength as the conductor is improved.

The solder 23 is a third element-added solder made by adding a third element to Pb-Sn solder. The solder 23 is, for example, 37.5% Pb-57.5% Sn-5% Sb, which is a solder composed of 37.5 w% Pb, 57.5 w% Sn, and 5 w% Sb.
37.5% Pb- which is a solder or a solder consisting of 37.5 w% Pb, 57.5 w% Sn and 5 w% In.
57.5% Sn-5% In solder is preferred.

A procedure for manufacturing the composite superconducting conductor 21 will be described. First, a superconducting cable 25 in which a plurality of superconducting element wires 22 are covered with a cover 27 is produced, and a plurality of the superconducting cables 25 are twisted to form a rectangular whole shape. Next, flux is applied to the surface of the superconducting cable 25 and the wall surfaces of the stabilizing Cu materials 24a and 24b to be soldered. Next, the plurality of superconducting cables 25 are housed in the housing space formed by the stabilized Cu materials 24a and 24b to produce a housing. Next, a plurality of superconducting cables 25 in the storage space of the storage body are embedded in the solder 23 by filling the storage space of the storage body with the solder 23 heated to 230 ° C. and melted.

Next, the results of measuring the specific resistance of the composite superconducting conductor formed by adding the third element to the Pb-Sn solder as described above will be described. The specific resistance was measured by the specific resistance measuring device shown in FIG. As shown in FIG.
The specific resistance measuring device 60 includes a cylindrical first container 61 with a bottom.
And a bottomed tubular second container 62 arranged to accommodate the first container 61 and a bottomed tubular third container 63 arranged to accommodate the second container 62. .

A ring-shaped background magnet 66 is arranged in the first container 61, and a support tool 68, in which a subject 67 for measuring a specific resistance is wound around its tip without induction, is provided at a central opening of the background magnet 66. Has been inserted inside. The inside of the first container 61 is filled with liquid helium 64, and the subject 67 and the background magnet 6 are
6 is immersed in liquid helium 64. First container 6
A lid 73 having a good heat insulating property is attached to the first opening.
Therefore, the first container 61, the second container 62, and the third container 6
3 and the lids 73 and 74 form a heat insulating container.

The side surface of the second container 62 has a double structure, and the inside thereof is filled with liquid nitrogen 65. A vacuum layer 69 is provided between the first container 61 and the second container 62 and between the second container 62 and the third container 63. A lid 74 having good heat insulation is attached to the openings of the second container 62 and the third container 63.

A conductor wire 75 is connected to one end of a subject 67 wound in a coil on the tip of the support 68, and a conductor wire 76 is connected to the other end. A power source 72 is connected to the conductor wire 76, and the conductor wire 76 is connected to the power source 72 via a shunt resistor 71. An XY recorder 70 is connected to both ends of the shunt resistor 71.

Next, the measuring method will be described. First, a current is supplied from the power source 72 to the subject 67 via the lead wires 75 and 76. The voltage at this time is measured by the XY recorder 70 from both ends of the shunt resistor 71. The generated voltage is V (unit: V) when the maximum energizing current value is I (unit: A)
And the length of the subject 67 is L (unit: m) and the cross-sectional area of the subject 67 is S, the specific resistance ρ (unit: Ωm)
Is expressed by the following equation ρ = V · S / I · L (3) The specific resistance measurement was performed when the energizing current value I was 10 A, and the values at 4.2 K and 4.3 T were obtained.

The measurement results are shown in FIG. As shown in FIG. 5, in this measurement, when the third element to be added is Sb, the specific resistance in the case where 0 to 10 w% of Sb is added to Pb-60Sn solder is calculated. Is I
In the case of n, 0 to 15w% of In is added to Pb-60Sn solder.
The specific resistances in the case where was added were obtained respectively.

First, in the case where the third element to be added is Sb, if the addition concentration is increased from 0 to 3w%, the specific resistance increases as compared with the case where Sb is not added, but the addition is made at about 3w% as a boundary. It was found that the resistivity decreased with increasing concentration. When the third element to be added is In,
It was found that when the added concentration was increased from 0 to 10 w%, the specific resistance was increased as compared with the case where In was not added, but when the added concentration was increased with 10 w% as the boundary, the specific resistance was decreased. If the specific resistance increases, the equivalent resistance value increases, and as a result, the time constant of the coupling loss decreases, so that the coupling loss of the composite superconducting conductor is reduced.

