JP2000091651A - Superconducting current lead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact superconducting current lead by reducing the deterioration of the critical current value of a superconducting conductor. SOLUTION: A first oxide superconducting conductor (positive side) 11 is arranged on a supporting member 14 having a low coefficient of thermal conductivity and a second oxide superconducting conductor (negative side) 12 is arranged on a supporting member 13 having a low coefficient of thermal conductivity and the members 13 and 14 are coaxially arranged in parallel with each other. Since the flowing directions of the currents flowing to the conductors 11 and 12 are opposite to each other, the magnetic fields impressed upon the conductors 11 and 12 are canceled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current lead structure connected to both ends of a superconducting coil housed in a liquid helium container in a vacuum insulated container together with liquid helium, and for passing current from an external power supply.

[0002]

2. Description of the Related Art Since a superconducting coil of a superconducting magnet device is cooled by a cryogenic refrigerant such as liquid helium to maintain a superconducting state, a liquid in a vacuum insulation container having a radiation shield using liquid nitrogen and a multilayer insulation layer is provided. It is stored in a state immersed in helium. In addition, the current lead is cooled by a low-temperature helium gas that is vaporized from liquid helium, and is configured to minimize intrusion of heat from the room temperature side and Joule heat generated by the current lead from entering the cryogenic part. . In the past, electric current conductors such as copper were used for current leads, but copper is an electric conductor and also a good heat conductor. There is a disadvantage that helium vaporization loss increases.

Therefore, an oxide superconductor, which is a high-temperature superconductor, is used on the low-temperature side of the current lead to reduce the Joule heat to zero, and at the same time, greatly reduce the heat entering the cryogenic side by utilizing its low thermal conductivity. Current leads are used. Such a current lead is composed of a high-temperature conductor made of a good electrical conductor such as copper and a low-temperature conductor made of an oxide superconductor such as a silver sheath oxide superconductor. The parts are connected by a conductive coupling part.

[0004]

The problem in the case of using a current lead using an oxide superconducting conductor having a low heat penetration as the conductor of the low-temperature side conductor is that the critical current value is reduced by the self-magnetic field of the superconducting conductor. Deterioration. Further, as the number of silver sheath materials required increases with an increase in the energizing current, the shape of the installation portion of the oxide superconductor in the low-temperature portion increases, so that a more compact shape is required. .

An object of the present invention is to provide a current lead having a compact structure in which the deterioration of the critical current value of the superconducting conductor is reduced.

[0006]

In order to solve the above-mentioned problems, in the present invention, a high-temperature-side conductor portion made of an electric conductor and a low-temperature conductor made of an oxide superconducting conductor obtained by laminating a tape-shaped oxide superconducting wire are used. A pair of conductor portions composed of a side conductor portion, and the oxide superconducting conductor of one of the conductor portions is arranged on a cylindrical low thermal conductivity support member with its tape surface parallel to the circumferential direction in the cylindrical coordinate system, The tape surface of the oxide superconducting conductor of the other conductor part is placed on a cylindrical low thermal conductivity support member having an outer diameter different from the outer diameter of the cylindrical low thermal conductivity support member in a circumferential direction in a cylindrical coordinate system. The two low thermal conductivity support members were arranged in parallel and coaxially in parallel.

In the above superconducting current lead,
An insulating spacer was arranged between both oxide superconducting conductors.

[0008]

FIG. 1 is a perspective view of a low-temperature side conductor portion of a superconducting current lead showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view of FIG. In FIG. 1, 11
Is a first oxide superconducting conductor (positive side), 12 is a second oxide superconducting conductor (minus side), and 13 and 14 are supporting members having a low thermal conductivity. Low thermal conductivity support member 13
And 14 are each cylindrical and are arranged coaxially parallel. The first and second oxide superconducting conductors 11 and 12 are formed by laminating tape-shaped oxide superconducting wires, and the tape surfaces are respectively formed on cylindrical support members 13 and 14 in a circumferential direction in a cylindrical coordinate system. They are arranged in parallel. The first oxide superconducting conductor (positive side) 11 arranged on the inner low thermal conductivity support member 14 is connected to the positive side of a power supply installed outside, and a current flows in the direction shown in FIG. The second oxide superconducting conductor (minus side) 12 arranged on the support member 13 having low thermal conductivity is connected to the minus side of a power supply installed outside, and a current flows in the direction shown in the figure. In other words, the directions of the two currents are opposite to each other, and among the magnetic fields applied to the oxide superconductor by the mechanism described later, particularly the magnetic field in the direction perpendicular to the tape surface is canceled and reduced, and the criticality is increased. The deterioration of the current value is reduced.

