Gas total component analysis device and method based on low-temperature refrigerator

Abstract

The invention discloses a gas total-component analysis device based on a low-temperature refrigerator. The gas total-component analysis device comprises a closed test chamber provided with a gas inlet-gas exhaust switching valve pipeline; the low-temperature refrigerator is used for refrigerating the test chamber, and a cold head of the low-temperature refrigerator is positioned in the test chamber; the 3D profile measuring instrument is used for detecting the surface roughness of the cold head; the pressure-temperature sensor module is used for detecting the temperature and the pressure in the test chamber; the frost layer removing device is used for removing a frost layer on the surface of the cold head; and the data processing and control module is used for receiving roughness signals, temperature signals and pressure signals of the 3D profile measuring instrument and the pressure-temperature sensor module, and outputting a detection result according to the received signals. The low-temperature control precision, the gas condensation detection sensitivity and the defrosting efficiency are remarkably improved, the method is widely applied to the fields of low-temperature physics, spaceflight exploration, the superconducting technology and the like, and an efficient and reliable gas component analysis technical scheme is provided.

Description

Technical Field

[0001] This invention relates to a gas analysis device, and more particularly to a gas composition analysis device and method based on a cryogenic refrigerator. Background Technology

[0002] With the development of cutting-edge technologies such as superconductivity, quantum computing, and high-energy physics, the demand for gas composition analysis is increasing. Taking high-end medical equipment—magnetic resonance imaging (MRI) systems—as an example, the superconducting magnet inside the system is placed within a vacuum chamber and operates at a temperature of 4 K (corresponding to -269°C). However, due to gas release from the materials inside the vacuum chamber, it is difficult to maintain the vacuum level, causing external heat to be conducted to the superconducting magnet, which can easily lead to quenching failure and inoperability. In the field of cryogenic liquid transportation such as liquefied natural gas, the vacuum level of the interlayer between the inner and outer layers of the tank container directly affects the safety of transportation. Gas release from the materials inside the interlayer leads to a decrease in vacuum level, and heat leakage from the environment to the cryogenic liquid causes it to evaporate. If the internal pressure of the tank container rises to a certain level, an explosion may occur. To reduce the impact of material release, adsorbents are commonly used in current industrial production to adsorb the released gas. The key to placing adsorbents is determining the type of gas released, which can generally include helium, hydrogen, nitrogen, and water vapor.

[0003] The characteristics of the gas release from the aforementioned materials are as follows: 1. The environment in which they are located is generally under high vacuum, making sampling difficult and rendering most conventional gas composition analysis methods unable to directly measure them; 2. The amount of gas released from the materials is relatively small, making it difficult for conventional gas composition analysis methods to accurately determine all components. Furthermore, conventional gas composition analysis methods typically require gas pretreatment before testing, which may introduce other impurities, leading to reduced reliability of the measurement results. Especially under low-temperature conditions, phase changes in the gas may trigger the formation of frost or solid particles, placing higher demands on the sensitivity and accuracy of the detection equipment.

[0004] In existing technologies, methods such as infrared absorption and mass spectrometry typically require room temperature operation, making them difficult to adapt to low-temperature environments. Furthermore, these systems are complex and consume significant power, failing to meet the requirements for energy conservation and environmental protection.

[0005] The main problem faced by existing technologies in gas component detection is the difficulty in balancing accuracy, sensitivity, and real-time performance, especially in high vacuum, low temperature, and negative pressure trace gas detection scenarios. Traditional methods cannot effectively meet the detection requirements under these complex conditions, so there is an urgent need for a gas component analysis device that can operate efficiently in low temperature and negative pressure environments. The device should have the following characteristics: (1) Modular design, supporting flexible configuration to adapt to various gas component detection needs; (2) Precise temperature range control, covering the range from room temperature to ultra-low temperature, suitable for the accurate detection of trace gases such as water vapor, helium, hydrogen, and nitrogen; (3) Combining advanced pressure-temperature feedback control technology to ensure high stability and real-time performance of the detection process; (4) Optimized energy-saving design to reduce power consumption and improve the environmental adaptability and long-term operation capability of the equipment. Summary of the Invention

