JPH09107131A - Pressurized superfluid cryostat - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a saturated helium tank and a pressurized superfluid tank which are communicated with each other through a communication pipe in a vacuum heat insulation container, and to cool liquid helium in the pressurized superfluid tank to superconduct. (EN) Provided is a pressure-controlled superfluid cryostat in which the total height can be significantly reduced in a configuration in which a heat exchanger for changing to fluid helium is arranged, and thus the apparatus configuration can be made compact and equipment costs can be reduced. . SOLUTION: Inside a vacuum heat insulation container (1), a pressurized superfluid tank (2), a saturated helium tank (3) and a liquid nitrogen tank (4) each formed in a hollow annular cylinder are installed from inside. A helium gas cylinder (13) is branched and connected to an adiabatic conduit (10) that is sequentially arranged concentrically and that connects an external liquid helium supply source (11) and a saturated helium tank (3), while a saturated helium tank ( In the communication conduit (5) that connects the 3) and the pressurized superfluid tank (2), the supply valve is a check valve that operates in reverse at the set operating pressure above atmospheric pressure.
(5a) and the pressure release valve (5b) are arranged in parallel in a branch manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superfluid helium generator, and more particularly to a pressurized superfluid cryostat using pressurized superfluid helium (unsaturated superfluid helium) for cooling a superconducting magnet.

[0002]

2. Description of the Related Art When using a superconducting magnet in a superconducting state, it is necessary to set the operating temperature as low as possible.
It is possible to improve the Ic (critical current value) of the superconducting wire of the magnet and generate a higher magnetic field. Liquid helium is generally used to obtain extremely low temperatures, but in recent years, as liquid coolant used for cooling superconducting magnets, normal liquid helium, that is, normal-flow helium at 4.2 K or so, is used at a λ point under certain pressure conditions. Superfluid helium, which is cooled to a temperature below (2.17K), is attracting attention. This superfluid helium has a very high thermal conductivity and exhibits advantageous properties both in the temperature range achieved at cryogenic temperatures and in its heat transfer properties.

An apparatus for generating and holding such superfluid helium to cool the superconducting magnet is a superfluid helium cooling type cryostat. And, in the past, superfluid helium generator that generates and retains saturated superfluid helium by cooling normal fluid helium to a temperature of λ point or less under reduced pressure of 38 torr or less has been studied. When the superconducting magnet is cooled by superfluid helium, it is expected that the Ic of the superconducting wire will be improved by lowering the magnet temperature, but there are some technical problems such as a decrease in discharge voltage and a decrease in heat flux under a reduced pressure atmosphere. However, the actual application range was considerably restricted by the need for additional equipment to deal with these.
Therefore, consideration was added to those points.
As disclosed in 60-4121, JP-B-62-1275, U.S. Pat. No. 5,220,800 and the like, by cooling the normal-flowing helium to a temperature of λ point or less under a pressure higher than atmospheric pressure,
Devices have been developed to generate and hold pressurized superfluid helium (unsaturated superfluid helium). When the superconducting magnet is operated in the pressurized superfluid helium generated by these devices, the discharge voltage can be prevented from lowering and the heat flux in the pressurized superfluid helium can be maximized, and the lead wire for supplying current to the superconducting magnet can be used. The heat generation of the superconducting magnet can be efficiently removed without applying special insulation / discharge prevention.

The basic configuration of these conventional cryostats will be described with reference to FIG. In a cryostat of a pressurized superfluid helium cooling type shown in FIG. 3 (hereinafter referred to as a pressurized superfluid cryostat), a saturated helium tank (22) accommodating liquid helium is added to a vacuum heat insulation container (21). The pressure superfluid tank (23) is arranged vertically, and
Saturated helium tank (22) above via a conduit (24) (or capillary) with a valve-type supply valve (24a)
And the lower pressurized superfluid tank (23) are communicated with each other, whereby liquid helium in the pressurized superfluid tank (23) is maintained at a pressure equal to or higher than atmospheric pressure. In addition, liquid helium in the saturated helium tank (22) is vaporized in the upper part (outer side or inside) of the pressurized superfluid tank (23), and the heat of vaporization causes the liquid helium in the pressurized superfluid tank (23) to be evaporated. A heat exchanger (25) for cooling the above is arranged, and under this configuration, pressurized superfluid helium is generated and held in the pressurized superfluid tank (23), It is supposed that the superconducting magnet (26) arranged at the inner bottom of (23) is cooled. In the figure, (24b) is a discharge valve, (25a) is a Joule-Thomson valve, (27) is an exhaust pump, (28) is a liquid nitrogen tank, and (29) is an insert dewar.

