JPH07221489A - Superconductive magnetic shield substance - Google Patents

Abstract

PURPOSE:To provide a superconductive magnetic shield substance which has enough magnetic shielding effect without using a large combustion furnace. CONSTITUTION:This is a multiple structure of superconductive magnetic shielding substance where two or more tubular superconductors are coupled in longitudinal direction, using a superconductive material of the same composition as the said tubular superconductor so as to constitute a first tube 14, and further two or more tubular superconductors are coupled in a longitudinal direction, using a superconductive material of the same composition as the this tubular superconductor so as to constitute a second tube 15, and this tube is set on or inserted into the first tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super electric magnetic shield.

[0002]

2. Description of the Related Art In the case of biomagnetic measurement for measuring a minute magnetic field generated from a human body, disturbance caused by an external magnetic field such as terrestrial magnetism adversely affects accurate measurement of the minute magnetic field. In order to avoid this, a magnetic shield body for shielding external magnetic noise is used. A magnetic shield using a superconductor is convenient for measuring a small magnetic field because it can obtain a high shielding effect. In particular, a magnetic shield using a high-temperature superconductor having superconductivity at a liquid nitrogen temperature or higher is drawing attention. .

The shape of the magnetic shield body may be a plate shape, a cylinder shape, a box shape, a spherical shape, etc. In the case of biomagnetism measurement, a cylindrical magnetic shield body is being studied. As a performance of the magnetic shield used for such a purpose, it is necessary to make ambient environmental noise a magnetic field of about 10 ⁻¹² T.

[0004]

Since the shape of the magnetic shield used for biomagnetism measurement needs to surround the human body, the diameter is 1 to 2 m and the length is 2 m or more. Advanced technology is required to manufacture the magnetic shield body. Therefore, a method is conceivable in which a material such as a metal that tends to increase in size is used as a support and a film-shaped high-temperature superconductor layer is formed thereon. In this case, forming a thick high-temperature superconductor is disadvantageous in terms of weight increase, price, and manufacturing technology. Even when a high-temperature superconductor layer is formed on a metal support, a large-sized product having a diameter of 1 to 2 m and a length of 2 m or more requires a firing furnace with a uniform temperature distribution over a length of 2 m or more. Therefore, manufacturing becomes difficult.

Further, an example of producing a magnetic shield by combining a plurality of superconductors (for example, Proceedings of the 39th Joint Lecture on Applied Physics, 29p-V-2, March 28-March 1992). 31 days) was also reported, but even in this case, a sufficient magnetic shield effect was not obtained due to the leakage of the magnetic field from the gap of the superconductor. The present invention provides a superconducting magnetic shield which does not have the above problems.

[0006]

As a result of various studies to solve the above problems, the inventors of the present invention have used tubular superconductors having short lengths with superconductor materials having the same composition. To produce a long first tubular body, and further connect short tubular superconductors to the outside or inside of the first tubular body,
Moreover, it has been found that a high magnetic shield effect can be obtained by joining the connecting portion using a superconducting material having the same composition as that of the cylindrical superconductor, as in the above case.

In the present invention, two or more tubular superconductors are connected in the longitudinal direction thereof, and the connecting portions are joined with a superconductor material having the same composition as the tubular superconductor to form a first tubular body. Further, two or more other tubular superconductors are connected to the outside or the inside of the first tubular body in the longitudinal direction thereof, and the connecting portions are joined with a superconductor material having the same composition as the tubular superconductor. Then, the present invention relates to a superconducting magnetic shield body having a multiple structure in which a second tubular body is formed.

In the present invention, the object of the present invention can be achieved even if the connecting portion of the first tubular body and the connecting portion of the second tubular body overlap each other, but they are combined in different positions. And is preferable because the magnetic field dependency of the magnetic shield effect is further improved. The tubular shape of the tubular body in the present invention means a cylindrical shape, a rectangular tube, an elliptic tube, and the like, but generally, a cylindrical shape is preferable because it can be easily manufactured.

For joining the cylindrical superconductors, for example, a green sheet laminated base material in which a green sheet for a superconductor is heated and pressure-bonded to the outer circumference of a silver cylinder is fired to form a cylindrical superconductor, and the cylindrical superconductor is formed in the longitudinal direction thereof. Two or more of them are connected to each other, and a paste having the same composition as that of the cylindrical superconductor is applied to the connecting portion or is fired after the application.

The superconductor used in the present invention mainly means a high temperature superconductor, but the composition of this high temperature superconductor is not particularly limited, and for example, Y-Ba-Cu-O is used.
System, Bi (Pb) -Sr-Ca-Cu-O system, Tl (Pb)
A -Sr (Ba) -Ca-Cu-O system or the like is preferable because its critical temperature is higher than the boiling point of liquid nitrogen. Further, since it is difficult to manufacture a large-sized high-temperature superconductor, it is preferable to form the high-temperature superconductor on a support such as a noble metal or a metal. Support materials include Ag, Ag alloys, precious metals such as Au, F
It is preferable to use a metal having high heat resistance such as an e-Ni alloy. If a high-temperature superconductor is formed directly on a metallic support such as an Fe-Ni alloy, peeling of the high-temperature superconductor, deterioration of superconductivity, and the like occur, one or more intermediate layers are provided, and a high-temperature superconductor is formed on the upper surface of the intermediate layer. do it.

