JP2001066354A - Cryogenic container for superconducting quantum interference device storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cryogenic container for SQUID(Superconducting Quantum Interference Device) element storage which eliminates the vaporization of a cooling medium for cooling SQUID elements, uniformly cool a group of many arranged SQUID elements, and can be arranged at all directional attitudes. SOLUTION: The cryogenic container 1 for SQUID element storage consists of an internal container 4 which contains SQUID elements and a cooling medium 3 having a higher solidification point than the cooling temperature of the SQUID elements 2 and cooling the SQUID elements 2, a heat conductor 30 which comes into contact with the outer peripheral part of the internal container 4 to cover the internal container 4, a heat shield plate 13b which covers the internal container 4 containing the heat conductor 30, an external container 6 which covers the heat shield plate 13b and forms a heat insulation space 5 with the heat shield plate 13b, and a pulse tube refrigerator 89 which is provided above the external container 6 and cools the heat conductor 30 and heat shield plate 13b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a medical diagnostic apparatus for measuring a magnetic field generated from an object such as a human body or a living body, and a physical property measuring apparatus for measuring the magnetic permeability of a material. The present invention relates to a cryogenic container for storing a superconducting quantum interference device suitable for storing a superconducting quantum interference device used as a transducer for signal transmission.

[0002]

[Prior Art] Superconducting quantum interference device (Sujperconduct
ing Quantum Interference Devices (hereinafter abbreviated as SQUID element) is a superconducting loop that is maintained at a very low temperature in an insulated container (such as a cryostat) by liquid helium or liquid nitrogen as a cooling means and includes a Josephson junction in the loop. When a DC current is applied as a bias current to the SQUID element loop and driven, and an external magnetic flux is coupled and applied to the SQUID element loop via a pickup coil, an input coil, and the like, the SQUID element loop is applied to the SQUID element loop. By utilizing the fact that a circulating current is induced and acts as a transducer that converts a small change in the applied external magnetic flux into a large change in the output voltage due to the quantum interference effect at the Josephson junction in the loop, This is an element for measuring a minute magnetic flux change.

Therefore, in order to bring the Josephson junction into a superconducting state, it is necessary to cool the junction below the superconducting generation temperature. Therefore, the SQUID element is immersed in a cooling medium of liquid helium or liquid nitrogen in the cryogenic container for storing the SQUID element and cooled. Alternatively, there is a structure in which the SQUID element is directly cooled by a refrigerator as a cooling means.

An object and a cryogenic container for storing a SQUID element are arranged in a magnetically shielded room surrounded by a ferromagnetic material such as permalloy for shielding from an external magnetic field to generate a magnetic flux generated from the object. Measure with a SQUID element.

A conventional cryogenic container for storing a SQUID element, which is cooled by immersion in a cooling medium of liquid helium or liquid nitrogen, is a cryogenic heat insulating container described in JP-A-7-321382 or a cryogenic container described in JP-A-7-321382. JP-A-321382 discloses a cryogenic heat insulating container.

In a conventional cryogenic container for storing a SQUID element, which is immersed and cooled in a liquefied refrigerant such as liquid helium, the SQUID element group is cooled by being buried in the refrigerant, so that the SQUID element group is kept at the same temperature. Although the cryogenic container for storage has heat intrusion from room temperature to the cryogenic part, the cryogenic container for storage is composed of a vacuum insulated container to minimize the heat infiltration. Evaporate. For this reason, it is necessary to replenish the liquid helium, which is a refrigerant, every week, and this charging operation is complicated, and there is a problem that the operation cost increases because the refrigerant is expensive liquid helium.

[0007] To solve this, Japanese Patent Laid-Open No. 7-32 is disclosed.
The nuclear magnetic resonance imaging apparatus using a medical superconducting magnet described in Japanese Patent No. 1382 incorporates a refrigerator in a vacuum-insulated low-temperature container in order to suppress the amount of liquid helium that cools the superconducting magnet. In addition, the heat infiltration from the room temperature to the extremely low temperature portion is cooled by the cooling of the refrigerator to reduce the evaporation amount of the liquid helium.

However, in this configuration, it is necessary to replenish the liquid helium every six months, and this filling operation is complicated, and when the vacuum of the vacuum insulated container is broken due to an earthquake or the like, the liquid helium in the stored cryogenic container is lost. Disappears instantaneously,
There is a problem that the temperature inside the container rises and measurement becomes impossible.

