JP3302773B2 - electromagnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnet, and more particularly to a superconducting magnet using an oxide superconductor.

[0002]

2. Description of the Related Art In recent years, oxide superconductors showing a superconducting transition at a temperature of liquid nitrogen or higher have been found one after another, and various applications have been attempted by processing them into wires, tapes and the like. A superconducting magnet using an oxide superconducting wire is a typical application example, and since it has a higher transition temperature than conventional metal-based wires, a superconducting coil that operates at liquid nitrogen temperature,
Further, since the critical magnetic field is higher than that of the conventional material at a temperature of 20 K or less, application of the hybrid coil for generating a strong magnetic field as an inner layer coil is expected.

[0003] Recently, the production of coils for electromagnets using an oxide superconducting wire has been actively performed, and as a method for producing an oxide superconducting wire, a metal sheath method, a doctor blade method, a dip coating method and the like are known. Have been. However, since oxide superconductors are ceramics, they are very brittle and easily broken. For this reason, in a coil using an oxide superconductor, generally, a wire in the form of a thin tape is often used in order to reduce bending strain. In order to further reduce the distortion, the wire is wound and formed into a coil shape and then heat-treated, that is, a so-called wind and react method is used.

The form of the coil used at this time is as follows:
There is a so-called pancake coil in which a tape-shaped wire is wound into a roll. Since the pancake coil is relatively easy to mold, it is a form suitable for a coil using a brittle oxide superconducting wire.

However, in a pancake coil, the generated magnetic field distribution in the direction of the coil central axis is steep, that is, the generated magnetic field decreases rapidly as the distance from the center position in the coil central axis direction increases. Therefore, in order to generate a uniform magnetic field over a wide range, a large number of pancake coils must be stacked in the direction of the coil center axis so that the gap between the pancake coils is as small as possible. This makes the coil lamination and assembly process very difficult.

Particularly, in the case of an oxide superconducting wire produced by a doctor blade method or a dip coating method, a silver substrate wider than the superconducting layer portion of the tape is required in the manufacturing process, so that the substantial gap of the coil conductor portion is less than 5 mm. It is very difficult to make the size smaller, and there is a problem that when the pancake coils are stacked, the generated magnetic field distribution in the direction of the coil center axis becomes non-uniform.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a coil having a small outer diameter for an electromagnet made of a brittle wire having a tape-like form and having a non-steep magnetic field distribution in the coil axis direction, Another object of the present invention is to provide a coil in which the axial magnetic field distribution of the laminated coil is uniform even if the gap in the central axis direction between the coils is wide.

[0008]

According to the present invention, there is provided a coil structure in which a tape-shaped conductor is wound, wherein at least a part of adjacent tapes overlaps, and the tape is displaced in the axial direction of the coil. An object of the present invention is to provide an electromagnet having a coil structure configured as described above.

One embodiment of the present invention will be described with reference to FIG. In FIG. 1, a tape-shaped conductor is wound around one axis. This tape partially overlaps every circumference, but is shifted in the axial direction. This shift need not always be in a fixed direction from the center to the periphery, but may be shifted downward once in the drawing and then shifted upward. Further, there may be a winding in which there is no partial displacement.

When two or more coil structures of the present invention are laminated in the axial direction, the effect is further increased, which is preferable. For example, as shown in FIG. 2, it is particularly preferable to stack coils having the same misalignment structure, since the coils can be stacked in the central axis direction such that a part of the coils overlaps when viewed perpendicularly to the axis.

When a plurality of coils are stacked, it is preferable to connect the conductive paths of each coil in series.

The tape-shaped conductor used at this time has a small effect of being wound spirally when the conductor has a thickness relative to the tape width, and it is difficult to obtain strength when fixed in a spiral shape. For this reason, the ratio of the width to the thickness of the tape-shaped conductor is preferably 100: 1 or more.

It is desirable to use a superconducting conductor for the tape-like conductor of the coil for the electromagnet which generates a strong magnetic field with high efficiency. In particular, a composite of a Bi-based oxide superconductor and silver in which the c-axis of the crystal is oriented in the longitudinal direction of the tape, which has a high critical temperature and allows current to flow at a high density, is desirable.

[0014]

【Example】

Example 1 A silver tape was fed into a slurry containing Bi ₂ Sr ₂ Ca ₁ Cu ₂ O _y (y is the amount of oxygen), a calcined powder, an organic solvent and a binder, so that the silver tape was 25 mm wide and 50 μm thick. An oxide layer having a width of 20 mm and a thickness of about 50 μm was dip-coated. This tape was wound in a pancake coil shape, and after the solvent was removed, a melt-solidification treatment was performed. The melting and solidification process is performed by raising the temperature to 892 ° C. at about 300 ° C./h, 5
And slowly cooled to 835 ° C at 5 ° C / h,
It was kept for a while and cooled to room temperature. From oxide superconductor to B
In order to prevent volatilization of the i component, the sample was placed on Bi-Al-O powder and subjected to a melt-solidification treatment in a semi-closed container.

