JP2007142075A - Cryostat - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cryostat easy to reduce in size and weight. <P>SOLUTION: The cryostat includes an approximately hermetically structured low temperature vessel 3 in which an extremely low temperature liquid 4 for cooling an object 6 to be cooled is stored, a vacuum vessel 2 for forming a vacuum and heat-insulated space 12 around the vessel 3, and an external through-pipe 5 having both ends supported on the vessel 3 and provided in the vicinity of the object 6. A diaphragm 3d for absorbing a difference in thermal expansions between the pipe 5 and the vessel 3 is formed on the support of the vessel 3 for supporting the external through-pipe 5. Since the diaphragm 3d absorbs the difference in thermal expansions between the pipe 5 and the vessel 3, distortion or stress can be prevented from occurring on the support of the vessel 3. In addition, since bellows protruding out of the vessel 3 can be eliminated, the vacuum vessel 2 for storing the low temperature vessel 3 can be downsized, thereby reducing size and weight of the entire cryostat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cryostat that contains a cryogenic liquid such as liquid helium that cools an object to be cooled such as a superconducting coil or a superconducting sensor.

Various industrial products, physicochemical experimental devices, inspection devices, and medical devices that have conventionally used superconducting coils and superconducting sensors have a cryogenic liquid (cooling agent) to cool the object to be cooled, such as superconducting coils and superconducting sensors. The housed cryostat is used.
There are various cryostats having various structures depending on the application, and for example, Patent Document 1 discloses a part thereof.
The cryostat described in Patent Document 1 includes a vacuum container formed so that an annular space exists therein, a liquid helium container concentrically housed with the vacuum container, the liquid helium container and the vacuum container, Between the radiant heat shield plate and the radiant heat shield and the vacuum vessel and between the radiant heat shield plates. Contains liquid helium that cools the conduction coil.

However, in the cryostat having the above-described configuration, when cooling from room temperature to liquid helium temperature (−269 ° C.), the temperature distribution temporarily becomes nonuniform, and the through pipe and the liquid helium container provided in the vicinity of the object to be cooled. Since a difference in thermal expansion occurs between the liquid helium container and the through pipe, strain and stress are generated at the connection between the liquid helium container and the through pipe, thereby deteriorating the durability and reliability of the cryostat.
In order to solve this problem, for example, as shown in FIG. 3, a cryostat in which the difference in thermal expansion is absorbed by a bellows has been put into practical use.

The cryostat shown in FIG. 4 is provided with a cryogenic container c in which a cryogenic liquid b such as liquid helium or liquid nitrogen is accommodated in a vacuum container a whose inside is evacuated. A heat insulating space k is formed.
An outer through pipe e having one end fixed to one end plate d of the low temperature container c is provided at the center of the low temperature container c, and the outer through pipe e has an outer peripheral surface to be cooled like a superconducting coil. A body f is attached.
The other end of the outer through-pipe e protrudes outside the cryogenic vessel c from the through-hole h opened in the other end plate d of the cryogenic vessel c, and the tip of the outer through-pipe e and the opening edge of the through-hole h Between them, a metal bellows i that retains the liquid tightness of the cryogenic container c while absorbing the linear expansion of the outer through pipe e is provided.
Further, an inner through tube j having a smaller diameter than the outer through tube e is provided at the center of the outer through tube e, and both end portions of the inner through tube j are connected to an end plate g provided on the end surface of the vacuum vessel a. They are hermetically fixed by means such as welding, or are hermetically connected via sealing means such as an O-ring.

When the cryostat having the above-described configuration is used as, for example, a foreign substance inspection apparatus for inspecting foreign substances in food, the subject is placed in the inner through-pipe j, and the object to be cooled f cooled by the cryogenic liquid b is energized. By generating a strong magnetic field in the through-tube j, it is inspected whether a foreign object such as a metal is mixed in the subject, but a cryogenic liquid is supplied to a cryostat in a room temperature state to cool the object f to be cooled. When the use is stopped and the cryostat is returned to the room temperature state, the outer through pipe e provided in the vicinity of the object to be cooled f expands or contracts, and the cryogenic container c containing the cryogenic liquid is stored. There is a difference in thermal expansion between them, but since the bellows i absorbs this difference in thermal expansion, no strain or stress is generated at the connection between the low temperature container c and the outer through pipe e.
Japanese Patent Laid-Open No. 7-22658

However, as in the conventional cryostat, the structure in which the thermal expansion difference between the cryogenic vessel c and the outer through pipe e is absorbed by the bellows i is sufficiently resistant to the pressure difference between the vacuum vessel and the cryogenic vessel c. The expensive bellows i is required, and the number of parts increases, so that there is a problem that the parts cost increases.
In addition, since many man-hours are required for liquid-tightly connecting the tip of the outer through pipe e, the end plate d of the cryogenic container c, and both ends of the bellows i, the workability during assembly is poor, and the bellows i portion is the cryogenic container. Since it protrudes to the outside of c, there is a problem that the vacuum container that accommodates the cryogenic container c becomes large and obstructs the downsizing of the cryostat.
The present invention has been made to improve such a problem, and an object thereof is to provide a cryostat that can be easily assembled and reduced in size and weight.

