JPH0745991A - Superconducting magnetic shielding structure - Google Patents

Abstract

PURPOSE:To improve magnetic shielding efficiency to an intrusion magnetic field from the axial direction of a cylindrical superconductor and the vertical direction to an axis while shortening length as ensuring the extent of the opening section of the cylindrical superconductor. CONSTITUTION:A cylindrical high permeability body 12 consisting of a high permeability material is disposed onto the outer circumference of a cylindrical superconductor 11 in at least one section of the opening section of the cylindrical superconductor 11 composed of a superconducting material or a section having a lowest magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnetic shield structure for making a relatively large magnetic shield space in the fields of minute magnetic field measurement such as biomagnetic field measurement and precision physical measurement, and EB exposure of semiconductor manufacturing equipment. Regarding things.

[0002]

2. Description of the Related Art A magnetic shield structure using a superconductor is a magnetic shield structure utilizing the Meissner effect that magnetic field lines cannot enter the inside of the superconductor. For example, a material having the Meissner effect is formed into a tubular structure, This is cooled to below the critical temperature and transformed into a superconducting state to magnetically shield the internal space of the cylindrical structure. Such a cylindrical structure has good shielding efficiency against a magnetic field parallel to the central axis of the cylinder, but has poor shielding efficiency against a magnetic field perpendicular to the central axis. Therefore, the length must be increased relative to the inner diameter of the cylinder. However, when a desired low magnetic field space is obtained with a diameter that humans can enter, it becomes a particular problem. In order to solve this, in Japanese Patent Laid-Open No. 4-218998, conventionally, as shown in FIG. 5, an opening is formed in a tubular superconductor 1 made of a superconducting material along the longitudinal direction of the tubular superconductor 1. It proposes a method of arranging the cylindrical high-permeability body 2 having a space with the inner wall of the cylindrical superconductor 1. According to this, magnetic induction occurs in the cylindrical high-permeability body 2 with respect to the intruding magnetic field showing the attenuation distribution in the central direction on the longitudinal axis of the cylindrical superconductor 1, and as a result, the intruding magnetic field is magnetically induced. To reduce the magnetic field penetrating inside the tubular superconductor 1.

[0003]

However, in the above-mentioned conventional method, the cylindrical high-permeability body 2 is arranged in the opening of the cylindrical superconductor 1, so that a person can enter and leave using the opening. In this case, the cylindrical high-permeability body 2 becomes an obstacle, and the inner diameter of the cylindrical shield body 1 is correspondingly increased, so that the length must be increased to obtain a desired low magnetic field space. There is.

The present invention solves the above problems and improves the magnetic shielding efficiency against the magnetic field penetrating from the axial direction of the cylindrical superconductor and the direction perpendicular to the axis.
An object of the present invention is to provide a superconducting magnetic shield structure capable of shortening the length of the tubular superconductor while ensuring the width of the opening.

[0005]

To this end, the superconducting magnetic shield structure of the present invention is provided with a cylindrical superconducting material in at least one of the opening or the lowest magnetic field portion of the cylindrical superconductor 11 made of a superconducting material. It is characterized in that cylindrical high magnetic permeability bodies 12 and 13 made of a high magnetic permeability material are arranged on the outer periphery of the body 11. The cylindrical high magnetic permeability body 13
May have a multiple hollow cylindrical shape. The numbers added to the above configuration are for comparison with the drawings to facilitate understanding of the present invention, and the configuration of the present invention is not limited thereby.

[0006]

In the present invention, as shown in FIGS. 1 to 4, for example, the external magnetism from the axial direction of the tubular superconductor 11 is shielded by the tubular superconductor 11 and the tubular high-permeability bodies 12, 13. Also, external magnetism in the direction perpendicular to the axis is mainly shielded by the cylindrical high magnetic permeability bodies 12 and 13.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show each embodiment of the superconducting magnetic shield structure of the present invention. FIG. 1A is an axial sectional view, and FIG. 1B is an arrow along line BB in FIG. 1A. It is sectional drawing seen in the direction.