However, whether the third element to be added is Sb or In, or when the third element addition concentration is increased beyond the boundary point, the specific resistance value is the value when the third element is not added. It is understood that the value is larger than the value of (value on the vertical axis of FIG. 5). Therefore, when the added third element is Sb, the added concentration x is in the range of 0 <x ≦ 10w%, and when the added third element is In, the added concentration x is 0 <x ≦ 10w%.
It was found that the range of 15 w% is an effective range for increasing the specific resistance.

The third element is α, and the concentration added is x (w
%), It is necessary to reduce the composition ratio of Pb and Sn by the amount of α added. If the Pb and Sn are equally reduced, the produced solder will have a weight ratio (40-
x / 2) percent Pb and weight ratio (60-x / 2)
Percent Sn and weight percentage x% α.

However, in general, m and n are set to 0 <m <1,
A real number 0 <n <1, m + n = 1, and P within this range
If subtracted from both b and Sn, the solder produced will consist of Pb at a weight ratio of (40-mx) percent, Sn at a weight ratio of (60-nx) percent, and α at a weight ratio of x percent. .

From the above results, it is considered that the effect of reducing the coupling loss is effective not only when the number of the added elements is one but also when the number of the elements is two. For example, Sb and I
This is the case where both n are added as the third element and the fourth element, respectively. In this case, it can be considered from the graph of FIG. 5 that Sb and In are within the effective range for reducing the coupling loss. For example, with respect to Sb, the addition concentration y is in the range of 0 <y ≦ 10 w% and
For example, the addition concentration z is in the range of 0 <z ≦ 15w%.

The third element is α, and the concentration added is y (w
%), The fourth element is β, and the concentration added is z (w
%) And x = y + z, it is necessary to reduce the composition ratio of Pb and Sn by the amount of addition of α and β. Pb and S
If it is equally reduced from both n, the solder produced will have a Pb of (40-x / 2) percent by weight,
Weight ratio (60-x / 2) percent Sn and weight ratio y
It is composed of α of percentage and β of z percentage by weight.

However, in general, m and n are 0 <m <1,
A real number 0 <n <1, m + n = 1, and P within this range
If subtracted from both b and Sn, the solder produced will have a weight ratio (40-mx) percent Pb, a weight ratio (60-nx) percent Sn, and a weight ratio y percent α. It consists of β in the weight ratio z percent.

Further, it is considered that there is a combination which is effective in reducing the coupling loss even when three or more kinds of elements are added.

Next, the result of measuring the coupling loss of the composite superconducting conductor formed by adding the third element to the Pb-Sn solder as described above will be described. The coupling loss was measured by the coupling loss measuring device shown in FIG. As shown in FIG. 6, this coupling loss measuring device has a bottomed cylindrical heat insulating container 8
1, a ring-shaped background magnet 84 is arranged in the heat insulating container 81, and a subject 85 whose coupling loss is measured and a pickup coil 86 wound around the subject are connected to the background magnet 84. It is inserted in the central opening. Liquid helium 82 is filled in the heat insulating container 81, and the subject 85, the pickup coil 86, and the background magnet 84 are immersed in the liquid helium 82. A lid 83 having a good heat insulating property is attached to the opening of the heat insulating container 81.

A lead wire 88 is connected to one end of a pickup coil 86 wound around the subject 86, and a lead wire 89 is connected to the other end. The other end of each conductor 88, 89 is connected to a shunt resistor 90. The tap output line of the shunt resistor 90 is connected to the integrator 87. A power supply (not shown) and a control device are connected to the background magnet 84.

Next, the measuring method will be described. First, the background magnetic field of the background magnet 84 is changed by a power supply and a control device (not shown). The voltage induced in the subject 85 by this magnetic field fluctuation is detected by the pickup coil 86. Pickup coil 8
The current detected at 6 is conducted to the shunt resistor 90 by the conductors 88 and 89, and is input to the integrator 87 as a voltage. The integrator 87 converts the magnetic flux into the input to obtain the coupling loss of the subject 85.

The measurement results are shown in Table 1.

[Table 1]

As shown in Table 1, whether the third element to be added is Sb or In, the value of the coupling loss is the value when the third element is not added (the value in Pb-60Sn in Table 1). It is proved that it is smaller than 50% to 70%.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention.

For example, in the above-mentioned second embodiment, the superconducting wire embedded in the solder is a U-shaped stabilized Cu--
Although an example in which it is housed in a Ni material has been described, the present invention is not limited to this. For example, a superconducting wire embedded in solder may be housed in a U-shaped stabilized Cu material. You may comprise.

