JPH09306405A - Sample cooling device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To cryogenic temperature of a sample cooling device such as an electron microscope and to compensate the temperature. A two-tank structure refrigerant storage container 16 in which a liquid helium storage container 18 is provided inside a liquid nitrogen storage container 17
And two independent first and second heat conduction members 23 and 26 connected to the liquid helium storage container 18 and a third heat conduction member 20 connected to the liquid nitrogen storage container 17 are connected to the first heat conduction member 23. Each of them is contained in a substantially cylindrical shape on the outside and has both heat conduction and heat shield. The first heat conducting member 23 is hollow so that the refrigerant can flow in, and the heat conducting area can be changed by the piezo element 27. The sample 1 or the sample holder 2 or the cooling member 3 on which the sample 1 or the sample holder 2 is mounted is provided with a heater 25 and a temperature sensor 28,
By controlling the temperature control device 29 and the piezo element driving device 30 in a closed loop, the temperature is controlled to be set to an arbitrary temperature and the temperature is compensated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic sample cooling device used in combination with a device for placing a sample in a vacuum container such as an electron microscope.

[0002]

2. Description of the Related Art As a conventional cryogenic sample cooling device such as an electron microscope, for example, there is a device capable of cooling a sample to a cryogenic region of 5 K or less as described in JP-A-63-32847.

FIG. 1 shows the structure of a conventional cryogenic sample cooling device such as an electron microscope.

A first cooling member 3 which makes thermal contact with the sample 1 or the sample holder 2 to cool it to a cryogenic temperature, and a second and a third cooling member 4 which surrounds the first cooling member 3 in a substantially cylindrical shape to perform heat shield, The sample stage 6 composed of 5 is installed inside the electron microscope body 7, and outside the electron microscope body 7 independently of each other,
A first liquid helium storage container 8 that cools the first cooling member 3, and a second liquid helium storage container 9 and a liquid nitrogen storage container that cools the second and third cooling members 4 and 5 that perform heat shield. 10 are installed. First and second liquid helium storage containers 8 and 9 and liquid nitrogen storage container 1
0 is coupled to the first cooling unit 3 and the second and third cooling members 4 and 5, respectively, by the first heat conduction member 11 and the second and third heat conduction members 12 and 13, respectively, and the sample is cooled to a cryogenic temperature. Was allowed to cool. As described above, in the conventional cryogenic sample cooling device, the amount of heat flowing into the low temperature part due to the heat conduction and the heat radiation is smaller as the temperature of the high temperature part which is in contact with or is lower than the low temperature part is small. And the liquid nitrogen cooling member 5 cooled to about 100K is interposed between the liquid nitrogen cooling member 5 and the liquid nitrogen cooling member 3 having a temperature of about 100 degrees. Or to avoid relative
The second liquid helium cooling member 4 is interposed between the liquid helium cooling member 3 and the liquid nitrogen cooling member 5 for cooling the sample 1 and the sample holder 2, and the sample 1 and the sample holder 2
The structure has a triple heat shield structure that surrounds the three cooling members, and cools the three cooling members from the three refrigerant storage containers via the three heat conducting members. However, in this method, one liquid nitrogen storage container and two liquid helium storage containers are required, and the amount of heat flowing into the low temperature part due to heat conduction and heat radiation can be changed, and the sample temperature can be set arbitrarily by heat input from a heater or the like. When set to, the latent heat of vaporization of liquid helium is as small as 1/10 that of liquid nitrogen, and the consumption of liquid helium is greatly influenced by a slight heat inflow. Therefore, when the conventional liquid helium storage container is a two-tank system, the liquid helium consumption of each storage container differs depending on the experimental conditions of sample cooling, and the sample cooling possible (sample cooling experiment) time is two tanks of liquid helium. It is determined by the liquid helium on the faster consuming side. This means that expensive liquid helium cannot be effectively used, and a large amount of liquid helium is consumed, which is also economically disadvantageous. Further, the work of putting the liquid helium into the storage container is performed twice, and the workability is poor. Naturally, the manufacturing cost of the storage container also becomes three storage containers, and there is a problem that the manufacturing cost increases because the refrigerant container becomes large. Further, vibrations due to evaporation of the refrigerant and air vibrations such as sound waves received from the outer surface of the refrigerant container are transmitted to the sample or the sample holder via the heat conducting member, thereby deteriorating the performance of the electron microscope and the like.

