JPH05340640A - Liquid helium cooling magnetic refrigerator - Google Patents

Abstract

PURPOSE:To improve heat transfer between a magnetic actuator and liquid helium by so composing the actuator reciprocating between a hollow part of a superconducting coil and a hollow part of a cylindrical superconducting magnetic shield as to be brought into surface contact with a heat transfer member connected to a low temperature side helium tank. CONSTITUTION:A hollow superconducting magnetic shield 3 is so disposed near at hand coaxially with an axial center direction of a superconducting coil 1 for generating a strong magnetic field, and a vacuum chamber 6 is formed to communicate the hollow part of the shield 3 with that of the coil 1. A columnar magnetic actuator 2 attached to an end of an elevation rod 71 in an elevation unit 7 of an upper part of a vacuum heat insulation tank 8 is vertically movably disposed in the chamber 6, a high temperature side helium liquid tank 4 is provided at an end of the chamber 6 at the side of the coil 1, and a low temperature side helium liquid tank 5 is provided at an end of the tank 4 at the side of the shield 3. A smooth flat surfacelike end face is provided at the actuator 2, brought into surface contact with a flat surface of a heat transfer member 52 formed on the tank 5 to satisfactorily transfer heat between the actuator and the helium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic actuator which reciprocates between a strong magnetic field in the hollow portion of a superconducting coil and a zero magnetic field in the hollow portion of a cylindrical superconducting magnetic shield arranged in the vicinity thereof. The present invention relates to a magnetic refrigerator used in the extremely low temperature range of liquid helium by utilizing the cold generated.

[0002]

2. Description of the Related Art A magnetic refrigerator utilizing an adiabatic degaussing process is used to achieve and maintain an ultralow temperature below liquid helium temperature in a continuous process. The magnetic refrigerator is a strong magnetic field formed by a superconducting magnet or the like, and a zero magnetic field in the vicinity thereof, a substance having a large entropy change with respect to a change in the magnetic field strength, such as a magnetic working body such as gadolinium-potassium-garnet. By rotating and moving, the heat generated by the magnetic actuator in a strong magnetic field is transferred to the high temperature side heat source, and the cold generated by the magnetic actuator due to adiabatic demagnetization in the zero magnetic field is transferred to the low temperature side heat source. The side heat source is constantly cooled.

Such a non-stationary magnetic refrigerator has an advantage that the superconducting magnet can be used in the permanent current mode to avoid Joule heat loss due to interruption of the coil exciting current.
On the other hand, the zero magnetic field region used in the degaussing process is inevitably far away from the strong magnetic field magnet, and it is necessary to increase the moving process of the magnetic actuator. In this regard, the conventional technique uses a method in which the intermediate position of a pair of superconducting coils that oppose each other is used for a zero magnetic field, or arranges an auxiliary coil that generates an opposite magnetic field in the vicinity of the main coil to separate the zero magnetic field from the strong magnetic field. The method of shortening the distance was adopted.

The present inventors have already arranged a cylindrical superconductor coaxially with the superconducting coil and utilized the magnetic shielding effect of the superconductor to form a perfect zero in the hollow portion of the superconductor. We proposed a magnetic refrigerator in which the parallel movement stroke of the magnetic actuator was shortened by making the magnetic field a degaussing space (Japanese Patent Application No. 2-32).
5586).

Further, in the non-stationary refrigerator, the reciprocating magnetic actuating body transmits heat generated in the exciting process to the high temperature side heat source, and effectively transmits cold generated in the next demagnetizing process to the low temperature side heat source. Although a thermal switch mechanism is required, in the prior art, the high temperature side thermal switch mechanically makes thermal contact between the heat transfer member from the auxiliary cooler and the magnetic actuator, while the low temperature side thermal switch, for example, A method has been adopted in which gaseous helium is brought into contact with the surface of the magnetic actuator to liquefy and liquefy low temperature helium in a container.

[0006]

In the non-static type magnetic refrigerator, the magnetic actuator repeatedly moves, so in order to exchange heat with the heat source on the low temperature side, a clever heat switch mechanism like a static magnetic refrigerator is used. However, the method was limited to the method of cooling and liquefying the gas by bringing it into contact with the gas phase in the upper part of the liquid tank.