  The cryostat of the present invention is supported at both ends by a cryocontainer having a substantially sealed structure containing a cryogenic liquid that cools an object to be cooled, a vacuum container forming a vacuum insulation space around the cryocontainer, and a cryogenic container. And a cryostat including an outer through pipe attached in the vicinity of the cooled body, and a thermal expansion difference between the outer through pipe and the cryogenic container is absorbed by a support portion of the cryogenic container that supports the outer through pipe. A diaphragm is formed.

With the above configuration, the diaphragm absorbs the thermal expansion difference between the outer through-tube and the low-temperature container that is generated due to the contraction, so that it is possible to prevent distortion and stress from being generated in the support part of the low-temperature container, This can improve the durability and reliability of the cryostat.
In addition, since it is only necessary to form a diaphragm in the cryocontainer, the assembly work of liquid-tightly connecting both ends of the bellows to the connecting portion of the cryocontainer and the outer through pipe is not required, as compared with the conventional one provided with the bellows. As a result, the assemblability of the cryostat is remarkably improved and the bellows protruding to the outside of the cryogenic container is not required, so that the vacuum container accommodating the cryogenic container can be miniaturized, and thereby the cryostat as a whole can be reduced in size and weight.

  In the cryostat of the present invention, the diaphragm is formed by making the thickness around the support portion of the cryogenic container thinner than other portions.

  With the above configuration, an expensive bellows is not required and the number of parts can be reduced, so that the part cost can be reduced.

  The cryostat according to the present invention is provided with an inner through tube having both ends hermetically fixed to the vacuum vessel in the outer through tube.

  By the said structure, it can apply easily to various industrial products, a physicochemical experiment apparatus, a test | inspection apparatus, and a medical device.

  According to the cryostat of the present invention, since the diaphragm absorbs the difference in thermal expansion between the outer through pipe and the cryogenic container, it is possible to prevent distortion and stress from being generated in the support portion of the cryogenic container, and Since the bellows projecting outward is not necessary, the vacuum container for accommodating the cryogenic container can be reduced in size, whereby the cryostat as a whole can be reduced in size and weight.

Embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a cryostat, and FIG. 2 is an enlarged view showing a main part of the cryostat.
A cryostat main body 1 shown in FIG. 1 has a cylindrical vacuum vessel 2 having a sealed structure.
The vacuum vessel 2 includes a cylindrical body 2a having a substantially horizontal axis and end plates 2b that close both end faces of the cylindrical body 2a, and is entirely reinforced with a metal such as stainless steel or aluminum, glass fiber, or carbon fiber. The fiber reinforced plastic (FRP) is formed.
One end plate 2b of the vacuum vessel 2 is detachable, and is fixed to a flange 2d formed at the end of the vacuum vessel 2 by a fastener 13 such as a bolt, and between the end plate 2b and the flange 2d. A sealing means 14 composed of an O-ring for maintaining airtightness is interposed between the two.
In the vacuum vessel 2, a cryogenic vessel 3 comprising a cylindrical body 3a having a smaller diameter than the vacuum vessel 2 and end plates 3b for closing both end faces of the cylindrical body 3a is concentrically housed.
The cryogenic vessel 3 is formed in an almost sealed structure entirely by FRP reinforced with glass fibers or carbon fibers, and contains a cryogenic liquid 4 made of liquid helium or liquid nitrogen inside. The vacuum heat insulating space 12 is formed around the cryogenic container 3 by making the vacuum state.