In addition, when the storage cryogenic container is used at an angle or is measured upside down from below, the liquid surface of a cooling cooling medium such as a liquid helm is inclined so that the head of the element group is exposed and the element is cooled. There was a problem that it could not be measured due to lack or spillage from the container.

As a method for solving the above-mentioned problem, a cryogenic container for storing a SQUID element for directly cooling the SQUID element by refrigeration of a refrigerator described in Low Temperature Engineering, Vol. 28, No. 8, page 430 (1993) When the element is cooled by the cooling of the refrigerator, the element cooling support made of a solid such as a metal is cooled by the cooling of the refrigerator, and the element is cooled in vacuum through the cooling support.

However, since the SQUID element is used to measure a small magnetic flux, the cooling support near the SQUID element must be made of a non-conductor to prevent the generation of eddy current due to the measured magnetic flux. Non-conductor thermal conductivity is small. In addition, in consideration of maintenance and inspection and replacement of the SQUID element, a structure that allows the SQUID element to be easily attached to and detached from the cooling support is necessary.Since the SQUID is lightly supported on the cooling support with screws, the transmission between the cooling support and the SQUID element is required. The degree of thermal contact is different for each SQUID
The element cannot be controlled constantly. For this reason, there is a problem that the cooling temperature of each SQUID element varies.

Further, since the cooling support and the SQUID element body are arranged in a vacuum, the cooling support and the SQUID element are arranged in a vacuum.
Radiation heat enters the UID element body from surrounding components at a temperature higher than this temperature, and the size of the radiation heat varies depending on the arrangement position and the heat receiving surface area.
There is a problem in that the amount of infiltration heat varies in the D element body, and thus the cooling temperature of each SQUID element varies.

Since the sensitivity of the SQUID element is sensitive to the cooling temperature, if the SQUID element temperature fluctuates as described above, the sensitivity fluctuates between the SQUID elements of the SQUID element group, and the measurement accuracy is greatly reduced. There is an important problem.

[0014]

The object of the present invention is to provide a SQUI
Eliminates the evaporation of the cooling medium for cooling the D element
An object of the present invention is to provide a cryogenic container for storing a superconducting quantum interference device that can be arranged in all directions and uniformly cools a group of SQUIDs in which ID elements are arranged.

[0015]

In order to achieve the above object, a cryogenic container for storing a superconducting quantum interference device according to the present invention is characterized in that the superconducting quantum interference device and the cooling temperature of the superconducting quantum interference device are higher than the cooling temperature. A cooling medium that has a freezing point and cools the superconducting quantum interference device is wrapped with a heat conductor around the outer periphery of the internal container in which the cooling medium is stored,
Another object of the present invention is to surround the inner container containing the heat conductor with a heat shield plate and cool the heat conductor and the heat shield plate with a refrigerator.

Specifically, the present invention provides the following cryogenic containers. The present invention provides an inner container in which a superconducting quantum interference device and a cooling medium having a freezing point higher than the cooling temperature of the superconducting quantum interference device and cooling the superconducting quantum interference device are stored, and an outer peripheral portion of the inner container. A heat conductor surrounding the inner container, a heat shield plate surrounding the inner container including the heat conductor, and an outer container surrounding the heat shield plate and forming an adiabatic space between the heat shield plate and the heat shield plate And a refrigerator provided on an upper part of the outer container for cooling the heat conductor and the heat shield plate.

Further, the present invention has a plurality of superconducting quantum interference devices, a first heat conductor spirally wound around the outer periphery of each superconducting quantum interference device, and a freezing point higher than a cooling temperature of the superconducting quantum interference device. An inner container in which the first heat conductor and a cooling medium for cooling the superconducting quantum interference device are stored, and an outer peripheral portion of each of the first heat conductors provided at the center of the inner container. A second heat conductor in contact with a portion thereof, a heat shield plate surrounding the inner container including the second heat conductor, and an insulating space between the heat shield plate and the heat shield plate And a cryogenic container for storing a superconducting quantum interference device, comprising a refrigerator provided on an upper portion of the external container and cooling the second heat conductor and the heat shield plate. provide

Further, the present invention provides an internal container in which an object to be cooled and a cooling medium having a freezing point higher than the cooling temperature of the object to be cooled and for cooling the object to be cooled are stored; A heat conductor provided inside and thermally integrated with the object to be cooled, a heat shield plate surrounding the inner container including the heat conductor, and a heat shield plate surrounding the heat shield plate and An outer container forming an adiabatic space between the outer container and a refrigerator provided at an upper portion of the outer container and cooling the heat conductor and the heat shield plate, wherein a cryogenic container for storing a cooled object is provided. provide.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cryogenic container for storing a SQUID element according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing an entire configuration of a cryogenic container for storing a SQUID element according to a first embodiment of the present invention. FIG. 2 is an enlarged view of a SQUID element mounting portion of FIG. FIG. 3 is a sectional view taken along line XX of FIG.

