JP4431793B2 - Cryostat - Google Patents

Description

The present invention can provide a measurement environment for a wide range of temperatures from various cryogenic temperatures of about 20 mK (milli Kelvin) or higher to various temperatures ranging from about 300 K to room temperature or above, and at a desired temperature. The present invention relates to a cryostat capable of measuring physical properties.

  In fields such as physical physics, material science, material engineering, and electrical / electronic engineering, liquid helium has long been used as a cryogen for cooling materials to cryogenic temperatures and investigating their physical properties. Although the boiling point of liquid helium at 1 atm is 4.2K, the temperature can be lowered just by lowering the vapor pressure using a vacuum pump, and the lowest reached temperature of about 1K is realized.

  A cryostat using such liquid helium has been manufactured, and experiments to investigate its physical properties have been carried out. However, when the temperature of the cryostat is increased by applying heat to the sample, a large amount of heat flows from the sample into the liquid helium. Therefore, the evaporation of liquid helium becomes faster. However, since the amount of liquid helium stored in the cryostat is limited, if the experiment cannot be completed before the liquid helium once pumped evaporates, the operation is once stopped and the liquid helium once again. After additional pumping of helium, the experiment had to start again. Therefore, it was a cryostat that was not very suitable for experiments in which the temperature was raised to a wide range of temperatures, particularly high temperatures around room temperature, and physical properties were examined.

  In addition, liquid helium is expensive and difficult to handle, so it can only be handled by those who have received specialized education. Furthermore, helium is also a limited resource that cannot be recovered once released into the air.

  For this reason, instead of a cryostat using liquid helium, the Gifford McMahon refrigerator (hereinafter referred to as the GM refrigerator) and the pulse tube refrigerator, which have a high introduction cost but a low running cost, are generally low in cost. A cryogen-free cryostat that achieves cryogenic temperatures using so-called cryocoolers such as Stirling refrigerators has been developed. Details of the GM refrigerator will be described later. A pulse tube refrigerator is connected in the order of a compressor, radiator, regenerator, heat exchanger, and pulse tube. The pulse tube refrigerator is reciprocated between the pulse tube and the compressor and cooled by the heat exchanger. is there. A Stirling refrigerator is a refrigerator composed of a displacer and a piston, a regenerator, a cylinder surrounding them, and a heat exchanger of a high temperature part and a low temperature part. The refrigerant is compressed by the piston, and then the displacer and piston are The refrigerant expands and cools by moving, and the displacer returns to the original position and repeats this cycle.

  On the other hand, there is a demand for applying a magnetic field to the sample, and independent of the development of the above-described cryogen-free cryostat, a cryogen-free superconducting magnet that cools the superconducting magnet by conduction cooling using a GM refrigerator. ) Has been developed.

A cryogen-free cryostat is an expensive device as compared with a cryostat using liquid helium ( ⁴ He). Like a cryostat combining two cryogen-free superconducting magnets and a cryogen-free cryostat, It can be said that installing two or more cryocoolers inside is an overlapping configuration. Then, the following cryostat which used one GM refrigerator was proposed (patent documents 1 and 2).

  FIG. 9 is a configuration diagram of a conventional cryostat. As shown in FIG. 9, in the cryostat of Patent Document 1, a sample 112 is provided in a liquid pot portion in a chamber 110, and liquid helium is vaporized by being heated to a predetermined temperature by a heater 114 near the sample 112, thereby causing convection. Thus, a thermosiphon circulating through the pipes 118 and 124, the condensing unit 128, and the thin pipe 130 is configured. These are housed in a 40K radiation shield 148 provided in the outer container 132 for thermal insulation from the surroundings.

  The radiation shield 148 is provided with a GM refrigerator 122 having a heat exchanger of the 40K first stage 120 and a heat exchanger of the 4K second stage 126, and the heat of the second stage 126 passes through the pipe 124. The helium gas exchanged with the exchanger is condensed and accumulated in the condensing unit 128, and returned to the liquid pot portion in the chamber 110 as 4K liquid helium. Although not shown here, a superconducting magnet is disposed around the sample 112 so that physical properties in a strong magnetic field can be measured. By operating the needle valve 134, the flow rate of liquid helium flowing through the thin pipe 130 is controlled. The reservoir tank 140 is filled with helium gas at a predetermined pressure.

  The sample 112 is suspended from the tip of a pipe-shaped sample rod that passes through an air lock mechanism provided at the top of the cryostat and a gate valve 136. The sample 112 is immersed in liquid helium or placed in gaseous helium. Therefore, when exchanging the sample, the mechanism is not clarified, but the sample rod is pulled up and reinserted while the pressure state in the chamber 110 is maintained by operating the air lock mechanism. Into the liquid helium or gaseous helium in the liquid pot.

  When the heater 114 is controlled, the cryostat disclosed in Patent Document 1 does not clarify the reason why measurement at a high temperature is possible, but it is possible to measure the physical properties of a sample in a temperature range of 1.5K to 300K. Become. The cryostat disclosed in Patent Document 2 has substantially the same configuration as the cryostat disclosed in Patent Document 1.

International Publication No. 01/96020 JP 2005-274113 A

  As described above, a cryostat using liquid helium has a high running cost because expensive liquid helium evaporates, and can only maintain a low temperature for about one or two days. In order to add liquid helium, the operation of the cryostat has to be temporarily stopped, and it is a device that requires specialized knowledge for handling and is difficult to use. And above all, this cryostat was unsuitable for examining physical properties over a wide range of temperatures.

  In addition, an apparatus that combines two refrigerant-free superconducting magnets and two refrigerant-free cryostats is inevitably an extremely expensive apparatus due to the redundant configuration in which two GM refrigerators are installed.

  In this regard, the cryostats of Patent Documents 1 and 2 use a single GM refrigerator to cool the sample and the superconducting magnet, so that the manufacturing cost is reduced and the running cost can be reduced and the size can be reduced. The temperature can be continuously measured in the range of 1.5K to 300K.

  However, the cryostats of Patent Documents 1 and 2 must have a sample mounted on the tip of the sample rod, immersed in liquid helium, or placed in helium gas. For this reason, the heat flowing from the sample rod is transmitted to the GM refrigerator via helium gas and becomes a heat load. Moreover, in order to continuously measure the physical properties of the sample over a wide range of temperatures, it is necessary to heat the liquid helium with the heater 114, which is also a load on the GM refrigerator. If measured normally, for example, measurement at 300K is extremely difficult.

  When the cryogen-free superconducting magnet is installed in the cryostats of Patent Documents 1 and 2, the heat from the heater 114 is transferred to the cryogen-free superconducting magnet via the cooling stage (not shown) via helium gas or liquid helium, and quenched. There was a possibility of causing a phenomenon. The specific heat of the sample must be performed in a vacuum adiabatic atmosphere. However, in the cryostats of Patent Documents 1 and 2, the heat applied to the sample escapes through helium gas or liquid helium, and measurement is impossible. In the cryostats of Patent Documents 1 and 2, since heating by the heater 114 is performed through convection of helium gas or liquid helium, temperature unevenness is likely to occur between the sample position and the position of the temperature sensor, and accurate temperature measurement cannot be performed. .

  In summary, the conventional cryostat using liquid helium is not suitable for measuring physical properties over a wide range of temperatures, and the cryostats of Patent Documents 1 and 2 have the advantage of having only one GM refrigerator. However, it is difficult to reduce the heat load of the refrigerator when continuously measuring over a wide range of temperatures, and there is a possibility of quenching the superconducting magnet, making it impossible to measure specific heat or accurately measure temperature.

Therefore, the present invention can measure in the temperature range from room temperature to room temperature or higher from various cryogenic temperatures of about 20 mK or higher, and is capable of continuous operation, has low manufacturing costs and low maintenance costs, and avoids quenching. An object of the present invention is to provide a cryostat that is small and easy to mount a sample.

The cryostat of the present invention includes a vacuum vessel capable of maintaining the inside in a vacuum atmosphere, a low heat source provided in the vacuum vessel, and a low temperature by exchanging a sample with a low heat source in the vacuum vessel. A sample mounting device that can measure the physical properties of the sample mounting device, and the sample mounting device is detachably mounted from outside in a vacuum atmosphere to a heat transfer member that is thermally connected to a low heat source. A cryostat that locally raises the temperature of a sample by a provided heater, in which a sample mounting device locks the sample and is detachably mounted on a heat transfer member, and thermally connects between them. And an operation part detachably attached to the sample holder, the sample holder having a first attachment / detachment part for attaching / detaching to / from the heat transfer member and a second attachment / detachment part for attaching / detaching to the operation part And is provided The thermal connection between the heat transfer member and the sample holder includes a first heat transfer level at which heat conduction is performed only between the heat transfer member and the first attachment / detachment portion, and the heat transfer member and the first attachment / detachment portion. And a second heat transfer level at which heat conduction is performed through the sample holder and a third heat transfer level at which heat transfer is not performed due to separation of the heat transfer member and the sample holder. The main feature is that the heat transfer member and the sample holder are thermally connected .