In the embodiment of FIG. 1, a cylindrical high-permeability material made of a high-permeability material is formed at a distance from the outer periphery of the cylindrical superconductor 11 so as to extend over the opening of the cylindrical superconductor 11 made of a superconducting material. A magnetic susceptibility body 12 is provided. A well-known material that becomes a superconductor at an extremely low temperature is used as the superconducting material, and a well-known material such as permalloy or a silicon steel sheet is used as the high magnetic permeability material.

In the embodiment of FIG. 2, the tubular superconductor 1
A hollow double cylindrical high-permeability body 13 made of a high-permeability material is arranged at a distance from the outer periphery of the cylindrical superconductor 11 so as to straddle the opening 1. The hollow double tubular high magnetic permeability body 13 includes an inner cylinder 13a, an outer cylinder 13b, and a spacer member 13c fixed between the inner cylinder 13a and the outer cylinder 13b. The cylinder is not limited to the double cylinder, but may be a triple cylinder or more.

In the embodiment of FIG. 3, the cylindrical superconductor 1
A space is placed around the lowest magnetic field inside 1
An example in which a cylindrical high magnetic permeability body 12 similar to that shown in FIG.
In the embodiment of FIG. 4, an example in which a hollow double cylindrical high magnetic permeability body 13 similar to that of FIG. 2 is arranged at an outer circumference of a portion having the lowest magnetic field inside the cylindrical superconductor 11. Is shown. The present invention is not limited to the above embodiment, and a method of combining the configuration of FIG. 1 and the configuration of FIG. 3 or 4 or a method of combining the configuration of FIG. 2 and the configuration of FIG. Can be mentioned.

With the above structure, the external magnetism in the axial direction of the tubular superconductor 11 is shielded by the tubular superconductor 11 and the tubular high-permeability bodies 12 and 13, and the external magnetism perpendicular to the axis is mainly in the tubular form. Are shielded by the high magnetic permeability bodies 12, 13.

[0012]

As is apparent from the above description, according to the present invention, the magnetic shielding efficiency against the intruding magnetic field from the axial direction and the direction perpendicular to the axis of the tubular superconductor is improved, and the tubular superconductor The length can be shortened while ensuring the width of the opening.

[Brief description of drawings]

1A and 1B show an embodiment of a superconducting magnetic shield structure of the present invention, FIG. 1A is a vertical sectional view, and FIG. 1B is seen in a direction of an arrow along line BB in FIG. 1A. FIG.

2A and 2B show another embodiment of the superconducting magnetic shield structure of the present invention, in which FIG. 2A is a vertical sectional view and FIG.
FIG. 4 is a sectional view taken along line BB in FIG.

3A and 3B show another embodiment of the superconducting magnetic shield structure of the present invention, FIG. 3A is a vertical sectional view, and FIG.
FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 4 shows another embodiment of the superconducting magnetic shield structure of the present invention, where FIG. 4A is a vertical sectional view and FIG.
FIG. 4 is a sectional view taken along line BB in FIG.

FIG. 5 is a sectional view showing an example of a conventional superconducting magnetic shield structure.

[Explanation of symbols]

 11 ... Cylindrical superconductor, 12 ... Cylindrical high magnetic permeability body 13 ... Hollow double cylindrical high magnetic permeability body

Front page continued (72) Shinichi Shibuya, 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd. (72) Sumio Mukaiyama, 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Construction Co., Ltd.

Claims (2)

[Claims] 1. A tubular superconductor made of a superconducting material, at least at least one of an opening or a portion having the lowest magnetic field,
A superconducting magnetic shield structure characterized in that a cylindrical high-permeability body made of a high-permeability material is arranged around the outer periphery of the cylindrical superconductor. 2. The superconducting magnetic shield structure according to claim 1, wherein the cylindrical high-permeability body has a multi-hollow cylindrical shape.