As shown in FIG. 1, a cryogenic container 1 for storing a SQUID element includes a SQUID element 2, a cooling medium 3 as a medium for cooling the SQUID element 2, and a SQUID element 2 and a cooling medium 3. An inner container 4 that can be stored, a heat conductor 30 surrounding the inner container 4 so as to be in contact with the outer peripheral portion, a heat shield plate 13b surrounding the inner container including the heat conductor 30, and a heat shield plate 13b. And an outer container 6 forming an insulating space 5 between itself and the heat shield plate 13b, and a flange 8 for shutting off the inside air and the insulating space 5 from the outside air.
A pulse tube refrigerator 89 provided on the upper surface of the flange 8 for cooling the heat conductor 30, a measuring wire 9 for guiding the measured current from the SQUID element 2 to the outside of the SQUID element storing cryogenic container 1, A screw 42 for fixing and supporting the upper portion of the inner container 4 to the cooling plate 27 is provided.

The SQUID element 2 is a SQUID made of a material such as NbTi which is in a superconducting state at a critical temperature of about 7 K or less (for example, 4.2 K of liquid helium temperature at atmospheric pressure).
The element 2a or a high critical temperature of about 90K or less (for example,
Y in superconducting state at atmospheric liquid nitrogen temperature (77 K)
There is a SQUID element 2aa made of a material such as Ba2Cu3O7.

Before the cooling of the SQUID element 2, the cooling medium 3 contains fluid silicon oil (boiling point at atmospheric pressure of 410 K or more), perfluorocarbon (boiling point at atmospheric pressure of 313 K or more), and wax having a melting point at room temperature or higher. There are cooling media such as paraffin and wax which have fluidity at atmospheric pressure and room temperature or higher, and cooling media having a boiling point at a temperature exceeding the cooling temperature of the SQUID element.

Reference numeral 11 denotes an atmospheric outlet of a measuring lead. The inner container 4 and the outer container 6 are made of a non-conductive material, such as a non-magnetic material such as a glass epoxy resin, in order to prevent eddy currents from being generated by the measured magnetic flux.

Further, in the heat insulating space 5, laminated heat insulating materials 12 a, 12 b, 12 c such as aluminum vapor-deposited mylar for preventing radiant heat from entering from the external container 6, and noise generated due to a magnetic field fluctuation from the outside. A heat shield plate 13a composed of a strip-shaped copper plate or a small-diameter enamel-coated copper wire and a heat shield plate 13b composed of an enamel-coated copper wire, in which eddy current is unlikely to be generated, surround the outside of the inner container 4 group. It is provided in.

In a heat insulating space around the heat shield plate 13b, a laminated heat insulating material 15 such as an aluminum vapor-deposited mylar is provided.
a is arranged. The heat shield plates 13a and 13b
The first cooling stage 94 and the second cooling stage 9 of the first cooling stage 94 and the second cooling stage 95 of the pulse tube refrigerator 89 at a predetermined temperature of, for example, 50K and 5K or lower.
5 is directly or thermally indirectly integrated into the wall.

Here, the pulse tube refrigerator 89 includes a first regenerator 90, a second regenerator 91, a first pulse tube 92,
A second pulse tube 93, a first cooling stage 94, a second cooling stage 95, a pipe 96 for supplying gas from the compressor and exhausting gas to the compressor, and a pipe 96 in the first and second pulse tubes. Pressure holding tank 97 for adjusting the pressure of each gas
a, a pressure holding tank 97b, and pipes 98a, 98b communicating with the normal temperature portion of each pulse tube and the pressure holding tank 97, and adjusting a predetermined gas flow resistance pressure loss by size and length.

The first regenerator 90 and the second regenerator 91 are connected in series, and a first pulse tube 92 and a second pulse tube 93 are connected.
Are communicated in parallel, the end of the first pulse tube 92 communicates with the first regenerator 90 in the first cooling stage 94, and the end of the second pulse tube 93 is in the second cooling stage 95. The center of the second pulse tube 93 is thermally integrated with the first cooling stage 94, communicating with the end of the pulse tube 93.

