JPH08172012A - Superconducting magnet - Google Patents

Abstract

PURPOSE: To provide a compact and flexible superconducting magnet having a small contact heat resistance as the conductor used for connecting a refrigerator to a radiation shield. CONSTITUTION: In a superconducting magnet provided with a refrigerator 1 which cools a magnetic shield 7 and radiation shield 4 coaxially arranged against a cryostat 3 surrounding a main coil 2, conductors 9 are constituted of a plurality of sheets of copper foil and the end sections of the conductors 9 are fixed to terminal blocks with diffused junctions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a conductor of a superconducting magnet for MRI apparatus.

[0002]

2. Description of the Related Art An MRI apparatus equipped with a general refrigerator has a structure as shown in FIG. In FIG. 14, the first radiation shield 4 and the second radiation shield 4 arranged coaxially with the cryostat 3 surrounding the main coil 2 are provided.
The radiation shield 5 is provided and housed in the vacuum container 6. Further, a magnetic shield 7 that comprehensively surrounds the vacuum container 6 is provided to shield a high magnetic field. Furthermore, the first
And the refrigerator 1 is attached to the vacuum container 6 located on the outer peripheral side of the second radiation shields 4 and 5, and the cooling part thereof is inserted in the axial direction, and the first and second radiation shields are inserted in the cooling part. The radiation shields 4 and 5 are cooled by connecting the wires 4 and 5 by means of a flat wire conductor 8.

[0003]

The conductor 8 connecting the refrigerator 1 and the first and second radiation shields 4 and 5 is
It is important to have good thermal conductivity, flexibility, and to minimize the thermal resistance of the contact part.

Conventionally, in a superconducting magnet having such a structure, as shown in FIG. 15, a flat wire conductor 8 has an end portion of the flat wire 8a inserted into a hollow portion of a terminal plate 8b formed in a rectangular tube shape. Then, the end surface is bonded to the terminal board 8b by soldering or brazing.

However, in the flat mesh conductor 8 having such a structure, the solder material and the brazing material do not completely flow into the flat mesh wire 8a,
The contact area could not be taken. Further, in order to efficiently cool the first and second radiation shields 4 and 5 by the refrigerator 1, it is necessary to increase the cross-sectional area of the flat wire 8a, the shape becomes large, and the flexibility is lost. Moreover,
The contact resistance between the flat screen wire 8a and the terminal plate 8b becomes very large.

Further, there is a drawback that the solder flows into the flat mesh portion due to the capillary phenomenon and impairs the flexibility. The present invention has been made in view of the above circumstances, and provides a superconducting magnet that is compact and has low contact thermal resistance and flexibility as a conductor that connects a refrigerator and a radiation shield. The purpose is to

[0007]

In order to achieve the above object, the present invention provides a superconducting magnet having the following conductors. The invention corresponding to claim 1 to claim 3 is a superconducting magnet equipped with a cryostat that cools a magnetic shield and a radiation shield arranged coaxially with a cryostat that surrounds a main coil, wherein the refrigerator and the radiation shield are provided. The conductor to be connected is composed of a plurality of copper foils or aluminum foils, or copper foils and aluminum foils.

According to the invention of claim 4, the conductor is composed of a plurality of foils, and the ends of the conductor are diffusion-bonded together with the terminal plate. In the invention corresponding to claim 5, the conductor is composed of a plurality of foils, the ends of the conductor are fixed by diffusion bonding, and the fixing portion and the terminal plate are silver-soldered. .

In the invention corresponding to claim 6, the conductor is composed of a plurality of foils, and the ends of the conductor are fixed by a plurality of rivets and fixed by diffusion bonding. The invention corresponding to claim 7 is a superconducting magnet equipped with a refrigerator for cooling a radiation shield arranged coaxially with a cryostat surrounding a main coil, wherein a conductor connecting the refrigerator and the radiation shield is made of high-purity aluminum. It is composed of foil.

