JP3026048B2 - Manufacturing method of magnetically shielded cylinder using oxide superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shield cylinder for reducing an external leakage magnetic field of a strong magnetic field coil such as an NMR analysis coil, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Since a strong magnetic field coil used for a conventional NMR analysis coil or the like has an extremely large effect on other devices, it is generally covered with a cylindrical shield made of a magnetic material to reduce the leakage magnetic field. Means of shielding are used.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic shield using a novel oxide superconductor, which can effectively shield a leakage magnetic field or the like accompanying a magnetic field generating coil. is there.

[0004]

The gist of the present invention is a cylindrical shape.
After firing between the inner metal coating and the cylindrical outer metal coating,
A ceramic powder exhibiting superconductivity is interposed, and this is rolled in the radial direction by a ring rolling method, fired, and
A method for producing a magnetically shielded cylinder using an oxide superconductor, which is performed after rolling by a ring rolling method .

[0005]

The oxide superconductor crystal is oriented in the rolling direction by rolling the ceramic powder exhibiting superconductivity between the inside and the outside with a metal coating in the radial direction by a ring rolling method, and firing it. This makes it possible to improve the superconducting characteristics in the direction perpendicular to the axis of the cylinder. Therefore, it is possible to provide a cylindrical magnetic shield that can perform good shielding.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a state where the magnetic shield cylinder of the present invention is applied to an actual magnetic field generating solenoid coil, and FIG. 2 is a transverse sectional view for explaining a method of manufacturing a magnetic shield. That is, the magnetic shield cylinder 1 is provided outside the solenoid coil 2 to shield the external leakage magnetic field 3 generated from the solenoid coil 2 for generating a magnetic field. The magnetic shield cylinder 1 is formed by interposing ceramic powder having superconductivity between the inner and outer metal coatings, rolling this in the radial direction by a ring rolling method, and then firing. Hereinafter, the manufacturing method will be described with reference to FIG.

As a ceramic powder having superconductivity,
Bi2223 oxide superconductor 11 is used. Then, the inner and outer surfaces are covered with silver cylinders 12 and 13 as metal coverings to form the cylinder 1. This cylinder 1 is prepared by preparing silver cylinders 12 and 13 having predetermined thicknesses and lengths having different inner and outer diameters, and arranging them concentrically.
Is formed by filling the powdered oxide superconductor 11 into the gap. As shown in FIG. 2, the thus obtained cylindrical body 1 is a ring rolling roll 1 having a horizontal axis.
The cylindrical body 1 is rolled to a predetermined thickness while being sandwiched between the rollers 4 and 15 while driving the rolls for ring rolling 14 and 15 and rotating as shown by the arrows. The cylindrical body 1 becomes thinner while rotating while being rolled, and has a larger diameter.

The thus obtained cylinder is then placed in an oxygen atmosphere at a temperature of about 840 ° C. for 50 to 150 days.
After firing for a period of time, a cylinder having a dense and crystal-oriented oxide superconductor layer is obtained. By repeating rolling and firing of the obtained cylinder, the denseness and crystal orientation of the oxide superconductor are further improved, and the superconductivity can be improved. That is, Bi ₂ Sr _{2 is} currently used as an oxide superconductor exhibiting excellent superconductivity at a liquid nitrogen temperature of 77 K.
Commonly known Bi222 represented by a molecular formula of Ca ₂ Cu ₃ O _y
There are three materials. This material has strong crystal anisotropy and tends to be oriented so that the rolling axis becomes the C axis by rolling. The superconducting property of the oriented Bi2223 is improved.

On the other hand, a cylindrical body is required to magnetically shield the leakage magnetic field of the strong magnetic field generating coil 2.
A good magnetic shield is obtained by sandwiching the inner and outer surfaces of the cylindrical body 23 between the silver cylindrical bodies 12 and 13 which do not react with the oxide superconductor during firing and have oxygen permeability and are rolled in the radial direction and fired. A cylinder 1 can be formed. That is, since the magnetic shield has a cylindrical shape and superconductivity in the direction perpendicular to the rolling axis is important, ring rolling is suitable. The silver used as the inner and outer coatings of the cylinder may be a silver alloy containing a small amount of elements such as gold, copper, nickel, manganese, and magnesium.

[0010]

As described above, according to the magnetic shield cylinder made of the oxide superconductor of the present invention and the method of manufacturing the same, an excellent magnetic shield having superconductivity at a liquid nitrogen temperature of 77 K and having a magnetic shield function can be obtained. . Also, B
By manufacturing the i2223 oxide superconductor by a ring rolling method, it is possible to provide a magnetic shielding function of a higher magnetic field.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state where a magnetic shield according to the present invention is applied to a magnetic coil;

FIG. 2 is a cross-sectional view showing a method of manufacturing a magnetic shield.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical magnetic shield 2 Coil 3 Leakage magnetic field 11 Oxide superconductor 12, 13 Silver cylinder 14, 15 Ring rolling roll

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadao Otani 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture "Inside System Materials Research Laboratories, Hitachi Cable, Ltd." 3550 No., "Hitachi Line Co., Ltd. Advanced Research Center" (56) References JP-A-3-11505 (JP, A) JP-A-3-34398 (JP, A) JP-A-3-146459 (JP, A) JP-A-3-217083 (JP, A) JP-A-3-217084 (JP, A) JP-A-5-145272 (JP, A) JP-A-5-160596 (JP, A) JP-A-6 −342089 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 9/00 ZAA

Claims (1)

(57) [Claims] 1. A post-firing between the cylindrical inner metal coating a cylindrical outer metal coating is interposed a ceramic powder showing superconductivity, which was rolled in the radial direction by the ring rolling method, and fired After further rolling by the ring rolling method,
A method for producing a magnetic shield cylinder using an oxide superconductor, which is characterized by firing .