The high-pressure helium gas supplied from the compressor 20 through the flow path switch 23 a is supplied to the upper end of the pulse tube refrigerator 89 from the pipe 96, and first flows into the head of the first regenerator 90. Then, after being cooled to a temperature of about 50 K by the cold heat of the first regenerator, it flows into the head of the second regenerator 91 and the bottom of the first pulse tube 92. The remaining gas is stored in the second regenerator 9
At 1, the temperature is cooled to about 5K and flows into the bottom of the second pulse tube 93.

The high-pressure helium gas that has flowed into the bottom of the first pulse tube 92 adiabatically expands when it is switched to the compressor low-pressure circuit by the flow path switch 23a, generating cold, and cooling the first cooling stage 94. Thereafter, the first regenerator 90 is cooled and returns to the compressor 20. At the same time, when the high-pressure helium gas flowing into the bottom of the second pulse tube 93 is switched to the compressor low-pressure circuit, it adiabatically expands to generate cold, cools the second cooling stage 95, and then cools the second regenerator 91. Compressor 20
Return to

The center of the second pulse tube 93 is cooled by the first cooling stage 94. The temporal pressure waveform in each pulse tube head is represented by a holding tank 97a and a holding tank 97.
The pressure is adjusted so that a phase difference is temporally generated with the pressure waveform of the flow path switch 23a in b, so that cold can be generated efficiently.

When the pulse tube type refrigerator 89 is used as the refrigerator, the vibration of the refrigerator is small, so that the vibration noise to the element is small. Even if the refrigerator is operated during adjustment movement setting while measuring, noise can be reduced, so that movement setting can be performed easily and in a short time.

Further, in order to almost eliminate the vibration and electric noise of the refrigerator, the refrigerator operation is temporarily stopped only at the time of measuring the magnetic flux.

Hereinafter, a method for cooling the SQUID element 2 will be described. A cooling medium 3 having a fluidity at room temperature, such as silicone oil, is put in a predetermined volume in the inner container 4 when the SQUID element is incorporated or before the SQUID element is cooled.
The element 2 is immersed.

When wax, wax, paraffin, or the like is used as the cooling medium 3 having fluidity at a temperature higher than the normal temperature, the cooling medium is heated by a heater or a hot-air drier to be fluidized. In a separate container (not shown), the air and volatile components are removed by vacuum degassing, and the air is injected into the heated internal container 4. Further, the air that has entered at the time of injection is degassed and then released at room temperature. By cooling and solidifying,
The cooling medium does not move even if it is tilted or turned upside down at room temperature, so that it can be transported in all directions and the device can be transported and moved more easily.

Open the valve 17 and use the vacuum pump 19
Is evacuated. The inside of the inner container 4 has ventilation holes 14a, 14
The pressure becomes uniform with the heat insulating space 5 via b and 14c.

Next, the pulse tube refrigerator 89 is operated.
Simultaneously with the start of the refrigerator operation, the first cooling stage 94 and the second cooling stage 95 gradually cool down, and the cooling plate 26 thermally integrated with the first cooling stage 94 has a temperature of about 50 ° C.
K, and the cooling plate 27 thermally integrated with the second cooling stage 95 is cooled to a temperature of about 4K. Cooling plate 2
The cooling plate 6 and the cooling plate 27 are made of a material such as aluminum, copper, or sapphire, which is a non-magnetic material and has good thermal conductivity.

The heat shield plate 13 is provided on the outer periphery of the cooling plate 26.
b and the heat shield plate 1 so as to surround the inner container 4 group.
3a is provided, and silicon grease or the like is applied so that thermal contact with the flange portion 28 of the heat shield plate 13a can be made favorable, or the heat conduction function is improved through an indium sheet.
Cool to a temperature of about 50K.

On the other hand, the inner container 4
A heat shield plate 13b is provided so as to surround the group, silicon grease or the like is applied so that thermal contact with the flange portion 29 of the heat shield plate 13b can be made good, and the heat conduction function is improved via an indium sheet, and the temperature is improved. Cool down to 7K or less.