According to an eighth aspect of the invention, in a superconducting magnet equipped with a cryostat surrounding the main coil and a radiation shield arranged coaxially with the cryostat, heat intrusion between the high temperature side and the low temperature side is reduced. A conductor connecting a radiation shield and a thermal anchor conductor provided in the middle of the cryostat for the purpose is made of high-purity aluminum foil.

The invention corresponding to claim 9 comprises a cryostat surrounding the main coil, a liquid helium reservoir for supplying liquid helium to the coil, and a radiation shield arranged on the outer periphery of the cryostat and the liquid helium reservoir. In the superconducting magnet described above, a conductor having flexibility for heat transfer between the radiation shield on the cryostat side and the radiation shield on the liquid helium reservoir side is made of high-purity aluminum foil.

According to a tenth aspect of the invention, the conductor of the invention according to any one of the seventh to ninth aspects is constituted by one or more sheets of high-purity aluminum foil, and the ends thereof are welded or It is glued and joined.

According to an eleventh aspect of the invention, the conductor of the invention according to any one of the seventh to ninth aspects is constituted by one or more high-purity aluminum foils, and the end portions thereof are terminal plates. It is joined by cold press compression molding or diffusion joining together with.

[0014]

In the inventions corresponding to claims 1 to 3, since the conductor is composed of a plurality of copper foils or aluminum foils, or copper foils and aluminum foils, the adhesiveness is increased and the contact resistance is increased. Less. Moreover, since copper foil or aluminum foil is used as the material, it is possible to obtain excellent thermal characteristics by using a material having flexibility and good thermal conductivity.

In the invention according to claim 4, the conductor is made of a plurality of foils, and the end portion of the conductor is fixed by diffusion bonding together with the terminal plate, so that the adhesion of the conductor is enhanced. The temperature difference due to the thermal resistance between the radiation shield cooled by the refrigerator and the conductor is reduced, and the cooling characteristics are improved.

In the invention corresponding to claim 5, since the end portions of the conductor composed of a plurality of foils are fixed by diffusion bonding and the fixing portion and the terminal plate are silver-soldered,
It can be used for a terminal plate of any shape of the conductor, which is also advantageous in terms of standardization.

In the invention corresponding to claim 6, the contact thermal resistance is reduced by fixing the end portions of the conductor composed of a plurality of foils with a plurality of rivets, and further by diffusion bonding. Since they are fixed, the contact thermal resistance can be reduced to zero.

In the invention corresponding to claims 7 to 9, by using one or more high-purity aluminum foils,
In particular, it can have high thermal conductivity at a temperature of 20 K or less. In the invention corresponding to claims 10 and 11, further 1
The contact resistance of the end portions can also be reduced by directly welding, adhering or joining the end portions of one or more sheets of high-purity pure aluminum foil together with the terminal plate by room temperature press compression molding and diffusion joining. Further, since high-purity aluminum is a very soft material, it is also flexible.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a partial sectional view of an MRI apparatus showing a first embodiment of a superconducting magnet according to the present invention, and FIG. 2 is an enlarged view of the conductor shown in FIG. The same parts as those in FIG. 14 will be described with the same reference numerals.

In FIG. 1, a first radiation shield 4 and a second radiation shield 5 arranged coaxially with a cryostat 3 surrounding the main coil 2 are provided inside and housed in a vacuum container 6. Further, a magnetic shield 7 that comprehensively surrounds the vacuum container 6 is provided to shield a high magnetic field. Further, the refrigerator 1 is attached to the vacuum container 6 located on the outer peripheral side of the first and second radiation shields 4 and 5, and the cooling part thereof is inserted in the axial direction. The two radiation shields 4 and 5 are connected by a conductor 9 to cool these radiation shields 4 and 5.

The conductor 9 is made of Cu (RRR = 20) having a high thermal conductivity among various metals shown in FIG. 3 as its material.
0) (non-oxidized copper) is selected, and a plurality of box-shaped connecting portions 9b formed in the connecting end face of the terminal plate 9a connected to the cooling portion of the refrigerator and opening in the vertical direction are shown in FIG. Copper foil 9
The end of c is inserted.