In a refrigerator that constantly obtains superfluid helium by using a liquid helium bath as a heat source on the low temperature side, the equilibrium vapor pressure of helium is low because of the ultralow temperature, so the heat transfer coefficient between the magnetic actuator and helium gas is small, and helium is small. The cooling liquefaction rate of the gas is reduced, the reciprocating cycle of the magnetic actuator cannot be increased, and the efficiency of the refrigerator is reduced. Therefore, it is necessary to efficiently cool liquid helium to a temperature below the superfluid helium temperature without interposing a vapor phase. Particularly, in a magnetic refrigerator used in outer space, it is necessary to cool superfluid helium in a closed container.

The present invention is intended to utilize the cold generated by demagnetizing the magnetic actuator in the hollow portion of the cylindrical superconducting magnetic shield, and to use the inside of the hollow portion and the low temperature side heat source for cooling. Had to be connected in a heat transferable manner.

Further, in a superconductor of a superconducting coil or a superconducting magnetic shield, Nb-Ti is used at a temperature below liquid helium.
Alloys can be used, but due to flux jump and other unstable factors, there was a limit to the maximum magnetic field generated by the superconducting coil and the maximum magnetic field shielded by the magnetic shield, which was an important factor in determining the capacity of the magnetic refrigerator. .. When the magnetic field strength in the excitation process is constant, the entropy change of the magnetic actuator also decreases with the temperature decrease, so the amount of cold in the demagnetization process also decreases, and therefore, in particular, cooling below the superfluid helium temperature. In doing so, it was necessary to increase the maximum generated magnetic field of the superconducting coil and the maximum shielded magnetic field of the magnetic shield to efficiently cool the liquid helium on the low temperature side. In order to cool the superconducting coil and the magnetic shield, there is a method to forcibly evaporate the liquid helium in each cooling tank to lower the liquid temperature, but it is necessary to replenish the liquid helium each time the liquid level drops. Therefore, the above instability of the superconductor due to the change in the liquid temperature such as the increase in the liquid temperature due to the replenishment is unavoidable.

In view of the above problems, the present invention is, first of all,
It is to provide a magnetic refrigerator capable of efficiently cooling liquid helium at a boiling temperature of normal pressure filled in a closed container of a low temperature side liquid tank to a superfluid temperature or lower. It is an object of the present invention to provide a refrigeration process in which the maximum generated magnetic field of a superconducting coil or the maximum shielded magnetic field of a magnetic shield is increased so as to compensate for a decrease in output of a magnetic actuator due to a decrease in temperature.

[0011]

The magnetic refrigerator of the present invention comprises:
A superconducting coil that generates a strong magnetic field, a hollow superconducting magnetic shield that is coaxially arranged in a row in the axial direction of the superconducting coil, a hollow portion of the superconducting coil, and a hollow portion of the magnetic shield. A vacuum chamber formed by being inserted into the vacuum chamber, a magnetic actuator disposed in the vacuum chamber so as to be capable of reciprocating by a reciprocating mechanism between the superconducting coil hollow portion and the magnetic shield hollow portion, and the vacuum chamber. At the end of the superconducting coil on the high temperature side, which is arranged so as to be able to transfer heat to and from the magnetic actuator, and at the end of the vacuum chamber on the side of the magnetic shield, which is so arranged as to be in contact with the magnetic actuator and at low temperature. Which consists of a side liquid tank, the process of heat transfer cooling of the heat of the magnetic actuator excited in the hollow portion of the superconducting coil to the high temperature side liquid tank and the cooling of the magnetic actuator demagnetized in the hollow portion of the magnetic shield. Repeat the process of cooling the liquid in the low temperature side liquid tank by As is the magnetic refrigerator.

In the magnetic refrigerator of the present invention, the superconducting coil and the superconducting magnetic shield are immersed in the liquid in the same or different cooling tank and cooled to the critical temperature or lower to maintain the superconducting state. When helium is used as the liquid in the cooling tank, the coil cooling tank of the superconducting coil and the cooling tank of the magnetic shield are connected to or integrated with the high temperature side liquid helium tank as shown in the embodiment. May be combined with.