At the lower part of the cooling plate 27, a material such as aluminum, copper, or sapphire, which is a non-magnetic material and has good thermal conductivity and is hard to generate eddy current, is provided so as to surround the outer peripheral portion of the inner container 4. A heat conductor 3 of, for example, an enamel-coated copper wire which is shaped and arranged at a position where eddy current is unlikely to be generated
0 is thermally integrated with the outer periphery of the inner container 4 with an adhesive 99.

The upper portion of the heat conductor 30 is provided with a cooling plate 27.
And a fastening agent 31 such as wax, grease, solder, low-melting wood metal, or indium.

The cooling medium 3 is uniformly cooled by the heat conductor 30 to a temperature of about 7 K or less via the inner container 4.
The upper part of the inner container 4 is covered with a lid 4a integrated with the inner container 4 with a screw part 4b, and the lid 4a is fixed to the cooling plate 27 with a screw 42, so that the inner container 4 is accurately positioned with respect to the cooling plate 27. Fixed to

Here, before the lid 4a is closed, the inner container 4
The SQUID element 2 and the cooling medium 3 are inserted into the inside. In this case, since the inside of the inner container 4 below the cooling plate 27 is surrounded by the heat shield 13b cooled to a temperature of about 7 K or less, the heat intrusion of radiant heat from the outside is very small.

The measuring conductor 9 is thermally integrated with the cooling plate 26 and the fixing body 31a, and the measuring conductor 9 is thermally integrated with the cooling plate 27 and the fixing body 31b. Therefore, the measuring conductor 9 is cooled at a temperature of 50K or less and 7K or less, respectively, and there is almost no heat infiltration through the measuring conductor 9 due to heat conduction from room temperature.

Therefore, the SQUI immersed in the cooling medium 3
The D element 2 has a very small influence of being heated by the infiltration heat from the outside.
, There is almost no temperature difference due to the thermal resistance between the heat conductor 30, the inner container 4, and the cooling medium 3, and the temperature is uniformly reduced to about 7K or less.

Further, the cooling plate 27 cooled by the pulse tube refrigerator 89 has a very low heat infiltration of radiant heat from the outside due to the heat shield plate 13a and has a uniform temperature as a whole. SQ thermally integrated from 27
The UID element group 2 also has a uniform temperature as a whole, which has the effect of improving the measurement performance of the SQUID element group by uniforming the temperature.

When the temperature of the first cooling stage 94 or the second cooling stage 95 of the pulse tube refrigerator 89 is reduced to 70 K or less, residual moisture, carbon dioxide and the like in the inner container 4 are trapped on the surface of each stage and the cryopump effect is obtained. Then, the pressure in the inner container 4 starts to decrease, so that the valve 17 is closed and the vacuum pump 19 is stopped. Further, the vacuum pump 19 may be stopped while the valve 17 is open.

When the temperature of the second cooling stage 95 becomes equal to or lower than 20 K, the constant boiling point gas such as residual air in the inner container 4 is trapped on the surface of the second cooling stage 95 by a cryopump effect. The pressure is evacuated to high vacuum. However, the cooling medium 3 such as silicon oil or wax, which is a low-temperature cooling medium 3 having a low saturated vapor pressure, hardly evaporates even in a high vacuum atmosphere.

In the heat insulating space 5, inside the outer container 6, a cylindrical body 48 made of non-magnetic and non-conductive, for example, made of polyester and having aluminum deposited on its inner and outer surfaces, is rigid enough to hold a cylindrical shape. And serves as a guide tube when the pulse tube refrigerator 89, the heat shield plate 13a, and the like connected to the flange 43 are taken in and out of the external container 6. The aluminum vapor-deposited mylar is provided on the outside and bottom of the cylindrical body 48 for heat insulation. Is disposed. Even without the guide tube 48, there is no problem in the measurement function.

A non-magnetic, non-conductive, and thermally conductive heat conductor 45 is thermally integrated with the cooling plate 27 on the upper portion of the cooling plate 27. Activated carbon 46 is thermally integrated and cooled to the temperature of cooling plate 27.

Even after the valve 17 is closed and the vacuum pump 19 and the pipe are disconnected and separated, the residual gas in the heat insulating space 5 and the gas generated from the surface of the component facing the heat insulating space 5 are adsorbed by the low-temperature activated carbon 46. In addition, the degree of vacuum in the heat insulating space 5 can be increased, and the heat insulating performance can be maintained.

