JPH06290933A - Oxide superconducting double-pancake coil - Google Patents

Abstract

PURPOSE:To lessen an oxide superconducting pancake coil in current loss by a method wherein the oxide superconducting pancake coils are electrically connected together through the intermediary of a bobbin which is large enough in conductive cross-sectional area and excellent in electrical conductivity. CONSTITUTION:Tape wires 1 and 2 both of oxide superconductor compounded with metal base are wound on a tubular conductive bobbin 3 overlapping each other. The tape wires 1 and 2 are wound in opposite directions respectively. The tape wires 1 and 2 are electrically connected to the bobbin 3 by connections 4 and 5, a current is made to flow in the tape wire 1 from outside, pass through the tape wire 2 from the connection 5 via the connection 4 and the bobbin 3, and flow out of the tape wire 2 from outside. By this setup, even if a tape- shaped fragile wire is used, superconducting coils which are small in current loss and easily connected together can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting double pancake coil.

[0002]

2. Description of the Related Art In recent years, oxide superconductors exhibiting a superconducting transition above the temperature of liquid nitrogen have been discovered one after another, and various applications have been tried by processing them into wire rods or tapes. A superconducting electromagnet using an oxide superconducting wire is a typical application example.Since it has a higher transition temperature than conventional metal-based wires, a superconducting coil that operates at liquid nitrogen temperature,
Further, since it exhibits a higher critical magnetic field than conventional materials at a temperature of 20 K or less, it is expected to be applied as an inner layer coil of a strong magnetic field generating hybrid coil.

Recently, a coil for an electromagnet made of an oxide superconducting wire has been actively produced. Known methods for producing the oxide superconducting wire include a metal sheath method, a doctor blade method, a dip coating method and the like. However, since the oxide superconductor is a ceramic, it is very brittle and easily broken. For this reason, in the coil using the oxide superconductor, a wire in the form of a thin tape is often used in order to reduce bending strain, and further, the wire is wound and then formed into a coil. It is manufactured by a so-called wind and react method in which heat treatment is performed.

As the form of the coil used at this time,
There is a so-called pancake coil in which a tape-shaped wire is rolled and solidified. Since the pancake coil is relatively easy to form, it is suitable for a coil using a brittle oxide superconducting wire.

In order to generate a sufficiently uniform high magnetic field by the pancake coil, it is necessary to stack the pancake coils over several layers. When stacking pancake coils, a so-called double pancake-wound coil is often used, which has good connection workability and makes coil-to-coil connection in the coil outer peripheral region where the generated magnetic field is low, but oxide superconductors are fragile. Since it easily breaks and bends, it is very difficult to make a double pancake roll shape. Therefore, a method of connecting the single pancake coil to the inner circumference and the outer circumference of the coil is adopted. A normal conductive metal such as silver is usually used for the conductive wire connecting the coils.

However, since such a metal connecting conductor has a finite electric resistance even at a temperature below the superconducting transition of the tape-shaped superconducting wire, there is a problem that there is a conduction loss and a large amount of heat is generated due to the conduction loss. It was In order to reduce the conduction loss, a connecting conductor with a sufficiently large cross section is necessary compared to the tape-shaped superconducting wire, but using a connecting conductor with a large cross section at the inner peripheral part of the pancake coil disturbs the coil shape, That part becomes the cause of quenching. Also, in the case of pancake coils, it is possible to generate a uniform magnetic field by making the coil stacking distance as small as possible, but using a connecting wire with a large cross-section makes connecting work extremely difficult at small stacking intervals. There was a problem.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a superconducting coil which uses a brittle wire having a tape-like shape, has a small current loss, and is easy to connect between coils.

[0008]

SUMMARY OF THE INVENTION The present invention has a coil having a pipe-shaped conductive bobbin and a tape-shaped wire made of an oxide superconductor compounded with a metal base and wound around the bobbin. An oxide superconducting double pancake coil having two structures stacked in the axial direction of a bobbin, wherein the two coils are wound such that tape-shaped wire rods are in opposite directions, and (EN) An oxide superconducting double pancake coil in which a tape-shaped wire is electrically connected via a bobbin.

