Open type low-temperature heat exchange cooling table system
By utilizing a cryogenic gas cooling system and flexible gas path connection, the vibration problem of the cryogenic stage system for scanning electron microscopes was solved, achieving efficient and stable sample observation and low-cost temperature control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2026-03-10
AI Technical Summary
The existing cryogenic stage system of scanning electron microscopes introduces minute vibrations during sample observation due to gas-liquid phase changes or refrigerator vibrations, which affects the stability of sample images and the observation effect, especially in experiments with harsh vibration requirements.
An open-type low-temperature heat exchange cold stage system is adopted, which uses low-temperature gas to cool the low-temperature sample stage. Through flexible gas path connection and regenerator pre-cooling design, gas-liquid phase change and vibration transmission are avoided. Temperature control is achieved in combination with a temperature controller.
It effectively avoids sample image vibration, improves observation stability and efficiency, reduces liquid helium/liquid nitrogen consumption, simplifies the maintenance process, reduces costs, and improves the observation quality of scanning electron microscopes.
Smart Images
Figure CN223985418U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to the field of ultralow temperature refrigeration technology, specifically relates to an open type low temperature heat exchange cold stage system. BACKGROUND
[0002] The scanning electron microscope is a common laboratory equipment, which can observe the sample under high magnification without damaging the sample. In order to ensure the observation accuracy and stability of the scanning electron microscope, the sample stage needs to be controlled at a very low temperature. At this time, the cold stage system of the scanning electron microscope is particularly important. The application of the cold stage system in the scanning electron microscope mainly has the following aspects: first, providing a stable low temperature environment, the cold stage system can control the temperature of the sample stage to keep it at a very low temperature, which helps to improve the observation accuracy and stability of the scanning electron microscope. Second, protecting the sample, the low temperature environment can slow down the decay process of the sample, thereby protecting the sample from damage. Third, improving the observation effect, in the low temperature environment, the physical and chemical properties of the sample change, which can help scientists more accurately observe the morphology and structure of the sample.
[0003] At present, two technical forms are mainly used to meet the low temperature requirement: the first one is to use liquid helium / liquid nitrogen in the Dewar flask, through the low temperature transmission pipeline, to deliver the low temperature liquid helium / liquid nitrogen to the sample stage, and to cool the sample stage by using the latent heat and sensible heat of the low temperature liquid helium / liquid nitrogen, so as to achieve the low temperature effect; the second one is to use the technology of combining compressor and low temperature refrigerator to expand the high pressure helium / nitrogen gas for refrigeration, so as to achieve the purpose of low temperature. The first method above will cause gas-liquid phase change in the cold stage, which will produce gas-liquid expansion, and then when the scanning electron microscope observes the sample, the sample image will vibrate. The second method above rigidly connects the refrigerator and the scanning electron microscope through the cold guide mechanism, and the vibration generated by the refrigerator during operation will be transmitted to the sample stage of the scanning electron microscope, which also causes the sample image to vibrate and affects the observation effect.
[0004] In fact, the vibration introduced by the above two methods is relatively small and can be ignored in general experiments. Nobody will pay attention to these small vibrations. The above two methods will introduce vibration only when the demand for vibration is very harsh. In some special cases, the experiment which is very sensitive to vibration needs to avoid any small vibration of the image as much as possible, so the above two methods are not suitable for the scanning electron microscope sample observation experiment which is very sensitive to vibration. UTILITY MODEL CONTENTS
[0005] Therefore, the utility model provides an open type low temperature heat exchange cold stage system, which can cool the low temperature sample stage by using low temperature gas during the experiment, and solves the problem of vibration of the sample image when the scanning electron microscope observes the sample.