The low temperature side liquid helium tank is arranged at the end of the vacuum chamber on the side of the magnetic shield so as to be in contact with the magnetic actuating member via the heat transfer member so as to be able to transfer heat. On the other hand, it is insulated from the magnetic shield. The members are disposed so as to be thermally isolated from each other. The low temperature side liquid helium tank is filled with liquid helium in a pressurized state of about 1 atm, and no gas is present in the helium tank.

The simplest contact heat transfer means between the magnetic actuator and the low temperature side liquid helium tank is the heat transfer projecting at the demagnetizing position of the magnetic actuator, that is, toward the hollow portion of the magnetic shield. A member is connected to the liquid helium tank so that the liquid can flow and come in contact with the end surface of the magnetic actuator. In this case, the end surface of the heat transfer member and the end surface of the magnetic actuation are mirror-finished smooth flat surfaces.

In the present invention, in particular, the low temperature side liquid helium tank is also used in communication with or integrally formed with a cooling tank for cooling the superconducting magnetic shield in the liquid helium. The tank includes a vacuum tank or a magnetic refrigerator that is thermally isolated by interposing a heat insulating member.

Further, the low temperature side liquid helium tank is connected to the coil cooling tank for cooling the superconducting coil in the liquid helium together with the shield cooling tank for cooling the superconducting magnetic shield, or formed integrally. A magnetic refrigerator that is thermally isolated from the above-mentioned high temperature side liquid helium tank by a vacuum tank or a heat insulating member is preferably used.

[0017]

[Operation] The superconducting coil and the cylindrical superconducting magnetic shield are coaxially arranged and fixed, and the hollow portion of the superconducting coil forms a strong magnetic field space, while the superconducting magnetic shield has a hollow portion. Since the magnetic field formed by the superconducting coil does not penetrate, a zero magnetic field space is formed.

A vacuum chamber is formed in the hollow portion between the superconducting coil and the magnetic shield, and the magnetic actuator connected to the reciprocating mechanism is reciprocally movable in the vacuum chamber. The body is excited in the strong magnetic field space of the superconducting coil to generate heat, and is demagnetized in the zero magnetic field space of the superconducting magnetic shield to generate cold. Since the magnetic actuator is in the vacuum chamber, it is thermally isolated in a high vacuum.

At the end of the vacuum chamber on the side of the superconducting coil, the heat transfer member cooled by the high temperature side liquid helium tank, which is the high temperature side liquid tank, is arranged so as to be able to come into contact with the magnetic actuator, so that the exciting process is performed. The heat generated by the magnetic actuator in (1) is transferred to the liquid helium bath to be cooled.

Since the low temperature side heat transfer member of the low temperature side helium liquid tank fixed to the other end of the vacuum chamber, that is, the end portion on the magnetic shield side, comes into surface contact with the magnetic actuation body, so that the demagnetization space of the magnetic actuation body is maintained. The generated cold cools the liquid helium in the liquid tank. Since the end surface of the low temperature side heat transfer member and the contact surface of the magnetic actuating body that is in contact with this end surface are both smooth flat surfaces that are mirror-finished, the magnetic actuating body and the helium bath in the low temperature side liquid tank are Increase the heat transfer coefficient between.

When liquid helium is usually kept under a pressure of about atmospheric pressure, a helium gas phase does not occur in the tank, and therefore liquid helium directly contacts the low temperature side heat transfer member without interposing the gas phase. The heat transfer coefficients of the liquid helium bath and the low temperature side heat transfer member can be maintained well. Therefore, it becomes easy to bring the low temperature side liquid helium to the superfluid helium temperature or lower.

When the low temperature side liquid helium tank contains the superconducting magnetic shield and is cooled at the same time by the low temperature side liquid helium bath, the superconducting flux jumps the superconductor as the temperature of the superconductor of the magnetic shield decreases. The burning phenomenon is less likely to occur, and the maximum magnetic shield amount of the magnetic shield increases.
Therefore, in the initial stage of operation of the magnetic refrigerator, the magnetic refrigerator is excited and operated with a relatively low magnetic field strength, and as the temperature becomes lower, the exciting current of the superconducting coil can be increased to increase the magnetic field strength. Compensation for or increase in the decrease in entropy change during demagnetization can be realized to maintain the efficiency as a magnetic refrigerator for superfluid helium.