In this case, the inner cylindrical container group 4 below the cooling plate 27 is surrounded by the heat shield 13b cooled to a temperature of about 7 K or less, so that the heat radiated heat from the outside is very small. Further, since the cooling plate 27 is supported at the lower part of the refrigerator, there is no heat infiltration due to heat conduction from room temperature.

When the group of SQUIDs 2 is cooled to a predetermined temperature, the preparation for measurement is completed, and the bed 35 in the magnetic shield wall 34 is set.
The weak magnetic flux generated from the upper subject 36 is measured.
During the measurement for several minutes, the operation of the pulse tube refrigerator 89 is temporarily stopped for the several minutes, and the measurement accuracy can be improved by eliminating the refrigerator vibration.

After the measurement, the operation of the pulse tube refrigerator 89 is started again and cooled. This operation stop is performed by stopping the compressor 20 or by operating the flow path switch 23 while the compressor is operating.
It is sufficient to stop only the operation of a.

When the SQUID element 2 is taken out to the atmosphere for repair or the like, the operation of the refrigerator is stopped or the operation cycle of the refrigerator is reversed to perform a heating operation to bring the inside of the inner container 4 to room temperature. After that, air or dry nitrogen is injected from the valve 17 to make the inside of the inner container 4 atmospheric pressure, and the flange 8
The following components are extracted to the outside, the fixing agent 31 such as wax is melted by heat, and the SQUID element 2 is extracted from the inner container 4 and replaced.

Therefore, in this embodiment,
The SQUID element 2 immersed in the cooling medium 3 has an extremely small effect of being heated by external heat of penetration.
Since the entire UID element 2 is in contact with the cooling medium 3, there is almost no temperature difference due to the thermal resistance between the heat conductor 30, the inner container 4, and the cooling medium 3, and the UID element 2 is uniformly cooled to a temperature of about 7K or less.

The cooling plate 27 cooled by the pulse tube refrigerator 89 has a very low heat penetration of radiant heat from the outside due to the heat shield plate 13a and has a uniform temperature as a whole. SQ thermally integrated from 27
The UID element group 2 also has a uniform temperature as a whole, which has the effect of improving the measurement performance of the SQUID element group by uniforming the temperature.

Even if the cryogenic container 1 for storing the SQUID element is tilted or inverted, the cooling medium 3 is solidified.
Since there is no change in the cooling performance of the SQUID element 2 group, and the cooling medium 3 does not spill even if it is tilted or turned upside down, it can be arranged in all directions and can be measured in all directions.

Further, in this embodiment, since the pressure inside and outside the internal container 4 can be uniformly maintained, the internal container 4 does not need to be a pressure container, and the wall thickness of the wall of the internal container 4 and the bottom plate 3 are not required.
7 can be made thinner.

Accordingly, the thickness of the wall of the inner container 4 is set to be equal to 0.
By reducing the thickness to about 5mm, the thermal resistance is reduced,
The SQUID element 2 is cooled to a lower temperature and more uniformly to a temperature of about 7 K or less by the heat conductor 30 via the inner container 4.

Further, since the bottom plate 37 can be thinned to about 0.5 mm or less, the SQUID element 2 can be brought closer to the subject 36, and the SQUID element 2 group can be closer to the magnetic flux generation source of the subject 36. The measurement accuracy can be further improved.

Here, in order to increase the thermal conductivity of the cooling medium 3, for example, a copper net having a higher thermal conductivity than that of the cooling medium 3 is laminated, or solder particles, aluminum fine particles, electric insulating Copper or stainless steel metal spheres sealed with helium gas or nitrogen gas, etc., whose material has a specific heat greater than that of the cooling medium 3, or a group of thin metal tubes sealed with helium gas, nitrogen gas, etc. In order to prevent thermal deformation after solidification of the cooling medium 3 or the like, a contaminant such as glass fiber is mixed with the contaminant to increase the cooling rate of the cooling medium 3 or to increase the heat capacity at extremely low temperatures, By reducing the temperature change of the SQUID element 2 when the operation of the refrigerator is stopped for a short time, it is possible to reduce the deformation of the solidified body and prevent cracks from occurring.

At this time, if the contaminant is conductive, it is better to prevent generation of eddy current and reduce noise at the time of measurement by coating an electric insulating agent such as a surface enamel coating.

Further, in the refrigerator of this embodiment, a device using helium, nitrogen, air, hydrogen, or chlorofluorocarbon as a working cooling medium or an electronic device using a Peltier element may be used. Good. Other types of refrigerators that use gas as a working fluid include Gifford McMahon type, Solvay type, Stirling type, Claude type, expansion turbine type, expansion valve type, and devices with a Joule-Thomson expansion valve that combines these. Etc. may be used.