[0005]

In the cryogenic sample cooling device of the prior art described above, the ultimate cooling temperature is determined by the cooling characteristics of the refrigerant and the cryogenic sample cooling device, and when the temperature is set and controlled to the high temperature side, If heat is applied to the sample or sample holder or the heat conduction member to be loaded by a heater, etc., the evaporation of the refrigerant will be accelerated, which inevitably shortens the sample cooling holding time and consumes a large amount of expensive refrigerant. Become. Therefore, it is necessary to reduce the consumption of the refrigerant and improve the economical efficiency. Also, the latent heat of vaporization of liquid helium is as small as 1:10 compared to liquid nitrogen, and the consumption of liquid helium in the two storage containers differs due to a slight heat inflow, and the sample cooling occurs due to the consumption of liquid helium in one of the two storage containers. The holding time is limited and the liquid helium filled in the two storage containers cannot be effectively used.

Further, since the liquid nitrogen storage container has a one-tank and liquid helium storage container has two-tank refrigerant container construction, it takes a lot of time to fill the storage container with the refrigerant. It is necessary to shorten the working time.

[0007]

According to the present invention, a cryogenic sample cooling device has a refrigerant storage container having a two-tank structure of a liquid nitrogen storage container and a liquid helium storage container provided inside the liquid nitrogen storage container, which is connected to the liquid nitrogen storage container. A heat conducting member connected to the liquid helium storage container is provided inside the heat conducting member, and the other end of the heat conducting portion connected to the liquid helium storage container is divided into two or two independent heat conducting members. The heat conducting part has a three-layer structure. Further, by varying the heat conduction area of the heat conduction member that cools the sample or the sample holder, or by dividing the heat conduction member by the heat conduction surface and controlling the heat contact time between the divided portion heat conduction surfaces, liquid helium It is possible to control and compensate the temperature of the sample or the sample holder by limiting the consumption amount of the sample and providing the sample and the sample holder or the cooling member mounted with the sample and the sample holder with a heat input function and a temperature detection function.

Inside the heat conducting member cooled by liquid nitrogen, two heat conducting members cooled by liquid helium are included in a three-layer structure to provide a heat shield layer, and the heat flowing into the intermediate layer is heated by liquid helium. It absorbs heat. Further, a heater and a temperature sensor are installed on a cooling member that cools the sample or the sample holder, and the heat conduction area of the heat conduction member can be changed, or the heat conduction member is divided by a heat conduction surface, and the division portion By controlling the thermal contact time of, the temperature is controlled to be set to an arbitrary temperature on the high temperature side and the temperature is compensated. This reduces the consumption of liquid helium.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 (a) shows an embodiment of the present invention in which a heat conducting member is projectingly connected to a two-tank structure refrigerant storage container, and the other end of the heat conducting member connected to the low temperature side refrigerant storage container has two ends. FIG. 2B is a configuration diagram of a cryogenic sample cooling device that is divided into a substantially tubular shape and has three layers of heat conduction and heat shield, and FIG. The sample 1 or the sample holder 2 is brought into thermal contact with the present cooling device and cooled to a cryogenic temperature by heat conduction using liquid nitrogen 14 and liquid helium 15. The refrigerant storage container 16 provided outside the electron microscope body 7 is provided with a liquid helium storage container 18 inside the liquid nitrogen storage container 17, and includes the liquid helium storage container 18 with a heat shield member in thermal contact with the liquid nitrogen storage container. Then, the liquid nitrogen storage container 17 and the liquid helium storage container 18 are adiabatically supported, and are constituted by a two-tank structure refrigerant storage container fixed to the refrigerant storage container 16. The first cooling member 3 that cools the sample 1 or the sample holder 2 is heat-shielded by the second and third cooling members 4 and 5 in a substantially cylindrical shape. One end of a first heat conducting member 19 is joined to the liquid helium storage container 18, the first heat conducting member 19 is divided into a substantially cylindrical shape, and the first cooling member 3 and the second cooling member 4 are joined and cooled. To be done. The second heat conducting member 20 connected to the liquid nitrogen storage container 17 is formed in a substantially cylindrical shape outside the first heat conducting member 19, is connected to the third cooling member 5, and is connected to the second cooling member 4. Heat shielding is performed together with the first heat conduction member 19. Thus, the liquid nitrogen storage container 17 and the liquid helium storage container 1
Refrigerant storage container 16
Liquid helium storage container 18 without increasing the volume of
The volume of can be increased. Furthermore, the external heat input flowing into the sample 1 or the sample holder 2 by heat conduction or radiation has a large evaporation latent heat (about 10 times that of the liquid helium refrigerant).
Liquid nitrogen refrigerant 14 is absorbed in the first stage and the temperature lower than the boiling point of liquid nitrogen refrigerant 14 is liquid helium refrigerant 15
Therefore, it is absorbed. From the above, the other end of the first heat conducting member 19 in which the first cooling member 3 for cooling the sample 1 or the sample holder 2 and the first cooling member 3 for performing the intermediate heat shield are connected to the liquid helium storage container 17 By dividing into a substantially tubular shape, the heat input to the first cooling member 3 and the second cooling member 4 and the first heat conducting member 19 which perform intermediate heat shield are taken as evaporation latent heat of the liquid helium refrigerant, and the first cooling member. 3 and the second cooling member 4 can be provided with a temperature difference.
Liquid nitrogen storage container 17 and liquid helium storage container 18
A part of the first heat conducting member 19 and the second heat conducting member 20 coupled to the above is projected into each refrigerant container to facilitate heat exchange with the refrigerant. Further, a damping material 21 is provided on the outer wall of the refrigerant storage container 16 to reduce vibration due to evaporation of the refrigerant and air vibration such as sound waves received from the outer surface of the refrigerant container to reduce the inflow of vibration into the sample.