In particular, when the low temperature side liquid helium tank accommodates both the superconducting magnetic shield and the superconducting coil and is cooled by the low temperature side liquid helium bath at the same time, the superconducting coil is cooled at a low temperature to ensure stable operation. Since the generated magnetic field can be increased, the maximum generated magnetic field can be controlled to increase according to the temperature decrease of the low temperature side liquid helium during operation, and the efficiency as a magnetic refrigerator can be maintained even at the temperature of ultralow temperature helium. .

[0024]

Embodiments of the magnetic refrigerator of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a magnetic refrigerator for cooling liquid helium. A double cylindrical tubular container 81 filled with liquid nitrogen is arranged and fixed inside the vacuum heat insulating container 8. A cylindrical high-temperature-side liquid helium tank 4 serving both for coil cooling and shield cooling is fixed inside thereof, and below the high-temperature-side helium tank 4, a heat insulating plate 9 having an annular layer thickness is interposed. The low temperature side liquid helium tank 5 is fixed.

Inside the high temperature side helium tank 4, the superconducting coil 1 and a cylindrical superconducting magnetic shield 3 below the superconducting coil 1 are coaxially arranged, and the hollow portion of the superconducting coil 1 has a cylinder for coil winding. The body 11 and the cylindrical body 31 for holding the magnetic shield in the hollow portion of the magnetic shield 3 are air-tightly connected, and the collar ring 32 at the lower end of the cylindrical body 31 forms the bottom portion 3 of the high temperature side helium tank 4.
The two are integrally and airtightly joined.

A high temperature side heat transfer member 42 having an upper surface exposed in the liquid helium 41 of the high temperature side helium tank 4 and a lower end inserted into the cylindrical body 11 is provided above the hollow cylindrical body 11 of the superconducting coil 1. Placed and fixed in an airtight manner.

The upper surface of the high temperature side liquid helium tank 4 is closed by a heat insulating flange 83, and the flange 83 is connected to an exhaust pump 46 (not shown) via a pressure adjusting valve 45.

The high temperature side helium tank 4 is filled with liquid helium at a pressure of about 1 atm, and can be depressurized to about 760 to 400 mmhg by the pressure control valve 45. The high temperature side heat transfer member 42 and the superconducting coil 1 And the cylindrical superconducting magnetic shield 3 are immersed and cooled to about 4.2 to 3.6K.

A low temperature side helium tank 5 is hermetically fixed to the lower end of the hollow cylindrical body 31 of the superconducting magnetic shield 3 via a heat insulating member 9, and the low temperature side helium tank 5 is moved upward from the low temperature side helium tank 5. The protruding low temperature side heat transfer member 52 is the cylindrical body 3
It is arranged in a state that it is inserted in 1.

As described above, the insides of the hollow cylinders 11 and 31 of the superconducting coil 1 and the magnetic shield 3 are hermetically sealed and kept at a high vacuum to form the vacuum chamber 6. ..

In the vacuum chamber 6, a cylindrical magnetic actuator 2 attached to the front side of an elevating rod 71 connected to an elevating device 7 fixed to the upper surface of the vacuum heat insulating tank 8 can be moved up and down. It is arranged. When the magnetic actuator 2 is in the hollow portion of the superconducting coil 1, the upper end surface 21 of the magnetic actuator 2 is in surface contact with the lower end surface 43 of the above-mentioned high temperature side heat transfer member 42, while the magnetic actuator 2 is lowered. When the body 2 is in the hollow portion of the superconducting magnetic shield 3, the upper end surface 53 of the heat transfer plate 54 of the low temperature side heat transfer member 52.
It has been adjusted to fit in.