The opening of the connecting portion 9b is sized so that the ends of the plurality of copper foils 9c are inserted, and the ends of the plurality of copper foils 9c inserted into the opening of the connecting portion 9b. As for the parts, the front surface 10 of the connection part 9b is fixed by room temperature press-compression molding or diffusion bonding by hot pressing in vacuum. In this case, in order to provide flexibility, the copper foil 9c preferably has a plate thickness of 0.1 mm to 0.2 mm.
The cross-sectional area of b and the cross-sectional area of the copper foil 9c do not have to be equivalent, and the size of the connecting portion 9b and the number of copper foils 9c are determined by the heat load.

According to the conductor 9 having such a structure, the copper foil 9c and the connecting portion 9b of the terminal plate 9a are improved in adhesiveness by press-compression molding or by diffusion bonding by hot pressing in a vacuum, thereby making contact. There is less resistance. Also, from 0.1 mm
Since the copper foil 9c has a thickness of 0.2 mm, flexibility can be obtained.

Since the copper foil 9c and the connecting portion 9b of the terminal plate 9a are press-contact-molded as described above, the adhesion of the conductor 9 is enhanced and the first and second radiation shields 4 for cooling by the refrigerator 1 are provided. , 5 and the conductor 9 have a reduced temperature difference due to thermal resistance, and the cooling characteristics are improved.

Further, since the copper foil 9c and the terminal plate 9a can be completely fixed by diffusion bonding by hot pressing in a vacuum, the characteristics are further improved and the contact thermal resistance becomes zero. In the case of a superconducting magnet used in vacuum, a very large effect can be obtained.

Furthermore, since the material of the conductor 9 is selected to have good thermal conductivity, the cooling characteristics are stable, and the thickness of the copper foil 9c is 0.1 mm to 0.2 mm, which is flexible. The property is improved.

In addition, when the temperature between the refrigerator 1 and the first and second radiation shields 4 and 5 is to be made as small as possible, the cross-sectional area of the conductor 9 is easier than that of a conventional flat wire. A compact conductor 9 can be manufactured.

FIG. 4 is an enlarged view of a conductor in the second embodiment of the superconducting magnet according to the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. I will describe the points.

In the second embodiment, as shown in FIG. 4, as a conductor 9 for connecting the cooling part of the refrigerator and the radiation shield, a plurality of sheets are provided in the opening of the connecting part 9b formed on the terminal board 9a. Insert the end of the copper foil 9c, the front surface 1 of the connecting portion 9b
0 is press-bonded and molded at room temperature or is hot-pressed in a vacuum to be diffusion-bonded and fixed, and the end faces of the plurality of copper foils 9c existing on the upper opening face of the connection part 9b are silver-brazed.

According to the conductor having such a structure, the ends of the copper foil 9c inserted into the box-shaped connecting portion opening in the vertical direction of the terminal plate 9a are diffusion-bonded in advance and then soldered or brazed. Therefore, it can be used for a terminal plate having an arbitrary shape, which is also advantageous in terms of standardization.

FIG. 5 is an enlarged view of the conductor in the third embodiment of the superconducting magnet according to the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. I will describe the points.

In the third embodiment, as shown in FIG. 5, as a conductor 9 for connecting the cooling section of the refrigerator and the radiation shield, a plurality of sheets are provided in the opening of the connecting section 9b formed on the terminal board 9a. Insert the end of the copper foil 9c into the front surface 1 of the connecting portion 9b.
A plurality of rivets 19 are inserted and fixed from 0, and further fixed by press bonding or hot pressing in vacuum.

With the conductor having such a structure, by fixing the end portions of the plurality of copper foils 9c with the rivets 19, a greater pressure-bonding effect can be obtained. Therefore, the contact thermal resistance is reduced, and the contact thermal resistance can be made almost zero by diffusion bonding.

