JPH08240353A - Cryostat and its operating method - Google Patents

Abstract

PURPOSE: To attain a substantial shortening of a pre-cooling time at a starting time of operation, while restricting an entire height of a cryostat and to facilitate a helium supplementing operation. CONSTITUTION: A first cryostat C1 and a second cryostat C2 are arranged side by side in a lateral direction. Helium stored in a pressurized ultra-fluid helium tank 22 in the second cryostat C2 is cooled through a heat exchanging with saturated ultra-fluid helium stored in a saturated ultra-fluid helium tank 12 of the first cryostat C1, thereby pressurized ultra-fluid helium is generated and its cold heat insulation can be attained. A neck tube 40 is extended upwardly from the pressurized ultra-fluid helium tank 22, and a separator 42 is arranged at either an intermediate part or a lower part of this neck tube 40 and then a liquid helium 45 for use in restricting thermal invasion is stored above the separator 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryostat for producing pressurized superfluid helium for cooling a superconducting magnet and an operating method thereof.

[0002]

2. Description of the Related Art Conventionally, as superconducting magnets have been applied to a nuclear magnetic resonance analyzer (MRS device), a nuclear magnetic resonance computer tomography device for medical diagnosis (MRI device), etc., the superconducting magnet is cooled with liquid helium. The development of cryostats, etc. for Furthermore, in recent years, a cryostat that combines two cryostats has been developed in order to generate pressurized superfluid helium, which has better temperature uniformity than normal fluid helium and has a stable liquid state. . An example is shown below.

A) The device shown in FIG. 7 is disclosed in US Pat.
Superconducting magnet 8 disclosed in No. 800
An upper liquid helium tank 82 is arranged above the pressurized superfluid helium tank 81 that stores 0. Both tanks 81, 82
A space is secured between them by cylindrical spacers 83 and 84, and the spacer 84 is opened and closed by a valve 79. The circumference of both tanks 81 and 82 is housed in a cold insulation container in which a radiation shield plate 85, a liquid nitrogen tank 86, and a vacuum container 87 are stacked in order from the inside, and a central tube 89 vertically penetrates the center of the cryostat. . The upper part of the upper liquid helium tank 82 is communicated with the outside through a neck tube 88 penetrating the cold insulation container. The bottom of the upper liquid helium tank 82 is connected to the heat exchanger 92 in the pressurized superfluid helium tank 81 through the helium introducing pipe 90, and the inside of the heat exchanger 92 is discharged through the spacer 83 and the neck tube 88. The pipe 94 communicates with the outside.

According to this apparatus, the upper liquid helium tank 8
Liquid helium in 2 is introduced into the heat exchanger 92 as saturated superfluid helium while being expanded by the helium introduction pipe 90 and the JT valve in the middle thereof, and the pressurized superfluid helium tank 81 is introduced by heat exchange in the heat exchanger 92. By cooling the helium therein, pressurized superfluid helium can be generated in the pressurized superfluid helium tank 81 and kept cold. The upper liquid helium tank 82 can be replenished with liquid helium through the neck tube 88, and the neck tube 88 is kept cool by the vaporized helium gas rising in the discharge pipe 94.

B) In the apparatus shown in FIG. 8, a first cryostat C1 and a second cryostat C2 are arranged side by side in the lateral direction.

The first cryostat C1 accommodates an upper liquid helium tank 10 and a saturated superfluid helium tank 12 provided below the upper liquid helium tank 10, and both tanks 10, 12 are surrounded by The radiant heat shield plate 16, the liquid nitrogen tank 18, and the vacuum container 20 are sequentially stacked from the inside. In the upper liquid helium tank 10 and the saturated superfluid helium tank 12, the tubes 10a and 12 are individually provided.
a is connected. Then, the inside of the saturated superfluid helium tank 12 is appropriately exhausted through the pipe 12a, and the liquid helium (HeI) in the upper liquid helium tank 10 is supplied to the saturated superfluid helium tank 12 while being cooled through the JT valve 14. In the saturated superfluid helium tank 12, saturated superfluid helium (S-HeII) is generated.

The second cryostat C2 comprises a pressurized superfluid helium tank 22 for accommodating a superconducting magnet 24. The pressurized superfluid helium tank 22 is surrounded by 4K radiant heat shield plates 26, 40K radiant heat in order from the inside. The shield plate 28, the 80K radiant heat shield plate 30, and the vacuum container 32 are stacked.