As illustrated in FIG. 3, in the conventional pressurized superfluid cryostat, the liquid helium is supplied to the pressurized superfluid tank (23) by releasing the supply valve (24a). Because it is performed by a capillary that is in constant communication,
The pressure in the pressurized superfluid tank (23) is the saturated helium tank (2
It is the sum of the head pressure and the atmospheric pressure due to the liquid column below the liquid level in 2), and this maintains the liquid helium in the pressurized superfluid tank (23) at a pressure above atmospheric pressure and Generates superfluid helium. The discharge valve (24b) of the communication line (24)
Is a check valve arranged for the purpose of releasing pressure when superfluid helium in the pressurized superfluid tank (23) is gasified by sudden heat generation due to quenching of the superconducting magnet (26).

[0006]

As described above, in the conventional pressurized superfluid cryostat, the pressure in the pressurized superfluid tank is kept above the atmospheric pressure by the liquid column head of the saturated helium tank. The helium tank must be located above the pressurized superfluid tank. However, when such a configuration is adopted, the total height of the cryostat becomes extremely high, and the ceiling height lower limit of the installation place is also restricted. Further, when an insert dewar for performing measurement using a magnetic field environment is provided at the center of the cryostat, the depth of insertion of the measurement sample or the like into the insert dewar becomes deep, and special handling or jigs are required. Is required. Furthermore, as illustrated in [FIG. 3], in order to block the radiant heat input to the deep-cooled portion of the pressurized superfluid cryostat,
If a circular liquid helium temperature shield (22a) and a liquid nitrogen temperature shield (28a) are installed on the upper and lower parts of the saturated helium tank (22) and liquid nitrogen tank (28), respectively, those shields (22a), (28a) Must be extended axially downward so as to cover the pressurized superfluid tank (23) below, which incurs the disadvantage of increased cost due to an increase in the number of members and assembly steps.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The apparatus does not lose its original function of generating pressurized superfluid helium to cool the superconducting magnet to a critical temperature or lower, and It is an object of the present invention to provide a pressurized superfluid cryostat capable of significantly reducing the overall height, thus making the entire apparatus compact and reducing the equipment cost, and relaxing the restrictions on the installation location.

[0008]

To achieve the above object, the present invention has the following arrangement. That is, the pressurized superfluid cryostat according to the present invention has, in a vacuum heat insulating container, a saturated helium tank containing liquid helium fed from an external supply source through a heat insulating conduit, and a superconducting magnet in the lower part. In addition, a pressurized superfluid tank which stores liquid helium at a pressure equal to or higher than atmospheric pressure, which is communicated with the lower bottom portion of the saturated helium tank through a communication conduit having a supply valve, and the saturated helium tank In the pressurized superfluid cryostat, which is provided with a heat exchanger for decompressing the liquid helium and cooling the liquid helium in the pressurized superfluid tank into superfluid helium by its heat of vaporization, the saturated helium tank Is formed in a hollow annular cylinder shape and is arranged so as to concentrically surround the pressurized superfluid tank, and the adiabatic pipeline is the atmosphere on the liquid helium liquid surface in the saturated helium tank. While being branched and connected to the pressurized helium gas supply means for applying the above pressure, the supply valve of the communication conduit is operated to open in the pressurized superfluid tank direction at a set operating pressure of atmospheric pressure or higher. It is characterized as being a valve.

Further, the lower bottom portion of the saturated helium tank and the pressurized superfluid tank are communicated with each other through a communication pipe line provided with a pressure release valve, and the pressure release valve has a working pressure equal to or higher than atmospheric pressure. Thus, the check valve may be operated so as to open toward the saturated helium tank.

Further, the supply valve and the pressure release valve may be branched and installed in parallel in a common communication line that connects the lower bottom portion of the saturated helium tank and the pressurized superfluid tank.

