JPH06216565A - Superconductive magnetic shield body formed of beltlike superconductive sheet - Google Patents

Abstract

PURPOSE:To manufacture a cylindrical magnetic body having an optional sectional shape from a laminated sheet of narrow width by removing a beltlike sheet of a laminate consisting of a superconductive layer and a normal conductive metal layer in the longitudinal direction for being made a sheet of a seamless closed loop while making the closed loop sheet a unit magnetic shield body. CONSTITUTION:When a beltlike sheet 10 is provided with the cut-out parts 6 about on the central line in the longitudinal direction excepting both ends 21, 22 and doubly folded on the broken lines 5 of both ends 21, 22, a pair of beltlike part pieces 11, 13 integrally mounted on both common end parts 21, 22 are formed. When a pair of these beltlike part pieces 11, 13 are curved, a closed loop sheet 1, where the cut-out parts of the beltlike part pieces 11, 13 form opening part end edges, can be formed, and this closed loop sheet 1 is made a unit magnetic shield body. In case the closed loop sheet 1 is circularly formed, its inner diameter is determined by the length of the cut-out parts 6 of the beltlike sheet 10, and a loop magnetic shield body having a diameter of an optional size can be made by properly selecting the length of the beltlike sheet 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-diameter superconducting magnetic shield formed from a band-shaped superconducting sheet.

[0002]

2. Description of the Related Art A technique for cooling a multi-layer laminate of a superconductor such as an Nb-Ti alloy and a normal-conducting metal such as Cu or Al at a liquid helium temperature and utilizing it as a superconducting magnetic shield is known. (JP-A-61-183979), a cylindrical body formed by stacking a large number of disc-shaped annular plates formed of the Nb-Ti laminated body shields an external strong magnetic field,
A magnetic shield in which the hollow portion has a zero magnetic field has already been disclosed (Japanese Patent Laid-Open No. 2-97098).

Nb--Ti laminates for magnetic shields are Nb
-The normal conductive metal layer such as Al or Cu interposed between the Ti alloy layers conducts the heat generated during the flow of the magnetic flux penetrating the Nb-Ti alloy layer to the helium liquid phase for cooling, Prevents flux jumps in the Nb-Ti alloy layer,
Further, it has already been disclosed that the maximum magnetic shield magnetic field of the entire Nb-Ti laminated body is significantly increased by making the Nb-Ti alloy layer a thin layer of 20 μm or less and laminating it in multiple layers.

For this Nb-Ti laminated body, a multi-layer vapor-deposited sheet formed by alternately vapor-depositing Nb-Ti alloy and metallic Al on the surface of a sheet substrate by sputtering is used. In this multilayer vapor-deposited sheet, the Nb—Ti alloy layer can be formed to be extremely thin with a layer thickness of 1 μm or less, and a magnetic shield excellent in stability can be configured. Further, a long sheet having a three-layer structure has been proposed by bonding a metal Al layer to both surfaces of a Nb-Ti plate or foil and forming it by cold rolling (JP-A-3-
No. 283475), an annular plate (foil) cut out from this sheet is laminated to form a cylindrical magnetic shield. Although this rolled sheet has a limited layer thickness, a large amount of lattice defects are introduced as a cold-working structure into the Nb-Ti alloy layer, and a large number of fine α-Ti fine particles are formed by aging treatment after cold-working. By precipitating the particles,
It has become possible to improve the magnetic stability by increasing the critical shielding current density.

On the other hand, in a tubular magnetic shield, Nb-Ti is used.
There is also known a crimping method in which tubes and Cu tubes are alternately inserted coaxially and hot rolled, and there is also a technique of using such a multilayer coaxial tube as a magnetic shield (Japanese Patent Laid-Open No. 3-2737).
No. 00).

[0006]

When the cylindrical superconducting magnetic shield is formed by laminating annular plates, the magnetic shield can be adjusted to desired inner and outer diameters and heights. It is advantageous for formation.

In recent years, with the increase in size of equipment using superconducting magnets, it has become necessary to use a large magnetic shield with an inner diameter of 20 cm to 2 m.
-Ti laminated plates have also been required to have a large diameter.

However, if a large-diameter magnetic shield is formed from the annular plate, there is a problem that a wide laminated rolled sheet is required, and the hollowed-out portion of the inner diameter is large, resulting in poor yield. . Further, when the above coaxial tube is used, a complicated rolling process for expanding the diameter is required, which is not realistic.