As shown in FIG. 2, the cryogenic vessel 3 has a screw hole 3 c opened at the center of one end plate 3 b, and an outer through-tube 5 provided concentrically with the cryogenic vessel 3 in the screw hole 3 c. One end is screwed after applying an adhesive such as an epoxy resin.
A large-diameter portion 5a is formed on one end side of the outer through-tube 5, and a screw portion 5b that is screwed into the screw hole 3c is formed on the outer peripheral surface of the large-diameter portion 5a. On the other end side, a fitting portion 5c is formed that is liquid-tightly fitted into a fitting hole 3d formed in the center portion of the other end plate 3b of the cryogenic container 3.
A stopper 5d that abuts the inner surface of the end plate 3b is annularly projected in the circumferential direction at the inner end of the cryogenic container 3 of the fitting portion 5c, and the end of the fitting portion 5c opposite to the stopper 5d is provided. A threaded part 5e is formed in the part, and the other end of the outer through pipe 5 is fixed to the other end plate 3b of the cryogenic vessel 3 by tightening a nut 6 screwed into the threaded part 5e. .

An annular recess 3f is formed on the outer surface of the other end plate 3b so as to surround the fitting portion 5c.
The width W of the recess 3f is, for example, about 20 mm when the outer diameter of the fitting portion 5c is, for example, 50 mm, and the depth D is 10 mm, when the thickness T of the end plate 3b is, for example, 15 mm. Accordingly, a thin diaphragm 3d having a thickness t of 1 to 5 mm is formed on the inner bottom portion of the recess 3c.
The diaphragm 3d absorbs thermal expansion and thermal contraction differences between the outer through pipe 5 and the cryogenic vessel 3 by an action described later.
As shown in FIG. 1, a cooled body 6 made of a superconducting coil is provided on the outer peripheral portion of the outer through pipe 5.
Electric power is supplied to the object 6 to be cooled by a power supply line (not shown), and the object 6 to be cooled is cooled by the cryogenic liquid 4 accommodated in the cryogenic container 3. A superconducting state can be obtained.

On the other hand, an inner through pipe 7 having a smaller diameter than the outer through pipe 5 is concentrically provided in the outer through pipe 5.
One end side of the inner through tube 7 is fixed to the center portion of the end plate 2b of the vacuum vessel 2 by means such as welding, and the other end side is connected to the center portion of the end plate 2b via a sealing means 15 such as an O-ring. It is fitted in an airtight manner, and a subject (not shown) can be inserted into the inner through-tube 7 from an end surface opening 2c that opens to the outside of each end plate 2b.
In addition, a cylindrical introduction pipe 8 having a lower end hermetically connected to the outer peripheral surface of the vacuum container 2 is protruded in the vertical direction at the upper part of the vacuum container 2, and a signal line (not shown) is provided in the introduction pipe 8. ) Is provided concentrically.
The upper end of the cryogenic liquid injection tube 9 is hermetically connected to an end plate 8 a that closes the upper end surface of the introduction tube 8, and the load of the cryogenic vessel 3 and the cooled object 6 provided in the cryogenic vessel 3 is evacuated. The container 2 is supported, and the upper surface opening of the cryogenic liquid injection tube 9 is closed by a lid body 10, and the cryogenic liquid 4 is injected into the lid body 10 into the cryogenic container 3, An injection / discharge port 11 for discharging the evaporating gas is provided.

Next, the operation of the cryostat constructed as described above will be described.
When the cryostat body 1 is used for a foreign substance inspection apparatus, the subject is inserted into the inner through-tube 7 from the end opening 2c opened at the center of the both end plates 2b of the vacuum vessel 2 and mixed into the subject. Inspection of foreign matter such as metal pieces.
In the foreign matter inspection, the cooled object 6 cooled by the cryogenic liquid 4 filled in the cryogenic container 3 is energized to generate a strong magnetic field in the inner through-tube 7. When the cooled body 6 is cooled by supplying the cryogenic liquid, the internal temperature of the cryogenic vessel 3 becomes uneven, and the outer through pipe 5 provided in the vicinity of the cooled body 6 and the cryogenic liquid containing the cryogenic liquid are accommodated. A thermal contraction difference occurs between the container 3 and the container 3.

However, a diaphragm 3d is formed on the end plate 3b on the other end side of the outer through pipe 5 whose both ends are fixed to the both end plates 3b of the low temperature container 3, and the low temperature container 3 generated when the outer through pipe 5 contracts. Is absorbed by the elastic deformation of the diaphragm 3d, so that it is possible to prevent distortion and stress from being generated in the attachment portion of the cryogenic vessel 3 and the outer through pipe 5.
Further, when the use is stopped and the cryostat body 1 is returned to the room temperature state, the outer through pipe 5 provided in the vicinity of the cooled object 6 is thermally expanded, and between the low temperature container 3 and the outer through pipe 5. Although a difference in thermal expansion occurs, the difference in thermal expansion is absorbed by the elastic deformation of the diaphragm 3d, so that it is possible to prevent distortion and stress from being generated in the attachment portion of the cryogenic vessel 3 and the outer through pipe 5. .
Furthermore, since it is only necessary to form the diaphragm 3d on the end plate 3b of the cryogenic container 3, both ends of the bellows are made liquid-tight on the end plate 3b and the outer through pipe 5 of the cryogenic container 3 as compared with the conventional bellows. Assembling work to be connected is not necessary, and as a result, the assemblability of the cryostat is remarkably improved, and the bellows protruding to the outside of the cryogenic container is unnecessary, so that the vacuum container 2 for housing the cryogenic container can be reduced in size. The entire cryostat can be reduced in size and weight.