FIG. 3 (a) shows an embodiment of the present invention in which the heat conducting member coupled to the low temperature side refrigerant storage container of the above embodiment is formed into two independent substantially cylindrical shapes, and has three layers of heat conduction. A block diagram of a cryogenic sample cooling device that also serves as a heat shield is shown in (b) and (a).
AA sectional drawing of the heat conduction member of FIG. That is, in this example, the first heat conducting member 19 coupled to the liquid helium storage container 18 of the embodiment of FIG. A conductive member 23 is provided and connected to the liquid helium storage container 18. Thereby, the heat transfer system of the first heat conducting member 22 and the second heat conducting member 23 can be separated, and the heat shield characteristic and the sample cooling arrival characteristic can be improved.

FIG. 4 (a) shows an embodiment of the present invention in which the heat conducting member coupled to the low temperature side refrigerant storage container of the above embodiment is hollow and the refrigerant filled in the refrigerant storing container is a hollow portion of the heat conducting member. The configuration diagram of the cryogenic sample cooling device that flows into the
(B) shows the AA sectional view of the heat conductive member of (a). In the case of this example, the liquid helium storage container 18 of the embodiment of FIG.
Liquid helium refrigerant 15 filled in liquid helium storage container 18 with hollow first heat conduction member 22 coupled to the first heat conduction member 24 flows into the hollow portion of first heat conduction member 24, and liquid helium refrigerant 1
5 was filled. As a result, the size of the cryogenic sample cooling device is increased, so that the distance between the refrigerant storage container 16 and the sample 3 to be cooled is increased and the sample cooling arrival characteristics are deteriorated even if the heat conduction members (20, 23, 24) are lengthened. There is no. At this time, the hollow portion of the first heat-conducting member 24 can be slightly inclined so that the vaporized gas of the cooling refrigerant can be easily discharged.

In the embodiment shown in FIG. 4, the first heat conducting member 24 is hollow, but the second and third heat conducting members 20 and 23 are similarly hollow to further improve the heat shield characteristics and the sample cooling arrival characteristics. You can

FIG. 5 (a) shows an embodiment of the present invention in which the heat conduction area is made variable at an arbitrary position of the heat conduction member coupled to the low temperature side refrigerant storage container of the above embodiment to perform temperature control and temperature compensation. The block diagram of the cryogenic sample cooling device made possible is shown, (b) shows the AA sectional view of the heat conductive member of (a). As shown in the figure, if the temperature of the cooled sample 1 or the sample holder 2 is set and controlled to the high temperature side by the heat input of the heater 25 or the like, the cooling refrigerant is evaporated by the heat input. The first heat conducting member 26 is divided in order to reduce the consumption of the refrigerant, and the heat conducting area of the divided portion is made variable to control the heat transfer amount, thereby cooling the sample 1 or the sample holder without evaporating the cooling refrigerant. The temperature of 2 can be set and controlled to the high temperature side at an arbitrary temperature. In this embodiment, a piezo element 27 is provided in the divided portion of the first heat conduction member 26, and a heater 25 and a temperature sensor 28 are provided in the first cooling member 3 on which the sample 1 or the sample holder 2 is mounted, and a temperature control device is provided. By controlling 29 and the piezo element driving device 30 in a closed loop, the heat conduction area of the divided portion of the first heat conduction member 26 is made variable, and the temperature of the sample 1 or the sample holder 2 is arbitrarily set and controlled to compensate the temperature. . In the case of other driving means regardless of the piezo element 27, it is necessary to take a driving means so that heat is not input to the first heat conducting member 26.