Further, a liquid nitrogen tank, which is formed in the shape of a hollow annular cylinder and contains liquid nitrogen therein, is arranged in the vacuum heat insulating container so as to concentrically surround the saturated helium tank. good.

Further, liquid helium temperature shields in the shape of a fork covering the inner pressurized superfluid tank are provided on the upper and lower parts of the saturated helium tank, and an inner saturated helium temperature shield is provided on the upper and lower parts of the liquid nitrogen tank. A dome-shaped liquid nitrogen temperature shield that covers the helium tank may be provided.

Further, the pressurized superfluid tank is formed in the shape of a hollow circular cylinder, and the inner axial center portion of the pressurized superfluid tank is
A cylindrical insert dewar containing liquid helium may be arranged.

In the pressurized superfluid cryostat of the present invention, the saturated helium tank is not disposed above the pressurized superfluid tank as in the prior art, but the saturated helium tank is formed into a hollow annular cylindrical shape. Since the pressurized superfluid tanks are concentrically surrounded and arranged while being formed, both tanks can be arranged so as to have the same height, and the total height of the cryostat can be significantly reduced. Further, liquid helium from an external supply source is fed through an adiabatic pipeline to fill the saturated helium tank and pressurized superfluid tank, and saturated helium is supplied by a pressurized helium gas supply means branched and connected to the adiabatic pipeline. By applying a pressure above atmospheric pressure to the liquid helium surface of the tank, the liquid helium in the pressurized superfluid tank is heated above atmospheric pressure and cooled by a heat exchanger to a temperature below the λ point. By generating pressurized superfluid helium in the pressurized superfluid tank, the superconducting magnet arranged at the inner bottom of the pressurized superfluid tank can be cooled.

Here, the filling of liquid helium from the saturated helium tank to the pressurized superfluid tank is carried out through the supply valve of the communication conduit. And, since the saturated helium tank and the pressurized superfluid tank are arranged at the same height, at the time of initial filling, the liquid helium liquid level of the pressurized superfluid tank is the same as the liquid helium liquid level of the saturated helium tank. Although it can be filled only to the same level, the liquid helium liquid level becomes the top of the pressurized superfluid tank due to a slight negative pressure in the pressurized superfluid tank when it is cooled by the heat exchanger. Reaching the whole is filled. On the other hand, a pressure above atmospheric pressure is applied to the liquid surface of the saturated helium tank, and the supply valve in the communication line is a check valve that opens to the pressurized superfluid tank at a set operating pressure above atmospheric pressure. Therefore, the liquid helium in the pressurized superfluid tank is filled and held at a pressure higher than atmospheric pressure. That is, by making the supply valve of the communication line connecting the saturated helium tank and the pressurized superfluid tank a check valve, at the time of the initial filling of liquid helium, the liquid helium liquid level in the saturated helium tank is kept at an atmospheric pressure or higher. By simply applying pressure, the pressurized superfluid tank can be filled and held with liquid helium at a pressure higher than atmospheric pressure, so that the saturated helium tank and the pressurized superfluid tank are concentric and both tanks have the same height. With the configuration arranged as described above, pressurized superfluid helium can be generated in the pressurized superfluid tank.

Further, the lower bottom portion of the saturated helium tank and the pressurized superfluid tank are communicated with each other via a communication pipe line provided with a pressure release valve, and the pressure release valve is set to an operating pressure higher than atmospheric pressure. By using a check valve that opens in the direction of the saturated helium tank, the liquid helium in the pressurized superfluid tank can always be set to an operating pressure above atmospheric pressure, and suddenly due to quenching of the superconducting magnet. When the superfluid helium in the pressurized superfluid tank is gasified due to the heat generation, the pressure can be released toward the saturated helium tank.

Further, by interposing the supply valve and the pressure release valve in a branched and parallel manner in a common communication line for connecting the lower bottom portion of the saturated helium tank and the pressurized superfluid tank, the supply valve and the pressure release valve are provided. It is possible to suppress heat intrusion into the pressurized superfluid tank via the communication pipe line in which the pressure release valve is interposed.