According to the cryostat of the present invention, the physical properties of a sample can be measured in a temperature range from a very low temperature of about 20 mK or more to a temperature range from room temperature to a room temperature or higher, continuous operation is possible, and manufacturing costs and maintenance costs are low. Therefore, quenching of the superconducting magnet can be avoided, high-precision temperature measurement can be performed, and the sample can be easily mounted with a small size.

The first aspect of the present invention is a vacuum vessel capable of maintaining the inside in a vacuum atmosphere, a low heat source provided in the vacuum vessel, and heat exchange of a sample with a low heat source in the vacuum vessel. The sample mounting device is equipped with a sample mounting device that can measure the physical properties at a low temperature. The sample mounting device is detachably mounted from outside in a vacuum atmosphere to a heat transfer member that is thermally connected to a low heat source. A cryostat that locally raises the temperature of a sample by a heater provided on the mounting device, and the sample mounting device is detachably mounted on a heat transfer member by locking the sample and thermally connected between them. A sample holder that is attached to the sample holder in a separable manner, a first attachment / detachment portion that is attached to and detached from the heat transfer member, and a second attachment / detachment portion that is attached to and detached from the operation portion. The detachable part is provided and heat transfer The thermal connection between the material and the sample holder includes a first heat transfer level in which heat conduction is performed only between the heat transfer member and the first attachment / detachment portion, and the heat transfer member, the first attachment / detachment portion, and the sample. A second heat transfer level in which heat conduction is performed through the holder and a third heat transfer level in which the heat transfer member and the sample holder are separated and heat conduction is not performed are provided. The cryostat is characterized in that the member and the sample holder are thermally connected, and since the heater is provided independently of the low heat source, the cryogenic temperature is around 20 mK or various cryogenic temperatures of about 20 mK or higher, or room temperature or higher. The physical properties of the sample can be measured in the above temperature range, continuous operation is possible, manufacturing costs and maintenance costs are low, high-accuracy temperature measurement is possible, small size, and easy sample mounting it can. Further, the sample holder can be mounted in the vacuum container and can be left in the vacuum container. In the case of the second heat transfer level between the heat transfer member and the sample holder where the main body of the sample holder is directly thermally connected, the temperature of the sample holder can be close to the temperature of the heat transfer member, In the case of being thermally connected at the first heat transfer level performed only through the first attaching / detaching portion, the temperature of the sample holder is slightly higher than that of the heat transfer member without shock because the thermal coupling is gentle. Can be temperature. Furthermore, in the case of the third heat transfer level in which the heat transfer member and the sample holder are separated, since heat conduction is not performed, the temperature can be changed over a wide range by heating. In the second heat transfer level substantially the same cryogenic without affecting the low heat source cryogenic and low heat source temperature, the first heat transfer level cryogenic higher than cryogenic first heat transfer level slightly In the third heat transfer level, the temperature of the room temperature or higher can be realized above the temperature of the first heat transfer level, the continuous operation is possible, the maintenance cost is low, and the temperature is independent of the low heat source. Highly accurate temperature measurement is possible because it can be controlled.

Second embodiment of the present invention is a form that depends on the first aspect, a cryostat, wherein the first detachable portion is constituted by a member of the high thermal resistance from the sample holder, the first In addition to the operational effects of the form, heat conduction to the heat transfer member can be suppressed.

A third form of the present invention is a form subordinate to the first or second form, wherein the first attachment / detachment portion includes a first right-hand thread portion and is screwed into the heat transfer member. 1 screwed right-hand thread portion is provided, and the second attaching / detaching portion is provided with a second left-hand thread portion, and the operation portion is provided with a second screwed left-hand screw portion to be screwed thereto. It is a cryostat characterized by this. With this configuration, only a sample holder is mounted in a vacuum vessel and continuously operated, and a simple configuration of right and left screws is provided. The sample can be measured in the above temperature range, continuous operation is possible, the manufacturing cost and the maintenance cost are low, the temperature can be measured with high accuracy, the size is small, and the sample can be easily mounted.

The 4th form of this invention is a form subordinate to the 1st or 2nd form, Comprising: The 1st attachment / detachment part is provided with the 1st left-hand-thread part, and the heat-transfer member is screwed together with this. 1 screwed left-hand thread portion is provided, and the second attaching / detaching portion is provided with a second right-hand screw portion, and the operation portion is provided with a second screwed right-hand screw portion to be screwed with the second screw portion. This is a sample mounting device. With this configuration, only a sample holder is mounted in a vacuum vessel and continuously operated, and a simple configuration of right and left screws is provided. The physical properties of the sample can be measured in the above temperature range, continuous operation is possible, manufacturing costs and maintenance costs are low, high-accuracy temperature measurement is possible, small size, and easy sample mounting it can.

Fifth aspect of the present invention is in a form dependent on the first to third in any form, the heater raises the local temperature around the sample from a temperature cooled by the heat transfer member the a cryostat, wherein, since a heater is provided independently of the refrigerator, it is possible to measure the physical properties of the sample at room temperature or a higher temperature range of 20mK around cryogenic temperature measurement of the sample Can be performed with high accuracy.

The sixth aspect of the present invention is a form subordinate to the first form, and when the heat transfer member and the sample holder are thermally connected at the second or third heat transfer level, the first heat transfer is performed. The cryostat is characterized in that it is thermally connected at the second or third heat transfer level after being gradually thermally connected via the first attaching / detaching portion depending on the level, and is externally attached when the sample holder is mounted. When heat is transferred to a low heat source, there is a high possibility that the low heat source will be damaged by a rapid temperature change, but the temperature can be gradually lowered through the attaching / detaching portion, and a shockless operation can be performed.

Example 1
Hereinafter, a cryostat according to the first embodiment of the present invention, particularly a refrigerant-free cryostat provided with a refrigerant-free superconducting magnet, a sample mounting device for mounting a sample on the cryostat, and a temperature control method for controlling the temperature of the sample holder will be described. The cryostat of Example 1 is a cryogenless type cryostat equipped with a GM refrigerator, and in addition to the GM refrigerator, a ³ He refrigerator of the second refrigerator is provided in the cascade as a low heat source. . In addition, although the following description is performed about GM refrigerator, it is the same also with a pulse tube refrigerator and a Stirling refrigerator. The ³ He refrigerator is a refrigerator that liquefies ³ He gas by expanding under an enthalpy condition and obtains a low temperature of about 0.7 K by reducing the pressure of the liquid ³ He with a vacuum pump.

  1 is an explanatory view of a cryostat in Embodiment 1 of the present invention, FIG. 2 is an explanatory view of a sample mounting device of the cryostat in Embodiment 1 of the present invention, FIG. 3 is a fragmentary fragmentary view of the main part of the sample mounting device in FIG. 4 (a) to (e) are explanatory diagrams when the sample mounting device of the cryostat according to the first embodiment of the present invention is fixed to a low temperature stage, and FIGS. 5 (a) to (e) are cryostats according to the first embodiment of the present invention. It is explanatory drawing when isolate | separating this sample mounting apparatus from a low-temperature stage.

  In FIG. 1, reference numeral 1 denotes a cryostat vacuum vessel provided with a refrigerant-free superconducting magnet. The vacuum vessel 1 is depressurized by a vacuum pump to eliminate heat transfer with the outside through gas. Reference numeral 2 denotes a heat radiation shield, which cuts off heat radiation from the outside and thermally insulates the heat radiation shield 2. Reference numeral 3 denotes a GM refrigerator. In the case of the first embodiment, the GM refrigerator has two stages including a 40K stage and a 4K stage. Furthermore, the number of stages can be increased.

  The basic structure of the GM refrigerator 3 will be described. Since there is no direct relationship with the feature of the present invention, a detailed structure is not shown, but a cylinder that can be filled with gas, and an upper space and a lower space in the cylinder are provided. A displacer divided into two is provided, and the displacer is reciprocated by a drive mechanism. The GM refrigerator 3 of Example 1 is provided with such a basic configuration in two stages in series, and cools to 40K in the first stage and cools to 4K in the second stage. Around each stage is a heat exchanging portion, and members (40K plate 13 and flexible heat conductor 14a, which will be described later) in contact with the outside can be constantly cooled to 40K and 4K, respectively.