The interiors of both cryostats C1 and C2 are communicated with each other via a transfer tube 34. Inside the transfer tube 34, a heat exchange pipe 38, a helium supply pipe 39a, and a helium gas return pipe 39b are provided. Heat exchange pipe 38
Communicates the inside of the pressurized superfluid helium tank 22 with the inside of the heat exchanger 36 provided in the saturated superfluid helium tank 12, and the cold in the saturated superfluid helium tank 12 is a heat exchanger. The helium in the pressurized superfluid helium tank 22 is cooled by being transmitted to the helium in 36 (that is, the same helium in the pressurized superfluid helium tank 22). Pressurized superfluid helium (P-HeII) is generated therein and kept cold.

[0009]

[Problems to be Solved by the Invention]

A) In the apparatus shown in FIG. 7, further above the large pressurized superfluid helium tank 81 that houses the superconducting magnet 80,
Since the upper liquid helium tank 82 is arranged, the height of the entire apparatus becomes extremely large, which makes it difficult to install the apparatus indoors.

B) In the apparatus shown in FIG. 8, since the two cryostats C1 and C2 are arranged side by side in the lateral direction, the height dimension can be suppressed, and the pressurized superfluid helium tank 22 is sealed. Therefore, there is an advantage that the cold insulation property is high, but there are the following problems to be solved.

A) Since the pressurized superfluid helium tank 22 is sealed, in order to supply helium into the pressurized superfluid helium tank 22 during precooling after starting the apparatus, the saturated superfluid helium tank 12 is used. To the helium supply pipe 39a. Here, in the apparatus shown in FIG. 7, since the pressurized superfluid helium tank 81 and the upper liquid helium tank 82 are arranged vertically, the valve 79 in the same figure is opened and liquid is introduced into the upper liquid helium tank 82. When helium is poured, this liquid helium is automatically injected from the upper liquid helium tank 82 into the pressurized superfluid helium tank 81 by its own weight. In the apparatus shown in FIG.
Since the bottom surface of the saturated superfluid helium tank 22 and the bottom surface of the pressurized superfluid helium tank 22 are substantially at the same height, the liquid helium in the saturated superfluid helium tank 12 cannot be filled into the pressurized superfluid helium tank 22 at one time. In fact, first, the saturated superfluid helium tank 1
It is necessary to store liquid helium only in the bottom portion of No. 2 and wait for evaporation of this liquid helium before supplying the next liquid helium. This precooling time becomes very long. In addition, the same problem occurs when the pressurized superfluid helium tank 22 is appropriately supplemented with helium during operation.

As a means for reducing the precooling time, it is considered that supercritical pressure helium from the saturated superfluid helium tank 12 is forced to flow into the pressurized superfluid helium tank 22. In this case, Therefore, it is necessary to install and operate a pumping means such as a circulation pump, and an increase in initial cost and running cost cannot be avoided.

B) Since the inside of the pressurized superfluid helium tank 22 is sealed, it is very difficult to arrange the wiring when the superconducting magnet 24 is housed therein, and especially the structure inside the transfer tube 34 becomes complicated. Become.

C) Since the pressurized superfluid helium tank 22 is sealed, when the superconducting magnet 24 is quenched in the pressurized superfluid helium tank 22 and helium is evaporated, the pressurized superfluid helium tank 22. It is not possible to avoid the pressure rise in the interior promptly. In addition, if a safety valve or the like is installed as such an avoiding means, the structure becomes complicated and the cold insulation property is deteriorated.

In view of the above situation, the present invention avoids an increase in height dimension and secures excellent cold insulation in a pressurized superfluid helium tank while shortening the precooling time to replenish helium. A cryostat and its operation that can be easily done, and when the superconducting magnet is housed in the pressurized superfluid helium tank, the wiring of the superconducting magnet can be easily handled, and the increase in tank pressure when a quench occurs can be quickly avoided. The purpose is to provide a method.

[0016]

According to the present invention, a first cryostat for cooling liquid helium in a liquid helium tank to replenish the superfluid helium tank, and a pressurized superfluid helium tank in a cold storage container. The second cryostat that has been operated is arranged in parallel in the lateral direction, and both cryostats are connected via a transfer tube, and through this transfer tube, the superfluid helium in the superfluid helium tank in the first cryostat and the pressurized In the cryostat configured to generate the pressurized superfluid helium by cooling the latter helium by exchanging heat with the helium in the superfluid helium tank, the upper part of the cold insulating container is vertically moved to the second cryostat. To communicate the inside of the pressurized superfluid helium tank with the outside of the cryostat. A neck tube is provided, and a separator that can be switched between a state in which the inside of the neck tube is vertically cut off and a state in which the neck tube is vertically connected to the middle portion or the lower end portion of the neck tube is provided, and a liquid helium storage space is formed above the separator. (Claim 1).