A large-diameter magnetic shield can be formed by winding a band-shaped laminated sheet around the outer surface of a cylindrical support a number of times. Magnetic shielding is performed on magnetic force lines in the axial direction of the cylinder. In addition, the Nb-Ti alloy layer, which is a superconductor, needs to be short-circuited in the circumferential direction so that a shield current around the axis flows. Therefore, there is also a method of joining both ends of the sheet of the laminated body with a superconducting low melting point alloy so that adjacent Nb-Ti alloy layers are in contact with each other, but heat is generated due to a slight electric resistance at this joining portion. However, there is a problem that the magnetic shielding ability becomes unstable and disappears due to local normal conduction transition.

In view of the above problems, the present invention is Nb-Ti.
Using a cold-rolled sheet or a multilayer vapor-deposited sheet that is easy to form into a laminate of a superconducting layer such as an alloy and a normal-conducting metal layer such as Cu or Al, a narrow and long sheet can be formed into a desired arbitrary diameter. It is intended to provide a formed tubular magnetic shield.

[0011]

SOLUTION: The superconducting magnetic shield of the present invention has a strip-shaped sheet of a laminate composed of a superconductor layer and a normal-conducting metal layer, which is cut in the longitudinal direction to form a closed annular sheet having no joint. An annular superconducting magnetic shield having a closed annular sheet as a unit magnetic shield.

The closed ring-shaped sheet of the present invention is integrally formed from a strip-shaped sheet of a laminated body composed of a superconductor layer and a normal-conducting metal layer. The strip-shaped sheet is double-folded with a fold line portion in the longitudinal center thereof. None, the fold line portion is cut open leaving both ends to form a pair of strip-shaped pieces, and the pair of strip-shaped pieces are curved to opposite sides to form a closed ring. Is a unit magnetic shield.

Further, the closed annular sheet may be formed by a pair of strip-shaped pieces having both ends in common and separated from each other, curved in opposite directions, and the closed annular sheet may be used as a unit magnetic shield. .

The present invention includes a superconducting magnetic shield formed by laminating a plurality of such unit magnetic shields in a plurality of layers and forming the annular superconducting magnetic shield with a cylindrical support. A cylindrical superconducting magnetic shield is provided on the peripheral surface of the superconducting magnetic shield in the axial direction of the cylinder so as to be covered and fixed.

As such a cylindrical magnetic shield, in particular, a second annular superconducting magnetic shield is arranged in parallel on the outer periphery of a first annular superconducting magnetic shield which is arranged in parallel on the peripheral surface of the support. The first annular superconducting magnetic shield is surrounded by the peripheral body of the second annular superconducting magnetic shield.
Some are formed by coating. The first and second superconducting layers of each annular superconducting magnetic shield are placed in a non-contact state.
The above-mentioned annular superconducting magnetic shield is preferably arranged.

As the strip-shaped sheet, the cold-rolled sheet or the multilayer vapor-deposited sheet as described above can be used. First, for a cold rolled sheet, a Nb-Ti alloy layer is used for the superconductor layer, and a Cu layer or an Al layer is used for the normal conductive metal layer, and the laminate is cold rolled to form a strip. A sheet is preferably used. This strip-shaped sheet is obtained by rolling the laminate with a reduction rate of 25 to 99% and aging heat treatment after the cold rolling step to precipitate and disperse the α-Ti phase fine particles in the Nb-Ti alloy layer. Is especially good.

On the other hand, in the case of the multilayer vapor-deposited sheet, the Nb-Ti alloy, the NbN compound and the NbN-T are used as the superconductor layer.
A laminate formed by alternately sputter-depositing any one layer of an iN mixed crystal, a Cu layer or an Al layer as the normal conducting metal layer on a long sheet substrate having an appropriate width, and forming the strip sheet. Is used.

[0018]

The superconducting magnetic shield of the present invention will be described below with reference to the drawings. 1A and 1B, a strip-shaped sheet 10 is formed by cold rolling from a three-layer laminated body of an Nb-Ti alloy layer 40 and an Al layer 41 as shown in FIG. 3 shows the unit magnetic shield formed in FIG.

The strip-shaped sheet 10 shown in FIG. 1 (A) is provided with an incision 6 substantially on the center line in the longitudinal direction except both end portions 21 and 22, and on the fold line 5 of both end portions 21 and 22. When double-folded, as shown in FIG. 1B, the pair of strip-shaped pieces 1 integrally attached to the common end portions 21 and 22.
1 and 13 are formed, and when the pair of strip-shaped pieces 11 and 13 are curved, the closed annular sheet 1 in which the cutout portion 6 of the strip-shaped pieces 11 and 13 serves as the edge of the opening can be formed. 1 is used as a unit magnetic shield. Closed ring seat 1
On the outer side, the end portions 21 and 22 of the strip-shaped sheet 10 are left in an ear shape on the outer side.