Subsequently, the description of FIG. 1 will be given. ³ He tank coolant ³ He gas ³ He refrigerator is filled 4, 5 sample mounting device for mounting a sample in Example 1, 5a upper support cylindrical portion for supporting a sample mounting device 5, 5b is a sample mounting It is a lower support cylinder portion that supports the device 5. Details of the sample mounting device 5 will be described later. 6 was vaporized by no refrigerant superconducting magnet, ³ He refrigerator vacuum pump 7a is vaporizing in vacuo the ³ He in liquid, 7b vacuum pump 7a for performing measurement of a sample in a magnetic field consist of superconducting coil A compressor of a ³ He refrigerator that pressurizes ³ He gas, 8 is a liquid pot of the ³ He refrigerator in which condensed ³ He accumulates, and 9 is a thermal and physical cover that covers the top surface of the liquid pot 8 and the tip of the sample mounting device 5. This is a low-temperature stage (heat transfer member of the present invention) for heat exchange in contact with the heat.

In addition, although the refrigerant-free superconducting magnet 6 of Example 1 is for measuring physical properties, it can be replaced with a ³ He refrigerator and a refrigerant-free superconducting magnet of a magnetic refrigerator. This will be described in detail in Example 3. The low temperature stage in Example 1 is thermally connected to a ³ He refrigerator, but other refrigerators such as a GM refrigerator, a pulse tube refrigerator, a dilution refrigerator, a magnetic refrigerator, a Stirling refrigerator, It may be a cooling stage of a cryogen cooler such as liquid helium or liquid nitrogen. A cryostat using a dilution refrigerator is in Example 2, a cryostat using a magnetic refrigerator is in Example 3, a cryostat using a GM refrigerator is in Example 4, and a cryostat using a cryocooler is This will be described in Example 5.

  Now, the detailed structure of the cryostat will be described below. A flange 10 serves as a cover for the vacuum container 1 and supports the GM refrigerator 3 and the sample mounting device 5. Reference numeral 11 denotes a first stage at 40K of the GM refrigerator 3 and reference numeral 12 denotes a second stage at a temperature of 4K of the GM refrigerator 3. Reference numeral 13 denotes a copper 40K plate that covers the heat radiation shield 2 and exchanges heat with the first stage of the GM refrigerator 3 to reach a temperature around 40K. Reference numeral 14 denotes 4K that exchanges heat with the second stage of the GM refrigerator 3. The copper 4K plate 14a having a temperature close to is a flexible heat conductor that absorbs the vibration of the GM refrigerator 3 and transfers the heat of the 40K plate 14 to the second stage.

Next, 15 is an exhaust pipe that guides the ³ He gas of the vaporized refrigerant from the liquid pot 8 and communicates with the vacuum pump 7a. Reference numerals 16a and 16b are flow paths for guiding the ³ He gas pressurized by the compressor 7b through the vacuum pump 7a to the liquid pot 8, and the first flow path 16a allows ³ He to flow only at the initial stage of the cooling operation. The other flow path 16b is a flow path for flowing ³ He in other cases (during normal operation).

^{The 3} He refrigerator uses the Joule-Thomson effect to liquefy ³ He. At this time, it is necessary to reduce the flow rate. For this reason, when cooling only by the flow path 16b, it takes a long time until the flow rate is reduced and the temperature reaches a very low temperature. Therefore, the temperature of the liquid pot 8 is set to 4K in a short time using the flow path 16a only at the initial stage of operation, and thereafter, the cryogenic temperature is realized by the flow path 16b. Reference numerals 17a, 17b, 17c and 17d are valves. The valves 17a and 17b are valves for switching the flow paths 16a and 16b, the valve 17c is a valve for setting the circulation amount of ³ He gas of the ³ He refrigerator, and the valve 17d is replenished with ³ He gas. It is a valve for.

Reference numerals 18a and 18b are heat exchangers which are provided in thermal contact with the 40K plate 13 and make the ³ He gas pressurized by the compressor 7b substantially the same temperature as the 40K plate 13. Further, 19a, 19b are provided to be in thermal contact to 4K plate 14, respectively the heat exchanger 18a, the heat exchanger 18b and the suction filter 20 to ³ He gas sent through the (later) 4K plate 14 It is a heat exchanger that makes the temperature almost the same. Adsorption filter 20 is for removing foreign matters in the ³ He, 21 is ³ cold increases the exhaust pipe 15 and ³ He cooled by a coiled heat exchanger 19b in the exhaust pipe 15 inside He A JT (Joule-Thomson) heat exchanger for exchanging heat with gas, 22 is a JT (Joule-Thomson) valve.

The JT valve 22 is expanded by restricting the flow rate of the refrigerant, and is cooled by lowering the temperature by the pressure drop at this time. Accordingly, the ³ He gas that has been brought to a high pressure by the compressor 7b is cooled by the heat exchangers 18b and 19b in the cooling path 16b, and then cooled by the JT heat exchanger 21 and then expanded and cooled by the JT valve 22 except for the initial stage of operation. Then, it condenses, accumulates in the liquid pot 8, and is vaporized to achieve about 0.7K.

  The cryostat of the first embodiment described above cools the 40K plate 13 to about 40K on the first stage by the GM refrigerator 3, and cools the heat exchangers 18a and 18b to around 40K by heat conduction. Similarly, the GM refrigerator 3 cools the 4K plate 14 to about 4K through the flexible heat conductor 14a in the second stage, and the refrigerant-free superconducting magnet 6 and the heat exchangers 19a and 19b in thermal contact with the 4K plate 14 are in the vicinity of 4K. Cool down to.

The ³ He gas cooled to about 4K is condensed by the heat exchange by the JT heat exchanger 21 and the JT valve 22 to become a liquid. As a result, ³ He in liquid accumulated in the liquid pot 8 becomes cryogenic about 0.7 K, and about 0.7 K cold stage 9 also by thermal conduction is a cover of liquid-pot 8 by ³ He in this cryogenic Become. Since the 40K plate 13, 4K plate 14, liquid pot 8, and low temperature stage 9 in the vacuum container 1 of Example 1 need to have good heat conduction, all are made of copper having the highest thermal conductivity. ing. As a result, the tip of the sample mounting device 5 that is thermally connected to the low-temperature stage 9 of Example 1 can also achieve a cryogenic temperature of around 0.7K.

  Next, a detailed structure of the sample mounting device 5 according to the first embodiment and a structure for mounting the sample mounting device 5 on the low temperature stage 9 will be described. 1, 2, and 3, reference numeral 23 denotes a sample mounting guide that is erected from a copper liquid pot 8 and a low-temperature stage 9. When the sample mounting device 5 is inserted through the flange 10 which is a cover of the vacuum vessel 1 and the 40K plate 13, the sample mounting guide 23 guides the sample mounting guide 23 to fix it at a predetermined position of the low temperature stage 9. Therefore, the cylindrical guide 23 is provided with a conical widened edge portion for guiding the sample mounting device 5.

  Next, the tip portion of the sample mounting device 5 will be described with reference to FIGS. 1, 2, and 3. Reference numeral 30 denotes a copper sample holder, and reference numeral 31 denotes a physical property measurement sample (sample) that is locked to the sample holder 30. ). 32 is a heater wound with a manganin wire that raises the temperature of the sample 31, and 33 is a temperature sensor such as a thermocouple, a germanium resistor, carbon glass, or a thermistor that detects the temperature of the sample 31. This temperature sensor 33 is embedded in a recess formed in the sample holder 30. The sample holder 30 is formed with a D-cut recess and a small-diameter portion close to each other, and the sample 31 is mounted on the D-cut flat portion while being exposed to a vacuum atmosphere (vacuum space). The heater 32 is wound. Heating by the heater 32 can be adjusted with a small sample holder 30 so that the temperature of the sample 31 can be raised with high sensitivity even if the calorific value is small, and a right-hand thread portion 35 (described later) screwed with the low-temperature stage 9 is loosened. If separated, the inflow of heat to the low temperature stage 9 can be suppressed. The lead wire 37 and the pipe 34 (which will be described later) have both a small thermal conductivity and a small cross-sectional area, thereby suppressing the inflow of heat from the outside. The heater 32 locally heats the temperature sensor 32 and the sample 31 through the sample holder by heat conduction. At this time, since the sample holder 30, the temperature sensor 32, and the sample 31 are small, the influence of heat radiation on other components is extremely small.