FIG. 4 is an enlarged view of the SQUID element mounting portion of the cryogenic container for storing a SQUID element according to the second embodiment of the present invention, and FIG. 5 is a sectional view taken along line YY of FIG. .

In the present embodiment, four SQUID elements 2 are arranged as one unit in the inner container 80 and the cooling medium 3
Is injected into the internal container 80. Each SQUID
An enamel-coated copper wire, for example, is spirally wound around the outer periphery of the element 2 as a first heat conductor 81 and is thermally integrated with an adhesive or the like.

A part of the outer peripheral portion of each of the first heat conductors 81 is formed, for example, around an epoxy resin core 82a containing a glass fiber, for example, by enamel-coated copper wire 82b.
A second thermal conductor 82 which is bundled and integrated with an adhesive or the like;
The tangential portion is thermally integrated with an adhesive or wax, and the upper portion of the core 82a is fixed to the cooling plate 27 with screws 42, and the upper portion of the enamel-coated copper wire 82b is bonded with an adhesive or wax. It is thermally integrated with the cooling plate 27.

Each SQUID element 2 in the inner container 80 is immersed in the cooling medium 3, and the measurement line 9 is led to the outside of the inner container 80 through the hole 84, and the inside and the outside of the inner container 80 communicate with each other through this hole.

In the SQUID element 2, in the upper enamel-covered copper wire 82b cooled by the cooling plate 27, heat transfer in the vertical direction along the copper wire having a small thermal resistance in the copper wire occurs with a small temperature difference. Cool the lower part.

On the other hand, in the lower portion, the enamel-coated copper wire of the first heat conductor 81 causes heat transfer in the circumferential direction along the copper wire having a small thermal resistance in the copper wire in a state where the temperature difference is small, and SQ
The entire UID element 2 can be cooled uniformly. Here, the upper part of the inner enamel-coated copper wire 82b of the second heat conductor 82 may be formed in a spiral shape.

According to the present embodiment, a plurality of SQUID elements 2 are housed in the same inner container 80 and can be cooled via the heat conductor without passing through the inner container wall, so that the thermal resistance can be further reduced. Since the cooling can be uniformly performed at a low temperature closer to the temperature of the cooling plate 27, the measurement accuracy is further improved. Also,
Since the number of heat conductors attached to the cooling plate 27 can be reduced, the structure is simplified and the manufacturing cost can be reduced.

FIG. 6 is an enlarged view of the SQUID element mounting portion in FIG. 4, and is a cross-sectional view in the ZZ direction shown in FIG. As shown in FIG. 6, even when the filling position of the cooling medium 3 is only on the lower side of each SQUID element 2, the cooling medium 3 is transmitted through the spiral enamel-coated copper wire of the first heat conductor 81 to cool the lower part. The upper part of each SQUID element 2 can also be uniformly cooled by the cooling medium 3 thus obtained.

Therefore, even if the filling amount of the cooling medium 3 is erroneously reduced during the injection operation, the plurality of SQUID elements 2 can be cooled via the heat conductor, so that the thermal resistance can be reduced and the temperature of the cooling plate 27 can be reduced. Therefore, even if the amount of cooling medium 3 is insufficient during the charging operation, measurement accuracy can be obtained.

FIG. 7 is an enlarged view of the SQUID element mounting portion of the cryogenic container for storing a SQUID element according to the third embodiment of the present invention. This embodiment is different from FIG.
A cavity 84 is provided inside the SQUID element, and an enamel-coated copper wire, for example, as a third heat conductor 85 is inserted into the cavity 84 and thermally integrated with an adhesive or the like.

A communication port 86 is provided above the cavity 84 and communicates with the outside of the device. In the present embodiment, the cavity 84
The inside of the SQUID element 2 is also filled with the cooling medium 3 and acts so as to eliminate the temperature difference in the vertical direction from the inside of the SQUID element 2, so that the element temperature can be more uniformly cooled.
The group can be cooled uniformly. Therefore, according to the present embodiment, the measurement accuracy can be further improved.

In the SQUID element of the above embodiment, in order to prevent the cooling refrigerant from directly penetrating into the Josephson element portion and to prevent thermal deformation due to solidification, the Josephson element electronic device is made of resin or the like so that the cooling refrigerant does not directly penetrate. Even if only the circuit portion is sealed, a similar effect is obtained for cooling and the like.