FIG. 6 is an enlarged view of the conductor in the fourth embodiment of the superconducting magnet according to the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. I will describe the points.

In the fourth embodiment, the material of the conductor 11 connected between the refrigerator of the MRI apparatus and the first and second radiation shields 4 and 5 is selected from various metals shown in FIG. A box (Al) having excellent conductivity (RRR = 1000) (pure aluminum) is selected, and a vertically opened box is formed on the connection end face of the terminal plate 11a connected to the cooling part of the refrigerator as shown in FIG. A plurality of aluminum foils 11c are inserted into the shaped connection portion 11b.

The opening of the connecting portion 11b is sized so that the end portions of the plurality of aluminum foils 11c are inserted, and the end portions of the plurality of aluminum foil 11c inserted into the opening portions of the connecting portion 11b. As for the parts, the front surface 10 of the connecting part 11b is press-bonded and molded at room temperature, or is diffusion-bonded and fixed by hot pressing in vacuum. In this case, in order to have flexibility, the plate thickness of the aluminum foil 11c is 0.1 mm.
.About.0.2 mm is desirable, and it is not necessary that the cross-sectional area of the connecting portion 11b of the terminal board 11a and the cross-sectional area of the aluminum foil 11c be equivalent, and the size of the connecting portion 11b and the number of aluminum foils 11c are determined by the heat load. .

With the conductor 11 having such a structure, the end portion of the aluminum foil 11c and the terminal plate 11a can be adhered to each other by press-compression molding or by diffusion bonding by hot pressing in vacuum to improve the contact resistance. Is less. Also,
Since the aluminum foil 11c having a thickness of 0.1 mm to 0.2 mm is used, flexibility can be obtained. In addition, the cooling characteristics are excellent, and the excellent cooling efficiency is improved.

Therefore, in the fourth embodiment, the aluminum foil 11c having excellent thermal conductivity is selected as the material of the conductor 11, so that the cooling efficiency is very high and the refrigerator 1 and the first and second refrigerators are used. When the temperature difference between the radiation shields 4 and 5 is minimized, it can be performed with a smaller cross-sectional area than the copper foil 9c of the above-described embodiment.

FIG. 7 is an enlarged view of the conductor in the fifth embodiment of the superconducting magnet according to the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. I will describe the points.

In the fifth embodiment, the material of the conductor 13 connected between the refrigerator of the MRI apparatus and the first and second radiation shields 4 and 5 is selected from various metals shown in FIG. Cu with good conductivity (RRR = 200) (copper oxide free)
And Al (RRR = 1000) (pure aluminum) having excellent thermal conductivity are selected, and Al (RRR = 1000) is used for the terminal plate 14 as shown in FIG. A plurality of aluminum foils 15 and a plurality of copper foils 16 are combined and inserted into a box-shaped connection portion 14a formed in the connection end surface of the terminal plate 14 and opened in the vertical direction.
Adhesion is provided by press-press molding from the front surface 10 side of a.

In this case, when a plurality of aluminum foils 15 and copper foils 16 are combined, the aluminum foils 15 are combined with the copper foils 16 so as to be on the end face side of the terminal board 14. Further, in order to have flexibility, the plate thickness of the aluminum foil 15 and the copper foil 16 is preferably 0.1 mm to 0.2 mm, and it is not necessary that the cross-sectional areas of the terminal board 14 become equivalent, and the terminal board 14 is not affected by heat load. Size, aluminum foil 1
5. Determine the number of copper foils 16. At this time, the number of the aluminum foils 15 and the number of the copper foils 16 are determined depending on the set temperature condition, so it does not matter which one is larger.

With the conductor 13 having such a structure, as can be seen from the graph of thermal conductivity shown in FIG. 3, the aluminum foil 15 and the copper foil 16 contribute to heat transfer depending on the temperature. That is, in the combination of the aluminum foil 15 and the copper foil 16,
Copper foil 16 above 50K, aluminum foil 15 below
Is effective, so that very high cooling efficiency characteristics can be achieved and flexibility can be exhibited.