  Next, the overall structure of the sample mounting device 5 will be described with reference to FIG. 2 and FIG. 3. 34 is a stainless steel pipe, 35 is formed integrally with or separate from the sample holder 30, and protrudes as a male screw at the tip. It is a right thread part (the 1st right thread part of the present invention). The right-hand thread portion 35 is made of copper in the same manner as the sample holder 30 when integrated with the sample holder 30, but when the heat conduction is lowered as in the first embodiment, it is a separate plastic having a lower thermal conductivity than copper. To make. The plastic right-hand thread portion 35 produced separately is the heat resistance member in the first embodiment of the present invention. Reference numeral 36 denotes a left screw portion (second left screw portion of the present invention) provided as a male screw provided integrally with the sample holder 30.

  In the first embodiment, the state of the thermal connection between the sample holder 30 and the low temperature stage 9 is divided into three levels by making the right screw portion 35 with a material having a lower thermal conductivity than the sample holder 30. Can be realized. That is, by adjusting the physical tightening degree of the right screw portion 35, the heat conduction path between the sample holder 30 and the low temperature stage 9 is changed, and the heat conduction path, the heat conduction path through the heat resistance member, and the heat conduction are changed. In the absence, three heat transfer levels can be achieved by three paths.

That is, when the right screw portion 35 is strongly tightened to the low temperature stage 9, the lower surface (sample holder main body) of the sample holder 30 is in direct contact with the low temperature stage 9, and both are made of a material having high thermal conductivity. 0.7K to 1.5K in a temperature range ( second heat transfer level of the present invention) in which the heat conduction is good and the heating by the heater 32 does not affect the low heat source from a cryogenic temperature almost the same as the temperature of the low heat source. Can be realized. Next, when the right screw portion 35 is loosened from this state, the direct contact between the sample holder 30 and the low temperature stage 9 is cut off, and indirect thermal connection via the right screw portion 35 that is a heat resistance member. Therefore, since there is more thermal resistance than in the case of direct contact, heat conduction is reduced. By adjusting the tightening strength, the heat transfer area between the right screw portion 35 and the low temperature stage 9 can be changed, the amount of heat flowing into the low temperature stage 9 can be reduced, and the temperature range up to 4K of the second stage (this The first heat transfer level ) of 1.5K to 4K can be realized. Further, when the right screw portion 35 is completely separated from the low temperature stage 9, the heat of the heater 32 does not flow into the low temperature stage 9, and if it is gradually heated from 4K, the temperature from 4K to room temperature or higher (the first of the present invention) . 3 heat transfer level ). Thereby, the GM refrigerator 3 can be protected from overheating.

  2 and 3, reference numeral 37 denotes a plurality of lead wires that are inserted through the pipe 34 to supply power to the heater 32 and take out the output of the temperature sensor 32. Reference numeral 38 denotes a pipe 34 that is sealed and inserted. A sliding seal mechanism 39 is a gate valve that shuts off at the position of the lower support cylinder portion 5 b when the sample mounting device 5 is lifted, and 39 a is a valve body of the gate valve 39. Reference numeral 40 denotes a connector for connecting the lead wire 37 of the sample mounting device 5, reference numeral 41 denotes a detachable clamp that can attach and detach the upper support cylinder part 5a and the lower support cylinder part 5b, 42 denotes an O-ring of the sliding seal mechanism 38, 43 Is a leak valve, and 44 is a vacuum pump that evacuates the vacuum vessel 1 via the upper support cylinder part 5a and the lower support cylinder part 5b. The vacuum pump 44 and the leak valve 43 shown in FIG. 2 are not shown in FIG. The same applies to FIGS. 1 and 6 to 8.

  Further, as shown in the fragmentary fragmentary view of FIG. 3, 45 is a cylindrical connecting portion provided at the tip of the pipe 34, and is a female screw threadedly engaged with the left screw portion 36 on the opposite side of the pipe 34. A second screwing portion 46 (described later) is provided. The pipe 34 and the connecting portion 45 constitute an operation portion according to the first embodiment of the present invention. An insertion hole is formed in the center of the connecting portion 45 from the bottom of the second screwing portion 46 (the front end side of the male screw protruding from the left screw portion 36) to the top surface side of the connecting portion 45. Therefore, the hole of the pipe 34 and this insertion hole are provided in communication. The left screw portion 36 and the connecting portion 45 are detachable by being screwed together, and constitute a second detachable portion in Embodiment 1 of the present invention. 46 is a second threaded portion (second threaded left-hand threaded portion of the present invention) that is a female screw provided in the connecting portion 45, and 47 is projected from the left-hand threaded portion 36 of the sample holder 30 to the pipe 34 side. A guide pipe 47 a inserted into the insertion hole and slidable in the insertion hole 47 a is provided at the tip of the guide pipe 47.

  The hole of the guide pipe 47 is opened into a D-cut recess of the sample holder 30 through a through hole provided at the center of the left screw 36, and the lead wire 37 connected to the sample 31 and the temperature sensor 33 is the recess. Is inserted through the through hole and connected to the connector 40 through the guide pipe 47 and the pipe 34. Therefore, both the output from the sample 31 and the output from the temperature sensor 33 are output to the connector 40 via the lead wire 37.

  Next, reference numeral 48 denotes a first threaded portion (a first threaded right-hand thread portion of the present invention) of a female screw formed on the low temperature stage 9 to which the right thread portion 35 is threaded. The right screw portion 35 and the first screwing portion 48 are detachable by being screwed together, and constitute the first detachable portion in Embodiment 1 of the present invention. Even though the right and left screw portions 35 and 36 are opposite to each other, the male screw and the female screw are in a complementary relationship. Therefore, the second screwing portion 46 and the first screwing portion 48, and the male screw and the female screw are used. This is the same even if the relationship is reversed. When the second screwing portion 46 and the first screwing portion 48 are male screws, the male screw portion is provided on the low temperature stage 9 and the connecting portion 45 side. The right thread portion 35 and the left thread portion 36 are arranged coaxially with the pipe 34.

  Next, the mounting of the sample holder 30 on the low temperature stage 9 will be described with reference to FIGS. 4 (a), (b), (c), and (d). First, the sample 31 is mounted on the sample holder 30, the left-hand thread portion 36 of the sample holder 30 is screwed into a connecting portion 45 provided at the tip of the pipe 34, and the sample mounting device 5 and the upper support cylinder portion 5 a are joined together. Inserted into a position higher than the gate valve 39 of the lower support cylinder part 5b, and the upper support cylinder part 5a and the lower support cylinder part 5b are connected using the detachable clamp 41 with the gate valve 39 closed to form a sealed space. To do. In this state, the vacuum pump 44 is operated, the air in the upper support cylinder 5a and the like is discharged, and the pressure is reduced to the same degree of vacuum as in the vacuum vessel 1. When the gate valve 39 is opened in this state, the upper support cylinder 5a, the lower support cylinder 5b, and the vacuum vessel 1 are all in a vacuum state, and the sample holder 30 is inserted therein. Therefore, when the pipe 34 of the sample mounting device 5 is further pushed in, the sample holder 30 at the tip of the sample mounting device 5 is inserted into the sample mounting guide 23 and guided as it is, and the state shown in FIG.

  Next, the left screw portion 36 is screwed into the connecting portion 45 and inserted into the first screwing portion 48 of the low temperature stage 9 in a state where the sample holder 30 and the connecting portion 45 are integrated, as shown in FIG. The screwing is started. At this time, even if the right screw part 35 starts screwing with the first screwing part 48, the tightening torque of the sample holder 30 and the left screw part 36 is large. The screw part 35 is screwed into the first screwing part 48. When this tightening torque is greater than the tightening torque of the sample holder 30 and the left screw portion 36, as shown in FIG. 4C, the sample holder 30 and the left screw portion 36 begin to release the screwed state, and the separation between the two becomes difficult. Start. When the sample holder 30 and the left screw portion 36 are completely separated, the pipe 34 can be pulled up, and only the sample holder 30 remains in the low temperature stage 9 as shown in FIG.

  Thus, in the sample mounting device 5, the left and right screw portions 36 and 35 are formed in the sample holder 30, and the right screw is in a state where the left screw portion 36 is screwed as shown in FIG. Since the portion 35 is screwed together, the rotation of the sample mounting device 5 is continued, and when the right screw portion 35 is fixed to the low temperature stage 9 as shown in FIG. Can be released, and the sample holder 30 can remain on the low temperature stage 9 as shown in FIG.

  For the remaining sample holder 30, the heat conduction path by the lead wire 37 and the heat conduction path by the point contact between the pipe 34 and the guide stopper 47 a are substantially the only heat conductions that conduct heat outside the vacuum vessel 1. The heat conduction to the sample holder 30 is almost completely cut off except for the low temperature stage 9. Therefore, if the liquid pot 8 is, for example, 0.7K, the low temperature stage 9, the sample holder 30, the sample 31, and the temperature sensor 32 are also maintained at approximately 0.7K. In the first embodiment, a guide stopper 47a is provided at the tip of the guide pipe 47, and the pipe 34 is brought into contact with the upper portion of the insertion hole of the connecting portion 45 telescopically, as shown in FIG. The sample holder 30 is prevented from being physically separated. Therefore, the pipe 34 and the sample holder 30 are thermally disconnected from each other, but are physically connected to each other. In order to allow the lead wire 37 to be stretched and twisted in the guide pipe 47, the lead wire 37 is provided with a retractable coil-like slack portion as shown in FIG.