[0006] This invention provides a gas composition analysis device based on a cryogenic refrigerator, aiming to offer a highly efficient and accurate gas composition analysis technology capable of precisely detecting various trace gas components in cryogenic environments. The device employs a modular design, combining advanced technologies such as cryogenic refrigeration, frost monitoring and removal, gas circulation, and temperature control to achieve efficient and stable gas composition analysis. The device can perform gas composition analysis over a wide temperature range from room temperature to 4 K, and is suitable for detecting gases in liquid natural gas, superconducting magnets, and other cryogenic applications.

[0007] A gas composition analysis device based on a cryogenic refrigerator, comprising:

[0008] A sealed test chamber connected to a gas valve system via piping;

[0009] A cryogenic refrigerator for cooling the test chamber, wherein the cold head of the cryogenic refrigerator is located inside the test chamber;

[0010] 3D profile measuring instrument for detecting surface roughness of cold heads;

[0011] Pressure-temperature sensor module for detecting and testing indoor temperature and pressure;

[0012] Frost removal device for removing frost from the surface of a cold head;

[0013] The data processing and control module receives roughness signals, temperature signals, and pressure signals from the 3D profile measuring instrument and the pressure-temperature sensor module, and outputs the detection results based on the received signals.

[0014] Furthermore, the data processing and control module generally includes a data processing module that receives data and processes and calculates the data, and a control module. The data processing module can be a computer, etc., and the control module is used for outputting results and issuing control commands, and can be a PLC or a microcontroller, etc.

[0015] Preferably, the cryogenic refrigerator is a GM refrigerator. The GM refrigerator provides cooling capacity from 4 K to ambient temperature and can be connected to a test chamber with an observation window via a flange, ensuring airtightness and observability. The GM refrigerator provides multiple temperature zones; taking the triple point as an example, these include 273.16 K (water vapor), 216.58 K (carbon dioxide), 63.15 K (nitrogen), 54.36 K (oxygen), and 13.81 K (hydrogen). The control module adjusts the cold head temperature according to the gas composition and the target temperature zone, ensuring stable temperature zone switching and accurate detection.

[0016] The 3D profile measuring instrument is installed outside the test chamber, with its detection head positioned corresponding to the surface of the cold head. It is used to monitor the frost layer formed by gas condensation on the cold head of the GM refrigerator. The 3D profile measuring instrument monitors changes in the frost layer in real time and feeds this data back to the data processing and control module. Based on the roughness data, if the gas composition requirements are met, the module outputs the detection result. After the detection is completed, a frost removal device is triggered to remove the frost layer, ensuring uninterrupted subsequent detection. Preferably, the detection head of the 3D profile measuring instrument is located on the outer wall of the test chamber and corresponds to the surface of the cold head of the cryogenic refrigerator; a transparent window is provided on the portion of the outer wall of the test chamber corresponding to the detection head of the 3D profile measuring instrument.

[0017] The control module automatically adjusts the temperature and defrosting operation based on frost monitoring and gas composition data to ensure the accuracy and stability of gas composition analysis.

[0018] The pressure-temperature sensor module includes a pressure sensor and a temperature sensor, which collect gas pressure and temperature data in real time and transmit them to the control module. The control module adjusts the operation of the GM refrigerator according to the feedback signal to maintain the target temperature range.

[0019] Preferably, a heating unit is also provided to raise the temperature of the test chamber. After the test is completed, the control module can rapidly raise the temperature of the test chamber through the heating unit. Furthermore, the heating unit is a heating resistance wire installed on the inner wall of the test chamber. The heating resistance wire is arranged on the inner wall of the chamber under test, and its power is adjusted by the temperature control unit to complete the reheating operation of the test chamber after cooling by the refrigerator, restoring it to its initial state and verifying the test results in the corresponding temperature range.