FIG. 6 (a) shows an embodiment of the present invention in which the heat conducting member connected to the low temperature side refrigerant storage container of the embodiment is divided at any position, and the heat contact time between the heat conducting surfaces of the divided portions is divided. 2A is a configuration diagram of a cryogenic sample cooling device capable of controlling temperature control and temperature compensation, and FIG. 6B is a sectional view taken along line AA of the heat conducting member of FIG. This drawing is another embodiment having the same purpose as the embodiment of FIG. In order to set and control the temperature of the cooled sample 1 or the sample holder 2 to an arbitrary temperature on the high temperature side, a piezo element 32 is provided in the divided part of the first heat conducting member 31 in the present embodiment, and further the sample 1 or the sample Holder 2
The heater 25 and the temperature sensor 28 are provided on the mounted first cooling member 3, and the thermal contact time between the divided heat conducting surfaces of the first heat conducting member 31 is controlled by the temperature controller 29 and the piezoelectric element driving device 30 in a closed loop. By controlling, the temperature is set and controlled to an arbitrary temperature and the temperature is compensated. In the case of other driving means instead of the piezo element 30, as in the embodiment of FIG. 5, it is necessary to take a driving means so that heat is not input to the first heat conducting member 31.

As described above with reference to the embodiments, when the heat conducting member having a substantially cylindrical shape according to the embodiment is divided for manufacturing and the means for joining is integrally formed, means for sufficiently considering heat conduction should be used. Need to take.

[0017]

As a result of the above, the cooling ultimate temperature of the cryogenic sample cooling device can be improved, and the temperature can be compensated by setting and controlling the temperature toward the high temperature side. Further, it is possible to reduce the consumption amount of the cooling refrigerant, particularly the consumption amount of liquid helium which is expensive due to the small latent heat of vaporization, which can reduce the operating cost and improve the sample cooling operating time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional cryogenic sample cooling device such as an electron microscope.

FIG. 2 (a) is a configuration diagram of a cryogenic sample cooling device showing an embodiment of the present invention, and FIG. 2 (b) is a heat-conducting member AA of FIG. 2 (a).
Sectional view.

FIG. 3A is a configuration diagram of a cryogenic sample cooling device showing another embodiment of the present invention, and FIG. 3B is a view A- of the heat conduction member of FIG.
A sectional drawing.

FIG. 4A is a configuration diagram of a cryogenic sample cooling device showing another embodiment of the present invention, and FIG. 4B is a view of A- of the heat conduction member of FIG.
A sectional drawing.

5A is a block diagram of a cryogenic sample cooling device showing another embodiment of the present invention, and FIG. 5B is a view of A- of the heat conduction member of FIG.
A sectional drawing.

6 (a) is a configuration diagram of a cryogenic sample cooling device showing another embodiment of the present invention, and FIG. 6 (b) is A- of the heat conducting member of FIG.
A sectional drawing.

[Explanation of symbols]

1: sample, 2: sample holder, 3: first cooling member, 7:
Electron microscope microscope body, 8: first liquid helium storage container, 9:
Second liquid helium storage container, 10: liquid nitrogen storage container,
11: first heat conducting member, 12: second heat conducting member, 13:
Second heat conduction member, 14: Liquid nitrogen refrigerant, 15: Liquid helium refrigerant, 16: Refrigerant storage container, 17: Liquid nitrogen storage container, 18: Liquid helium storage container, 19: First heat conduction member, 20: Second Heat conduction member, 21: Damping material, 22: First heat conduction member, 23: Second heat conduction member, 24: First heat conduction member, 25: Heater, 26: First heat conduction member, 27: Piezo element , 28: temperature sensor, 29: temperature control device,
30: Piezo element driving device, 31: First heat conducting member, 3
2: Piezo element.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masayoshi Matsunami 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Stock Company Hitachi Research Laboratory (72) Inventor Tsuyoshi Matsuda 2520 Akanuma, Hayama, Hiki-gun, Saitama Prefecture Stock Company Hitachi Research Laboratory (72) Inventor Takeshi Kawasaki 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Stock Company Hitachi Ltd. Basic Research Laboratory (72) Inventor Tadao Furitsu 2520 Akanuma, Hatoyama-cho, Hiki-gun, Saitama Hitachi Ltd. Basic Research Center