The present invention is a method of operating a cryostat, wherein the neck tube is kept cold by storing liquid helium in the liquid helium storage space of the cryostat (claim 2).

The cryostat is particularly effective when the superconducting magnet is housed in the pressurized superfluid helium tank (claim 3).

This cryostat further comprises a helium transfer pipe for extracting helium from the liquid helium tank and discharging it as helium gas through the transfer tube into the space above the separator in the neck tube. It is preferable (Claim 4).

Here, when the cold insulation container in the second cryostat is divided into a plurality of layers having different operating temperatures, the helium transfer pipe drawn from the liquid helium tank through the transfer tube is
Of the plurality of layers, first, the low temperature side layer close to the pressurized superfluid helium tank is passed, then the high temperature side layer far from the pressurized superfluid helium tank is passed, and then the neck tube is connected (claim 5). A first helium transfer pipe connected to the neck tube through a transfer tube from the liquid helium tank and a low temperature side layer of the plurality of layers close to the pressurized superfluid helium tank; and a transfer tube from the liquid helium tank. And a second helium transfer pipe connected to a position above the connection position of the first helium transfer pipe in the neck tube through a high temperature side layer far from the pressurized superfluid helium tank among the plurality of layers. It is more preferable to provide (Claim 6).

[0021]

According to the cryostat of claim 1, liquid helium can be directly supplied into the pressurized superfluid helium tank through the neck tube by opening the separator of the neck tube communicating with the pressurized superfluid helium tank,
Pre-cooling at the time of starting can be performed quickly. Moreover, after the liquid helium is filled, the separator is closed, and liquid helium is stored in the space inside the neck tube (liquid helium storage space) above the separator (claim 2), whereby the cold heat can suppress heat intrusion through the neck tube. , It is possible to maintain high cold insulation in the pressurized superfluid helium tank.

In such a cryostat, when the superconducting magnet is housed in the pressurized superfluid helium tank as claimed in claim 3, its wiring may be led out to the outside through the neck tube. No need to turn the wiring. Further, even if the superconducting magnet is quenched and helium in the pressurized superfluid helium tank is evaporated, the internal pressure can be promptly avoided by opening the separator.

In the above cryostat, the liquid helium stored above the separator receives heat from the side wall of the neck tube and is cooled by the pressurized superfluid helium in the pressurized superfluid helium tank via the separator. . Therefore, if there is no operation from the outside, the liquid level of liquid helium is kept constant and the macroscopic helium gas flow ceases when the cooling and the heat intrusion are balanced, so the amount of heat invading into the liquid helium Is likely to increase.

However, as described in claim 4, a helium transfer pipe for extracting helium from the liquid helium tank and discharging it as helium gas into the space above the separator in the neck tube through the transfer tube. With the above, the inflow of heat is suppressed by the upward flow of the discharged helium gas, and the cold insulation in the pressurized superfluid helium tank is further enhanced.

Here, when the cold insulation container in the second cryostat is divided into a plurality of layers having different operating temperatures, the helium transfer pipe derived from the liquid helium tank through the transfer tube is
When passing through the high temperature side layer suddenly among the above multiple layers, since the difference between the temperature in the high temperature side layer and the transfer helium temperature is large, the cold heat of the transfer helium is significantly dissipated, and the thermal efficiency is poor. According to claim 5, the helium transfer pipe is first passed through a low temperature side layer close to the pressurized superfluid helium tank among the plurality of layers, and then through a high temperature side layer distant from the pressurized superfluid helium tank. If it is then connected to the neck tube, the temperature of the transfer helium flowing while increasing the temperature in the helium transfer pipe and the temperature around it (the temperature in the cold storage container) become closer to each other, and the thermal efficiency is improved.