In FIG. 1B, when the magnetic field lines 9 in the direction penetrating the opening of the closed annular sheet 1 act, the shielding current 91 flowing through the Nb-Ti superconductor layer 40 forming the sheet 1 is A closed loop is formed so as to flow through the pair of strip-shaped pieces 11 and 13, the ear-shaped ends 21 and 22, and the bent portion 5, and the shielding current 91 acts to shield the external magnetic field. Then, Nb− forming the closed loop 91.
Since the Ti superconducting layer 40 has no connecting portion, a persistent current with high temporal stability flows.

FIG. 1 (C) shows another embodiment of the closed annular sheet 1 constituted by the strip-shaped sheet 10 shown in FIG. 1 (A). In this case, the pair of strip-shaped pieces 11 and 13 of the strip-shaped sheet 10 provided with the cutout portion 6 are curvedly displaced in the normal direction of the sheet surface and opened in a ring shape. A closed loop of the shielding current 91 flowing in the Nb-Ti superconducting layer 40 is formed around the sheet 1, and the superconducting layer 40 also has no connection portion.

When the closed annular sheet 1 is formed in a circular shape, its inner diameter is determined by the length of the cutout portion 6 of the belt-shaped sheet 10. Therefore, by appropriately selecting the length of the belt-shaped sheet 10, regardless of the sheet width. It can be an annular magnetic shield of any diameter.

When the α-Ti phase precipitation cold-rolled sheet as described above is used for the strip-shaped sheet 10, this cold-rolled sheet is anisotropic in that the maximum shielding current density in the rolling direction is larger than that in the vertical direction. However, since the incision line 6 is parallel to the rolling direction 7, most of the superconducting flow loop 91 around the closed annular sheet 1 flows parallel to the rolling direction 7 (FIG. 1 (B)). Therefore, the maximum shielded magnetic field can be increased. On the other hand, in the end portions 21 and 22, the superconducting current flow loop 91 is substantially orthogonal to the rolling direction 7. However, by relatively increasing the end portion length to relatively reduce the shield current density, this magnetic instability is caused. You can escape from it. Therefore, the superconducting magnetic shield of the present invention exhibits a superior magnetic shielding ability as the anisotropy increases the maximum shielding current in the rolling direction of the strip material sheet 10.

FIG. 2 (A) shows a unit magnetic shield formed by stacking three closed annular sheets 1 of FIG. 1 (B) and laminating them. Thus, the magnetic shielding ability can be increased by forming a multilayer closed annular sheet.

In FIG. 2B, the end portions 21 and 22 protruding like ears on the outer periphery of the closed annular sheet 1 are folded so as to be attached to the outer peripheral surface.

FIG. 2C shows a cylindrical superconducting magnetic shield 8 formed from the unit magnetic shields 3 of the multilayer closed annular sheet 1.
However, four rows of unit magnetic shields 3a ... Are provided on the outer periphery of the cylindrical support 80 (usually made of aluminum).
Are arranged side by side to form a first superconducting magnetic shield. Next, the unit magnetic shield 3a of the first superconducting magnetic shield
.. are provided on the outer periphery of the unit magnetic shields 3b ..
In this case, the closed annular sheet 1 forming the unit magnetic shield 3
The larger the number of stacked layers, the better the magnetic shielding ability against the magnetic field in the axial direction.

Further, the unit magnetic shields 3b ... Forming the outer second magnetic shield constitute the inner second magnetic shield, and the adjacent unit magnetic shields 3a .. The magnetic shield ability to the magnetic field in the radial direction is increased by arranging so as to cover the peripheral edge and the gap therebetween. In this case, the first and second annular superconducting magnetic shields are arranged so that the superconducting layers 40 of the annular superconducting magnetic shields 3a ... It is preferable to make the maximum radial shield magnetic field uniform in each part of the shield. The superconducting layers 40 are brought into non-contact with each other because the superconducting layer 40 and the normal conducting metal layer 41 are provided on the annular sheet 1 of the unit magnetic shield.
It can be easily realized by using the laminate sheet of and.