Above the outside of the vacuum insulation container 8, a separate vacuum cylinder 78 is fixed in communication with the upper end of the vacuum chamber 6 by the high temperature side heat transfer member 42 and the vacuum pipe 62. The lifting device 7 includes a lifting rod 71 inserted through the vacuum pipe 62.
In the vacuum cylinder 78, the fixed rack 72 is connected to the pinion 73 connected to the rotating shaft of an external motor (not shown).
It is arranged so as to mesh with. The magnetic actuator 2 attached to the elevating rod 71 is repeatedly moved up and down by the rotation of the external motor. Then, the vacuum cylinder 78 is attached to the vacuum pump 6
By reducing the pressure by 4 (not shown), the inside of the vacuum chamber 6 can be maintained at a high vacuum.

The low temperature side helium tank 5 is filled with liquid helium 51 pressurized to near atmospheric pressure through a helium supply pipe 56 and is in contact with the inner surface of the heat transfer plate 54. Further, a large number of concentric cylindrical thin-layer heat transfer bodies 56 project from the lower surface of the heat transfer plate 54 toward the inside of the helium tank 5.

In the structure of the magnetic refrigerator as described above,
The superconducting coil 1 is a Nb-Ti alloy thin wire wound many times, is immersed and cooled in liquid helium 41, and has a constant current of 3 to 5T in the coil hollow portion due to a permanent current.
In a strong magnetic field.

The superconducting magnetic shield 3 is made of Nb- of the superconductor.
An annular thin layer of Ti alloy is formed of a normal conductive metal such as Al or C.
It has a cylindrical shape formed by alternately laminating a plurality of annular thin layers of u or Ag, and both ends thereof are between a pair of collar rings 32, 32 fixed to both ends of the hollow portion inner tubular body 31. Is sandwiched between. In the hollow portion of the magnetic shield 3, the strong magnetic field from the upper superconducting coil is completely shielded and a completely zero magnetic field is formed. The magnetic shield 3 is not a single superconductor, but a thin layer of a metal having high electrical conductivity and high thermal conductivity such as Al is interposed to limit the magnetic flux flow generated in the superconductor layer, and
The heat generated by the flow of magnetic flux can be dissipated and dissipated to liquid helium to facilitate cooling, prevent an unstable phenomenon leading to a flux jump, and stably shield a strong magnetic field of 3 to 5T. You can do it.

The magnetic actuator 2 is preferably made of gadolinium-gallium-garnet, preferably a single crystal, and has no cylindrical shape. The upper end surface 21 and the lower end surface 22 are mirror-polished to be a smooth flat surface. Further, the heat transfer members 42 and 54 are
Both are made of Al, Cu, or Ag having high thermal conductivity. On the other hand, a glass fiber reinforced synthetic resin body is preferably used for the heat insulating member from the viewpoint of low temperature strength and thermal conductivity.

FIG. 1 shows the excitation process. In the strong magnetic field in the hollow portion of the superconducting coil 1, the magnetic actuator 2 is adiabatically excited and generates heat. The heat is generated by the end face 21 of the magnetic actuator 2. The heat transfer member 42 is transmitted by transmitting the contacting end surface 43 of the heat transfer member 42.
Is absorbed by the liquid helium 41 from the magnetic activating element 2
Is cooled to near liquid helium temperature. The liquid helium 41 is heated by a large number of fins projecting from the heat transfer member 42, but is evaporated at the liquid surface 44 and kept at a constant temperature by the latent heat of evaporation.

FIG. 2 shows the demagnetization process, but the lifting rod 7
When 1 is lowered, the magnetic actuator 2 is housed in the hollow portion of the magnetic shield 3 to be cooled and emits cold, but conducts the heat transfer plate 54 which is in contact with the lower surface 22 of the magnetic actuator 2, The heat of the low-temperature-side liquid helium 51 is taken and cooled. Magnetic actuator 2
Lower surface 22 and the heat transfer plate 54 upper surface 5 of the low temperature side heat transfer member 52
3 is a mirror surface, and the lower surface of the magnetic actuator presses the heat transfer plate 54 when the magnetic actuator 2 descends.
No. 2 completely faces the surface to enhance heat transfer, and magnetic actuator 2
The heat conduction between the low temperature side helium bath 41 and the low temperature side helium bath 41 can be enhanced.