Further, by arranging a liquid nitrogen tank, which is formed in the shape of a hollow annular cylinder and stores liquid nitrogen therein, in a concentric circle of a saturated helium, the vacuum heat insulation container is It is possible to block heat intrusion into the inner saturated helium tank, and moreover, the saturated helium tank concentrically surrounds the pressurized superfluid tank, which is the deep cooling section, so the inner deep cooling section It is possible to effectively block heat invasion into the.

Further, a circular lid-shaped liquid helium temperature shield covering the inner pressurized superfluid tank is provided above and below the saturated helium tank, and a circular lid covering the inner saturated helium tank is provided above and below the liquid nitrogen tank. By providing each of the liquid nitrogen temperature shields, it is possible to more effectively block the radiant heat input to the inner deep cooling portion. On the other hand, since the saturated helium tank and the liquid nitrogen tank are arranged concentrically with the pressurized superfluid tank and at the same height, the liquid helium temperature shield and the liquid nitrogen temperature shield are As in the case, it is not necessary to extend it to the lower side in the axial direction, and a circular lid having a relatively low height may be used, which facilitates its manufacture and assembly work.

Further, the pressurizing superfluid tank is formed in a hollow annular cylinder shape, and a cylindrical insert dewar containing liquid helium is arranged at the inner axial center portion thereof, so that the insert dewar is inserted. It is possible to perform measurement using the magnetic field environment of the shaft center. Moreover, since the overall height of the device is made low as described above, the height of the insert dewar itself is inevitably low, so that the special handling or jig unlike the prior art is not required for the measurement. Insertion of samples etc. becomes easy.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. [FIG. 1] is a schematic sectional view showing a schematic configuration of one embodiment of a pressurized superfluid cryostat according to the present invention.

In the cryostat of the present embodiment shown in FIG. 1, a vacuum superheated vessel (2) each formed in a hollow annular cylinder shape is provided in a vacuum heat insulating container (1) having a lower lid (1a). ), The saturated helium tank (3) and the liquid nitrogen tank (4) are sequentially arranged at predetermined intervals from the inside, concentrically with respect to the axis of the vacuum heat insulating container (1), and the upper ends of the two are the same. It is arranged so that it is at the height level.

The saturated helium tank (3) surrounding the pressurized superfluid tank (2) has its top connected to an external liquid helium supply source (11) via a heat insulating pipe (10). The liquefied helium fed from the liquid helium supply source (11) is introduced into the inside and accommodated therein. Furthermore, the heat insulating pipeline (10) connected to the saturated helium tank (3) is branched and connected to the helium gas cylinder (13) via a branch pipeline (12) provided with an opening / closing valve (12a). By introducing helium gas having a predetermined pressure from the helium gas cylinder (13) at any time, a pressure above atmospheric pressure can be applied to the liquid surface of the liquefied helium in the saturated helium tank (3).

This saturated helium tank (3) is
The dimension in the height direction is slightly shorter than the tank,
The lower bottom of the pressurized superfluid tank is connected via a communication conduit (5) in which a supply valve (5a) and a pressure release valve (5b) are installed in parallel.
It connects to the bottom of (2). Here, the supply valve (5a) of the communication line (5) is a superfluid tank pressurized at a set operating pressure of atmospheric pressure or higher.
(2) is a check valve that opens in the direction, while the pressure release valve (5b) is a saturated helium tank at a set operating pressure above atmospheric pressure.
It is a check valve that operates to open in the direction (3), and liquefied helium in the saturated helium tank (3) passes through the supply valve (5a) in this communication line (5) to the pressurized superfluid tank (2). To be filled.

On the other hand, in the pressurized superfluid tank (2), a superconducting magnet (6) is arranged on the inner bottom portion, and a heat exchanger (7) is arranged on the lower outer periphery thereof. Where this heat exchanger (7)
Is connected to the lower bottom of the saturated helium tank (3) via a communication pipe (8) equipped with a Joule-Thomson valve (8a) and an external exhaust pump (15) via a discharge pipe (14). ), The liquid helium in the saturated helium tank (3) is decompressed by the Joule-Thomson valve (8a), and the heat of vaporization pressurizes the liquid helium in the superfluid tank (2) to a temperature below the λ point. It is supposed to cool.