Claims (10)

[Claims] 1. A sample stage equipped with a sample or a sample holder to be installed in a body of an electron microscope or the like is enclosed by a plurality of heat shield layers, and the sample stage and each of the heat shield layers are stored with a cooling medium. In a sample cooling device comprising a container and a heat conducting member connecting the two, one end of the heat conducting member is coupled to the refrigerant storage container, and the heat conducting portion of the heat conducting member is divided into a plurality of substantially tubular shapes, and a plurality of heat A sample cooling device, which also functions as a shield layer and is an independent heat conducting member. 2. When the refrigerant storage container and the heat transfer member are connected, one end of the heat transfer member is connected to the refrigerant storage container, and the heat transfer member is composed of a plurality of substantially cylindrical heat transfer portions. 2. The sample cooling device according to claim 1, wherein the sample cooling devices are arranged in such a manner that they also serve as a plurality of heat shield layers and are independent heat conducting members. 3. When the refrigerant storage container and the heat conducting member are joined together, one end of the heat conducting member projects into the refrigerant storing container so that the refrigerant and the heat conducting member are in direct contact with each other. The sample cooling device according to claim 1. 4. When the refrigerant storage container and the heat conducting member are combined, the heat conducting member is hollow so that the refrigerant filled in the refrigerant storing container flows into the hollow portion of the heat conducting member and is filled with the refrigerant. The sample cooling device according to claim 1, wherein the sample cooling device is configured. 5. A first heat-conducting member for cooling the sample or the sample holder and a second heat-conducting member provided in a substantially cylindrical shape outside the first heat-conducting member are coupled to one liquid helium refrigerant storage container. The third heat conducting member, which is provided in a substantially cylindrical shape outside the second heat conducting member, is configured to be coupled to the liquid nitrogen refrigerant storage container, and a heat shield layer is provided. Sample cooler. 6. A heat conduction area is made variable at an arbitrary position of the heat conduction member to control a heat conduction heat quantity, and a heat input function to a sample and a sample holder or a cooling member mounted with the sample and the sample holder. A temperature detection function is provided,
The sample cooling device according to claim 1 or 2, wherein the temperature of the sample or the sample holder is controlled and compensated. 7. A piezo element is provided in the heat conduction area variable portion, the heat conduction area of the heat conduction area variable portion is controlled by driving the piezo element, and the sample and sample holder or the sample and sample holder is mounted. The sample cooling device according to claim 6, wherein the cooling member is provided with a heat input function and a temperature detection function to compensate for the temperature of the sample or the sample holder. 8. The heat conducting member is divided at an arbitrary position to control the heat contact time between the heat conducting surfaces of the divided portions of the heat conducting member, and the sample and sample holder or the sample and sample holder mounted cooling. 3. The sample cooling device according to claim 1, wherein the member is provided with a heat input function and a temperature detection function to control and compensate the temperature of the sample or the sample holder. 9. A piezo element is provided in the divided portion of the heat conducting member, and the thermal contact time between the divided portion heat transfer surfaces of the heat conducting member is controlled by driving the piezo element, and the sample and the sample holder or the The sample cooling device according to claim 7, wherein the sample and the cooling member mounted on the sample holder are provided with a heat input function and a temperature detection function to compensate for the temperature of the sample holder. 10. A liquid nitrogen refrigerant storage container is provided outside the liquid helium refrigerant storage container, and the liquid helium refrigerant storage container is covered by a heat shield member in thermal contact with the liquid nitrogen refrigerant storage container. A heat-insulating support fixed to a refrigerant container including a nitrogen refrigerant storage container, a vibration damping material is provided on the outer circumference of the refrigerant container to reduce vibration due to evaporation of the refrigerant and air vibration such as sound waves received from the outer surface of the refrigerant container. 5. Sample cooling device according to 5.