[0020] Preferably, a vacuum pump may also be included (an external vacuum pump can also be used to evacuate the test chamber of the present invention). The vacuum pump evacuates the test chamber to 1×10⁻⁶ ppm via a vacuum extraction valve. -5 A high vacuum of Pa is used to introduce the gas to be tested through the inlet valve, and the gas inflow path is precisely controlled through the gas valve system and corresponding pipelines to ensure the accuracy of component detection.

[0021] Preferably, the system also includes a display module for displaying roughness signals and / or temperature signals and / or pressure signals. Further, the display module can utilize existing display components or screen components. The display module displays the pressure-temperature curve, detection results, and target temperature zone settings in real time, and supports data storage, remote transmission, and export functions.

[0022] Preferably, the frost removal device is automatically activated by the control module, removing frost from the surface of the cold head via a defrosting head, ensuring that frost removal does not affect gas composition detection. Preferably, the frost removal device includes:

[0023] A base that is fixed to the side wall of the test chamber;

[0024] Telescopic mechanism fixed to the base;

[0025] A defrosting head fixed to the top of the telescopic mechanism has a working position that contacts the surface of the cold head to perform defrosting operation after the telescopic mechanism is extended into position, and a standby position that moves away from the surface of the cold head after the telescopic mechanism is retracted.

[0026] When in the working position, the telescopic mechanism moves back and forth slightly, driving the defrost head to defrost the surface of the cold head and remove the frost layer on the surface of the cold head.

[0027] Furthermore, the defrosting head adopts an L-shaped brush head.

[0028] Furthermore, the telescopic mechanism includes a telescopic rod and a defrosting motor that controls the extension and retraction of the telescopic rod. After the telescopic rod extends to its full position, the brush head is positioned close to the cold head, and the defrosting motor operates. At this time, the brush head moves left and right to remove the frost layer on the surface of the cold head. After defrosting is completed, the telescopic rod returns to its initial position to avoid obstructing the 3D profile measuring instrument from detecting the roughness of the cold head.

[0029] The telescopic mechanism facilitates the removal of frost without affecting the detection of the cold head's roughness. Furthermore, positioning the cold head at the central axis position allows for more accurate detection of gas composition.

[0030] Furthermore, the control module includes a temperature control unit that controls the power of the heating resistance wire. The power is adjusted via a PWM signal to reheat the test chamber, and the accuracy of the test results is verified through voltage division changes. Simultaneously, a heating resistor is arranged at the second-stage cold head of the refrigerator, and its power is adjusted via a PWM signal to control the cold head temperature.

[0031] The device of this invention includes a vacuum pump (an external vacuum pump can also be used for evacuation), a testing chamber, a GM refrigerator, a 3D profile measuring instrument, a heating resistance wire, a pressure-temperature sensor module, a frost removal device, a data processing module, a control module, and a display module. The data processing module receives roughness data from the 3D profile measuring instrument and pressure and temperature data from the pressure-temperature sensor module, and outputs the processing results to the control module. Simultaneously, the GM refrigerator, 3D profile measuring instrument, heating resistance wire, and frost removal device can all be centrally controlled by the control module. All modules can be connected via a standard interface to form an integrated functional unit.

[0032] In this invention, the GM refrigerator's cooling end is placed in the testing chamber, providing cooling capacity from room temperature (approximately 300 K) to a minimum of 4 K to support gas detection needs across multiple target temperature zones. The refrigeration system, combined with a heating resistor for cold head temperature control, ensures smooth temperature zone switching and high detection efficiency. Pressure and temperature sensors collect real-time environmental data from the testing chamber and transmit the data to the control module for feedback regulation, dynamically adjusting the cooling power to ensure precise temperature zone control and stability.

[0033] Preferably, the temperature sensor module uses a rhodium-iron thermometer and a Cernox thermometer, covering a wide temperature range of 300 K to 4 K. The rhodium-iron thermometer is suitable for high-temperature areas, featuring linear response and high stability; the Cernox thermometer is used for low-temperature detection, possessing high sensitivity, radiation resistance, and low thermal conductivity, ensuring accurate temperature data acquisition in low-temperature environments. The pressure sensor uses a high-precision differential pressure sensor, suitable for negative pressure detection in low-temperature environments, with a measurement range of 0-10 kPa, exhibiting good data stability and low-temperature adaptability.