When a plurality of helium transfer pipes are provided, the first helium transfer pipe passing through the low temperature side layer is located at a relatively lower position, and the second helium passing through the high temperature side layer is provided. If the transfer pipes are connected to the neck tubes at relatively upper positions, the helium gas will be supplied at a temperature corresponding to the temperature distribution of the neck tubes (that is, the distribution in which the temperature rises upward). It will be discharged.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

The general structure of the cryostat shown in this embodiment is the same as that shown in FIG. In other words, this cryostat is such that the first cryostat C1 and the second cryostat C2 are arranged side by side in the lateral direction, and the first cryostat C1 includes the upper liquid helium tank 10 and the upper liquid helium tank 10 And a saturated superfluid helium tank 12 provided underneath, and a radiant heat shield plate 16, a liquid nitrogen tank 18, and a vacuum container 20 are sequentially stacked around the both tanks 10 and 12 from the inside. There is. Liquid helium can be supplied to the upper liquid helium tank 10 through a pipe 10a. The liquid helium in the upper liquid helium tank 10 is cooled through the JT valve 14 and stored in the saturated superfluid helium tank 12 as saturated superfluid helium. The second cryostat C2 includes a pressurized superfluid helium tank 22 that houses a superconducting magnet 24. Around the pressurized superfluid helium tank 22, a 4K radiant heat shield plate 26 and a 40K radiant heat shield plate 28 are sequentially arranged from the inside. , The 80K radiant heat shield plate 30 and the vacuum container 32 are laminated.

The interiors of both cryostats C1 and C2 are communicated with each other via a transfer tube 34, and a heat exchange pipe 38 is provided in the transfer tube 34. The heat exchange pipe 38 connects the pressurized superfluid helium tank 22 and the heat exchanger 36 provided in the saturated superfluid helium tank 12 to each other. The cold is transferred to the helium in the heat exchanger 36 (that is, the same helium in the pressurized superfluid helium 22), whereby the helium in the pressurized superfluid helium tank 22 is cooled and the pressurized superfluid helium is cooled. Are generated and kept cool.

Further, as a feature of this cryostat, a neck tube 40 is extended above the pressurized superfluid helium tank 22 in the second cryostat C2. The neck tube 40 includes the 4K radiant heat shield plates 26, 40K radiant heat shield plates 28, 80.
The K radiant heat shield plate 30 and the vacuum container 32 are penetrated upward, and an upper end opening thereof faces the outside of the cryostat, and a valve 41 is connected to the opening.

A separator 42 is provided at an intermediate portion or a lower portion (lower portion in the illustrated example) of the neck tube 40. The separator 42 includes a separator main body 43 having a wedge-shaped through hole in the center and a wedge-shaped valve 44 that opens and closes the through hole of the separator main body 43. Above the separator 42, liquid helium (normal flow A sufficient space is secured to store (helium) 45.

In this cryostat, pressurized superfluid helium is produced and kept cold in the following manner.

The upper liquid helium tank 10, the saturated superfluid helium tank 12, and the pressurized superfluid helium tank 22 are pre-cooled to a certain temperature by temporarily filling them with liquid nitrogen.

In the first cryostat C1, the tube 1
Liquid helium (HeI) is supplied to the upper liquid helium tank 10 through 0a, and the valve 44 of the separator 42 is opened to open the neck tube 4 in the second cryostat C2.
Liquid helium is supplied into the pressurized superfluid helium tank 22 from 0. After the supply, the valve 44 is closed, and an appropriate amount of liquid helium (HeI) 45 is stored above it.

By appropriately evacuating the saturated superfluid helium tank 12 through the pipe 12a and supplying the liquid helium in the upper liquid helium tank 10 to the lower saturated superfluid helium tank 12 while cooling it through the JT valve 14, Cryogenic saturated superfluid helium (S-HeII) is generated in the saturated superfluid helium tank 12. The saturated superfluid helium is heat-exchanged with the helium in the heat exchanger 36 (that is, the same helium in the pressurized superfluid helium tank 22), whereby the helium in the pressurized superfluid helium tank 22 is cooled. Pressurized superfluid helium (P-HeII) is produced in the pressurized superfluid helium tank 22 and kept cold.

According to such a cryostat, the first cryostat C1 and the second cryostat C
By arranging 2 and 2 side by side in the horizontal direction, the height dimension can be greatly suppressed as compared with the device shown in FIG. 7, and the following effects can be obtained.