In the sample mounting device 5 of the first embodiment, the sample holder 30 is not disposed in the liquid helium in the liquid pot 8 as in the prior art, but the liquid pot 8 and the sample holder 30 are separated and disposed in a vacuum atmosphere. Therefore, if the screws of the right screw portion 35 and the first screwing portion 48 are loosened, even when heated by the heater 32, the temporary heat conduction from the right screw portion 35 is small, and the sample 31 and the temperature sensor 33 are localized. Therefore, the temperature of ³ He in the liquid pot 8 and the exhaust pipe 15 does not rise so much. Further, the heat radiation to the refrigerant-free superconducting magnet 6 is blocked by the sample mounting guide 23, and the sample holder 30 is small, so that the refrigerant-free superconducting magnet 6 is not quenched by the heat radiation. And since the temperature sensor 32 can be arrange | positioned on the sample holder 30 of the high thermal conductivity right next to the sample 31 in a vacuum, exact temperature can be measured.

  Further, since the heat capacity of the sample holder 30 can be made extremely small compared to the heat capacity of the liquid pot 8 and the liquid inside the liquid pot 8 and the low temperature stage 9, the sample 31 and the temperature sensor are heated by heating the sample 31 with the heater 32. 32 responds sharply, and can quickly control the temperature of the sample 31 from an extremely low temperature of about 0.7 K to a target temperature of about 300 K at a room temperature in a short time.

  Similarly, separation of the sample holder 30 from the low temperature stage 9 will be described with reference to FIGS. 5 (a), 5 (b), 5 (c) and 5 (d). First, the pipe 34 is lowered as shown in FIG. 5A, and the connecting portion 45 at the tip of the pipe 34 and the left screw portion 36 of the sample holder 30 are screwed together as shown in FIG. And the sample holder 30 are integrated. When a large tightening torque is required by screwing the sample holder 30 and the left screw part 36 as shown in FIG. 5C, the right screw part 35 starts releasing the screwing with the first screwing part 48, Separation begins. When the sample holder 30 and the right-hand thread portion 35 are completely separated, the sample holder 30 and the pipe 34 can be pulled up as a unit as shown in FIG.

  The sample mounting device 5 of the first embodiment pulls up the sample mounting device 5 from the vacuum vessel 1 according to the procedure of FIG. 5 and pulls out the position of the sample holder 30 to a position higher than the gate valve 39 in FIG. When is closed, the sample mounting device 5 can be taken out while maintaining the vacuum state in the vacuum container 1. Thereafter, the leak valve 43 is opened, the detachable clamp 41 is released, and the upper support cylinder part 5a and the lower support cylinder part 5b are separated. By pulling out the sample mounting device 5 and the upper support cylinder part 5a together from the lower support cylinder part 5b, the sample holder 30 can be exposed to the outside air, and the sample 31 can be taken out.

  Accordingly, the sample mounting device 5 of the first embodiment includes a sequence for separating the sample holder 30 from the connecting portion 45 after fixing the sample holder 30 to the low temperature stage 9, and a connecting portion of the sample holder 30. If it is a means which can perform the sequence which connects with 45 and isolate | separates the sample holder 30 from the low temperature stage 9, it will not be restricted to the right-hand thread and the left-hand thread of a male thread. Even if it is a female screw, a right screw and a left screw may be provided interchangeably. Further, for example, the sample holder 30 is provided with a first attachment / detachment portion and a second attachment / detachment portion, and when the first attachment / detachment portion is fixed, this fixing becomes a trigger to release the second attachment / detachment portion, This may be a mechanical mechanism or electrical control means that can be used as a trigger to fix the second attaching / detaching portion.

  The sample mounting device 5 of Example 1 can basically maintain the vacuum atmosphere in the vacuum vessel 1 by opening and closing the sample holder 30 before and after the operation of the sample holder 30 by the gate valve 39 provided in the vacuum vessel 1. it can. That is, when the sample holder 30 is inserted into the cryostat, the inside of the insertion portion is previously evacuated, the gate valve 39 is opened, and the pipe 34 is lowered. Conversely, when pulling out the sample holder 30 from the cryostat, the internal vacuum degree can be maintained by closing the gate valve 39 after pulling up the pipe 34, and it is not necessary to break the vacuum of the entire cryostat. As described above, since the sample mounting device 5 can be attached to and detached from the vacuum vessel 1 while the inside of the vacuum vessel 1 is kept in vacuum, the sample 31 can be replaced, inspected, and replaced while the cryostat is continuously operated. Become.

  Further, since the temperature of the sample holder 30 can be separated from all the low-temperature parts connected to the second stage 12 of the GM refrigerator 3, heat does not flow from the sample holder 30 to the second stage 12, so that the refrigerant-free superconducting magnet 6 is quenched. Can be easily avoided.

The cryostat of Example 1, those having a ³ He refrigerator GM refrigerator and cascading from the low heat source, can be cooled to a cryogenic temperature of about 0.7 K. Since the sample mounting device 5 is provided, it is possible to provide a cryostat that can reduce manufacturing costs and running costs, avoid quenching, is small, and can be loaded and replaced easily in a short time. become.

Furthermore, since the temperature around the sample 31 can be locally increased by the heater 32 provided in the sample mounting device 5, the heater 32 is independent of the GM refrigerator or the ³ He refrigerator and the sample mounting device 5. Therefore, continuous operation is possible, and the physical properties of the sample can be measured in a temperature range from an extremely low temperature of about 0.7 K to a room temperature or higher.

(Example 2)
A cryostat in Embodiment 2 of the present invention, particularly a cryostat with a dilution refrigerator equipped with a refrigerant-free superconducting magnet, a sample mounting device for mounting a sample on the cryostat, and a temperature control method for controlling the temperature of the sample holder will be described. The cryostat with a dilution refrigerator of the second embodiment is a refrigerant-free cryostat equipped with a GM refrigerator, and the dilution refrigerator of the second refrigerator is provided in a cascade with the GM refrigerator as in the first embodiment. The sample mounting device 5 has the same configuration as that of the first embodiment. The description will be given for the GM refrigerator, but the same applies to a pulse tube refrigerator, a Stirling refrigerator, and a refrigerant cooler using liquid helium. These descriptions are as described above, and will be omitted. As described below, the dilution refrigerator achieves extremely low temperatures by using a dilution effect.

  FIG. 6 is an explanatory diagram of a cryostat according to the second embodiment of the present invention. Since the cryostat and sample mounting device of the second embodiment have the same basic configuration as the cryostat and sample mounting device of the first embodiment, the same reference numerals denote a common configuration. Therefore, the description of the same reference numerals, in particular, details of the sample mounting device 5 are omitted from the first embodiment.

Now, the cryostat with dilution refrigerator of the second embodiment is a cryostat capable of lowering the temperature than the cryostat of the first embodiment. That is, the refrigerant of Example 2 is ³ He and ⁴ He, ³ He is circulated with a pump, and ³ He is mixed with liquid ⁴ He. And when the temperature of this liquid mixture becomes 0.6K or less, the liquid mixture is separated into two phases, ³ He dilute phase liquid having a low ³ He concentration and high specific gravity below, and ³ He above it. A ³ He concentrated phase liquid having a high concentration and a small specific gravity is located. In the case of a dilution refrigerator, the concentration of the ³ He dilute phase liquid is less than the predetermined concentration (temperature dependence, 6.4% at absolute zero (0K), and gradually increases above 0K). ³ He is dissolved (diffused) from the ³ He concentrated phase liquid into the ³ He dilute phase liquid, and heat absorption (dilution refrigeration effect) based on the entropy difference between the two phases is generated, thereby realizing extremely low temperature. Thus, a temperature of about 20 mK, which is lower than that of Example 1, is obtained.

For this reason, in Example 2, the necessity of the further heat insulation arises and the double thermal radiation shield is provided. In FIG. 6, 2a is a 2nd heat radiation shield which is arrange | positioned inside the heat radiation shield 2 and insulates external heat twice. In FIG. 6, 1 is a vacuum vessel, 2 is a heat radiation shield, 3 is a GM refrigerator, 4 is a ³ He tank, 5 is a sample mounting device, 5a is an upper support cylinder, and 5b is a lower support cylinder. 6 is a refrigerant-free superconducting magnet, 7a is a vacuum pump, 7b is a compressor, and 9 is a low-temperature stage. These are the same as those of the cryostat of the first embodiment, and a description thereof will be omitted.