[0006] The open low-temperature heat exchange cold table system provided by the utility model adopts the following technical scheme:
[0007] An open low-temperature heat exchange cold table system, comprising a gas cylinder, a Dewar flask, a heat exchanger, a scanning electron microscope, a low-temperature thermostat and a low-temperature sample table;
[0008] The low-temperature sample table is installed on the scanning electron microscope, and the internal passage of the low-temperature thermostat is connected with the low-temperature sample table, and the low-temperature thermostat is used for regulating and controlling the temperature of the low-temperature sample table;
[0009] The heat exchanger is accommodated in the Dewar flask, and the Dewar flask can accommodate liquid helium / liquid nitrogen, and is used for cooling the helium / nitrogen entering the Dewar flask;
[0010] The gas cylinder is connected with the inlet of the heat exchanger through a pipeline, the outlet of the heat exchanger is connected with one end of the internal inflow passage of the low-temperature thermostat, and the other end of the internal inflow passage of the low-temperature thermostat is connected with the low-temperature sample table;
[0011] When working, the Dewar flask accommodates liquid helium / liquid nitrogen, and the helium / nitrogen in the gas cylinder flows along the path of: gas cylinder→heat exchanger inlet→heat exchanger→heat exchanger outlet→low-temperature thermostat inflow passage→low-temperature sample table→atmosphere under the pressure difference between the gas cylinder and the pipeline.
[0012] Further, a heat regenerator is further included;
[0013] The gas cylinder is connected with the hot end inlet of the heat regenerator through a pipeline, the hot end outlet of the heat regenerator is connected with the inlet of the heat exchanger through a pipeline, and the hot end inlet and the hot end outlet are in communication in the heat regenerator;
[0014] One end of the internal outflow passage of the low-temperature thermostat is connected with the low-temperature sample table, and the other end is connected with the cold end inlet of the heat regenerator, the cold end outlet of the heat regenerator is in communication with the atmosphere, and the cold end inlet and the cold end outlet are in communication in the heat regenerator;
[0015] When working, the helium / nitrogen in the gas cylinder flows along the path of: gas cylinder→heat regenerator hot end inlet→heat regenerator→heat regenerator hot end outlet→heat exchanger inlet→heat exchanger→heat exchanger outlet→low-temperature thermostat inflow passage→low-temperature sample table→low-temperature thermostat outflow passage→heat regenerator cold end inlet→heat regenerator cold end outlet, and the helium / nitrogen flowing from the low-temperature sample table into the heat regenerator pre-cools the helium / nitrogen flowing from the gas cylinder into the heat regenerator in the heat regenerator.
[0016] Further, when working, the helium / nitrogen flowing from the low-temperature sample table into the heat regenerator and the helium / nitrogen flowing from the gas cylinder into the heat regenerator are in countercurrent state in the heat regenerator.
[0017] Further, when working:
[0018] The Dewar flask contains liquid helium at 4.2K and liquid nitrogen at 77K.
[0019] The temperature of the helium / nitrogen flowing from the gas cylinder to the hot end inlet of the regenerator is 290K-300K;
[0020] The temperature of the helium / nitrogen gas flowing from the hot end outlet of the regenerator to the heat exchanger is 30K-210K;
[0021] The temperature of the helium / nitrogen gas flowing from the outlet of the heat exchanger to the cryogenic thermostat is 10K-100K;
[0022] The temperature of the helium / nitrogen gas flowing out of the cryostat is 20K-200K;
[0023] The temperature of the helium / nitrogen gas flowing out from the cold end outlet of the regenerator is 280K-300K.
[0024] Furthermore, the regenerator and piping are equipped with thermal insulation structures.
[0025] Furthermore, the cryostat is connected to a temperature controller, which regulates the temperature of the cryogenic sample stage.
[0026] Furthermore, the pipes connecting the regenerator and the Dewar flask, the pipes connecting the Dewar flask and the cryogenic thermostat, and the pipes connecting the cryogenic thermostat and the regenerator are all flexible hoses;
[0027] The inlet channel of the low-temperature thermostat is an air inlet pipe structure, and the outlet channel is an exhaust pipe structure. The air inlet pipe structure and the exhaust pipe structure are respectively connected to the low-temperature sample stage through the first hose and the second hose. A capillary expansion heat exchanger is fitted around the outer periphery of the end of the air inlet pipe structure connected to the first hose.