A) Since the neck tube 40 is extended from the pressurized superfluid helium tank 22 and communicates with the outside, at the time of precooling, the neck tube 40 is opened with the valve 44 open.
Therefore, the pressurized superfluid helium tank 22 can be filled with liquid helium directly and without requiring special power. Therefore, the precooling time can be significantly shortened as compared to the case where liquid helium is supplied little by little from the lateral saturated superfluid helium tank 12 to the pressurized superfluid helium tank 22 as in the conventional apparatus shown in FIG. , The transfer tube 34
The internal structure can also be simplified. Further, it is easy to replenish the pressurized superfluid helium tank 22 with liquid helium during operation. Moreover, despite the provision of the neck tube 40 in this manner, during operation, the separator 42 is closed by the valve 44 and the low temperature liquid helium 45 is stored above the separator 42, so that conduction along the side wall of the neck tube 40 is achieved. It is possible to suppress heat intrusion into the pressurized superfluid helium tank 22 due to.

B) Pressurized superfluid helium tank 2 as shown
When the superconducting magnet 24 is housed in the wiring 2, the wiring may be led out through the neck tube 40 by penetrating the separator 42, and the structure can be more simplified as compared with the case where the wiring is turned to the transfer tube 34 side.

C) Even if the superconducting magnet 24 is quenched and helium evaporates in the pressurized superfluid helium tank 22, the pressure rise in the pressurized superfluid helium tank 22 is promptly increased only by opening the separator 42. It can be avoided, and the safety is greatly improved.

Next, a second embodiment will be described with reference to FIG. In this embodiment, a plurality of neck tubes 40 are extended upward from the pressurized superfluid helium tank 22. Also in this case, the separator 4 is attached to each neck tube 40.
By providing 2 and storing the liquid helium 45 above it, the same effect as described above can be obtained.

Next, a third embodiment will be described with reference to FIG. In the first embodiment, the liquid helium 45 stored above the separator 42 receives heat from the side wall of the neck tube 40, and is pressurized in the pressurized superfluid helium tank 22 via the separator 42. It is cooled by superfluid helium. Therefore, if there is no operation from the outside, the liquid level of liquid helium is kept constant and the macroscopic flow of helium gas ceases when the cooling and the heat penetration are balanced, so that heat penetration into the liquid helium 45 occurs. The amount tends to increase.

Therefore, in this embodiment, the helium transfer pipe 46 from the bottom of the upper liquid helium tank 10 of the first cryostat C1 to the neck tube 40 via the transfer tube 34 and the second cryostat C2. The liquid helium in the upper liquid helium tank 10 is discharged as helium gas into the space above the separator 42 in the neck tube 40. According to such a configuration, the heat invasion is suppressed by the upward flow of the helium gas discharged into the neck tube 40, and the cold insulation in the pressurized superfluid helium tank is further enhanced.

Actually, the neck tube 40 has an inner diameter of 30.
In the case of a single stainless steel tube having a thickness of 0.5 mm and a wall thickness of 0.5 mm, the amount of heat penetration through the neck tube 40 is reduced by about 50% in the device shown in FIG. 3 as compared with the device shown in FIG. It has been confirmed. This means that the heat load and liquid helium consumption in the pressurized superfluid helium tank 22 are reduced by 50%. On the other hand, since the increase rate of the liquid helium consumption amount due to the transfer through the helium transfer pipe 46 is 35%, the liquid helium consumption amount is reduced by about 15%.

The route through which the helium transfer pipe 46 passes through the inside of the second cryostat C2 is not particularly limited.
When this helium transfer pipe 46 is suddenly passed through a cold layer on the high temperature side (for example, a layer between the 40K heat radiation shield plate 28 and the 80K heat radiation shield plate 30), the temperature inside the high temperature side layer and the transfer helium temperature are Due to the large disparity, the cold heat of the transferred helium is significantly dissipated, resulting in poor thermal efficiency. On the other hand, as shown in FIG. 3, the helium transfer pipe 46 is first connected to the low temperature side layer (4K heat radiation shield plates 26 and 40) close to the pressurized superfluid helium tank 22.
K heat radiation shield plate 28) to form a low temperature side heat exchange section 47, and then the high temperature side layer (40K heat radiation shield plates 28 and 80K) far from the pressurized superfluid helium tank 22. If the high temperature side heat exchange section 48 is formed through the layer between the heat radiation shield plate 30 and the neck tube 40, the transfer helium temperature in each of the heat exchange sections 47 and 48 and the temperature thereof can be obtained. Bringing it closer to the ambient temperature,
It becomes possible to improve the thermal efficiency.