Although not shown here, the pressurized superfluid tank (2) has a lower lid that can be opened and closed, and the lower lid is opened to open the superconducting magnet (6) at the inner bottom. It is said that the maintenance of Furthermore, this pressurized superfluid tank (2)
A cylindrical insert dewar (9) containing liquid helium inside has a vacuum insulation container with an upper opening at the inner axial center of the
(1) It is arranged so as to be closed by an upper lid (1b) provided at the center of the upper wall.

In the cryostat of this embodiment having the above-mentioned structure, the liquefied helium fed from the external liquid helium supply source (11) is introduced into the saturated helium tank (3) through the heat insulating pipe (10). Introduce the supply valve (5
Fill the pressurized superfluid tank (2) through a). Then, the helium gas from the helium gas cylinder (13) branched and connected to the heat insulation pipe (10) was introduced into the saturated helium tank (3), and the liquid helium liquid level in the saturated helium tank (3) was at atmospheric pressure or higher. By applying pressure, the liquid helium in the pressurized superfluid tank (2) is heated to atmospheric pressure or higher, and the heat exchanger (7) cools the liquid helium to a temperature of λ point or lower. It is possible to generate pressurized superfluid helium in the tank (2) and cool the superconducting magnet (6) arranged at the inner bottom of the tank to below the critical temperature.

Here, since the pressurized superfluid tank (2) and the saturated helium tank (3) are arranged with their upper ends at the same height level, when the liquid helium is initially charged, it is added. Liquid helium in pressurized superfluid tank (2) Saturated helium tank (3)
Liquid helium can be filled only to the same level as that of liquid helium, but as it is cooled by the heat exchanger (7), the inside of the pressurized superfluid tank (2) becomes a slight negative pressure, so liquid helium The entire liquid surface reaches the top of the pressurized superfluid tank (2) and is filled. On the other hand, a gas pressure above atmospheric pressure is applied to the liquid level of the saturated helium tank (3), and the supply valve (5a) of the communication conduit (5) is opened by that pressure and the flow in the opposite direction is blocked. Therefore, the liquid helium in the superfluid pressure tank (2) is filled and held at a pressure higher than atmospheric pressure.

On the other hand, a saturated helium tank at the time of initial filling
The pressure applied to the liquid surface of (3) is the differential pressure generated by the difference in height between the helium liquid surface in the saturated helium tank (3) and the top of the pressure superfluid tank (2) (that is, the initial filling liquid surface and pressure). Head difference to the top of the superfluid tank; for example, if the head difference = 200 mm, then ΔP = 2.45 × 10 ⁻² Pa, which is a pressure equal to or higher than the atmospheric pressure). A pressure slightly higher than this differential pressure is used as the set operating pressure of the supply valve (5a) and the pressure release valve (5b) of the communication conduit (5). Then, under such conditions, by applying pressure to the liquid surface of the saturated helium tank (3), a small amount of liquid helium is introduced from the saturated helium tank (3) into the pressurized superfluid tank (2). Supplied and pressurized superfluid tank (2)
If the inside pressure is higher than atmospheric pressure and the pressure rises too much, the pressure release valve (5b) will open, so the pressurized superfluid tank (2)
The liquid helium inside has a set pressure above atmospheric pressure (the same as the set dynamic pressure of the above valve), and then the saturated helium tank
Supply valve (5a) that operates in the opposite direction even when pressure is applied to (3)
Holds that pressure.

That is, in the cryostat of the present embodiment, the supply valve (5a) and the pressure release valve (5b) of the communication conduit (5) that connects the saturated helium tank (3) and the pressurized superfluid tank (2) are connected to each other. Since the check valves are operated in opposite directions at a set operating pressure above atmospheric pressure, it is only necessary to apply a pressure above atmospheric pressure to the liquid level of liquid helium in the saturated helium tank (3) during the initial filling of liquid helium. With this, liquid helium can be filled and held in the pressurized superfluid tank (2) at a set pressure above atmospheric pressure, and by cooling this with a heat exchanger (7), this pressurized superfluid tank (2) Pressurized superfluid helium can be generated inside. Moreover, unlike the above-mentioned prior art, the saturated helium tank and the pressurized superfluid tank are not arranged vertically, but the pressurized superfluid tank (2) and the saturated helium tank (3), and further the liquid nitrogen tank (4). Since they are arranged concentrically and at the same height level in the vacuum insulation container (1), the overall height of the device can be made significantly lower than that of the conventional technology, thus making the device configuration compact and reducing the equipment cost. In addition to being able to reduce the number, it is possible to ease restrictions on the installation location.