After the melt-solidification treatment, the superconducting layer has a thickness of 15 μm.
m, and in this superconducting layer, the c-axis of the crystal of the oxide superconductor was oriented perpendicular to the longitudinal direction of the tape. Insulated,
After the coiling, the coil was formed into a coil shape as shown in FIG. The lower part was fixed with resin, and after wax impregnation, the upper part was fixed with resin. The tape length of this one coil was 6 m, the inner diameter was 16 mm, and the outer diameter was 45 mm. The generated magnetic field distribution on the central axis of the coil thus manufactured is shown by white circles in FIG.

Example 2 As shown in FIG. 2, when the coil manufactured in Example 1 was laminated and integrated into five stages such that the large-diameter portion of the coil and the small-diameter portion of the coil overlapped, the conductive paths of each coil were connected in series. Are shown by white circles in FIG.

COMPARATIVE EXAMPLE The oxide superconductor tape produced in the same manner as in Example 1 was subjected to an insulation treatment, then wound, fixed with a resin without displacing the tape, and impregnated with wax. Then, a pancake coil was produced.

The generated magnetic field distribution on the central axis of the coil manufactured in this manner is shown by a black circle in FIG. In addition, the magnetic field distribution generated when the coils thus manufactured are stacked and integrated in five stages and the conductive paths of each coil are connected in series is shown by a black circle in FIG. At this time, the interval between the superconducting layers between the coils was 5 mm.

FIG. 3 shows that the coil wound with the tape shifted has a much smoother distribution of the generated magnetic field in the direction of the center axis than the coil without the tape shifted. From Fig. 4, it can be seen from Fig. 4 that even when the coils are stacked, the distribution of the magnetic field in the direction of the central axis is non-uniform for the coil that does not displace the tape, whereas the coil that is wound with the displaced tape exhibits a very uniform generated magnetic field distribution. I understand.

[0020]

According to the electromagnet of the present invention, the generated magnetic field distribution in the direction of the center axis of the coil becomes very smooth. When the coil structures are stacked and integrated, the generated magnetic field distribution of each single coil is extremely smooth, so that a very uniform generated magnetic field can be obtained over a wide range in the stacking axis direction.

[Brief description of the drawings]

FIG. 1 is an external view showing one embodiment of a coil of the present invention.

FIG. 2 is a cross-sectional view showing one embodiment in which the coils of the present invention are stacked in five stages.

FIG. 3 is a distribution diagram of a generated magnetic field around a central axis of the coil according to the first embodiment.

FIG. 4 is a distribution diagram of a generated magnetic field at a central axis of the coil of the second embodiment.

Continuing on the front page (72) Inventor Jin Kitaguchi 1-2-1 Sengen, Tsukuba, Ibaraki Pref., National Institute of Science and Technology Tsukuba Branch (72) Inventor Hiroshi Maeda 1-2-1, Sengen, Tsukuba, Ibaraki 1 Tsukuba Branch, National Institute for Metals Sciences, Science and Technology Agency (72) Inventor Junichi Shimoyama 2-12-7-321 Oshiage, Sumida-ku, Tokyo (72) Inventor Shigeaki Tomita 1150 Hazawacho, Kanagawa-ku, Yokohama-shi, Kanagawa Address Asahi Glass Co., Ltd. Central Research Laboratory (72) Inventor Katsumi Nomura 3550 Kida Yomachi, Tsuchiura City, Ibaraki Pref. Hitachi Cable Co., Ltd. Advanced Research Center (56) References Reference: Shokai Sho 60-141104 (JP, U) ) Surveyed field (Int.Cl. ⁷ , DB name) H01F 6/00-6/06

Claims (6)

(57) [Claims] 1. A coil structure in which a tape-shaped conductor is wound, wherein at least a part of adjacent tapes overlaps, and the coil structure is shifted in the axial direction of the coil. An electromagnet. 2. An electromagnet in which two or more coil structures according to claim 1 are laminated in the axial direction. 3. The electromagnet of claim 2, wherein at least a portion of adjacent coil structures overlap in a direction perpendicular to the axis. 4. The electromagnet according to claim 2, wherein each coil structure is connected in series. 5. A tape-shaped conductor having a ratio of width to thickness of 100:
The electromagnet according to any one of claims 1 to 4, wherein the number is one or more. 6. The electromagnet according to claim 1, wherein the conductor is a composite of silver and a Bi-based oxide superconductor in which the c-axis of the crystal is oriented in the longitudinal direction of the tape.