[0034] The 3D profile scanner is used to monitor the frost layer changes on the surface of the GM refrigerator's cold head in real time and read surface roughness data. Through high-precision 3D imaging technology, the device provides timely feedback data to the control module, triggering the frost removal device to ensure the accuracy and stability of the gas composition analysis process.

[0035] Furthermore, the testing chamber is constructed of stainless steel and features a glass observation window, providing visual observation capabilities. Stainless steel flanges are located at the top and bottom of the chamber; one end connects to a GM chiller for cooling, while the other end connects to the gas valve system via an inlet and inlet pipe, ensuring accurate introduction and uniform distribution of the gas to be tested. The testing chamber incorporates a roughness detection device that can monitor the formation of frost and solid particles in real time, transmitting roughness change data to the display module, providing reliable real-time data support for gas composition analysis.

[0036] Furthermore, the gas valve system of the test chamber can be connected to the chamber under test via piping. The chamber under test can be a container holding the gas to be tested or a vacuum device to be tested. During testing, the chamber under test is connected to the test chamber via a KF25 connector to contain the gas to be tested. The gas valve system connects the inlet pipe to the external unit. Generally, the gas valve system includes an inlet-exhaust switching valve, a chamber inlet valve, and a vacuum exhaust valve, which can precisely control the gas inflow path. The vacuum pump is connected to the test chamber via a vacuum exhaust valve and piping, and can evacuate the test chamber to 1×10⁻⁶. -5 Pa is a high vacuum state.

[0037] The heating unit can employ a heating resistance wire, which is installed on the inner wall of the test chamber. Its power is adjusted by the temperature control unit via a PWM signal to achieve reheating after cooling. The heating resistance wire not only restores the test chamber temperature but also verifies the gas composition detection results within the corresponding temperature zone, ensuring the accuracy and reliability of the system's results. The control module automatically adjusts the temperature of the chiller's cold head based on feedback signals to maintain stable testing conditions.

[0038] The display module is used to display the pressure-temperature curve of the test chamber, the test results, and the target temperature zone setting in real time. It supports data storage, remote transmission, and export functions, which facilitates subsequent data analysis and processing.

[0039] The 3D profile measuring instrument monitors the changes in frost on the surface of the cold head in real time and feeds back the roughness data to the control module. After comprehensive analysis with the pressure data, the frost removal operation is triggered after the temperature zone measurement is completed. The frost removal device is automatically started by the control module and scrapes off the frost on the surface of the cold head by a motor, ensuring that the frost on the surface of the refrigeration unit's cold head is effectively removed and minimizing the impact of frost on subsequent gas composition detection.

[0040] The temperature range required for detecting different gases is provided by a GM refrigerator. Taking the triple point temperature of each gas as an example, the temperature range includes 273.16 K (water vapor), 216.58 K (carbon dioxide), 63.15 K (nitrogen), 54.36 K (oxygen), and 13.81 K (hydrogen). The control module adjusts the temperature of the cold end of the GM refrigerator according to the target gas and its corresponding temperature range to ensure accurate detection of the gas composition in each temperature range. Preferably, this invention is suitable for detecting gases including water vapor, nitrogen, carbon dioxide, oxygen, hydrogen, and helium.

[0041] A method for performing full-component analysis of gas using the above-mentioned apparatus includes the following steps:

[0042] (1) After the test chamber is evacuated to the target vacuum state using a vacuum pump, the evacuation is stopped and the gas to be tested is introduced into the test chamber;

[0043] (2) The low-temperature refrigerator cools the test chamber and detects the temperature and pressure of the test chamber. When the temperature drops to the corresponding target temperature, the 3D profile measuring instrument is turned on and the temperature is maintained for the set time to detect the surface roughness of the cold head of the low-temperature refrigerator.