Next, a fourth embodiment will be described with reference to FIG. In this embodiment, two helium transfer pipes, a first helium transfer pipe 46A and a second helium transfer pipe 46B, are provided. Then, the first helium transfer pipe 46A passes through the relatively low temperature side layer (the layer between the 4K heat radiation shield plate 26 and the 40K heat radiation shield plate 28) in the second cryostat C2 to the neck tube 40. The second helium transfer pipe 46B is connected to the neck tube 40 through the relatively high temperature side layer (the layer between the 40K heat radiation shield plate 28 and the 80K heat radiation shield plate 30) in the second cryostat C2. And a second helium transfer pipe 46 connected to the neck tube 40.
The connection point of B is set above the connection point of the first helium transfer pipe 46A.

According to this embodiment, the neck tube 40
At a position relatively below the first helium transfer pipe 46
The relatively low temperature helium gas is discharged through A, and the relatively high temperature helium gas is discharged through the second helium transfer pipe 46B at a position relatively above the neck tube 40. Therefore, the helium gas can be discharged from a plurality of locations at a temperature corresponding to the temperature distribution of the neck tube 40 (that is, the distribution in which the temperature increases as it goes upward).

When a plurality of (for example, two) neck tubes 40 are provided, the end of the helium transfer pipe 46 is divided into branch pipes 46a and 46b as shown in FIG. 5 as a fifth embodiment. It may be branched and connected to each neck tube 40.
The helium transfer pipes 46 may be provided in the same number.

In each of the above embodiments, liquid helium is extracted from the bottom of the upper liquid helium tank 10 and evaporated to be discharged as helium gas to the neck tube 40. However, as a sixth embodiment. As shown in FIG. 6, the helium gas may be extracted from the upper part of the upper liquid helium tank and directly discharged to the neck tube 40. In this case, the temperature of the discharged helium gas becomes higher than that in the third embodiment and the like, and the helium consumption amount in the pressurized superfluid helium tank 22 increases accordingly, but conversely, the helium consumption amount in the upper liquid helium tank 10 is increased. As a result, the effect is almost the same when taken together.

[0049]

As described above, according to the present invention, the first cryostat and the second cryostat are arranged side by side in the lateral direction to suppress the height, and the second cryostat is provided with the cold storage container. A neck tube that communicates the inside of the pressurized superfluid helium tank and the outside of the cryostat through the upper part of the top and bottom is provided, and a separator is provided on this neck tube to form a liquid helium storage space above it. Liquid helium can be directly supplied into the pressurized superfluid helium tank through the neck tube without using a special pumping means such as a circulation pump, whereby precooling at the time of start can be promptly performed, and liquid helium is replenished. There is an effect that can be easily. Moreover, after such liquid helium is filled, the separator is closed and the liquid helium is stored in the neck tube internal space (liquid helium storage space) above the separator, so that the heat intrusion is effective despite the neck tube being provided. Therefore, it is possible to maintain high cold insulation in the pressurized superfluid helium tank.

Further, when a superconducting magnet is housed in the pressurized superfluid helium tank as described in claim 3,
The wiring may be led out through the neck tube, and it is not necessary to turn the wiring to the transfer tube side. Therefore, the wiring work can be facilitated and the structure inside the transfer tube can be simplified. Further, even if the superconducting magnet is quenched and helium in the pressurized superfluid helium tank is evaporated, the rise of the internal pressure can be quickly avoided by opening the separator, and there is an effect that more reliable safety can be obtained.

Further, in the cryostat according to claim 4, a helium transfer pipe for extracting helium from the liquid helium tank and discharging it as helium gas into the space above the separator in the neck tube through the transfer tube. As a result, the liquid helium in the upper liquid helium tank is effectively used to effectively prevent heat from entering into the pressurized superfluid helium tank from the above-mentioned neck tube, and keep cool in the pressurized superfluid helium tank. As a result, the helium consumption can be reduced, and the running cost can be reduced.

Here, in the cryostat of the second cryostat, wherein the cold insulation container is divided into a plurality of layers having different operating temperatures, in the cryostat according to claim 5, the helium transfer pipe is first of the plurality of layers. The temperature is increased in the helium transfer pipe because it is passed through the low temperature side layer close to the pressurized superfluid helium tank and then through the high temperature side layer far from the pressurized superfluid helium tank before connecting to the neck tube. Meanwhile, the temperature of the transferred helium and the temperature around it (the temperature in the cold storage container) can be made closer to each other, and the thermal efficiency can be further enhanced.