  Similarly to Example 1, 10 is a flange for mounting the sample mounting device 5, 11 is a first stage at 40K of the GM refrigerator 3, 12 is a second stage at 4K of the GM refrigerator 3, and 13 is A 40K plate, 14 is a 4K plate, and 14a is a flexible heat conductor. Reference numeral 15 denotes an exhaust pipe, reference numerals 16a and 16b denote flow paths, and reference numerals 17a, 17b and 17c denote valves. Reference numerals 18a, 18b, 19a and 19b denote heat exchangers. 20 is an adsorption filter, 21 is a JT heat exchanger, and 22 is a JT valve. Description is omitted.

Next, the dilution refrigerator of the cryostat with dilution refrigerator will be described in detail. In FIG. 6, 51 shown in the figure is a mixer that is mixed with ⁴ He when ³ He gas is condensed by the JT valve 22 and returned as a high concentration condensate of ³ He. Reference numeral 52 denotes a still, which is connected to the mixer 51 via a tube-in-tube heat exchanger 55 and a step heat exchanger 56 described later. The exhaust pipe 15 is connected to the still 52, and the vaporized ³ He gas is guided through the exhaust pipe 15 and then to the vacuum pump 7a. Still 52, by vaporizing at 0.7K of ³ He saturated vapor pressure is large vaporized faster compared to ⁴ the He, extracts the ³ He in the dilute phase fluid in the mixer 51, a continuous refrigeration Realize the cycle.

53 is a JT heat exchanger 21, a heat exchanger that absorbs heat of condensation from ³ He gas cooled to about 1K by a JT valve, and cools ³ He to about 0.7K, and 54 is a heat exchanger 53 for heat exchange. It is a plate of the ³ He vaporization stage that transmits the condensed heat to the ³ He diluted phase liquid in the still 52. 55 is a tube-in-tube heat exchanger, and 56 is a step heat exchanger. Tube-in-tube heat exchanger 55 is obtained by the coiled insert the small-diameter pipe in the large diameter pipe a thin, moves gradually to the ³ He dense phase fluid and still 52 back to the mixer 51 ³ A dilute phase liquid containing He is flowed oppositely, and heat exchange is performed between the two. The step heat exchanger 56 is for further lowering the minimum temperature of the dilution refrigerator, and the two chambers are in contact with each other with a metal partition sintered with silver powder, and the two chambers are diluted with the concentrated phase liquid and the dilute solution. The phase liquid flows oppositely. At that time, since the sintered body is porous, a very large heat exchange area (several m2 to several tens m2) can be secured.

As described in the first embodiment, the cryostat with dilution refrigerator of the second embodiment cools the 40K plate 13 to 40K in the first stage 11 of the GM refrigerator 3, and the 4K plate 14 in the second stage 12. Cool to 4K. As a result, the ³ He gas is cooled to about 40K by the heat exchanger 18b in the flow path 16b, cooled to about 4K by the heat exchanger 19b, further cooled by the JT heat exchanger 21, and liquefied by the JT valve 22. .

Thereafter, the ³ He cooled to about 0.7 K in the heat exchanger 53 flows through the tube-in-tube heat exchanger 55 and flows in opposition to the ³ He dilute phase liquid moving to the still 52. The heat is exchanged, and the temperature is further lowered by the step heat exchanger 56. The liquid ³ He entering the mixer 51 becomes a ³ He concentrated phase liquid located in the upper part of the mixer 51, and the temperature of 20 mK is increased by absorption of heat when ³ He dissolves in the ³ He diluted phase liquid located in the lower part. Can be realized.

At this time, the still 52 is heated to about 0.7K by heat from a heater (not shown), and ³ He having a saturated vapor pressure higher than ⁴ He is vaporized by the negative pressure by the vacuum pump 7a. Thus the concentration gradient is generated between the ³ He in ³ He dilute phase fluid in the ³ He and the mixer 51 in the Still 52, ³ in the mixer 51 to compensate for the shortage of the ³ He in Still 52 ³ He of the dilute He phase moves. To further supplement the concentration of ³ He in this ³ He dilute phase ^{liquid, 3} He diffuses from 3 He dense phase fluid. The ³ He gas evaporated from the still 52 rises in temperature through the exhaust pipe 15 and is sucked by the vacuum pump 7a and further pressurized by the compressor 7b. Thereafter, the ³ He gas is sent to the first stage heat exchanger 18b, and the refrigeration cycle described above is repeated.

  The structure of the sample mounting device 5 of the second embodiment has the same configuration as that shown in FIGS. 2 and 3 described in the first embodiment, and the mounting method is the same as the method described in FIGS. Therefore, detailed description will be repeated and will be omitted from the first embodiment. Also in the second embodiment, as shown in FIGS. 2 and 3, the first attaching / detaching portion (the right screw portion 35 and the connecting portion 48) for attaching / detaching the sample holder 30 to / from the low temperature stage 9, and the first attaching / detaching portion. Is attached to the low temperature stage 9, and the second attaching / detaching portion (the left screw portion 36 and the first screw) can be attached to the connecting portion 45 when the first attaching / detaching portion is separated from the low temperature stage 9. And a joint portion 45) may be provided.

  A sequence in which the sample holder 30 is fixed to the low temperature stage 9 to be separated from the connecting portion 45, and a sequence in which the sample holder 30 is connected to the connecting portion 45 to be separated from the low temperature stage 9 is As long as it is a reversible means, not only the right and left threads of the male thread, but also the female thread, the right and left threads can be provided interchangeably, or any other mechanical or electrical means Can be adopted.

  As described above, in the sample mounting device 5 of the second embodiment, as in the first embodiment, the mounting and the detachment with respect to the vacuum vessel 1 can be performed while keeping the inside of the vacuum vessel 1 in vacuum, so that the sample 31 is operated while the cryostat is continuously operated. Replacement, inspection, and parts replacement are possible. In addition, since the temperature of the sample holder 30 can be separated from all the low temperature parts connected to the second stage 12 of the GM refrigerator 3, heat does not flow from the sample holder 30 to the second stage 12, so that the refrigerant-free superconducting magnet 6 Quenching can be avoided.

  The cryostat with dilution refrigerator of Example 2 is provided with a dilution refrigerator as the GM refrigerator and the second refrigerator, so that the cryostat is heated to about 20 mK or, for example, from 20 mK to at least a few tens of mK or so. Further, it can be cooled to various cryogenic temperatures by using the thermal connection of the sample mounting device 5. Since the sample mounting device 5 is provided, it is possible to provide a cryostat that can reduce manufacturing costs and running costs, avoid quenching, is small, and can be loaded and replaced easily in a short time. become.

(Example 3)
A cryostat, particularly a cryostat with a magnetic refrigerator, a sample mounting device, and a temperature control method for controlling the temperature of the sample holder in Example 3 of the present invention will be described. The cryostat with a magnetic refrigerator of Example 3 is a cryostat with a low temperature heat source by providing a magnetic refrigerator of the second refrigerator in cascade with the GM refrigerator, and the sample mounting device 5 has the same configuration as that of Example 1. have.

  FIG. 7 is an explanatory diagram of a cryostat in Example 3 of the present invention. Since the cryostat and sample mounting device of the third embodiment have the same basic configuration as the cryostat and sample mounting device of the first embodiment, the same reference numerals denote a common configuration. Therefore, the description of the same reference numerals, in particular, details of the sample mounting device 5 are omitted from the first embodiment.

  In FIG. 7, 6a is a superconducting magnet for cooling a magnetic working material 60 to be described later by adiabatic demagnetization. A reverse-coiled compensation coil is incorporated in series to cancel the magnetic field and the magnitude of the magnetic field applied to the sample 31 portion. It is designed to be almost zero. Reference numeral 60 denotes a magnetic working substance in which a magnetic powder of chrome potassium alum is kneaded together with oil between a large number of thin copper wires. 6b is a superconducting magnet for applying a magnetic field to the sample. Reference numeral 65 denotes a magnetic field sensor for measuring the magnitude of the magnetic field at the position of the sample 31. The 4K plate 14 is thermally connected to the 4K second stage 12 of the GM refrigerator 3 via the flexible heat conductor 14a. The low temperature stage 9 is connected to the upper part of the magnetic working material 60, and the low temperature stage 9 is provided with a first screwing portion 48 (see FIG. 3) that is screwed with the right screw portion 35. A gas gap thermal switch 61 is inserted between the lower part of the magnetic working material 60 and the 4K plate 14 so that the magnetic working material 60 is thermally connected to the 4K plate 14 to reach a temperature of 4K or separated to be insulated. You can do it.