[0044] (3) If the increase in surface roughness and pressure drop both reach the set value within the set time, then the target gas is present; otherwise, it is determined that there is no target gas and the detection result is output.

[0045] As a preferred method, when testing a gas system containing multiple components, after step (3) is completed, the frost removal device is activated to remove the frost layer on the surface of the current low-temperature refrigeration unit cold head; steps (2) to (3) are repeated to test the next gas component.

[0046] Preferably, the target temperature is the triple point temperature of the target gas or the sublimation temperature of the target gas under different partial pressures, with an error range of ±0.1 K.

[0047] When testing a gas system containing multiple components, the target temperature for each component is determined based on the possible gas components. The temperature is then lowered to each target temperature in descending order to complete the testing of the corresponding gas components in sequence.

[0048] Preferably, when testing a gas system containing multiple components, the gas components are tested sequentially in order of decreasing target temperature.

[0049] As a preferred method, after the test is completed, the test chamber is heated using a heating unit, and the temperature and pressure curves are recorded to verify the test results.

[0050] More specifically, a method for performing full composition analysis of gases includes the following steps:

[0051] (1) After the test chamber is evacuated to the target vacuum state using a vacuum pump, the evacuation is stopped and the gas to be tested is introduced into the test chamber;

[0052] (2) The low-temperature refrigerator cools the test chamber and detects the temperature and pressure of the test chamber. When the temperature drops to the target temperature, the 3D profile measuring instrument and the detection light source are turned on to keep the temperature constant for a set time and detect the surface roughness of the cold head of the low-temperature refrigerator.

[0053] (3) During the set time, the data processing and control module analyzes the roughness and pressure data in conjunction with the pressure data collected by the pressure sensor. If the increase in surface roughness and the decrease in pressure both reach the set value, then the target gas is present; otherwise, it is determined that there is no target gas.

[0054] (4) After completing the test of the target temperature zone, start the frost removal device to scrape off the frost on the surface of the cold head. When the roughness returns to near the initial value, stop defrosting and cool the low temperature refrigerator to the next temperature zone for testing.

[0055] Follow steps (2) to (4) to complete the detection of all gas components in sequence, and finally output the detection results.

[0056] This invention provides a gas composition analysis device based on a cryogenic refrigerator. Through a combination of modular design, multi-target temperature zone control, a real-time feedback regulation system, and rapid defrosting technology, it can efficiently and accurately detect various trace gas components under low-temperature negative pressure conditions. With intelligent and energy-saving optimization as its core, this device significantly improves detection stability and environmental adaptability, providing a reliable technical solution for gas composition analysis under low-temperature negative pressure conditions.

[0057] This invention is primarily used for trace gas composition analysis in low-temperature, negative-pressure environments, providing an efficient and reliable solution. Through precise temperature control and automated operation, the device can accurately analyze gas components within a temperature range from room temperature to 4 K. Combining a modular design and a pressure-temperature feedback control system, this invention provides efficient and energy-saving technical support for trace gas detection, and has wide applications in fields such as low-temperature gas analysis, superconductivity technology, and liquefied natural gas.

[0058] This invention integrates cryogenic refrigeration, gas flow control, frost monitoring and removal, pressure and temperature regulation, and data acquisition and processing into a closed-loop feedback control system through modular design. The GM refrigerator provides cooling capacity from room temperature to a minimum of 4 K, supports setting multiple target temperature zones, and is suitable for the accurate detection of gases such as hydrogen, nitrogen, oxygen, carbon dioxide, and water vapor. A 3D profile measuring instrument is used for roughness detection, monitors the frost layer on the cold head surface in real time, and automatically triggers the frost removal device through feedback signals from the pressure-temperature sensor module and the control module, avoiding frost interference with detection. Compared with room temperature and pressure detection, the innovation of this invention lies in the gas composition detection under low-temperature negative pressure environment, which has higher sensitivity and accuracy. After detection, the system rapidly rewarms by heating the resistance wire, ensuring that the system quickly returns to its initial state. This invention significantly improves cryogenic control accuracy, gas condensation detection sensitivity, and defrosting efficiency, and is widely used in fields such as cryogenic physics, aerospace exploration, and superconducting technology, providing a highly efficient and reliable gas composition analysis technology solution. Attached Figure Description