The low temperature liquid helium 51 is
Same temperature as high temperature liquid helium 41 (4.2 at 1 atm)
However, by repeating the above-mentioned excitation process and demagnetization process, the temperature falls to a superfluid helium temperature of 1.9 K or less.

In FIG. 3, the superconducting coil 1 and the superconducting magnetic shield 3 are thermally isolated by the heat insulating member 9, and the superconducting coil 1 is cooled by the liquid helium 41 in the high temperature side liquid helium tank 4. The magnetic shield 3 is integrally housed in the low temperature side liquid tank 5 and represents a magnetic refrigerator of a type that is cooled by liquid helium 51 cooled by the low temperature side heat transfer member 52 during continuous operation. In this example, the magnetic shield 3 is kept at a low temperature, for example, about 1.9K, which is lower than that of liquid helium which is commonly used.

At the beginning of the operation of the magnetic refrigerator, the exciting magnetic field of the magnetic actuator 3 is set to, for example, 3T, and the magnetic field of the superconducting coil is controlled to increase as the temperature of the low temperature side helium 51 decreases. At low temperatures, especially in superfluid helium, the maximum magnetic field shield amount of the magnetic shield increases, so even if the excitation of the superconducting coil 1 is increased to about 5T, the risk of the shield magnetic field decreasing due to the flux jump is small. Since a complete zero magnetic field is obtained in the hollow portion of the magnetic shield, the refrigerating output is increased by the subsequent operation, and the achievement rate to the ultra-low temperature is increased.

FIG. 4 shows another embodiment in which the superconducting magnetic shield 3 as well as the superconducting coil 1 is cooled by the helium bath 51 of the low temperature side liquid helium tank 5. The low temperature side liquid helium tank 5 serves as a coil cooling tank. Also, the collar ring 1 of the superconducting coil 1
A ring-shaped insulating member 9 hermetically fixed to 2 isolates and separates the high temperature side liquid helium tank 4 and the low temperature side liquid helium tank 5.

In this example, the superconducting magnetic shield 3 and the superconducting coil 1 can be stabilized as the temperature of the superconducting magnetic shield 3 and the superconducting coil 1 is lowered by direct cooling by the cold generated by the magnetic actuator 2. , The magnetic actuator is excited with a relatively low magnetic field strength, but when the low temperature side helium bath 51 becomes extremely low in temperature, the exciting current of the conductive coil 1 is sequentially increased to increase the magnetic field strength to about 8T and the magnetic field due to the low temperature is increased. It becomes possible to compensate for the reduction of the refrigerating capacity, continue stable operation, increase the cooling rate of the low temperature side helium bath 51, and maintain it at a low temperature below the superfluid helium temperature.

By the continuous operation of the magnetic refrigerator described above, the liquid helium in the low temperature side liquid tank 5 can obtain a superfluid helium equilibrium temperature of 1.9 K or a temperature lower than it at near normal pressure. Although not shown, for example, an infrared imaging device 57 is provided on the outer surface of the low temperature side liquid helium tank 5 of the present apparatus.
Is used for infrared imaging with reduced thermal noise.

[0046]

According to the magnetic refrigerator of the present invention, the magnetic actuator reciprocates in the vacuum chamber that communicates the hollow portion of the superconducting coil and the hollow portion of the cylindrical superconducting magnetic shield so that the magnetic shield can move in the hollow portion of the magnetic shield. Since the end surface of the demagnetized magnetic actuator is arranged so as to be exactly in surface contact with the plane of the heat transfer member that transfers heat by contact with the pressurized liquid helium in the low temperature side liquid tank, the cold generated by the magnetic actuator is generated. Thus, liquid helium can be cooled to a temperature of superfluid helium or lower, and a magnetic refrigerator with good thermal efficiency can be configured.

The superconducting coil and the magnetic shield are coaxially arranged in a row, and the hollow cylindrical body is used as a vacuum chamber, so that the magnetic actuation can be utilized to the maximum in the exciting space and the degaussing space. Since it can be arranged, the movement stroke of the magnetic actuation body for excitation / demagnetization can be reduced, and the arrangement of the liquid helium bath on the low temperature side is easy, the refrigerator can be made smaller and more compact than the refrigeration functional force. ..