  The shape of the gas gap heat switch 61 is a cylinder, and a plurality of copper fins 62 extending inward from both bottom surfaces made of copper are arranged facing each other with a narrow space therebetween, and the side surface constituted by the high heat resistance material is kept airtight. At the same time, it also serves as a structural material. From the side surface of the cylinder, activated carbon 63 loosely thermally coupled to the 4K plate 14 is connected by a thin tube. The activated carbon 63 is equipped with a heater so that it can be heated. The degree of thermal coupling between the activated carbon 63 and the 4K plate 14 is set so small that the temperature of the 4K plate only slightly increases even when the heater is turned on.

  In order to turn on the gas gap heat switch 61, the activated carbon 63 is heated by the heater 64 to release the adsorbed helium gas, and the gap between the fins 62 is filled with helium gas. The helium gas exchanges heat between the fins 62 to transfer heat. In order to turn off the gas gap heat switch 61, heating of the activated carbon 63 by the heater 64 is stopped, and the activated carbon 63 is cooled to near 4K by heat conduction. The cooled activated carbon adsorbs helium gas to make the gap between the fins 62 vacuum, so that heat does not move.

  In the cryostat with a magnetic refrigerator of the third embodiment, the 4K plate 14 is cooled to 4K by the second stage 12, the gas gap heat switch 61 is turned on, and a strong force of several tesla (T) or more by the refrigerant-free superconducting magnet 6a. Isothermal magnetization is performed by applying a magnetic field. At this time, the magnetization heat is exhausted through the gas gap heat switch 61, the 4K plate 14, the flexible heat conductor 14 a, and the second stage 12 of the GM refrigerator 3. Thereafter, the gas gap heat switch 61 is turned off to insulate, and when the magnetic field is demagnetized and cooled to a cryogenic temperature of at least about several tens of mK, the low temperature stage 9 that is in thermal contact with the upper part of the magnetic working material 60 is It becomes low temperature. The sample mounting device 5 of Example 3 has the same configuration as that of Example 1, and is as described above. The sample mounting device 5 includes a sequence in which the sample holder 30 is fixed to the low temperature stage 9 and separated from the connecting portion 45, and the sample holder 30 is connected to the connecting portion 45 in the low temperature stage 9. Any means can be adopted as long as the sequence to be separated from can be reversible. It does not depend on the shape of the screw.

  Application of the magnetic field to the sample is performed by energizing the refrigerant-free superconducting magnet 6b. However, the leakage magnetic field from the refrigerant-free superconducting magnet 6b is also applied to the magnetic working material 60 as it is, and the temperature of the sample changes. In order to prevent this, the temperature sensor 33 monitors the temperature of the sample while controlling the current flowing through the refrigerant-free superconducting magnet 6a so as to cancel the influence of the refrigerant-free superconducting magnet 6b and eliminate the temperature change of the sample. Yes. This control can be performed manually or automatically by electrical feedback.

  The refrigerant-free superconducting magnet 6a that applies a magnetic field to the magnetic working material 60 has the above-described compensation coil, so there is almost no influence of the magnetic field on the sample portion, but the slight magnetic field remaining without being compensated is detected by the magnetic field sensor 65. The current flowing through the refrigerant-free superconducting magnet 6b is controlled and canceled. This control can be performed manually or automatically by electrical feedback.

  In Example 3, when the right screw part 35 is strongly tightened to the low temperature stage 9, the lower surface of the sample holder 30 is in direct contact with the low temperature stage 9 cooled by adiabatic demagnetization, and a cryogenic temperature equivalent to that of the magnetic working material 60 is obtained. It can be realized and can be controlled to a temperature somewhat higher than this by the heater. Next, in the state where the right screw portion 35 is loosened from this state, the direct contact between the sample holder 30 and the low-temperature stage 9 is cut off, and the heat conduction is lower than that in the case of direct contact. By adjusting the tightening strength, a state slightly higher than the extremely low temperature can be realized. Further, when the right screw portion 35 is completely separated from the magnetic working material 60, the heat of the heater 32 does not flow into the magnetic working material 60, and the temperature can be raised from this temperature to room temperature or higher.

  As described above, the cryostat with a magnetic refrigerator of Example 3 is provided with a magnetic refrigerator in a cascade with the GM refrigerator so as to be a low heat source. Therefore, temperature control is easy, and the temperature range is from extremely low temperature to room temperature or higher. The sample can be measured, and handling is easy because no refrigerant such as liquid helium is used. In addition, since the sample mounting device 5 of Example 3 can be mounted and removed from the vacuum vessel 1 while keeping the inside of the vacuum vessel 1 in vacuum, the sample 31 can be easily replaced, inspected, and replaced.

Example 4
A cryostat, particularly a cryostat with a GM refrigerator, its sample mounting device, and a temperature control method for controlling the temperature of the sample holder in Example 4 of the present invention will be described. The cryostat with a GM refrigerator of Example 4 uses the GM refrigerator as a low heat source, and the sample mounting device 5 has the same configuration as that of Example 1.

  FIG. 8 is an explanatory diagram of a cryostat in Example 4 of the present invention. Since the basic configuration of the cryostat and the sample mounting device of the fourth embodiment is the same as that of the cryostat and the sample mounting device of the first embodiment, the same reference numerals denote a common configuration. Therefore, the description of the same reference numerals, in particular, details of the sample mounting device 5 are omitted from the first embodiment.

  In FIG. 8, 6a is a superconducting magnet for applying a magnetic field to the sample, and 14 is a 4K plate thermally connected to the 4K second stage 12 of the GM refrigerator 3 through a flexible thermal conductor 14a. Reference numeral 9 denotes a low temperature stage connected on the 4K plate 14. The low temperature stage 9 is provided with a first threaded portion 48 that is threadedly engaged with the right thread portion 35.

  The cryostat with a GM refrigerator of Example 4 cools the 4K plate 14 and the low temperature stage 9 thereon to 4K by the second stage 12. The sample mounting device 5 has the same configuration as that of the first embodiment. The sample mounting device 5 is a sequence for fixing the sample holder 30 to the low temperature stage 9 to separate it from the connecting portion 45, and connecting the connecting portion 45 of the sample holder 30 to the low temperature stage 9. Any means can be adopted as long as the separation sequence is a reversible means. It does not depend on the shape of the screw.

  In the fourth embodiment, when the right screw portion 35 is strongly tightened to the low temperature stage 9, the lower surface of the sample holder 30 is in direct contact with the low temperature stage 9 cooled by adiabatic demagnetization, and an extremely low temperature equivalent to that of the low temperature stage 9 is realized. it can. Next, in the state where the right screw portion 35 is loosened from this state, the direct contact between the sample holder 30 and the low-temperature stage 9 is cut off, and the heat conduction is lower than that in the case of direct contact. By adjusting the tightening strength, a state slightly higher than the extremely low temperature can be realized. Further, when the right screw portion 35 is completely separated from the low temperature stage 9, the heat of the heater 32 does not flow into the low temperature stage 9, and the temperature can be raised from this temperature to room temperature or higher.

  Thus, since the cryostat with a GM refrigerator of Example 4 uses the GM refrigerator as a low heat source, temperature control is easy, and a sample can be measured in a temperature range from extremely low temperature to room temperature or higher, Handling is easy because no refrigerant such as liquid helium is used. In addition, since the sample mounting device 5 of Example 3 can be mounted and removed from the vacuum vessel 1 while keeping the inside of the vacuum vessel 1 in vacuum, the sample 31 can be easily replaced, inspected, and replaced.

(Example 5)
A cryostat, particularly a cryostat with a cooler, a sample mounting device, and a temperature control method for controlling the temperature of the sample holder in Example 4 of the present invention will be described. The cryostat with a cooler according to the fifth embodiment uses a cryogen such as liquid helium or liquid nitrogen as a low heat source, and the sample mounting device 5 has the same configuration as that of the first embodiment. Accordingly, the same reference numerals mean the same configuration, and the description thereof will be omitted to the first embodiment. FIG. 9 is an explanatory diagram of a cryostat in Example 4 of the present invention.