On the other hand, in the above-described embodiment, the horizontal cryostat in which the inner through pipe 7 and the outer through pipe 5 are provided in the horizontal direction has been described. However, as in the modification shown in FIG. 3, the inner through pipe 7 and the outer through pipe 5 are perpendicular to each other. The vacuum vessel 2 may be installed in the vertical direction so that a vertical cryostat is obtained.
In this modification, the lower end of the cryogenic liquid injection tube 9 for injecting the cryogenic liquid into the cryogenic vessel 3 is communicated with the cryogenic vessel 3 from the end plate 3b side of the cryogenic vessel 3, and the cryogenic liquid injection tube is provided. The upper end side of 9 is penetrated through the end plate 2 b of the vacuum vessel 2 and protrudes above the vacuum vessel 2, and the cryogenic liquid 4 is introduced into the cryogenic vessel 3 at the upper end portion of the cryogenic liquid injection tube 9. An injection / discharge port 11 for injecting or evaporating gas is provided.

Further, the outer peripheral surface of the cryogenic liquid injection tube 9 is hermetically connected to the end plate 2b, and the vacuum vessel 2 supports the load of the cryogenic vessel 3 and the cooled object 6 provided in the cryogenic vessel 3. ing.
A diaphragm 3d is formed on, for example, the upper end plate 3b of the cryogenic vessel 3, and the diaphragm 3d determines the difference between thermal expansion and thermal contraction with the cryogenic vessel 3 generated due to thermal expansion or thermal contraction of the outer through pipe 5. Although it absorbs by elastically deforming, it can prevent generating a distortion and a stress in the attachment part of the cryogenic container 3 and the outer side penetration pipe 5, The effect | action as a whole cryostat is the said embodiment. The description is omitted.

In the embodiment and the modification, the diaphragm 3d is formed only on one of the end plates 3b of the cryogenic vessel 3. However, the diaphragm 3d may be formed on both of the end plates 3b, and the outer through-tube 5 may be formed. Although the diaphragm 3d is formed by providing the annular recess 3c around the periphery, a plurality of circular recesses may be formed at equal intervals on the concentric circle around the outer through pipe 5, and the annular recess 3c is formed in the circumferential direction. You may make it divide into multiple.
In short, the diaphragm 3d may be formed by making the thickness of the periphery of the supporting portion of the cryogenic container 3 that supports the outer through pipe 5 thinner than other portions.
In addition to the superconducting coil, the object to be cooled 6 may be a superconducting magnetic sensor, a superconducting shield that cuts off the magnetic field, or a combination of these, and the cryostat may be used for foreign object inspection. The present invention can be applied not only to apparatuses but also to various industrial products, physicochemical experimental apparatuses, medical apparatuses, and the like.

1 is a cross-sectional view of a cryostat according to an embodiment of the present invention. It is an expanded sectional view showing the important section of the cryostat which becomes an embodiment of the invention. It is sectional drawing which shows the modification of the cryostat which becomes embodiment of this invention. It is sectional drawing of the conventional cryostat.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cryostat main body 2 Vacuum container 3 Cryogenic container 3d Diaphragm 4 Cryogenic liquid 5 Outer through-pipe 6 Superconducting coil 7 Inner through-pipe 12 Vacuum insulation space

Claims (3)

  A substantially sealed cryogenic container containing a cryogenic liquid that cools the object to be cooled, a vacuum container that forms a vacuum insulation space around the cryogenic container, both ends supported by the cryogenic container, and the object to be cooled A cryostat including an outer through pipe attached in the vicinity of the cooling body, and a thermal expansion difference between the outer through pipe and the cryogenic container is absorbed by a support portion of the cryogenic container that supports the outer through pipe A cryostat characterized by the formation of a diaphragm.   The cryostat according to claim 1, wherein the diaphragm is formed by making a wall thickness around the support portion of the cryogenic container thinner than other portions. The cryostat according to claim 1 or 2, wherein an inner through pipe having both ends hermetically fixed to the vacuum vessel is provided in the outer through pipe.

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