Further, in the cryostat according to the sixth aspect, the first helium transfer pipe passing through the low temperature side layer is at a relatively lower position, and the second helium transfer pipe passing through the high temperature side layer is at a relatively upper position. Since each of them is connected to the neck tube, there is an effect that the helium gas can be discharged at a temperature corresponding to the temperature distribution of the neck tube (that is, the distribution in which the temperature increases as it goes upward). .

[Brief description of drawings]

FIG. 1 is a sectional front view showing a main part of a cryostat according to a first embodiment of the present invention.

FIG. 2 is a sectional front view showing a main part of a cryostat according to a second embodiment of the present invention.

FIG. 3 is a sectional front view showing a main part of a cryostat according to a third embodiment of the present invention.

FIG. 4 is a sectional front view showing a main part of a cryostat according to a fourth embodiment of the present invention.

FIG. 5 is a sectional front view showing a main part of a cryostat according to a fifth embodiment of the present invention.

FIG. 6 is a sectional front view showing a main part of a cryostat according to a sixth embodiment of the present invention.

FIG. 7 is a sectional front view showing an example of a conventional cryostat.

FIG. 8 is a sectional front view showing an example of a conventional cryostat.

[Explanation of symbols]

 C1 1st cryostat C2 2nd cryostat 10 Upper liquid helium tank 12 Saturated superfluid helium tank 22 Pressurized superfluid helium tank 24 Superconducting magnet 26 4K heat radiation shield plate (constituting a cold container) 28 40K Heat radiation shield plate ( 30 Cooling container configuration 30 80K Heat radiation shield plate (Cooling container configuration) 32 Vacuum container (Cooling container configuration) 34 Transfer tube 40 Neck tube 42 Separator 45 Liquid helium 46 Helium transfer pipe 46A First helium transfer pipe 46B No. 2 helium transfer piping

Claims (6)

[Claims] 1. A first cryostat in which liquid helium in a liquid helium tank is cooled and replenished in a superfluid helium tank, and a second cryostat in which a pressurized superfluid helium tank is housed in a cold container. The cryostats are arranged side by side in a lateral direction, and both cryostats are connected via a transfer tube. Through the transfer tube, the superfluid helium in the superfluid helium tank and the helium in the pressurized superfluid helium tank in the first cryostat are connected. In the cryostat configured to cool the latter helium to generate pressurized superfluid helium by exchanging heat with, the second cryostat is vertically penetrated through the upper part of the cold insulation container to obtain the pressurized superfluid. A neck tube is provided to connect the inside of the helium tank with the outside of the cryostat. A cryostat characterized in that a separator that can be switched between a state in which the inside of the neck tube is vertically cut off and a state in which the neck tube is communicated is provided at a middle portion or a lower end portion of the neck tube, and a liquid helium storage space is formed above the separator. . 2. A method of operating a cryostat, characterized in that the neck tube is kept cold by storing liquid helium in the liquid helium storage space of the cryostat according to claim 1. 3. The cryostat according to claim 1, wherein a superconducting magnet is housed in the pressurized superfluid helium tank. 4. The cryostat according to claim 1 or 3, wherein helium is extracted from the liquid helium tank, and is discharged as helium gas into the space above the separator in the neck tube through the transfer tube. A cryostat characterized by having a transfer pipe. 5. The cryostat according to claim 4, wherein the cold insulation container in the second cryostat is divided into a plurality of layers having different operating temperatures, and the helium transfer pipe led from the liquid helium tank through a transfer tube is provided. Of the plurality of layers, first through the low temperature side layer close to the pressurized superfluid helium tank, then through the high temperature side layer far from the pressurized superfluid helium tank, and then connected to the neck tube Cryostat. 6. The cryostat according to claim 4, wherein the cold insulation container of the second cryostat is divided into a plurality of layers having different operating temperatures, and the liquid helium tank transfers the transfer tube and the plurality of layers to the pressure. A first helium transfer pipe connected to the neck tube through a low temperature side layer close to the superfluid helium tank, a transfer tube from the liquid helium tank, and a high temperature side far from the pressurized superfluid helium tank among the plurality of layers. A cryostat comprising: a layer and a second helium transfer pipe connected to a position above the connection part of the first helium transfer pipe in the neck tube.