If the cooling helium of the superconducting magnetic shield and the superconducting coil is cooled to a super low temperature at the same time as the low temperature helium bath, the instability phenomenon of the superconductor can be avoided and the maximum magnetic shielding ability can be enhanced. Therefore, the strong magnetic field for excitation can be increased to improve the refrigerating efficiency.

[Brief description of drawings]

FIG. 1 is a schematic sectional view according to an embodiment of a magnetic refrigerator, showing an exciting process.

FIG. 2 shows a partial cross-sectional view of a magnetic refrigerator in the process of demagnetization.

FIG. 3 is a partial cross-sectional view of a magnetic refrigerator in which the magnetic shield is also cooled at the same time by low temperature liquid helium.

FIG. 4 is a partial cross-sectional view of a magnetic refrigerator according to another embodiment in which the magnetic shield and the superconducting coil are cooled simultaneously with low temperature liquid helium.

[Explanation of symbols]

 1 superconducting coil 2 magnetic actuator 3 superconducting magnetic shield 4 high temperature side liquid helium tank 41 high temperature side liquid helium bath 5 low temperature side liquid helium tank 51 low temperature side liquid helium bath 52 low temperature side heat transfer member 54 heat transfer plate 6 vacuum chamber 7 Lifting device 71 Lifting rod 8 Vacuum heat insulation tank 9 Heat insulation plate

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[Procedure amendment]

[Submission date] March 5, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Sugioka 1-5 Doyamacho, Kita-ku, Osaka City High Pressure Gas Industry Co., Ltd. (72) Inventor Masaru Inoue 1-5 Doyamacho, Kita-ku, Osaka City High-pressure gas industry Co., Ltd. (72) Inventor Kohei Otani 1-5 Doyamacho, Kita-ku, Osaka City High-pressure gas industry Co., Ltd. (72) Inventor Manabu Sato 1-5 Doyama-cho, Kita-ku, Osaka City High-pressure gas industry Co., Ltd.

Claims (4)

[Claims] 1. A superconducting coil that generates a strong magnetic field, a hollow superconducting magnetic shield that is coaxially arranged in the axial direction of the superconducting coil, a hollow portion of the superconducting coil, and the magnetic shield. A vacuum chamber formed in communication with the hollow portion of the body, and a magnetic actuator disposed in the vacuum chamber so as to be capable of reciprocating by a reciprocating mechanism between the superconducting coil hollow portion and the magnetic shield hollow portion. , A high temperature side helium liquid tank arranged at the end portion of the vacuum chamber on the side of the superconducting coil so as to be able to transfer heat to the magnetic actuator, and at the end portion of the vacuum chamber on the side of the magnetic shield to be capable of contact heat transfer to the magnetic actuator And a low-temperature helium liquid tank disposed on the magnetic actuator, the magnetic actuator having a smooth flat end surface, and the low-temperature helium liquid tank has a smooth flat surface that is in contact with the end surface of the magnetic actuator. A heat transfer member having According to the structure, the process of heat transfer cooling of the heat generated by the magnetic actuator excited in the hollow portion of the superconducting coil to the high temperature side helium liquid tank and the cooling of the magnetic actuator demagnetized in the magnetic shield hollow portion A magnetic refrigerator for cooling liquid helium, wherein the process of cooling liquid helium filled in a low temperature helium liquid tank is repeated. 2. The magnetic refrigerator according to claim 1, wherein the low temperature side helium liquid tank communicates with or serves as a magnetic shield cooling tank for cooling the magnetic shield. 3. The low-temperature side helium liquid tank communicates with or serves as a coil cooling tank for cooling the superconducting coil together with a magnetic shield cooling tank for cooling the superconducting magnetic shield. Magnetic refrigerator. 4. The high temperature side helium liquid tank is also used as a coil cooling tank for cooling the superconducting coil, and the high temperature side helium liquid tank has a heat transfer member in contact with the high temperature side liquid helium of the magnetic actuator. The magnetic refrigerator according to claim 1, wherein the magnetic refrigerator has a smooth flat surface that can be brought into contact with a smooth flat end surface.