[0059] Figure 1 This is an overall structural diagram of the present invention;

[0060] In the diagram: 1. GM refrigerator; 2. Upper flange; 3. Test chamber with observation port; 4. 3D profile measuring instrument; 5. Brush head; 6. Telescopic rod; 7. Motor; 8. Temperature sensor; 9. Pressure sensor; 10. Heating resistance wire; 11. Programmable power supply; 12. Lower flange; 13. Inlet-exhaust switching valve; 14. Cavity inlet valve; 15. Test cavity; 16. Vacuum extraction valve; 17. Vacuum pump; 18. Display module; 19. Data processing and control module; 20. Heating resistor;

[0061] Figure 2 The frost removal process of the present invention is illustrated.

[0062] Figure 3 The cooling capacity curves for the GM refrigerator are shown, with T1 representing the first-stage cold head temperature and T2 representing the second-stage cold head temperature. This demonstrates that the refrigerator's cooling capacity meets the gas cooling testing requirements. It can provide a cooling capacity of up to 1.5 W at a minimum temperature of 4 K.

[0063] Figure 4 The figure shows the pressure-time curve of the test chamber during the cooling process of the device. It illustrates the pressure changes in the test chamber at the corresponding sublimation temperatures of the target gases: water vapor, carbon dioxide, nitrogen, oxygen, and hydrogen.

[0064] Figure 5 The figure shows the roughness-time curves during the cooling process of the device. The different peak values ​​correspond to the roughness increase caused by gas frosting at each gas sublimation temperature. Detailed Implementation

[0065] See Figure 1 A gas composition analysis device based on a cryogenic refrigerator includes a GM refrigerator 1, an upper flange 2, a sealed test chamber with an observation port 3, a 3D profile measuring instrument 4, a brush head 5, a telescopic rod 6, a motor 7, a temperature sensor 8, a pressure sensor 9, a heating resistance wire 10, a programmable power supply 11, a lower flange 12, an inlet-exhaust switching valve 13, a chamber inlet valve 14, a test chamber 15, a vacuum exhaust valve 16, a vacuum pump 17, a display module 18, a data processing and control module 19, and a heating resistor 20.

[0066] The telescopic rod 6, motor 7, etc., constitute the telescopic mechanism of the frost removal device. The telescopic mechanism and the L-shaped brush head 5 together form the frost removal device. The temperature sensor 8 and pressure sensor 9 constitute the pressure-temperature sensor module of the device; the air intake-exhaust switching valve 13, the cavity air intake valve 14, and the vacuum exhaust valve 16, etc., constitute the gas valve system of the device. The heating resistance wire 10 and its corresponding accessories constitute the heating unit of the device. The other end of the brush head 5 is fixed to the output end of the telescopic rod 6.

[0067] The axial direction of the telescopic rod 6 and the optical path of the 3D contour measuring instrument 4 are generally staggered (e.g., vertically arranged) to facilitate the detection of the surface roughness of the refrigeration unit's cold head while avoiding the influence of the brush head 5 on the detection results.