Although the cost of Cu increases as the value of RRR increases, a more inexpensive heat transfer plate 13 can be manufactured by combining Al and Cu. FIG. 8 is a partial sectional view showing a sixth embodiment of the superconducting magnet according to the present invention.

In FIG. 8, a first radiation shield 24 and a second radiation shield 25, which are arranged coaxially with a cryostat 23 surrounding the main coil 22, are provided.
It is housed in a vacuum container 26. Also, the first and second
The refrigerator 21 is attached to the vacuum container 26 located on the outer peripheral side of the radiation shields 24 and 25, and the cooling unit is axially inserted, and the first and second radiation shields 24 and 25 are inserted in the cooling unit. Fig. 3 shows high-purity aluminum with high thermal conductivity selected from various metals (RRR about 1000
These radiation shields 24 and 25 are cooled by connecting with the conductor 27 made of the above.

FIG. 9 is a partial sectional view showing a seventh embodiment of the superconducting magnet according to the present invention. In FIG. 9, a first radiation shield 24 and a second radiation shield 25 that are arranged coaxially with a cryostat 23 that surrounds the main coil 22 are provided inside and housed in a vacuum container 26. Further, the cryostat 23 is elastically supported by the vacuum container 26 by the bellows 34 as a thermal anchor conductor arranged through the openings provided on the outer circumferences of the first and second radiation shields 24, 25, and the bellows 34 are elastically supported by the vacuum vessel 26. 34, the open ends of the first and second radiation shields 24, 25 are connected by a conductor 27 made of high-purity aluminum (RRR of about 1000 or more) having a high thermal conductivity selected from various metals shown in FIG. The heat penetration between the high temperature side and the low temperature side is reduced.

FIG. 10 is a partial sectional view showing an eighth embodiment of the superconducting magnet according to the present invention. In FIG. 10, a cryostat 23 surrounding the main coil 22 and a liquid helium reservoir 28 for supplying liquid helium to the main coil 22 are provided, and a space between them is connected by a communication pipe, and these cryostat 23 and liquid helium are connected. A first radiation shield 24 and a second radiation shield 25 arranged on the outer peripheral portion of the reservoir 28 are provided,
It is housed in a vacuum container 26. In addition, the first radiation shield 24 and the second radiation shield 25 on the cryostat 23 side and the liquid helium reservoir 28 side are connected to each other as shown in FIG.
Conductor 27 made of high-purity aluminum (RRR about 1000 or more) with high thermal conductivity selected from the various metals shown in
To reduce heat intrusion between the high temperature side and the low temperature side.

Here, in the sixth to eighth embodiments, as the conductor 27, one or a plurality of high-purity aluminum foils 27a are used as shown in FIG. 11, and the ends are welded as they are, or As shown in FIG. 12, the adhesive 29 is used for adhesion.

Therefore, such a high-purity aluminum foil 27a
Moreover, by using the conductor 27 formed by welding or adhering the end portions as they are, not only the thermal conductivity is improved, but also the adhesion of the end portions is improved and the thermal contact resistance is reduced. Further, the flexibility is improved by setting the foil thickness to 0.1 to 0.3 mm.

As the conductor 27 used in the sixth to eighth embodiments, a plurality of high-purity aluminum foils 27a are used.
The end portions of the plurality of high-purity aluminum foils 27a are connected to the box-shaped terminal plate 27b as shown in FIG.
The same effect as described above can be obtained by using the conductor 27 which is inserted in the terminal 27b and is brought into close contact with the terminal plate 27b by room temperature press compression molding or diffusion bonding.