It is to be noted that the first oxide superconducting conductor 11 is disposed on the outer low thermal conductivity support member 13 and the second oxide superconducting conductor 12 is disposed on the inner low thermal conductivity support member 14. The same effect can be obtained. In the configuration of the low-temperature side conductor shown in FIGS. 1 and 2, particularly, if the support members 14 and 13 are formed of a metal having a low thermal conductivity such as stainless steel, the oxide superconductor 11 Or 12 quench, a current flows through the support member 14 or 13, so that the support member 1
3 and 14 can also have a function as a protective material.

In the configuration of the low-temperature side conductor shown in FIGS. 1 and 2, the first oxide superconducting conductor 11 disposed on the inner diameter side support member 14 and the outer diameter side support member 13 are disposed. The same number of second oxide superconducting conductors 12 are provided, and the circumferential position of each conductor of the first oxide superconducting conductor 11 and the circumferential position of each conductor of the second oxide superconducting conductor 12 And are arranged so as to face each other so as to match each other in a one-to-one relationship. When the first oxide superconducting conductor 11 on the inner diameter side and the second oxide superconducting conductor 12 on the outer diameter side are arranged in such a positional relationship, when currents in opposite directions flow through both conductors. In addition, among magnetic fields applied in the oxide superconducting conductor, particularly, a magnetic field in a direction perpendicular to the tape surface is canceled and reduced, so that deterioration of the critical current value is reduced.

The details of the mechanism for reducing the deterioration of the critical current value are as follows. That is, the conductors of the first oxide superconducting conductor 11 on the inner diameter side and the conductors of the second oxide superconducting conductor 12 on the outer diameter side are in a positional relationship facing each other as described above. When the directions of the currents flowing in the material superconducting conductor are opposite to each other, the magnetic field in the radial direction of the cylindrical support member, that is, the direction perpendicular to the tape surface, of the magnetic field applied in both oxide superconducting conductors is Reduced by working in directions that cancel each other,
The magnetic field in the circumferential direction of the support member, that is, in the direction parallel to the tape surface, increases in reverse by acting in directions that add to each other.
However, the tape-shaped oxide superconducting wire forming the oxide superconducting conductors 11 and 12 has a critical current value greatly reduced with respect to a magnetic field applied in a direction perpendicular to the tape surface. There is a characteristic that the critical current value does not decrease so much for a magnetic field applied in any direction. Therefore, the decrease in the magnetic field in the direction perpendicular to the tape surface according to the above configuration acts very effectively on the reduction in the critical current value, and reduces the critical current value as the oxide superconductor. be able to.

In the configuration of the low-temperature side conductor shown in FIGS. 1 and 2, the oxide superconductors 11 and 12 are formed by laminating tape-shaped oxide superconducting wires, but only one layer is formed. The oxide superconducting conductors 11 and 12 may be formed of the tape-shaped oxide superconducting wire of the present invention. Further, in the configuration of the low-temperature side conductor shown in FIGS. 1 and 2, the oxide superconducting conductor is formed of a tape-shaped oxide superconducting wire. Even in the formed configuration, it is possible to reduce the deterioration of the critical current value by utilizing the magnetic field direction dependency of the critical current-magnetic field strength characteristic as described above. Note that the bulk oxide superconductor applicable in this case has a cross-sectional shape such as a rectangular shape in which the length of the side in any direction is longer than the other, and has a larger width. The side surface corresponds to the tape surface of the tape-shaped oxide superconducting wire, and has the same magnetic field direction dependence of the critical current-magnetic field strength characteristics as in the tape-shaped oxide superconducting wire. The bulk-shaped oxide superconductor having such a shape is provided on the cylindrical support members 13 and 14 such that the wider surfaces thereof are parallel to the circumferential direction in the cylindrical coordinate form, similarly to the configuration shown in FIGS. The conductors are arranged so that the conductors on the inner diameter side and the conductors on the outer diameter side have a positional relationship to face each other. With such a configuration, when currents in opposite directions flow through both the inner diameter side and the outer diameter side conductors, among the magnetic fields applied in the oxide superconductor, particularly the bulk oxide superconductor The magnetic field in the direction perpendicular to the wider side surface is canceled and reduced, so that the deterioration of the critical current value is reduced.