[0068] The GM chiller 1 serves as the cryogenic chiller in this device, providing a low-temperature environment. Its cold head is located inside the test chamber 3 and is fixed to the top of the test chamber 3 via the upper flange 2 to ensure the airtightness of the test environment. A 3D profile measuring instrument 4 is installed outside the test chamber 3, scanning and detecting the roughness of the cold head of the GM chiller 1 through a transparent detection window on the side of the test chamber 3. The surface of the cold head of the GM chiller 1 is a polished copper surface. When the gas encounters cold, condensation forms a frost layer on the surface of the cold head, increasing the surface roughness. If the cold head temperature is not controlled after the GM chiller 1 is turned on, it will gradually decrease to a minimum value. Therefore, to ensure that each component of the gas is sufficiently cooled by the cold head while preventing the cold head temperature from continuously decreasing, a heating resistor 20 is installed at the second-stage cold head of the GM chiller. The heating resistor 20 is attached to the cold head for thermal connection. Simultaneously, combined with the temperature signal from the temperature sensor 8, the data processing and control module 19 adjusts the heating amount of the heating resistor 20 via a PWM signal to achieve stable temperature control of the cold head. After each gas component is detected, the telescopic rod 6 is driven by motor 7 to move horizontally back and forth, using brush head 5 to scrape off the frost layer formed on the surface of the cold head, reducing the surface roughness of the cold head to below or even below the set roughness value (e.g., slightly higher than or equal to the original roughness value), thus avoiding impact on subsequent tests. Pressure sensor 9 is located inside test chamber 3 to collect real-time pressure data of the mixed gas within test chamber 3; temperature sensor 8 is located at the secondary cold head to detect the temperature data at the secondary cold head, which is read and displayed by display module 18, and the data is transmitted to data processing and control module 19 for data processing and control response. Display module 18 can use an existing display screen, and data processing and control module 19 can be a computer or a combination of a computer and a microcontroller or other lower-level computer. During the detection process, display module 18 displays the real-time temperature and roughness of the GM refrigerator 1 cold head and the pressure inside test chamber 3, while also displaying the pressure-temperature-roughness curve in real time. When there are significant changes in pressure and roughness, the detection point is determined, and the gas type is displayed based on the temperature. Heating resistance wire 10 is positioned at the lower flange 12 of test chamber 3. Its power is regulated by the data processing and control module 19 via a PWM signal to achieve rewarming of test chamber 3 after the cooling test. Inlet-exhaust switching valve 13 connects to the chamber inlet valve 14 and the vacuum exhaust valve 16, and uses a vacuum pump 17 to evacuate the test chamber, ensuring that test chamber 3 reaches a high vacuum state (1×10⁻⁶) before gas composition detection. -5When the inlet-exhaust switching valve 13 and the vacuum extraction valve 16 are opened, the test chamber 3 can be evacuated. When the test chamber 3 reaches the target vacuum level, the vacuum extraction valve 16 is closed, and the inlet-exhaust switching valve 13 and the chamber inlet valve 14 are opened, connecting the test chamber 15 to the test chamber 3. The gas to be tested in the test chamber 15 enters the test chamber 3 for testing. The test chamber 15 can be a dedicated container for holding the gas to be tested, an existing vacuum equipment chamber, or a container used alone to hold the gas to be tested.

[0069] The specific operation steps of the present invention are as follows: (1) Vacuum pumping and gas introduction

[0070] First, start the vacuum pump 17, and simultaneously open the inlet-exhaust switching valve 13 and the vacuum extraction valve 16 to evacuate the test chamber 3 to a high vacuum state (1×10⁻⁶). -5 Pa). When the target vacuum level reaches the preset value, the vacuum extraction valve 16 is closed and the cavity inlet valve 14 is opened, and the gas to be tested in the cavity to be tested 15 enters the test chamber 3.

[0071] (2) Parameter monitoring

[0072] When the GM refrigerator 1 starts running, during the cooling process, the cold head roughness, temperature and internal pressure of the test chamber 3 are monitored by the 3D profile measuring instrument 4, temperature sensor 8 and pressure sensor 9 respectively, and displayed in real time on the display module 18.

[0073] (3) Gas composition detection

[0074] As the temperature of the cold head of the GM refrigerator 1 continuously decreases, the temperature and pressure inside the test chamber 3 also continuously decrease. When a sudden pressure change occurs (the pressure change value within the set time interval is greater than the set value of 0.2 Pa) or a significant increase in roughness occurs (the roughness change value within the set time interval is greater than the set value of 0.0001 mm), the heating amount of the heating resistor 20 is adjusted to maintain a stable cold head temperature, and the corresponding temperature is recorded. After the pressure and roughness data stabilize, the gas composition type is comprehensively determined in the display module 18 based on the pressure-roughness-temperature data. Taking the detection of a mixture of gases that may contain one or more of the following gases: water vapor, nitrogen, carbon dioxide, oxygen, hydrogen, and helium, as an example, since the triple point temperatures or sublimation temperatures of gases such as water vapor, nitrogen, carbon dioxide, oxygen, hydrogen, and helium differ significantly at different partial pressures, the target temperature corresponding to each gas component is determined based on its triple point temperature. That is, the triple point temperature corresponding to the component is the target temperature corresponding to that component.