Further, the supply valve (5a) and the pressure release valve (5b) may be provided in separate communication pipes as long as they are arranged in the lower portion of the apparatus near the deep cooling section, but in this embodiment, , These supply valves (5a)
Since the pressure release valve (5b) and the pressure release valve (5b) are provided in parallel in the common communication line (5), the pressurized superfluid tank (2) via the communication line (5)
It is possible to suppress heat invasion into the air. Further, when the superfluid helium in the pressurized superfluid tank (2) is gasified by the sudden heat generation due to the quench of the superconducting magnet (5), the pressure is passed through the pressure release valve (5b) to the saturated helium tank.
It can be released towards (3).

Since the liquid nitrogen tank (4) is concentrically surrounded by the saturated helium tank (3), liquid nitrogen is introduced into the liquid nitrogen tank (4) to It is possible to block heat ingress to the inner saturated helium tank (3),
Moreover, since the saturated helium tank (3) concentrically surrounds the pressurized superfluid tank (3), which is the deep-cooled section, it is possible to effectively block heat invasion into the deep-chilled section inside. You can

Further, since the insert dewar (9) containing liquid helium is arranged at the inner axial center of the pressurized superfluid tank (2), the axial center is inserted through the insert dewar (9). It is possible to perform measurement using the magnetic field environment of the part. Moreover, since the overall height of the device is low as described above, the height of the insert dewar (9) itself is inevitably low, so that special handling and jigs are required as in the prior art. In addition, insertion of a measurement sample or the like becomes easy.

In the above embodiment, the heat exchanger for cooling the liquid helium in the pressurized superfluid tank is arranged on the outer periphery of the lower part of the pressurized superfluid tank. If there is no restriction, it goes without saying that it may be placed by immersion in the outer surface of the top or the lower periphery of the pressurized superfluid tank, or in liquid helium in the pressurized superfluid tank. Also, a helium gas cylinder was used as a pressurized helium gas supply means for applying pressure to the liquid helium liquid surface of the saturated helium tank, but this is an example, and helium gas at atmospheric pressure or higher can be supplied. It goes without saying that other means such as a helium gas compressor may be used as long as they are used.
In addition, the pressurized superfluid tank was formed in a hollow annular cylinder shape, and the insert dewar for various measurements was arranged in the inner axial center part, but this insert dewar is omitted depending on the scale and application of the relevant device. . Further, in that case, the pressurized superfluid tank may not be a hollow annular cylindrical shape but may be a simple cylindrical shape.

FIG. 2 is a schematic sectional view showing the schematic constitution of another embodiment of the pressurized superfluid cryostat according to the present invention. The cryostat of this example is the same as that of the example shown in [FIG. 1] except that a temperature shield is provided, and therefore, detailed illustration is omitted here and [FIG. 1] The same reference numerals are given to the respective parts equivalent to the above, the description thereof will be omitted, and only the differences will be summarized and described.

In the cryostat of this embodiment shown in FIG. 2, a liquid helium temperature shield in the form of a circular lid covering the upper and lower sides of the inner pressurized superfluid tank (2) is provided above and below the saturated helium tank (3). 16) is provided, and furthermore, a liquid nitrogen temperature shield (17) in the shape of a fork that covers the upper and lower sides of the inner saturated helium tank (3) is provided above and below the liquid nitrogen tank (4).

In the cryostat of the present embodiment having the above-mentioned structure, the radiant heat input to the deep cooling section inside the cryostat, that is, the pressurized superfluid tank, is provided by the double-arranged shields (16) and (17). It can be blocked more effectively. On the other hand, the saturated helium tank (3) and the liquid nitrogen tank (4) are arranged concentrically and at the same height as the pressurized superfluid tank (2).
The shields (16) and (17) do not need to extend largely downward in the axial direction as in the case of the above-mentioned conventional technique, and may be circular lids having a relatively low height, and their manufacture and assembly work are easy. It will be

[0038]

As described above, the pressurized superfluid cryostat according to the present invention has a total height of the pressurized superfluid helium without losing its original function of cooling the superconducting magnet to below the critical temperature by generating pressurized superfluid helium. Can be significantly reduced, and thus the entire apparatus can be made compact to reduce the equipment cost, and the restrictions on the installation place can be eased.

