Cryostat

Abstract

The utility model discloses a cryostat, which belongs to the technical field of ultralow temperature refrigeration, and is characterized in that a first metal corrugated hose and a second metal corrugated hose are respectively arranged at one ends, close to a scanning electron microscope, of an air inlet pipe and an exhaust pipe, and are used for being connected with a sample table in the scanning electron microscope; during working, gas for cooling the sample table is introduced into the gas inlet pipe, and the gas sequentially flows through the gas inlet pipe, the first metal corrugated hose, the sample table, the second metal corrugated hose and the exhaust pipe. The problem that vibration is transmitted to the sample table in the gasification process of liquid nitrogen or liquid helium is effectively solved, so that stable and clear imaging quality is guaranteed, and the sample table can move freely in the working process through the connecting structure of the metal corrugated hose and is not affected by a low-temperature thermostat.

Description

Technical Field

[0001] This utility model belongs to the field of ultra-low temperature refrigeration technology, and specifically relates to a low temperature thermostat. Background Technology

[0002] Scanning electron microscopes (SEMs) are common laboratory equipment that allow for high-power microscopic observation of samples without damaging them. To ensure the accuracy and stability of SEM observations, some experiments require maintaining the sample stage at extremely low temperatures. In these cases, cryostats become particularly important. The applications of cryostats in SEMs mainly include the following: (1) Providing a stable low-temperature environment: Cryostats control the temperature of the sample stage, keeping it at extremely low temperatures. This helps improve the accuracy and stability of SEM observations. (2) Protecting the sample: A low-temperature environment can slow down the decay process of the sample, thus protecting it from damage. (3) Improving observation results: Under low-temperature conditions, the physical and chemical properties of the sample change, helping scientists to observe the morphology and structure of the sample more accurately. Currently, there are two main technologies used to meet the low-temperature requirements: one is a continuous flow cryostat using liquid helium or liquid nitrogen, which uses liquid helium or liquid nitrogen in a liquid helium or liquid nitrogen Dewar to transport the cryogenic liquid to the cold stage through a cryogenic transmission pipeline. The latent heat of phase change and sensible heat of the cryogenic liquid are used to cool the sample stage or cold stage to achieve the low-temperature effect; the other is a technology that combines a compressor and a cryogenic refrigerator to expand and cool high-pressure gas to achieve the purpose of low temperature.

[0003] However, most existing cryostats are used in optical electron microscopes (OEMs). Since scanning electron microscopes (SEMs) and OEMs work on different principles, existing cryostats cannot be directly applied to SEMs. Moreover, during observation in an SEM, the spatial position of the sample needs to be adjusted multiple times, which requires the cryostat connected to the sample stage to move along with it. Existing cryostats cannot meet the requirement of cold end mobility. Furthermore, cryogenic liquids such as liquid nitrogen undergo a gas-liquid phase change inside the cryostat, causing expansion and vibration of the sample stage, which in turn causes vibration of the sample image and affects the imaging effect. Utility Model Content

[0004] In view of this, the present invention provides a low-temperature thermostat, which solves the problems of existing low-temperature thermostats failing to meet the requirements for cold end mobility and the impact of sample stage vibration on imaging effect.

[0005] The low-temperature thermostat provided by this invention adopts the following technical solution:

[0006] A low-temperature thermostat is provided with an air inlet pipe and an exhaust pipe. The air inlet pipe and the exhaust pipe are respectively provided with a first metal corrugated hose and a second metal corrugated hose at the ends near the scanning electron microscope for connecting to the sample stage in the scanning electron microscope.

[0007] During operation, gas for cooling the sample stage is introduced into the air inlet pipe, and the gas flows sequentially through the air inlet pipe, the first corrugated metal hose, the sample stage, the second corrugated metal hose, and the exhaust pipe.

[0008] Furthermore, a capillary expansion heat exchanger is fitted around the outer periphery of the end of the air inlet pipe that is connected to the first metal flexible corrugated pipe.

[0009] Furthermore, the capillary expansion heat exchanger is equipped with a spirally bent copper tube to prevent the presence of a liquid phase.