[0028] The outer periphery of the end of the air inlet pipe and the exhaust pipe that is connected to the low-temperature sample stage is fitted with a cold screen for shielding thermal radiation.
[0029] 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 air inlet pipe and the air outlet pipe, which are arranged side by side in the vacuum shell of the low temperature thermostat, to prevent vibration when the gas flows in the air inlet pipe and the air outlet pipe.
[0030] Beneficial effects:
[0031] 1. Using cryogenic gas to cool the cryogenic sample stage ensures stable gas flow and heat exchange within the stage, effectively avoiding vibration issues caused by gas-liquid phase changes. Furthermore, the cooling mechanism connects to a cryostat and a scanning electron microscope (SEM) to supply cryogenic gas to the stage, essentially creating a flexible gas path. This further prevents the slight vibrations introduced by traditional cooling methods, thus avoiding image vibrations during SEM observation. This open-type cryogenic heat exchange stage system has a simple structure and is easy to maintain. Daily use only requires replacing the liquid nitrogen / liquid helium in the gas cylinders and Dewar flasks, resulting in low costs. Additionally, the open design of the system makes changing the cooling medium in the gas cylinders and Dewar flasks more convenient, reducing downtime and improving laboratory efficiency.
[0032] 2. The installed regenerator can use the cooling capacity of the helium / nitrogen gas to be discharged to pre-cool the helium / nitrogen gas to be entering the heat exchanger, thereby improving energy utilization and effectively reducing the consumption of liquid helium / nitrogen.
[0033] 3. The pipes connecting the regenerator and the Dewar jar, the pipes connecting the Dewar jar and the cryostat, and the pipes connecting the cryostat and the regenerator are all flexible hoses. This can further reduce the transmission of vibrations outside the scanning electron microscope to the low-temperature sample stage, ensuring that the sample image is vibration-free and improving the observation quality. In addition, these pipes and the regenerator are equipped with heat insulation structures to enhance the cooling effect on the low-temperature sample stage.
[0034] 4. The hose adopts a multi-layer composite structure, which can not only isolate external mechanical vibration, but also reduce heat loss in the pipeline, ensuring the stability of the low-temperature sample stage in complex experimental environments.
[0035] 5. A capillary expansion heat exchanger is fitted around the outer periphery of the end where the air inlet channel connects to the first hose. This design ensures that the liquefied liquid helium / liquid nitrogen is in a low-temperature saturated gaseous state when it enters the cryogenic cold stage, thus avoiding the presence of a liquid phase. This helps to further reduce vibrations caused by gas-liquid phase changes and improves the stability and performance of the equipment.
[0036] 6. The intermediate heat exchanger is not only connected to the cold screen, but also supports the air inlet pipe and the exhaust pipe, which are arranged side by side inside the vacuum shell of the low-temperature thermostat. The intermediate heat exchanger not only cools the cold screen, but also prevents vibrations caused by the gas flow in the air inlet pipe and the exhaust pipe. Attached Figure Description
[0037] Figure 1 A schematic diagram of an open-type low-temperature heat exchange cold table system provided in Embodiment 1 of this utility model;
[0038] Among them, 1-gas cylinder, 2-regenerator, 3-Dewar jar, 4-heat exchanger, 5-liquid nitrogen, 6-scanning electron microscope, 7-low temperature sample stage, 8-low temperature thermostat, 9-temperature controller. Detailed Implementation
[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0040] Example 1:
[0041] Reference Figure 1 An open-type cryogenic heat exchange stage system includes a gas cylinder 1, a Dewar jar 3, a heat exchanger 4, a scanning electron microscope 6, a cryostat 8, and a cryogenic sample stage 7, wherein:
[0042] The cryostat 8 is installed on the scanning electron microscope 6, and its internal channel is connected to the cryogenic sample stage 7 of the scanning electron microscope 6. The cryostat 8 is used to regulate the temperature of the cryogenic sample stage 7. The heat exchanger 4 is housed in a Dewar jar 3, which can hold liquid helium / liquid nitrogen and is used to cool the helium / nitrogen entering the Dewar jar 3. The gas cylinder 1 is connected to the inlet of the heat exchanger 4 through a pipeline, and the outlet of the heat exchanger 4 is connected to one end of the internal flow channel of the cryostat 8. The other end of the internal flow channel of the cryostat 8 is connected to the cryogenic sample stage 7. During operation, the Dewar jar 3 holds liquid helium / liquid nitrogen. The flow path of the helium / nitrogen in the gas cylinder 1 under the pressure difference between the inside of the gas cylinder 1 and the inside of the pipeline is as follows: gas cylinder 1 → heat exchanger 4 inlet → heat exchanger 4 → heat exchanger 4 outlet → cryogenic thermostat 8 flow channel → cryogenic sample stage 7 → atmosphere.