According to the above-described embodiment, the SQUID element can be uniformly cooled without evaporating the cooling medium for cooling the SQUID element and without replenishing the cooling medium. In addition, the cryogenic container inside the cryogenic container can be arranged so that the internal pressure of the cryogenic container does not increase above the atmospheric pressure during steady-state low-temperature operation, and the cryogenic container for storing the SQUID element can be placed in any measurement site and direction around the test object A possible structure can be realized.

In the above-described embodiment, the SQUID
Although the element has been described as an object to be cooled, a similar effect can be obtained even if the object to be cooled is a superconducting magnet, a semiconductor electronic element such as a CMOS having improved performance at low temperature, or a biological cell.

The present invention can also be applied to a cooling system for an object to be cooled including a superconductor which becomes superconductive below the cooling medium solidification temperature.

[0080]

According to the present invention, the cooling medium for cooling the SQUID element can be prevented from evaporating and the SQUID element group having a large number of SQUID elements can be uniformly cooled.
Variations in sensitivity among ID elements are eliminated, and measurement accuracy can be improved.

Further, by solidifying the cooling medium at the time of measurement, the cooling medium is prevented from spilling in any direction, the omnidirectional posture can be arranged, and the use of the cooling medium in medical diagnostic devices and the like is facilitated.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a cryogenic container for storing a SQUID element according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a SQUID element mounting portion of FIG.

FIG. 3 is a sectional view taken along line XX of FIG. 2;

FIG. 4 is an enlarged view of a SQUID element mounting portion of a cryogenic container for storing a SQUID element according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line YY of FIG. 4;

FIG. 6 is an enlarged view of a SQUID element mounting portion of FIG. 4;
It is sectional drawing of the ZZ direction shown in FIG.

FIG. 7 is an enlarged view of a SQUID element mounting portion of a cryogenic container for storing a SQUID element according to a third embodiment of the present invention.

[Explanation of symbols]

1. Cryogenic container for storing SQUID elements, 2. SQUID elements, 3.
Cooling medium, 4,80 inner container, 5 heat insulating space, 6 outer container, 8 flange, 13b heat shield plate, 30
Heat conductor, 81: first heat conductor, 82: second heat conductor, 89: pulse tube refrigerator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G017 AA04 AC04 AD32 4M113 AC06 CA17 CA34 4M114 AA02 AA08 AA19 BB05 CC08 CC11 DA08 DA13 DA15

Claims (3)

[Claims] 1. An inner container in which a superconducting quantum interference device and a cooling medium having a freezing point higher than a cooling temperature of the superconducting quantum interference device and cooling the superconducting quantum interference device are stored, and an outer peripheral portion of the inner container. A heat conductor that is in contact with and wraps the inner container, a heat shield plate that surrounds the inner container including the heat conductor, and an outer that surrounds the heat shield plate and forms an adiabatic space between the heat shield plate and the heat shield plate. A cryogenic container for storing a superconducting quantum interference device, comprising: a container; and a refrigerator provided on an upper portion of the outer container to cool the heat conductor and the heat shield plate. 2. A superconducting quantum interference device, a first heat conductor spirally wound around an outer periphery of each superconducting quantum interference device, and a first freezing point higher than a cooling temperature of the superconducting quantum interference device. And an inner container in which a heat conductor and a cooling medium for cooling the superconducting quantum interference device are stored, and a part of an outer peripheral portion of each of the first heat conductors provided at a central portion of the inner container. A second heat conductor, a heat shield plate surrounding the inner container including the second heat conductor, and an outside surrounding the heat shield plate and forming an adiabatic space between the heat shield plate and the outside. A cryogenic container for storing a superconducting quantum interference device, comprising: a container; and a refrigerator provided on an upper portion of the outer container to cool the second heat conductor and the heat shield plate. 3. An internal container for storing an object to be cooled and a cooling medium having a freezing point higher than the cooling temperature of the object to be cooled and cooling the object to be cooled, and provided outside or inside the internal container. A heat conductor thermally integrated with the object to be cooled, a heat shield plate surrounding the inner container including the heat conductor, and heat insulation surrounding the heat shield plate and the heat shield plate A cryogenic container for storing a cooled object, comprising: an outer container forming a space; and a refrigerator provided on an upper portion of the outer container to cool the heat conductor and the heat shield plate.