As described above, in the sixth to eighth embodiments, the conductor connecting the refrigerator 21 and the radiation shields 24 and 25, the heat anchor conductor, and the conductor connecting the radiation shields are used. Since the high-purity aluminum foil 27a is used as the material, the thermal conductivity is greatly improved especially at a temperature of 20 K or less, and the ends are directly welded, bonded, or cold-pressed at room temperature together with the terminal board 27b. Or by diffusion bonding, the temperature difference due to the contact thermal resistance at both ends of the conductor is reduced, and the heat transfer characteristic is improved. Moreover, since the contact thermal resistance becomes zero upon welding, a highly reliable superconducting magnet with less product variation can be obtained.

Further, since the high-purity aluminum foil 27a is very soft, it has high flexibility and can easily absorb the heat shrinkage when the superconducting magnet which is generally assembled at room temperature is cooled to a low temperature.

The present invention can be applied not only to the super-electric magnet for MRI but also to the superconducting magnet for particle detectors used in the research of high energy physics and the like. In this case, in the superconducting magnet for particle detector, when the calorimeter for measuring the particle energy is outside the electromagnet, the energy is measured after the generated particles pass through the electromagnet. It is necessary to minimize loss. Even in such a case, aluminum is very advantageous because the amount of substance is small.

[0053]

As described above, according to the present invention, the following effects can be obtained. (1) By selecting an aluminum foil or a copper foil having good thermal conductivity shown in FIG. 3, not to mention flexibility,
The heat conduction between the radiation shields from the refrigerator is improved, and the cooling efficiency is improved. (2) When the cooling efficiency is further increased, the cooling efficiency can be easily increased as compared with the conventional flat wire, and the construction method by soldering is perfect by performing diffusion bonding with a room temperature press or a hot press in a vacuum. Since it can be fixed to, the cooling efficiency characteristics are further improved and the contact thermal resistance becomes almost zero,
Product variation is reduced. Furthermore, the edges of the aluminum foil and copper foil are diffusion-bonded in advance, and then soldered,
Since it can be brazed, it can be used for terminal boards of any shape, which is also advantageous in terms of standardization. (3) Cu with good thermal conductivity shown in FIG. 3 (RRR = 200
Although it is expensive to produce a conductor only with 0), the cost is low (Al (RRR = 1000), Cu (RRR = 20).
00) can be made more inexpensive by selecting and combining them. Moreover, since the aluminum foil and the copper foil contribute to heat transfer depending on the temperature, a very high cooling efficiency characteristic can be obtained.

When cooling the radiation shield from the refrigerator to 10 K or less, expensive Cu (RRR = 200) is used.
It is desirable to select 0). (4) High-purity aluminum (RRR) with high thermal conductivity shown in FIG.
By selecting about 1000 or more), the thermal conductivity is significantly improved, especially at a temperature of 20 K or less, and the cooling efficiency is improved. (5) Aluminum foils and aluminum foils and terminal plates with both ends welded or diffusion bonded are completely fixed, so that the characteristics are further improved and the contact thermal resistance becomes zero, so there is little variation in products. The reliability is greatly improved. (6) Since soft, high-purity aluminum is used as a material, it is flexible and can easily absorb heat shrinkage when a superconducting magnet that is generally assembled at room temperature is cooled to a low temperature.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an MRI apparatus showing a first embodiment of a superconducting magnet according to the present invention.

FIG. 2 is an enlarged view of the conductor shown in FIG.

FIG. 3 is a diagram showing the thermal conductivity of various metal materials.

FIG. 4 is an enlarged view of a conductor according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of a conductor according to a third embodiment of the present invention.

FIG. 6 is an enlarged view of a conductor according to a fourth embodiment of the present invention.

FIG. 7 is an enlarged view of a conductor according to a fifth embodiment of the present invention.

FIG. 8 is a partial sectional view showing a sixth embodiment of the superconducting magnet according to the present invention.

FIG. 9 is a partial sectional view showing a seventh embodiment of the superconducting magnet according to the present invention.

FIG. 10 is a partial cross-sectional view showing an eighth embodiment of the superconducting magnet according to the present invention.