[0010] Furthermore, an instrument housing and a vacuum housing are fitted around the outer periphery of the intake pipe and the exhaust pipe;

[0011] When the cryogenic thermostat is installed in the scanning electron microscope, the vacuum housing, the instrument housing, and the chamber of the scanning electron microscope are interconnected and together form a vacuum space.

[0012] The vacuum space is used to reduce heat leakage from the intake pipe; an electrical connector is provided on the instrument housing, which can connect to temperature sensors and / or heater components.

[0013] Furthermore, the intake pipe is connected to the first metal corrugated hose through an expansion chamber.

[0014] Furthermore, both the expansion chamber and the intermediate heat exchanger are made of copper.

[0015] Furthermore, a cold shield for shielding thermal radiation is fitted around the outer periphery of the intake pipe and the exhaust pipe near the scanning electron microscope.

[0016] It also includes an intermediate heat exchanger, which is connected to the cold screen and is used to cool the cold screen. At the same time, the intermediate heat exchanger also supports the inlet pipe and the exhaust pipe to be arranged side by side in the vacuum shell of the low temperature thermostat to prevent vibration when the gas flows in the inlet pipe and the exhaust pipe.

[0017] The air intake pipe and the exhaust pipe are fitted with a heat-insulating vacuum cover around the outer periphery of the end opposite to the scanning electron microscope.

[0018] Beneficial effects:

[0019] 1. The cryostat on the scanning electron microscope is connected to the sample stage via a corrugated metal hose. These two corrugated metal hoses serve as the nitrogen inlet and outlet pipes flowing through the sample stage. They can be made of stainless steel. The unique connection design of the corrugated metal hoses increases flow resistance, further ensuring that the gas (such as helium or nitrogen) cooling the sample always enters the sample stage as a gas. This effectively solves the problem of vibration being transmitted to the sample stage during the vaporization process of liquid nitrogen or liquid helium, thus ensuring stable and clear imaging quality. Moreover, the connection structure of the corrugated metal hoses allows the sample stage to move freely during operation, unaffected by the cryostat.

[0020] 2. A capillary expansion heat exchanger is fitted around the outer periphery of the end where the inlet pipe connects to the first metal flexible bellows. This design ensures that the cryogenically liquefied liquid helium / liquid nitrogen is in a cryogenic saturated gaseous state when it enters the sample stage, thus avoiding the presence of a liquid phase. This helps to further reduce vibrations caused by gas-liquid phase changes, improving the stability and performance of the equipment.

[0021] 3. The outer periphery of the intake pipe and exhaust pipe is fitted with an instrument housing and a vacuum housing; when the low-temperature thermostat is installed in the scanning electron microscope, the vacuum housing, the instrument housing and the chamber of the scanning electron microscope are interconnected to form a vacuum space; the vacuum space is used to reduce the influence of air convection on the temperature of the cold head and reduce heat leakage of the intake pipe; the instrument housing is equipped with an electrical connector, which can connect to temperature sensors and / or heater components to regulate the gas temperature in the intake pipe.

[0022] 4. The intermediate heat exchanger can cool the cold screen and support the inlet and outlet pipes, so that the inlet and outlet pipes are arranged side by side inside the vacuum shell to prevent vibration caused by the gas flow in the inlet and outlet pipes.

[0023] 5. The outer periphery of the inlet and outlet pipes near the scanning electron microscope is fitted with a cold shield to protect against thermal radiation, while the outer periphery of the inlet and outlet pipes away from the scanning electron microscope is fitted with a vacuum cover to protect against thermal radiation. The cold shield and vacuum cover can reduce the influence of the external environment on the cryogenic piping, thereby reducing heat leakage. Attached Figure Description

[0024] Figure 1 A schematic diagram of a low-temperature thermostat structure provided for an embodiment of this utility model;

[0025] Figure 2 A schematic diagram of the internal structure of a low-temperature thermostat provided in this embodiment of the utility model;