[0043] Thus, using cryogenic gas to cool the cryogenic sample stage 7 ensures stable gas flow and heat exchange within the stage, effectively avoiding vibration issues caused by gas-liquid phase changes. Furthermore, the cooling mechanism connects to the cryogenic thermostat 8 and the scanning electron microscope 6, supplying cryogenic gas to the stage 7 within the microscope. This flexible gas path further prevents the slight vibrations caused by traditional cooling methods, thus avoiding image vibrations during microscope observation. This open-type cryogenic heat exchange stage system has a simple structure, requiring minimal specialized tools for replacing gas cylinder 1 and Dewar flask 3, making maintenance convenient. Daily use only requires replacing the liquid nitrogen / liquid helium in gas cylinder 1 and Dewar flask 3, resulting in low costs. In this embodiment, the cryostat 8 is connected to the temperature controller 9. The temperature controller 9 regulates the helium / nitrogen temperature of the cryogenic sample stage 7 in the scanning electron microscope 6. Through the coordinated control of the cryostat 8 and the temperature controller 9, the temperature of the cryogenic sample stage 7 can be adjusted in real time, with controllable temperature fluctuations, significantly improving the stability and data accuracy of the scanning electron microscope 6. The temperature controller 9 can dynamically adjust the gas flow rate and heat exchanger power using a PID algorithm to achieve closed-loop temperature control.
[0044] Example 2:
[0045] Based on Example 1, referring to Figure 1 A regenerator 2 is added, and the gas cylinder 1 is connected to the hot end inlet of the regenerator 2 via a pipeline. The hot end outlet of the regenerator 2 is connected to the inlet of the heat exchanger 4 via a pipeline. The hot end inlet and hot end outlet are connected inside the regenerator 2. One end of the outflow channel inside the cryogenic thermostat 8 is connected to the cryogenic sample stage 7, and the other end is connected to the cold end inlet of the regenerator 2. The cold end outlet of the regenerator 2 is connected to the outside atmosphere. The cold end inlet and cold end outlet are connected inside the regenerator 2. During operation, the gas cylinder... The flow path of helium / nitrogen in cylinder 1 is as follows: cylinder 1 → hot end inlet of regenerator 2 → regenerator 2 → hot end outlet of regenerator 2 → heat exchanger inlet 4 → heat exchanger 4 → heat exchanger 4 outlet → inlet channel of cryogenic thermostat 8 → cryogenic sample stage 7 → outlet channel of cryogenic thermostat 8 → cold end inlet of regenerator 2 → cold end outlet of regenerator 2; the helium / nitrogen flowing from cryogenic sample stage 7 into regenerator 2 precools the helium / nitrogen flowing from cylinder 1 into regenerator 2 inside regenerator 2.
[0046] In this way, the cooling capacity of the helium / nitrogen gas to be discharged can be used to pre-cool the helium / nitrogen gas to be entering the heat exchanger 4, thereby improving energy utilization and effectively reducing the consumption of liquid helium / nitrogen.