In FIG. 9, 9a is a cooling stage of a cryogen cooler that cools using a cryogen 74, which will be described later, and 15a is a measurement vacuum vessel for accommodating the sample mounting device 5 and measuring physical properties in a vacuum atmosphere. , 17e are valves for forming a vacuum, and 17f is a valve for releasing evaporated cryogen gas. The cooling stage 9a is installed at the lowest position of the measurement vacuum vessel 15a, and is in thermal contact with the cryogen through the bottom surface of the measurement vacuum vessel 15a, and is at the same temperature as the cryogen. In addition, 71 is a dewar in the cryogen cooler of Example 4, 73 is a dewar inner container that contains the cryogen 74, 72 is a supermarket that is wound around the outside of the dewar inner container 73 to block heat radiation from the outside and suppress the evaporation of the cryogen. Insulation 74 is a cryogen such as liquid ³ He, liquid ⁴ He, or liquid nitrogen stored in the dewar inner container 73.

  A vacuum is applied between the dewar inner container 73 and the dewar 71, and a super insulation 72 is disposed. As described above, the cryostat of the fourth embodiment accommodates the cryogen 74 as a low heat source in the dewar inner container 73 and the measurement vacuum container 15a in the cryogen 74, and the dewar 71 is an embodiment of the present invention. 1 corresponds to the vacuum container in 1. In addition, although the superconducting magnet 6c for measuring the physical properties is installed in the dewar inner container 73 of the fourth embodiment, this is made into a superconducting magnet of a magnetic refrigerator as in the third embodiment to realize further low temperature. You can also

  In order to operate the cryostat with a refrigerant cooler of the fifth embodiment, first, before the refrigerant is pumped in, the gate valve 39 is closed, and the air in the measurement vacuum vessel 15a is discharged from the valve 17e by a vacuum pump (not shown). Discharge. The refrigerant is pumped in, the sample mounting device 5 is set on the lower support cylinder portion 5b, and the detachable clamp 41 is attached. The space above the gate valve 39 is evacuated by a vacuum pump 44 (not shown), the gate valve 39 is opened, the sample mounting device 5 is inserted, and the sample holder 30 is mounted on the cooling stage 9a. The method for attaching and detaching the sample mounting device 5 is as described in the first embodiment. Note that the sample mounting device 5 has a sequence for fixing the sample holder 30 to the cooling stage 9a to separate it from the connecting portion 45, and connecting the connecting portion 45 to the connecting portion 45 of the sample holder 30 to start from the cooling stage 9a. Any means can be adopted as long as the separation sequence is a reversible means. It does not depend on the shape of the screw.

When the right screw portion 35 is strongly tightened to the cooling stage 9a, the lower surface of the sample holder 30 is in direct contact with the cooling stage 9a, and a cryogenic temperature equivalent to that of the cryogen 74 can be realized. At this time, the temperature that can be achieved by the cryogen 74 is liquid ³ He, liquid ⁴ He, liquid nitrogen, and the like. The liquid ³ He is about 0.7 K, the liquid ⁴ He is about 1 K, and the liquid nitrogen is about 77 K. Temperature. Next, when the right screw part 35 is loosened from this state, the direct contact between the sample holder 30 and the cooling stage 9a is cut off, and the heat conduction is lowered as compared with the case of direct contact. By adjusting the tightening strength, it is possible to reduce the amount of heat flowing into the cooling stage 9a and realize a state slightly higher than the above temperature. Further, when the right screw portion 35 is completely separated from the cooling stage 9a, the heat of the heater 32 does not flow into the cooling stage 9a, and the temperature can be raised from this temperature to room temperature or higher.

  Thus, since the cryostat with a cooler of Example 5 uses a cryogen as a low heat source, the configuration of the apparatus is simple and the manufacturing cost is low, and the sample is measured in a temperature range from various cryogenic temperatures to room temperature or higher. be able to. In addition, since the sample mounting device 5 of Example 5 can be mounted on and removed from the dewar 71 without breaking the vacuum of the measurement vacuum vessel 15a and the temperature of the cooling stage 9a is kept low, Replacement and inspection and parts replacement of the sample mounting device 5 can be easily performed.

The present invention can be applied to a cryostat capable of measuring a physical property of a sample at a desired temperature by providing a wide range of measurement environment around room temperature from various cryogenic temperatures of about 20 mK or higher.

Explanatory drawing of the cryostat in Example 1 of the present invention Explanatory drawing of the sample mounting apparatus of the cryostat in Example 1 of this invention Figure 2 shows a fragmentary view of the main part of the sample mounting device (A)-(e) Explanatory drawing when fixing the sample mounting apparatus of the cryostat in Example 1 of this invention to a low temperature stage (A)-(e) Explanatory drawing when isolate | separating the sample mounting apparatus of the cryostat in Example 1 of this invention from a low-temperature stage. Explanatory drawing of the cryostat in Example 2 of the present invention Explanatory drawing of the cryostat in Example 3 of the present invention Explanatory drawing of the cryostat in Example 4 of the present invention Explanatory drawing of the cryostat in Example 5 of the present invention Configuration diagram of conventional cryostat

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Thermal radiation shield 2a 2nd thermal radiation shield 3 GM refrigerator 4 ³ He tank 5 Sample mounting apparatus 5a Upper support cylinder part 5b Lower support cylinder part 6, 6a, 6b Refrigerant-free superconducting magnet 6c Superconducting magnet 7a Vacuum pump 7b Compressor 8 Liquid pot 9 Low temperature stage 9a Cooling stage 10 Flange 11 First stage 12 Second stage 13 40K plate 14 4K plate 14a Flexible heat conductor 15 Exhaust pipe 15a Vacuum container for measurement 16a, 16b Channels 17a, 17b , 17c, 17e, 17f Valves 18a, 18b, 19a, 19b Heat exchanger 20 Adsorption filter 21 JT heat exchanger 22 JT valve 23 Sample mounting guide 30 Sample holder 31 Sample 32 Heater 33 Temperature sensor 34 Pipe 35 Right thread 36 Left screw part 37 Lead wire 38 Sliding seal mechanism 39 Gate valve 39a Valve body 40 Connector 41 Detachable clamp 42 O-ring 43 Leak valve 44 Vacuum pump 45 Connection part 46 Second screw part 47 Guide pipe 47a Guide stopper 48 First screw thread Part 51 Mixer 52 Still 53 Heat exchanger 54 Plate 55 Tube-in-tube heat exchanger 56 Step heat exchanger 60 Magnetic working material 61 Gas gap heat switch 62 Fin 63 Activated carbon 64 Heater 65 Magnetic field sensor 71 Dewar 72 Super insulation
73 Dewar inner container 74 Cryogen

Claims (6)

A vacuum container capable of maintaining the inside in a vacuum atmosphere, a low heat source provided in the vacuum container, and a physical property of the sample that is mounted in the vacuum container to exchange heat with the low heat source in a vacuum atmosphere to a low temperature A sample mounting device capable of measuring the sample mounting device, wherein the sample mounting device is detachably mounted from outside in a vacuum atmosphere to a heat transfer member thermally connected to the low heat source. A cryostat that locally raises the temperature of the sample by a provided heater,
The sample mounting device includes a sample holder that detachably mounts on the heat transfer member by locking the sample and thermally connects the sample holder, and an operation unit that is detachably mounted on the sample holder. Prepared,
The sample holder is provided with a first attachment / detachment portion for attaching / detaching to the heat transfer member and a second attachment / detachment portion for attaching / detaching to the operation portion,
The thermal connection between the heat transfer member and the sample holder includes a first heat transfer level at which heat conduction is performed only between the heat transfer member and the first attachment / detachment portion, and the heat transfer member. A second heat transfer level at which heat conduction is performed through the first attaching / detaching portion and the sample holder, and a third heat transfer level at which the heat transfer member and the sample holder are separated and heat conduction is not performed are provided. A cryostat, wherein the heat transfer member and the sample holder are thermally connected at these three heat transfer levels. The cryostat according to claim 1, wherein the first attaching / detaching portion is configured by a member having a higher thermal resistance than the sample holder. The first attaching / detaching portion includes a first right-hand thread portion, and the heat transfer member is provided with a first screwed right-hand thread portion to be screwed with the first attaching / detaching portion, and the second attaching / detaching portion is second. The cryostat according to claim 1, wherein a second threaded left-hand threaded portion that is screwed with the operation portion is provided on the operation portion. The first attaching / detaching portion includes a first left-hand thread portion, and the heat transfer member is provided with a first screwed left-hand thread portion to be screwed thereto, and the second attaching / detaching portion is second. The cryostat according to claim 1, wherein a second screwed right screw portion that is screwed with the operation portion is provided on the operation portion. The cryostat according to any one of claims 1 to 3, wherein the heater raises a local temperature around the sample from a temperature cooled by the heat transfer member. When the sample holder and the heat transfer member is thermally connected with the second or the third heat transfer level is gradually thermally connected via the first removable portion by said first heat transfer level The cryostat according to claim 1, wherein the cryostat is thermally connected at the second or third heat transfer level.

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