The present invention will be described with reference to FIG. Figure 1
FIG. 3 is an explanatory view showing the structure of the double pancake coil of the present invention. Tape-shaped wire rods 1 and 2 made of an oxide superconductor compounded with a metal substrate are wound and overlapped on a pipe-shaped conductive bobbin 3. Tape-shaped wire 1
And 2 are wound so that they are opposite to each other.
The tape-shaped wire rods 1 and 2 are connected to the connecting portions 4 and 5, respectively.
Is electrically connected to the bobbin. The current is, for example,
It enters from the outside of the tape-shaped wire rod 1, passes through the bobbin from the connection portion 4, enters the tape-shaped wire rod 2 from the connection portion 5, and flows out from the outside of the tape-shaped wire rod 2.

At least the surface of the bobbin is required to be electrically conductive. The bobbin is preferably made of metal. When the portion of the bobbin that comes into contact with the oxide superconductor is silver, there is no risk of deteriorating the characteristics of the oxide superconductor, which is preferable. As the bobbin, a pipe made of metal or ceramics having a superconductor layer formed on the inner side, the outer side, or both sides can be preferably used.

In the present invention, the tape-shaped wire comprises an oxide superconductor compounded with a metal substrate. The substrate and the oxide superconductor are not particularly limited, but the substrate of the tape-shaped wire is silver, and the oxide superconductor has Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _y whose crystal c-axis is oriented perpendicular to the tape longitudinal direction.
A thick film (y is the amount of oxygen) is preferable because a long oxide superconductor tape wire having good characteristics can be obtained. In this case, the thickness of the oxide superconductor is preferably 5 to 50 μm in order to obtain a good orientation structure and bending resistance, and prevents cracks due to thermal stress at the interface between silver and the oxide superconductor. For this purpose, the thickness of the base silver tape is preferably 10 to 70 μm.

[0012]

【Example】

Example 1 By feeding a silver tape into a slurry containing a calcined powder of Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _y , an organic solvent, and a binder, the width of the silver tape having a width of 22 mm and a thickness of 50 μm was 15 mm, respectively, on both sides. An oxide layer having a thickness of about 50 μm was dip-coated. This tape was cut to a length of 6 m and wound in a pancake coil shape, and then Bi ₂ O ₃ -Al ₂ O ₃
After being placed on the mixed powder to remove the medium, the solidification process was performed in a semi-closed container to prepare two coils made of Bi-2212 / Ag composite tape-shaped wire. During the melting and solidifying process, the temperature was raised to 892 ° C at about 300 ° C / h and held for 5 minutes.
After gradually cooling at 5 ° C / h to 835 ° C, the temperature was maintained at 835 ° C for 1 hour, and then air-cooled to room temperature. The thickness of the oxide superconducting layer after the melt coagulation treatment was 15 μm on one side. In this oxide superconductor layer, the c-axis of the oxide superconductor crystal was oriented perpendicular to the longitudinal direction of the tape.

The inner layer is stainless steel and the outer layer is 500 μm thick.
One of the coils obtained above is placed on one end of a bobbin consisting of a composite pipe of silver having an outer diameter of 16 mm and a length of 50 mm, and the silver exposed portion at the innermost end of the tape-shaped wire is soldered. Attach it, insulate it tightly, and fix the lower part with resin.
After impregnation with wax, the upper part was fixed with resin. Further, solder the exposed silver part of the innermost end of another tape-shaped wire so that it is wound backwards on the other end of the pipe, tightly wind it after insulation treatment, fix the already fixed coil side with resin, wax After impregnation, the other part that was not fixed was fixed with resin. At this time, the distance between the superconducting layers in the coil axial direction is 5 mm, and the outer diameter of the coil is 45 mm.
It was mm.

4.2 to this double pancake coil
When energized in a bias magnetic field of K and 6T, the critical current was 360 A and the critical current density was 8.0 × 10 ⁴ A / c.
m ² and the maximum generated magnetic field was 1.5T.

Example 2 A bobbin used in Example 1 was further provided with a thickness of 15 on the silver outer peripheral portion.
c ₂ -axis oriented Bi ₂ Sr ₂ Ca ₁
Cu ₂ O _y was formed to produce a bobbin of a composite pipe having an outer diameter of 16 mm and a length of 50 mm. A double pancake coil was produced in the same manner as in Example 1 except that this bobbin was used.

When the double pancake coil thus produced was energized in a bias magnetic field of 4.2 K and 6 T, the critical current was 360 A and the critical current density was 8.0 ×.
It was 10 ⁴ A / cm ² , and the maximum generated magnetic field was 1.5T.