[0026] Wherein, 1-inlet pipe; 2-instrument housing; 3-electrical connector; 4-vacuum housing; 5-intermediate heat exchanger; 6-cold shield; 7-expansion chamber; 8-first metal corrugated hose; 9-sample stage; 10-vacuum hood; 11-exhaust pipe; 12-capillary expansion heat exchanger; 13-second metal corrugated hose. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Reference Figure 1 and Figure 2 A low-temperature thermostat is provided with an inlet pipe 1 and an exhaust pipe 11. The ends of the inlet pipe 1 and the exhaust pipe 11 near the scanning electron microscope are respectively provided with a first metal corrugated hose 8 and a second metal corrugated hose 13 for connecting to the sample stage 9 in the scanning electron microscope. During operation, gas for cooling the sample stage 9 is introduced into the inlet pipe 1, and the gas flows sequentially through the inlet pipe 1, the first metal corrugated hose 8, the sample stage 9, the second metal corrugated hose 13, and the exhaust pipe 11.

[0029] Thus, the cryostat on the scanning electron microscope is connected to the sample stage 9 via a corrugated metal hose. These two corrugated metal hoses, which serve as the inlet and outlet pipes for helium / nitrogen flowing through the sample stage 9, can be made of stainless steel. The unique connection design of the corrugated metal hoses increases flow resistance, further ensuring that the gas (such as helium or nitrogen) cooling the sample stage 9 is always gaseous when it enters the sample stage 9. This effectively solves the problem of vibrations being transmitted to the sample stage 9 during the vaporization process of cryogenic liquefied liquid nitrogen or liquid helium, thereby ensuring stable and clear imaging quality. Moreover, the connection structure of the corrugated metal hoses allows the sample stage 9 to move freely during operation, unaffected by the cryostat.

[0030] As an improvement, a capillary expansion heat exchanger 12 is fitted around the outer periphery of the end where the inlet pipe 1 connects to the first metal flexible bellows 8. This design ensures that the cryogenically liquefied liquid helium / liquid nitrogen is in a cryogenic saturated gaseous state upon entering the sample stage 9, thus avoiding the presence of a liquid phase. This helps to further reduce vibrations caused by gas-liquid phase changes, improving the stability and performance of the equipment. Specifically, the capillary expansion heat exchanger 12 is equipped with a spirally bent copper tube. This design ensures that the cryogenically liquefied liquid helium / liquid nitrogen is in a cryogenic saturated gaseous state upon entering the sample stage 9, thus avoiding the presence of a liquid phase. This helps to further reduce vibrations caused by gas-liquid phase changes, improving the stability and performance of the equipment.

[0031] More specifically, the outer periphery of the intake pipe 1 and the exhaust pipe 11 is fitted with an instrument housing 2 and a vacuum housing 4; when the cryogenic thermostat is installed in the scanning electron microscope, the vacuum housing 4, the instrument housing 2 and the chamber of the scanning electron microscope are interconnected to form a vacuum space; the vacuum space is used to reduce the influence of air convection on the temperature of the cold head and reduce heat leakage of the intake pipe 1; an electrical connector 3 is provided on the instrument housing 2, which can connect to temperature sensors and / or heater components to regulate the gas temperature in the intake pipe 1.

[0032] More specifically, it also includes an intermediate heat exchanger 5. Both the inlet pipe 1 and the exhaust pipe 11 can be made of round tubes, arranged side-by-side inside the vacuum casing 4. The intermediate heat exchanger 5 connects to the cold shield 6 to cool it. Simultaneously, it supports the inlet pipe 1 and exhaust pipe 11 within the vacuum casing 4 of the cryogenic thermostat, preventing vibrations caused by gas flow within them. Furthermore, the inlet pipe 1 is connected to the first corrugated metal hose 8 via an expansion chamber 7. Both the expansion chamber 7 and the intermediate heat exchanger 5 can be made of copper.