The intermediate layer may be made of any material as long as it can relax the difference in thermal expansion between the support and the superconductor and prevent deterioration of superconductivity. For example, ceramics such as MgO and ZrO ₂ or noble metals such as Ag and Au. Alternatively, a combination of these alloys is used.

[0012]

EXAMPLES Examples of the present invention will be described below. Example 1 233.0 g of Bi ₂ O ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 99.9%) so that the atomic ratio of bismuth, strontium, calcium and copper is 2: 2: 1: 2. Sr
CO ₃ (manufactured by Kojundo Chemical Laboratory, purity 99.9%) 14
7.6g, CaCO ₃ (manufactured by Kojundo Chemical Laboratory, purity 9
9.9%) 50.1 g and CuO (manufactured by Kojundo Chemical Laboratory Co., Ltd., purity 99.9%) 79.5 g are weighed, and then synthetic resin balls and distilled water 300 g are placed in a synthetic resin ball mill.
Fill with and mix for 72 hours, then at 100 ℃ for 12 hours
After drying for an hour, a raw material mixed powder was obtained. This raw material mixed powder was placed in an alumina container, calcined at 820 ° C. for 24 hours, then roughly crushed in a mortar, and then charged into a synthetic resin ball mill together with zirconia balls and 300 g of ethyl acetate,
After crushing for 24 hours, it was dried at 100 ° C. for 10 hours to obtain a calcined powder.

A portion of the above calcined powder is placed in an alumina container and heat-treated at 700 ° C. for 15 hours in a nitrogen stream to obtain a Bi-based oxide powder. 100 parts by weight of this Bi-based oxide powder is mixed with ethyl cellulose ( 5 Wako Pure Chemicals, 45 cp)
20 parts by weight of terpineol (manufactured by Wako Pure Chemical Industries, Ltd., first-class reagent) were added and uniformly mixed to obtain a Bi-based oxide paste.

On the other hand, polyvinyl butyral resin (manufactured by Wako Pure Chemical Co., Ltd., first-class reagent) was added to 100 parts by weight of the above calcined powder.
Parts by weight, phthalate ester (Wako Pure Chemical Industries, reagent first grade) 3
After adding 1 part by weight and 50 parts by weight of 1-butanol and mixing, deaeration was performed to obtain a slurry having a viscosity of 15 Pa · s. This slurry was supplied onto a polyester film (manufactured by Toray) having a thickness of 180 μm, and the thickness was adjusted to 0.1 by a doctor blade method.
A 2 mm green sheet for a superconductor (hereinafter referred to as a green sheet) was obtained.

Next, as shown in FIG. 1A, the outer diameter is 60 m.
The above green sheet was thermocompression-bonded to the outer surface of two silver cylinders 5 each having m, an inner diameter of 59 mm, and a length of 90 mm under the conditions of 60 ° C. and 30 MPa, and the green sheet laminated base material 1 and the green sheet laminated base material 2 (both Outer diameter 60.4 mm, inner diameter 60
mm and length 90 mm). On the other hand, as shown in FIG. 1 (b), the green sheet is heat-pressed on the outer surface of two silver cylinders 6 having an outer diameter of 65 mm, an inner diameter of 64 mm and a length of 90 mm under the same conditions as described above. 3 and green sheet laminated base material 4 (both have an outer diameter of 65.4 mm and an inner diameter of 6)
5 mm and a length of 90 mm) were obtained.

The above green sheet laminated base materials 1, 2, 3
And 4 were heated to 500 ° C. in the atmosphere at a rate of 300 ° C./hour, then heated to 885 ° C. at a rate of 100 ° C./hour, held at 885 ° C. for 15 minutes, and then heated to 850 ° C. at 5 ° C. 1 / c, and (d) of FIG. 1 after being cooled again to room temperature at a rate of 100 ° C./hour and then heated again at 700 ° C. for 15 hours in a nitrogen stream. Superconducting cylinder 7 shown (outer diameter 60.12 mm, inner diameter 6
0 mm and length 90 mm), superconducting cylinder 8 (outer diameter 60.12)
mm, inner diameter 60 mm and length 90 mm), superconducting cylinder 9 (outer diameter 65.12 mm, inner diameter 65 mm and length 90 mm) and superconducting cylinder 10 (outer diameter 65.12 mm, inner diameter 65 mm and length 90)
mm) was obtained.