[0050]

As described above, according to the present invention,
Since the Pb—Sn solder to which the third element is added is used as the solder constituting the composite superconducting conductor and the coupling loss of the composite superconducting conductor is reduced, the superconducting coil formed by winding the composite superconducting conductor is The likelihood of quenching can be reduced. Also, the cable in
In the conduit type composite superconducting conductor, the Cr plating on the surface of the superconducting element wire, which has been conventionally performed in order to reduce the coupling current time constant between the element wires, is not required, so the cost for expensive Cr plating is reduced. Can be economically advantageous.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross-sectional structure of a composite superconducting conductor which is a first embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a cross section of a composite superconducting conductor which is a second embodiment of the present invention.

FIG. 3 is a perspective view showing a cross-sectional configuration of a composite superconducting conductor which is a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a method for measuring the specific resistance of the composite superconducting conductor shown in FIGS. 1 to 3.

FIG. 5 is a characteristic diagram showing the specific resistance at 4.2K and 4.3T of the solder containing the third element forming the composite superconducting conductor shown in FIGS. 1 to 3.

6 is a diagram illustrating a method for measuring the coupling loss of the composite superconducting conductor shown in FIGS. 1 to 3. FIG.

FIG. 7 is a cross-sectional view showing a configuration of a conventional example of a composite superconducting conductor.

FIG. 8 is a cross-sectional view showing the configuration of another conventional example of the composite superconducting conductor.

FIG. 9 is a cross-sectional view showing the configuration of another conventional example of the composite superconducting conductor.

[Explanation of symbols]

 1 composite superconducting conductor 2 superconducting element wire 3 solder 4 stabilizing Cu material 6 lid material 11 composite superconducting conductor 12 superconducting element wire 13 solder 14 stabilizing Cu-Ni material 15 superconducting cable 21 composite superconducting conductor 22 superconducting element wire 23 solder 24a, 24b Stabilized Cu material 25 Superconducting cable 26 Conduit 27 Covering body 29 Groove 31 Composite superconducting conductor 32 Superconducting element wire 33 Solder 34 Stabilizing Cu material 36 Lid material 41 Superconducting conductor 42 Superconducting element wire 43 Solder 44 Stabilized Cu-Ni material 45 superconducting cable 51 composite superconducting conductor 53 solder 54a, 54b stabilized Cu material 55 superconducting cable 56 conduit 59 groove 60 resistivity measuring device 61 first container 62 second container 63 third container 64 liquid helium 65 liquid nitrogen 66 background magnet 67 Sample 68 Support tool 69 Vacuum layer 70 XY recorder 71 Shunt resistance 72 Power supply 73,74 Lid 75-78 Conductive wire 80 Coupling loss measuring device 81 Insulation container 82 Liquid helium 83 Lid 84 Background magnet 85 Subject 86 Pickup coil 87 Integral Instrument 88, 89 Conductor 90 Shunt resistance

Claims (9)

[Claims] 1. A composite superconducting conductor in which a plurality of superconducting element wires embedded in a solder are housed in stabilized Cu, wherein the solder is formed by adding a third element to Pb-Sn solder. A composite superconducting conductor characterized in that 2. The composite superconducting conductor according to claim 1, wherein the third element is either Sb or In. 3. The third element is α, the weight ratio of the third element is x percent, and m and n are 0 <m <1,
When the real number is 0 <n <1, m + n = 1, the solder has a weight ratio (40-mx) percent Pb, a weight ratio (60-nx) percent Sn, and a weight ratio x percent α. The composite superconducting conductor according to claim 1 or 2, comprising: 4. The third element is Sb, and the third element
The composite superconducting conductor according to claim 3, wherein the weight ratio x% of the element is a value within the range of 0 <x ≦ 10. 5. The third element is In, and the third element is
4. The composite superconducting conductor according to claim 3, wherein the weight ratio x% of the element is a value within the range of 0 <x ≦ 15. 6. A composite superconducting conductor comprising a plurality of superconducting element wires embedded in solder contained in stabilized Cu, wherein the solder is Pb—Sn solder to which a third element and a fourth element are added. A composite superconducting conductor characterized in that 7. The composite superconducting conductor according to claim 6, wherein the third element is Sb and the fourth element is In. 8. The third element is α, the weight ratio of the third element is y percent, the fourth element is β, the weight ratio of the fourth element is z percent, and x =
y + z and m and n are 0 <m <1,0 <n <1, m + n
When the real number is = 1, the solder has a weight ratio (40
-Mx) percent Pb, a weight ratio of (60-nx) percent Sn, a weight ratio of y percent α, and a weight ratio of z percent β. The composite superconducting conductor described. 9. The third element is Sb, the fourth element is In, and the weight ratio y percentage of the third element is a value within a range of 0 <y ≦ 10. 9. The composite superconducting conductor according to claim 8, wherein the weight ratio z percent of the fourth element is a value within the range of 0 <z ≦ 15.