[Brief description of the drawings]

FIG. 1 is a pressurized superfluid cryostat 1 according to the present invention.
It is a cross-sectional schematic diagram which shows the schematic structure of an Example.

FIG. 2 is a schematic sectional view showing the schematic constitution of another embodiment of the pressurized superfluid cryostat according to the present invention.

FIG. 3 is a schematic cross-sectional view for explaining the basic configuration of a pressurized superfluid cryostat according to a conventional technique.

FIG. 4 is a schematic cross-sectional view for explaining another configuration of the pressurized superfluid cryostat according to the conventional technique.

[Explanation of symbols]

 (1) --Vacuum insulation container (1a) --Lower lid (1b) --Upper lid (2) --Pressurized superfluid tank (3) --Saturated helium tank (4) --Liquid nitrogen tank (5) --Communication line (5a)-Supply valve (5b)-Pressure release valve (6) --Superconducting magnet (7) --Heat exchanger (8) --Communication pipe (8a)-Joule Thomson valve (9) --Insert Dewar (10)-Adiabatic pipeline (11)-Liquid helium supply source (12)-Branching pipeline (12a) --Open / close valve (13)-Helium gas cylinder (14)- -Exhaust pipe (15)-Exhaust pump (16)-Liquid helium temperature shield (17)-Liquid nitrogen temperature shield

Claims (6)

[Claims] 1. A vacuum helium vessel is provided with a saturated helium tank containing liquid helium fed from an external source through an adiabatic conduit, a superconducting magnet in the inner lower portion, and a feed valve interposed. A pressurized superfluid tank which communicates with the lower bottom portion of the saturated helium tank through a communication pipe and stores liquid helium at a pressure higher than atmospheric pressure, and liquid helium in the saturated helium tank is decompressed and vaporized. In a pressurized superfluid cryostat provided with a heat exchanger that cools liquid helium in the pressurized superfluid tank into superfluid helium by heat, the saturated helium tank has a hollow annular tubular shape. Pressurized helium that is formed and is arranged so as to concentrically surround the pressurized superfluid tank, and the adiabatic pipeline applies a pressure equal to or higher than atmospheric pressure to the liquid surface of liquid helium in the saturated helium tank. Gas supply While being connected to the supply means in a branched manner, the supply valve of the communication pipe is a check valve that operates to open toward the pressurized superfluid tank at a set operating pressure of atmospheric pressure or higher. Pressurized superfluid cryostat. 2. The lower bottom portion of the saturated helium tank and the pressurized superfluid tank are communicated with each other through a communication conduit having a pressure release valve, and the pressure release valve has a working pressure equal to or higher than atmospheric pressure. 2. The pressurized superfluid cryostat according to claim 1, wherein the check valve is a check valve that operates to open toward the saturated helium tank. 3. The supply valve and the pressure release valve are branched and installed in parallel in a common communication line that connects the lower bottom portion of the saturated helium tank and the pressurized superfluid tank. Pressurized superfluid cryostat. 4. A liquid nitrogen tank, which is formed in the shape of a hollow toroidal cylinder and stores liquid nitrogen therein, is arranged in the vacuum heat insulating container so as to concentrically surround the saturated helium tank. Item 4. A pressurized superfluid cryostat according to item 1, 2 or 3. 5. A liquid helium temperature shield in the shape of a fork that covers the inner pressurized superfluid tank is provided on the upper and lower portions of the saturated helium tank, and an inner saturated helium tank is provided on the upper and lower portions of the liquid nitrogen tank. The pressurized superfluid cryostat according to claim 4, further comprising a circular lid-shaped liquid nitrogen temperature shield that covers the helium bath. 6. The pressurized superfluid tank is formed in a hollow annular tubular shape, and a cylindrical insert dewar containing liquid helium inside is arranged at the inner axial center of the pressurized superfluid tank. The pressurized superfluid cryostat according to claim 1, 2, 3, 4 or 5.