[0047] Specifically, the helium / nitrogen flowing from the cryogenic sample stage 7 into the regenerator 2 and the helium / nitrogen flowing from the gas cylinder 1 into the regenerator 2 flow in a countercurrent state inside the regenerator 2, ensuring efficient cold energy recovery. More specifically, under operating conditions, the Dewar jar 3 contains liquid helium at 4.2K and liquid nitrogen at 77K; the temperature of the helium / nitrogen flowing from the gas cylinder 1 to the hot end inlet of the regenerator 2 is 290K-300K; the temperature of the helium / nitrogen flowing from the hot end outlet of the regenerator 2 to the heat exchanger 4 is 30K-210K; the temperature of the helium / nitrogen flowing from the outlet of the heat exchanger 4 to the cryogenic thermostat 8 is 10K-100K; the temperature of the helium / nitrogen flowing out of the cryogenic thermostat 8 is 20K-200K; and the temperature of the helium / nitrogen flowing out of the cold end outlet of the regenerator 2 is 280K-300K.
[0048] More specifically, the pipes connecting the regenerator 2 to the Dewar jar 3, the pipes connecting the Dewar jar 3 to the cryostat 8, and the pipes connecting the cryostat 8 to the regenerator 2 are all flexible hoses. This further reduces the transmission of vibrations from outside the scanning electron microscope 6 to the cryogenic sample stage 7 of the scanning electron microscope 6, ensuring that the sample image is vibration-free and improving the observation quality. Furthermore, these pipes and the regenerator 2 are equipped with an insulation structure to enhance the cooling effect on the cryogenic sample stage 7. Specifically, the flexible hose structure can have an inner layer of polytetrafluoroethylene (PTFE), an outer layer of stainless steel corrugated tubing, and a vacuum insulation layer in between. Alternatively, the flexible hose can be a metal corrugated hose. Specifically, the inlet channel of the cryogenic thermostat 8 is an inlet pipe structure, which is connected to the cryogenic sample stage 7 via a first flexible tube (helium / nitrogen flows into the flexible tube from the inlet pipe structure and then into the cryogenic sample stage 7). The outlet channel of the cryogenic thermostat 8 is an exhaust pipe structure, which is connected to the cryogenic sample stage 7 via a second flexible tube (helium / nitrogen in the cryogenic sample stage 7 flows out to the second flexible tube and then out to the exhaust pipe). Furthermore, a capillary expansion heat exchanger is fitted around the outer periphery of the end of the inlet channel of the cryogenic thermostat 8 that is connected to the first flexible tube. This design ensures that the liquefied liquid helium / liquid nitrogen is in a low-temperature saturated gaseous state when it enters the cryogenic sample stage 7, thereby avoiding the presence of a liquid phase. This helps to further reduce vibrations caused by gas-liquid phase changes and improves the stability and performance of the equipment. Furthermore, it also includes an intermediate heat exchanger and a cold screen. A cold screen is fitted around the outer periphery of the end where the inlet pipe structure is connected to the low-temperature sample stage 7. The intermediate heat exchanger is not only connected to the cold screen, but also supports the inlet pipe structure and the exhaust pipe structure, which are arranged side by side in the vacuum shell inside the low-temperature thermostat 8. The intermediate heat exchanger not only cools the cold screen, but also prevents vibrations from occurring when the gas flows in the inlet pipe structure and the exhaust pipe structure.
[0049] 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. An open cryogenic heat exchange cold table system, characterized by, The device comprises a gas cylinder, a Dewar flask, a heat exchanger, a scanning electron microscope, a cryostat and a low-temperature sample stage. The cryostat is installed on the scanning electron microscope, and an internal passage of the cryostat is connected with the low-temperature sample stage. The heat exchanger is accommodated in the Dewar flask, and the Dewar flask can accommodate liquid helium / liquid nitrogen, and is used for cooling helium / nitrogen gas entering the Dewar flask. The gas cylinder is connected with the inlet of the heat exchanger through a pipeline, the outlet of the heat exchanger is connected with one end of the internal inflow passage of the cryostat, and the other end of the internal inflow passage of the cryostat is connected with the low-temperature sample stage. In operation, the Dewar flask accommodates liquid helium / liquid nitrogen, and helium / nitrogen gas in the gas cylinder flows along a path of: the gas cylinder→the inlet of the heat exchanger→the heat exchanger→the outlet of the heat exchanger→the internal inflow passage of the cryostat→the low-temperature sample stage→the atmosphere.