[0033] More specifically, a cold shield 6 for shielding thermal radiation is fitted around the outer periphery of the inlet pipe 1 and the exhaust pipe 11 near the scanning electron microscope; a heat-insulating vacuum cover 10 is fitted around the outer periphery of the inlet pipe 1 and the exhaust pipe 11 away from the scanning electron microscope. The cold shield 6 and the vacuum cover 10 can be connected to the cryogenic thermostat by welding, screwing, snap-fitting, or other processes. The cross-sectional shape of the cold shield 6 and the vacuum cover 10 can be circular, square, or other irregular shapes, without specific limitations. The main function of the cold shield 6 and the vacuum cover 10 is to reduce the influence of the external environment on the cryogenic pipeline, thereby reducing heat leakage.

[0034] It should be noted that in this embodiment, the cryostat is operated by introducing gas into the inlet pipe instead of liquid. This is different from the traditional cryostat which introduces liquid to cool the sample stage 9. In this embodiment, the use of cryogenic gas to cool the sample stage can reduce the vibration of the sample stage 9.

[0035] In summary, the above are merely preferred embodiments of this utility model and are not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A cryostat, in which a gas inlet tube and a gas outlet tube are provided, characterized in that, The first metal corrugated hose and the second metal corrugated hose are arranged at the end of the gas inlet pipe and the gas outlet pipe close to the scanning electron microscope, and are used for connecting with the sample table in the scanning electron microscope. During operation, the gas for cooling the sample table is introduced into the gas inlet pipe, and the gas flows through the gas inlet pipe, the first metal corrugated hose, the sample table, the second metal corrugated hose and the gas outlet pipe in sequence.

2. A cryostat according to claim 1, characterised in that The outer periphery of the end of the gas inlet pipe connected with the first metal corrugated hose is sleeved with a capillary expansion heat exchanger.

3. A cryostat according to claim 2, wherein, The capillary expansion heat exchanger is provided with a spiral copper pipe for preventing liquid phase.

4. A cryostat according to claim 3, wherein, The outer periphery of the gas inlet pipe and the gas outlet pipe is sleeved with an instrument shell and a vacuum shell. When the cryostat is installed on the scanning electron microscope, the vacuum shell, the instrument shell and the cavity of the scanning electron microscope are in communication with each other, and together form a vacuum space. The vacuum space is used for reducing the heat leakage of the gas inlet pipe; the instrument shell is provided with an electric connector, and the electric connector can be connected with a temperature sensor and / or a heater component.

5. A cryostat according to claim 4, wherein, The gas inlet pipe is connected with the first metal corrugated hose through an expansion cavity.

6. A cryostat according to any one of claims 1 to 4, wherein The outer periphery of the end of the gas inlet pipe and the gas outlet pipe close to the scanning electron microscope is sleeved with a cold shield for shielding thermal radiation. Further, an intermediate heat exchanger is arranged, the intermediate heat exchanger is connected with the cold shield, and is used for cooling the cold shield; meanwhile, the intermediate heat exchanger also supports the gas inlet pipe and the gas outlet pipe in the vacuum shell of the cryostat, so as to prevent vibration caused by the gas flowing in the gas inlet pipe and the gas outlet pipe. The outer periphery of the end of the gas inlet pipe and the gas outlet pipe away from the scanning electron microscope is sleeved with a vacuum cover for heat insulation.

7. A cryostat according to claim 5, wherein, The outer periphery of the end of the gas inlet pipe and the gas outlet pipe close to the scanning electron microscope is sleeved with a cold shield for shielding thermal radiation. Further, an intermediate heat exchanger is arranged, the intermediate heat exchanger is connected with the cold shield, and is used for cooling the cold shield; meanwhile, the intermediate heat exchanger also supports the gas inlet pipe and the gas outlet pipe in the vacuum shell of the cryostat, so as to prevent vibration caused by the gas flowing in the gas inlet pipe and the gas outlet pipe. The outer periphery of the end of the gas inlet pipe and the gas outlet pipe away from the scanning electron microscope is sleeved with a vacuum cover for heat insulation.

8. A cryostat according to claim 7, wherein, The expansion cavity and the intermediate heat exchanger are made of copper.

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