FIG. 11 is an enlarged view of a conductor used in the sixth to eighth embodiments.

FIG. 12 is an enlarged view of different conductors used in the sixth to eighth embodiments.

FIG. 13 is an enlarged view of yet another conductor used in the sixth to eighth embodiments.

FIG. 14 is a partial cross-sectional view showing a conventional MRI apparatus.

FIG. 15 is an enlarged view of the conductor shown in FIG.

[Explanation of symbols]

1,21 ... Refrigerator, 2,22 ... Main coil, 3,23
...... Cryostat, 4,24 ...... First radiation shield, 5,25 …… Second radiation shield, 26 …… Vacuum container, 7 …… Magnetic shield, 9,11,13,27 …… Conductor, 9a, 11a, 21c ... Terminal plate, 9b, 11
b, 27 ... Conductor, 9c ... Copper foil, 11c ... Aluminum foil, 14,27b ... Terminal board, 15, 27a.
Aluminum foil, 16 ... Copper foil, 19 ... Rivet.

Claims (11)

[Claims] 1. A superconducting magnet equipped with a refrigerator for cooling a magnetic shield and a radiation shield arranged coaxially with a cryostat surrounding a main coil, wherein a plurality of copper conductors connecting the refrigerator and the radiation shield are used. A superconducting magnet characterized by being composed of foil. 2. The superconducting magnet according to claim 1, wherein the conductor is composed of a plurality of aluminum foils. 3. The superconducting magnet according to claim 1, wherein one conductor is composed of a plurality of copper foils and aluminum foils. 4. In a superconducting magnet equipped with a refrigerator for cooling a magnetic shield and a radiation shield arranged coaxially with a cryostat surrounding a main coil, the conductor is composed of a plurality of foils, and A superconducting magnet, characterized in that the end of the body is fixed together with the terminal plate by diffusion bonding. 5. In a superconducting magnet equipped with a refrigerator for cooling a magnetic shield and a radiation shield arranged coaxially with a cryostat surrounding a main coil, the conductor is composed of a plurality of foils, and A superconducting magnet, characterized in that an end portion of a body is fixed by diffusion bonding, and the fixing portion and a terminal plate are brazed with silver. 6. A superconducting magnet equipped with a refrigerator for cooling a magnetic shield and a radiation shield arranged coaxially with a cryostat surrounding a main coil, wherein a conductor is composed of a plurality of foils, and A superconducting magnet characterized in that an end of a body is fixed by a plurality of rivets and fixed by diffusion bonding. 7. A superconducting magnet equipped with a refrigerator for cooling a radiation shield arranged coaxially with a cryostat surrounding a main coil, wherein a conductor connecting the refrigerator and the radiation shield is made of high-purity pure aluminum foil. A superconducting magnet characterized by being constructed. 8. A superconducting magnet equipped with a cryostat surrounding a main coil and a radiation shield arranged coaxially with the cryostat, wherein the cryostat is provided in the middle of the cryostat for the purpose of reducing heat intrusion between the high temperature side and the low temperature side. A superconducting magnet, characterized in that the conductor connecting the provided radiation shield and the thermal anchor conductor is made of high-purity aluminum foil. 9. A superconducting magnet comprising a cryostat surrounding a main coil, a liquid helium reservoir for supplying liquid helium to the coil, and a radiation shield arranged around the outer periphery of the cryostat and the liquid helium reservoir. A superconducting magnet, wherein a conductor having flexibility for heat transfer between the radiation shield on the cryostat side and the radiation shield on the liquid helium reservoir side is made of high-purity aluminum foil. 10. A method according to any one of claims 7 to 9, characterized in that the end portions of a conductor made of one or more high-purity aluminum foils are joined by welding or bonding. Superconducting magnet. 11. The end portion of a conductor made of one or more sheets of high-purity aluminum foil is joined together with a terminal board by room temperature press-compression molding or diffusion joining. 9. The superconducting magnet according to any one of items 9 to 9.