2. The open cryogenic heat exchange cold table system of claim 1, wherein, The device further comprises a regenerator. The gas cylinder is connected with the hot-end inlet of the regenerator through a pipeline, the hot-end outlet of the regenerator is connected with the inlet of the heat exchanger through a pipeline, and the hot-end inlet and the hot-end outlet are in communication in the regenerator. One end of the internal outflow passage of the cryostat is connected with the low-temperature sample stage, and the other end of the internal outflow passage of the cryostat is connected with the cold-end inlet of the regenerator, the cold-end outlet of the regenerator is in communication with the atmosphere, and the cold-end inlet and the cold-end outlet are in communication in the regenerator. In operation, helium / nitrogen gas in the gas cylinder flows along a path of: the gas cylinder→the hot-end inlet of the regenerator→the regenerator→the hot-end outlet of the regenerator→the inlet of the heat exchanger→the heat exchanger→the outlet of the heat exchanger→the internal inflow passage of the cryostat→the low-temperature sample stage→the internal outflow passage of the cryostat→the cold-end inlet of the regenerator→the cold-end outlet of the regenerator, and helium / nitrogen gas flowing from the low-temperature sample stage into the regenerator is pre-cooled by helium / nitrogen gas flowing from the gas cylinder into the regenerator in the regenerator.
3. The open cryogenic heat exchange cold table system of claim 2, wherein, In operation, helium / nitrogen gas flowing from the low-temperature sample stage into the regenerator and helium / nitrogen gas flowing from the gas cylinder into the regenerator are in countercurrent flow in the regenerator.
4. An open cryogenic heat exchanger cold table system as claimed in claim 2 or 3, wherein, In operation: The Dewar flask contains liquid helium at a temperature of 4.2K or liquid nitrogen at a temperature of 77K; The temperature of helium / nitrogen gas flowing from the gas cylinder to the hot-end inlet of the regenerator is 290K-300K; The temperature of helium / nitrogen gas flowing from the hot-end outlet of the regenerator to the heat exchanger is 30K-210K; The temperature of helium / nitrogen gas flowing from the outlet of the heat exchanger to the cryostat is 10K-100K; The temperature of helium / nitrogen gas flowing out of the cryostat is 20K-200K; The temperature of helium / nitrogen gas flowing out of the cold-end outlet of the regenerator is 280K-300K.
5. An open cryogenic heat exchanger cold platform system according to any one of claims 1 to 3, wherein, The regenerator and the pipelines are provided with heat insulation structures.
6. An open cryogenic heat exchanger cold platform system according to any one of claims 1 to 3, wherein, The cryostat is connected with a temperature controller, and the temperature of the low-temperature sample stage is controlled by the temperature controller.
7. The open cryogenic heat exchanger cold table system of claim 2 or 3, wherein, The pipelines connecting the regenerator with the Dewar flask, the pipelines connecting the Dewar flask with the cryostat, and the pipelines connecting the cryostat with the regenerator are all flexible tubes. The low-temperature thermostat inflow channel is a gas inlet pipe structure, and the outflow channel is a gas outlet pipe structure; the gas inlet pipe structure and the gas outlet pipe structure are connected with the low-temperature sample table through a first hose and a second hose respectively, and the outer periphery of one end of the gas inlet pipe structure connected with the first hose is sleeved with a capillary expansion heat exchanger; The outer periphery of one end of the gas inlet pipe and the gas outlet pipe connected with the low-temperature sample table is sleeved with a cold shield for shielding thermal radiation; Further comprising an intermediate heat exchanger connected with the cold shield for cooling the cold shield, and the intermediate heat exchanger also supports the gas inlet pipe and the gas outlet pipe in parallel in the vacuum shell of the low-temperature thermostat to prevent vibration caused by gas flow in the gas inlet pipe and the gas outlet pipe.