Comparative Example Two coils made of Bi-2212 / Ag composite tape-shaped wire having a length of 6 m were prepared in the same manner as in Example 1. First,
A silver lead having a width of 5 mm and a thickness of 100 μm was soldered and connected to the exposed silver portion on the innermost end of the tape-shaped wire of one coil. Outer diameter 16 whose outer circumference is insulated as a bobbin
Using a stainless steel pipe of mm, a tape-shaped wire material that had been subjected to an insulation treatment was tightly wound around this, the lower part was fixed with resin, and after impregnating with wax, the upper part was fixed with resin. Furthermore, solder the exposed silver part of the innermost end of another tape-shaped wire to the other end of the above silver lead, and after insulation treatment, firmly close it in reverse winding and fix the already fixed coil side with resin. After impregnation with wax, the other part which was not fixed was fixed with resin. At this time, the distance between the superconducting layers in the axial direction of the coil is 7 mm, and the outer diameter of the coil is 45 mm.
It was mm.

4.2 in this double pancake coil
When a current was applied in a bias magnetic field of K and 6T, the critical current was 320 A and the critical current density was 7.1 × 10 ⁴ A / c.
m ² and the maximum generated magnetic field was 1.25T. This is because the silver lead in the innermost layer of the coil and its connecting part generate heat, and the silver lead is in the inner layer of the coil, so the winding method of the wire becomes uneven and a large bending strain is locally generated. It is considered that the critical current is low due to the occurrence of cracks and the like in a part of.

[0019]

In the oxide superconducting pancake coil of the present invention, since the coils are connected via a bobbin having a sufficient conductive cross-sectional area and good conductivity, the conduction loss is small. Furthermore, since the wire can be wound while suppressing the local deformation of the coil, a uniform generated magnetic field can be obtained and the probability of occurrence of quench is small. When an oxide superconductor is used for the bobbin, a coil with less conduction loss can be obtained.

When silver is used as the metal substrate of the tape wire and Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _{y in} which the c-axis of the crystal is oriented perpendicular to the longitudinal direction of the silver tape is used as the oxide superconductor, it is particularly high. A coil with high efficiency, small size, and large magnetic field can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the structure of a double pancake coil of the present invention.

[Explanation of symbols]

 1, 2: oxide superconductor tape wire 3: bobbin 4, 5: connection part between oxide superconductor tape wire and bobbin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroaki Kumakura, Inventor Hiroaki Kumakura 1-2-1, Sengen, Tsukuba-shi, Ibaraki Tsukuba Branch, Research Institute for Metals, Science and Technology Agency (72) Hitoshi Kitaguchi 1-chome, Sengen, Tsukuba, Ibaraki 2-1, No. 1 Tsukuba Branch, Research Institute for Metal Materials, Agency for Science and Technology (72) Inventor Hiroshi Maeda 1-2-1 Sengen, Tsukuba-shi, Ibaraki Within Tsukuba Branch, Institute for Metal Materials Technology (72) Inventor Shimoyama Junichi, Sumida-ku, Tokyo Oshiage 2-12-7-321 (72) Inventor Shigeaki Tomita 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture Central Research Institute, Asahi Glass Co., Ltd. (72) Toshiya Matsubara, Kanagawa-ku, Yokohama, Kanagawa Asahi Glass Co., Ltd. 1150, Hazawa-machi (72) Inventor Tsuyoshi Morimoto 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Asahi Glass Co., Ltd. Company within the central Research Institute (72) inventor Katsumi Nomura Tsuchiura, Ibaraki Prefecture Kidamari-cho, 3550 address Hitachi Cable, Ltd. Advanced Research within the center

Claims (4)

[Claims] 1. A conductive bobbin having a pipe shape,
What is claimed is: 1. An oxide superconducting double pancake coil, comprising a coil structure formed by winding a tape-shaped wire rod made of an oxide superconductor compounded with a metal substrate around a bobbin, in the axial direction of the bobbin. One coil is an oxide superconducting double pancake coil in which tape-shaped wire rods are wound in opposite directions, and the tape-shaped wire rods of the two coils are electrically connected via a bobbin. 2. The oxide superconducting double pancake coil according to claim 1, wherein the bobbin is a metal. 3. The oxide superconducting double pancake coil according to claim 1, wherein the bobbin is a pipe made of metal or ceramics having a superconducting layer formed on the inner side, the outer side, or both sides. 4. The tape-shaped wire is made of silver, and the oxide superconductor is made of Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _y (y is oxygen content) in which the crystal c-axis is oriented perpendicular to the tape longitudinal direction. The oxide superconducting double pancake coil according to any one of claims 1 to 3, which is a thick film.