FIG. 5 is a conceptual diagram of a superconducting device using a superconducting current lead according to an embodiment of the present invention. In FIG. 5, reference numeral 51 denotes a power source, 53 denotes a high-temperature side conductor portion made of a good electric conductor such as copper, 54 denotes a flange, 55 denotes a vacuum insulated container,
56 is a liquid nitrogen shield, 57 is a superconducting coil, 58 is GHe (helium gas), and 59 is LHe (liquid helium). In addition, the first oxide superconducting conductor 11 is disposed on the outer peripheral surface of the low thermal conductivity support member 14, and the second oxide superconducting conductor 12 is disposed on the outer peripheral surface of the low thermal conductivity support member 13, It constitutes a pair of low-temperature side conductors. The high-temperature side conductor 53 is connected to a power supply 51 installed in a normal temperature environment via a normal temperature terminal 71. Also, 1
Each of the paired high-temperature side conductor portions 53 is connected to the first oxide superconductor 11 and the second oxide superconductor 12 via the intermediate connection portions 72 and 72A. Further, each of the pair of coil terminals 74 of the superconducting coil 57 immersed in the liquid helium 59 is connected to the first oxide superconducting conductor 11 and the second oxide superconducting via the low-temperature terminals 73 and 73A. It is connected to the conductor 12. As described above, the power supply 51 is connected via the pair of conductors in which the high-temperature-side conductor and the low-temperature-side conductor are connected in series.
Supplies power to superconducting coil 57. FIG.
In FIG. 7, the configuration of the low thermal conductivity support member 14 on the inner diameter side and the first oxide superconducting conductor 11 is shown by partially crushing the low thermal conductivity support member 13 on the outer diameter side.

FIG. 3 is a longitudinal sectional view of a low-temperature side conductor portion of a superconducting current lead showing another embodiment of the present invention, and FIG. 4 is an external view of a spacer in FIG. In FIG. 3, a spacer 2 is provided between a first oxide superconducting conductor 11 and a supporting member 13 for a second oxide superconducting conductor 12.
1 to ensure insulation between the oxide superconductors 11 and 12. The configuration of the embodiment shown in FIG. 3 is the same as the embodiment shown in FIG. 1 except that a spacer 21 is provided. The length of the spacer 21 is the oxide superconducting conductor 11,
12 may be the same length, but the oxide superconducting conductor 1
A structure in which a plurality of spacers 21 as shown in the drawing are arranged in the length direction in a range where 1 and 12 are present may be adopted.

Electromagnetic forces generated by the oxide superconducting conductors 11 and 12 at the time of energization act in directions repelling each other, but the oxide superconducting conductors 11 and 12 are fixed by the support members 13 and 14 and the spacer 21 so as not to be distorted. I have. Further, as shown in FIG. 4, since the helium gas 58 can pass through the hole formed in the spacer 21, the first oxide superconductor 11 (positive side) 11 and the second oxide superconductor 11 (Minus side) The temperature difference between 12 is hardly generated. The spacer 21 is made of an insulating material such as aluminum nitride.

[0016]

According to the present invention, the low-temperature side conductor of the current lead using two conventional oxide superconducting conductors has a single coaxial structure, and the coaxial low-temperature side conductor has the same structure. The conductor structure on the inner diameter side and the outer diameter side is formed by laminating a tape-shaped oxide superconducting wire, and the oxide superconducting conductor is placed on a cylindrical low thermal conductivity support member with its tape surface parallel to the circumferential direction in the cylindrical coordinate system. Since the magnetic field applied in the direction perpendicular to the tape surface in the oxide superconducting conductor is cancelled and reduced in particular, the deterioration of the critical current value of the oxide superconducting conductor is reduced. In addition, the coaxial structure allows the oxide superconductor, whose cross-sectional area increases with increasing capacity, to be compactly arranged as a pair of low-temperature side conductors. Both have had the high temperature side and low temperature side can retain compatibility with current lead made of a good electrical conductors such as copper.

[Brief description of the drawings]

FIG. 1 is a perspective view of a low-temperature side conductor portion of a superconducting current lead showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a longitudinal sectional view of a low-temperature side conductor portion of a superconducting current lead showing a different embodiment of the present invention.

FIG. 4 is an external view of a spacer in FIG. 3;

FIG. 5 is a conceptual diagram of a superconducting device using a superconducting current lead according to an embodiment of the present invention.

[Explanation of symbols]

11: first oxide superconducting conductor (positive side), 12: second oxide superconducting conductor (minus side), 13, 14: low thermal conductivity support member, 21: spacer, 42: gap (G
He channel), 58 ... He (helium gas).

Claims (2)

[Claims] 1. A pair of a conductor portion composed of a high-temperature-side conductor portion made of a good electrical conductor and a low-temperature-side conductor portion made of an oxide superconducting conductor formed by laminating a tape-shaped oxide superconducting wire. The oxide superconducting conductor of the conductor portion is disposed on a cylindrical low thermal conductivity support member with its tape surface parallel to the circumferential direction in the cylindrical coordinate system, and the oxide superconducting conductor of the other conductor portion is connected to the cylindrical low thermal conductivity. The tape surface was arranged on a cylindrical low thermal conductivity support member having an outer diameter dimension different from the outer diameter dimension of the support member in parallel with the circumferential direction in the cylindrical coordinate system, and both low thermal conductivity support members were arranged coaxially parallel. A superconducting current lead. 2. The superconducting current lead according to claim 1, wherein an insulating spacer is disposed between both oxide superconducting conductors.