The closed annular sheet 1 is usually flexible,
The inner diameter or the size of the opening of the closed annular sheet 1 is
It can be freely adjusted by adjusting the length of the incision portion 6 when forming from the band-shaped sheet 10 or by adjusting the folding length of the end portions 21 and 22 protruding to the outer periphery of the closed annular sheet 1. The shape of the body 80 can be appropriately selected so as to match the shape of the magnetically shielded space, and can be formed into a superconducting magnetic shield having a desired shape and size. For example, the support 80
To a desired tubular shape such as a square tubular shape or a drum shape, or the bottom surface thereof to be a partial spherical surface or an end plate shape, and the closed annular sheet 1 is attached to the outer circumference or the inner circumference to form a magnetic shield. And

In the above-mentioned embodiment, the closed ring-shaped sheet 1 formed from a strip-shaped rolled sheet is used, but a laminated sheet formed by sputtering can also be used as the strip-shaped sheet. In this case, Nb-
A Ti alloy layer and an Al layer are alternately sputter-deposited to a thickness of 1 μm or less to form a multilayer vapor-deposited layer. The multilayer vapor-deposited sheet is cut into a predetermined length and cut in the longitudinal direction to form a closed annular sheet 1. To do.

FIG. 3 shows a larger-diameter unit magnetic shield in which the incision of the strip sheet 10 is devised. In this example, as shown in FIG. 1A, a first cutout 61 is formed in the belt-shaped sheet 10 by cutting out one end thereof at the central portion in the longitudinal direction of the sheet, and the first cutout 61 cuts the sheet. The second incision portion 62 has the first end 21 and 22 left uncut.
It is provided in the longitudinal direction so as to bypass the end of the incision 61, and when expanded as shown in FIGS. 3B and 3C, a large-diameter closed annular sheet 1 is obtained, which is a unit. Similarly, as a magnetic shield, a cylindrical superconducting magnetic shield can be formed by stacking layers.

Next, the magnetic shielding ability of the superconducting magnetic shield of the present invention was examined as follows. The strip-shaped sheet 10 is Nb-
A foil having a three-layer structure with a width of 50 mm formed by joining Al layers on both sides of a Ti alloy layer and performing cold rolling (Nb-Ti layer thickness 3
4 μm, Al layer thickness 8 μm, aging annealed material) length 150 m
m, a 90 mm long incision is made on the center line in the longitudinal direction to form a closed annular sheet 1 having a diameter of about 50 mm and a height of 25 mm, and then, as shown in FIG. Unit magnetic shield 3 by stacking 10 annular sheets 1
And

As shown in FIG. 2C, the unit magnetic shield 3 is made of aluminum and has an outer diameter of 50 mm and a height of 120 m.
The superconducting magnetic shield 8 was formed on the outer periphery of the cylindrical support 80 having a thickness of 3 mm and a thickness of 3 mm by covering the two layers of the upper layer and the lower layer with a low temperature adhesive in a total of 7 rows.

In the liquid helium, the Hall element magnetic sensor was fixed on the axis of the superconducting magnet, fixed inside the hollow portion of the magnetic shield, and a magnetic field was applied. With the unit magnetic shield 3 alone, an external magnetic field of 5000 G in the axial direction
Up to, the inside of the hollow portion could be made to have substantially zero magnetic field. Further, the superconducting magnetic shield 8 was able to shield an external magnetic field of about 1 T in the axial direction and the radial direction to a substantially zero magnetic field with a central axis in the hollow portion.

Next, the outer diameter is 400 mm, the height is 350 mm,
A large-scale magnetic shield was trial-produced by using the Nb-Ti rolled sheet having the above-mentioned three-layer structure on the outer circumference of a stainless steel support having a thickness of 3 mm, and the magnetic shield ability was examined.

The assembling is performed by cutting lines along the longitudinal direction of the rolled sheet having a width of 100 mm and having a diameter of 400 mm and a height of 50.
mm closed annular sheet is formed, and 6 rows of unit magnetic shields formed by stacking 20 closed annular sheets are axially adhered to the outer periphery of the support with a low temperature adhesive to form a magnetic shield. did.

The test results show that at liquid helium temperature,
With respect to the magnetic field 1500G in the axial direction of the magnetic shield, the inside of the hollow portion could be substantially zero magnetic field.

[0037]

The cylindrical superconducting magnetic shield of the present invention utilizes a closed annular sheet of a laminate of a superconducting layer and a normal conducting metal layer. The closed annular sheet is a narrow strip sheet of the laminate. The size and shape of the opening is not dependent on the width of the strip-shaped sheet, but is simply determined by the incision length of the central portion of the strip-shaped sheet, so that a closed annular sheet of any size can be easily obtained. The size of the material including the superconductor layer is not limited, and a large-sized superconducting magnetic shield can be manufactured.