Next, as shown in FIG. 1 (c), the superconducting cylinders 7 and 8 are vertically connected to form a cylinder having a length of 180 mm, and the Bi-based oxide paste 11 having a thickness of 1 is connected to the connecting portion.
Coated to 00 μm, 300 ° C / up to 500 ° C in air
The temperature is raised at the rate of time, and then at the rate of 100 ° C / hour for 8 hours.
After raising the temperature to 80 ° C and holding it at 880 ° C for 15 minutes,
The temperature is lowered to 50 ° C at a rate of 5 ° C / hour, and then 100 ° C.
/ Cylinder 12
Got

The superconducting cylinders 9 and 10 were also connected and joined in the same manner as described above to obtain a composite cylinder 13 as shown in FIG. 1 (d). This composite cylinder 12 and 1
3 was heat-treated at 700 ° C. for 15 hours in a nitrogen stream to obtain a first tubular body and a second tubular body.

Next, as shown in FIG. 2, the second cylindrical body 15 is inserted outside the first cylindrical body 14 to form a double cylinder, and a superconducting magnetic shield 16 is obtained. . Figure 2
Reference numeral 17 is a joint portion.

A magnetic field of 170 Hz was applied in the axial direction of the obtained superconducting magnetic shield 16 and the magnetic flux density on the central axis of the superconducting magnetic shield 16 was measured. For the measurement of the magnetic flux density on the side of the superconducting magnetic shield body 16 side, a detection coil whose output was calibrated in advance was used. In addition, the relationship between the coil current and the strength of the applied magnetic field was previously obtained using a Hall element, and the strength of the applied magnetic field was calculated from the coil current. The shield effect was calculated from the ratio of the applied magnetic field and the magnetic flux density at the center of the superconducting magnetic shield. The measurement results in the case of an applied magnetic field of 1 × 10 ⁻⁵ T are shown in FIG. As shown in FIG. 3, the shield effect on the central axis increases as the distance from the open end of the cylinder increases, and 7 × in the center.
It was 10 ⁴ . This value is almost the same as the value obtained from the relationship that the magnetic field leakage from the open end of the cylinder is proportional to exp (7.66z / d), where z is the distance from the open end and d is the diameter of the cylinder. To do.

Example 2 As shown in FIG. 4, instead of the superconducting cylinders 9 and 10 of Example 1, the lengths of the left and right superconducting cylinders are 45 mm, and the length of the central superconducting cylinder is 90 mm. A superconducting magnetic shield 18 was obtained through the same steps as in Example 1 except that the positions of the connecting portions were different from the connecting portions of the superconducting cylinders 7 and 8.

Example 3 A superconducting magnetic shield was obtained through the same steps as in Example 2 except that the Bi type oxide paste applied to the connecting portion was not baked.

Next, the dependence of the magnetic shield effect on the applied magnetic field in the central portion of the superconducting magnetic shield obtained in each of the examples was examined. The result is shown in FIG. As a result, when the applied magnetic field was 1 × 10 ⁻⁵ T, the shielding effect was 5 × 10 ⁴ or more, which was good (usually 5 × 10 ⁴ or more was considered good).

[0024]

The superconducting magnetic shield according to the present invention is
It is a superconducting magnetic shield that is industrially very suitable because a large one can be obtained without requiring a large baking furnace, and a sufficient magnetic shield effect can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing operation state of a superconducting magnetic shield body according to an embodiment of the present invention.

FIG. 2 is a sectional view of a superconducting magnetic shield according to an embodiment of the present invention.

3 is a graph showing the relationship between the shield effect and the distance from the open end of the superconducting magnetic shield shown in FIG.

FIG. 4 is a sectional view of a superconducting magnetic shield according to another embodiment of the present invention.

FIG. 5 is a graph showing a relationship between an applied magnetic field and a shield effect.

[Explanation of symbols]

 1 green sheet laminated base material 2 green sheet laminated base material 3 green sheet laminated base material 4 green sheet laminated base material 5 silver cylinder 6 silver cylinder 7 superconducting cylinder 8 superconducting cylinder 9 superconducting cylinder 10 superconducting cylinder 11 Bi-based oxide paste 12 composite Cylinder 13 Composite cylinder 14 First tubular body 15 Second tubular body 16 Superconducting magnetic shield body 17 Joined portion 18 Superconducting magnetic shield body

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[Procedure amendment]

[Submission date] February 4, 1994

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

[Title of the Invention] the superconducting magnetic shield

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

The present invention relates to a super-conductivity magnetic shield.

Claims (3)

[Claims] 1. A first tubular body is formed by connecting two or more tubular superconductors in a longitudinal direction thereof, and joining the connecting portions with a superconductor material having the same composition as the tubular superconductor, Further, two or more other tubular superconductors are connected in the longitudinal direction to the outside or inside of the first tubular body, and the connecting portions are joined with a superconductor material having the same composition as the tubular superconductor. A multi-structure super-electric magnetic shield body in which a second cylindrical body is formed. 2. A super-electric magnetic shield body at a position where the connecting portion of the first tubular body and the connecting portion of the second tubular body according to claim 1 overlap each other. 3. A super-electric magnetic shield body according to claim 1, wherein the connecting portion of the first tubular body and the connecting portion of the second tubular body are at different positions from each other.