Further, when the unit magnetic shield is formed from the strip-shaped sheet, the yield of the superconducting material is good, complicated hot working and machining are not required, and the magnetic shield having the desired shape can be easily obtained. .

[Brief description of drawings]

FIG. 1 is a plan view (A) of a strip sheet of a laminate of a superconductor layer and a normal conducting metal, a perspective view (B, C) of a closed annular sheet formed from the strip sheet, and a laminated structure of the strip sheet. Sectional drawing (D) shown.

FIG. 2 is a perspective view (A, B) of a closed annular sheet and a perspective view (C) of a cylindrical superconducting magnetic shield formed by combining the closed annular sheets.

FIG. 3 is a perspective view of the incised band-shaped sheet (A) and the expanded and closed annular sheet (B, C).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Closed annular sheet 10 Band-shaped sheets 21, 22 End part 3 Unit magnetic shield 6 Incision part (edge) 8 Superconducting magnetic shield 80 Support

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Inoue 1-5 Doyamacho, Kita-ku, Osaka City High-pressure gas industry Co., Ltd. (72) Inventor Kohei Otani 1-5 Doyama-cho, Kita-ku, Osaka High-pressure gas industry Co., Ltd. (72) Inventor Manabu Sato 1-5 Doyama-cho, Kita-ku, Osaka High-pressure gas industry Co., Ltd. (72) Kenji Hisada 3-6-8, Kutaro-cho, Chuo-ku, Osaka Toyo Aluminum Co., Ltd. (72) Inventor Takamasa Yokote 3-6-8, Kutaro-cho, Chuo-ku, Osaka City Toyo Aluminum Co., Ltd.

Claims (9)

[Claims] 1. A strip-shaped sheet of a laminate composed of a superconductor layer and a normal-conducting metal layer is cut in its longitudinal direction to form a closed annular sheet having no joint, and the closed annular sheet serves as a unit magnetic shield. Made annular superconducting magnetic shield. 2. A laminate sheet comprising a superconductor layer and a normal-conducting metal layer is double-folded with a fold line portion at the center in the longitudinal direction, and the fold line portion is cut out leaving both ends, and a pair is formed. 5. A ring-shaped superconducting magnetic shield, wherein the pair of band-shaped pieces are formed, and the pair of band-shaped pieces are curved to opposite sides to form a closed ring-shaped sheet, and the closed ring-shaped sheet serves as a unit magnetic shield. 3. A closed annular sheet integrally formed from a strip-shaped sheet of a laminate composed of a superconductor layer and a normal conductive metal layer, the closed annular sheet having both ends common and separated from each other. An annular superconducting magnetic shield comprising a pair of strip-shaped parts curved in opposite directions, and the closed annular sheet serving as a unit magnetic shield. 4. The annular superconducting magnetic shield according to claim 1, wherein the unit magnetic shield is laminated in a plurality of layers. 5. The annular superconducting magnetic shield according to any one of claims 1 to 4 is provided so as to cover the circumferential surface of a cylindrical support in parallel with each other in the axial direction of the cylinder. A tubular superconducting magnetic shield. 6. A second annular superconducting magnetic shield is provided in parallel on the outer periphery of a first annular superconducting magnetic shield which is provided in parallel with the peripheral surface of the support, and a first annular superconducting conductor is provided. 6. The cylindrical superconducting magnetic shield according to claim 5, wherein the adjacent peripheral edges of the magnetic shield are covered with the peripheral body of the second annular superconducting magnetic shield. 7. The superconducting layer is an Nb—Ti alloy layer, the normal conducting metal layer is a Cu layer or an Al layer, and the strip-shaped sheet is formed by cold rolling the laminate. 4. The annular superconducting magnetic shield according to any one of 1 to 3. 8. The annular superconducting magnetic shield according to claim 1, wherein the strip-shaped sheet is formed by subjecting the laminate to an aging heat treatment after a cold rolling step to precipitate an α-Ti phase. 9. The superconductor layer is an Nb—Ti alloy layer,
Any one of a NbN compound layer and an NbN-TiN mixed crystal layer, the normal conductive metal layer is a Cu layer or an Al layer, and the strip-shaped sheet is a sheet substrate on which the superconducting layer and the normal conductive metal are formed. The annular superconducting magnetic shield according to any one of claims 1 to 3, wherein the layer and the layer are composed of a laminated body formed by alternate sputter deposition.