[0075] (4) Frost removal

[0076] After each gas component is determined, the data processing and control module 19 controls the motor 7 to start, driving the telescopic rod 6 to move the brush head 5 to scrape off the frost layer on the surface of the cold head, avoiding interference with subsequent detection processes. When the roughness returns to the set level or below, the motor 7 drives the telescopic rod 6 to move the brush head 5 away from the cold head of the GM refrigerator 1, avoiding interference with the roughness detection of the 3D contour scanner 4. Then, the heating resistor 20 is turned off, and the cold head temperature continues to drop for the next gas component detection.

[0077] (5) Confirmation of helium composition

[0078] Because helium has an extremely low liquefaction temperature, the GM refrigerator 1 cannot condense helium. Therefore, when the cold head temperature of the GM refrigerator 1 drops to 4 K, the data processing and control module 19 determines whether the mixed gas contains helium based on the remaining partial pressure and outputs the final gas analysis result.

[0079] (6) Result verification

[0080] After the gas composition detection is completed, the GM refrigerator 1 stops operating, and the data processing and control module 19 outputs a PWM signal to adjust the power of the heating resistance wire 10, allowing the test chamber 3 to reheat. During the reheating process, the data processing and control module 19 monitors and compares the previous pressure and temperature data through the temperature sensor 8 and the pressure sensor 9 to verify the accuracy of the experimental results.

[0081] (7) Data transmission and storage

[0082] The test results are displayed in real time via display module 18, and can be exported to external devices or transmitted remotely. The system stores all test data for subsequent analysis and archiving.

[0083] See Figure 2This is a cross-sectional view of the frost removal device. The frost removal device includes a brush head 5, a telescopic rod 6, and a motor 7. The telescopic rod 6 specifically includes an outer cylinder 6-5 and a telescopic shaft 6-1 disposed inside the outer cylinder. It also includes fasteners 6-2, sealing rings 6-3, and supports 6-4. During installation, the brush head 5 is fixed to one end of the telescopic shaft 6-1, and the other end of the telescopic shaft 6-1 is connected to the output shaft of the motor. The motor 7 is fixed to the side wall of the test chamber 3 through the outer cylinder. Specifically, the outer cylinder is sealed and fixed to the support 6-4 fixed to the side wall of the test chamber 3 by fasteners 6-2, and the outer cylinder and fasteners 6-2 are sealed by sealing rings 6-3 to ensure that the vacuum degree of the test chamber 3 is not affected. Motor 7 drives telescopic shaft 6-1 in a reciprocating telescopic motion. Brush head 5 is fixed to the end of telescopic shaft 6-1 and fastened to the end of telescopic shaft 6-1 with screws. The brush head is an L-shaped defrosting head. During defrosting, the top tip is in close contact with the cold head of GM refrigerator 1. The reciprocating motion of telescopic shaft 6-1 drives brush head 5 to move, scraping off the frost layer on the cold head of GM refrigerator 1. After the frost layer is removed, it is deposited at the bottom of the test chamber and will not affect subsequent tests. After defrosting is completed, telescopic shaft 6-1 moves to the left, moving brush head 5 away from the cold head of GM refrigerator 1 to avoid obstructing the 3D profile measuring instrument from detecting the roughness of the cold head.

[0084] See Figure 3 The figure shows the cooling capacity curve of the GM refrigerator, where T1 is the temperature of the first-stage cold head and T2 is the temperature of the second-stage cold head. This device mainly uses the second-stage cold head of the GM refrigerator, which can provide 1.5 W of cooling capacity at a temperature of 4 K, meeting the requirements for gas cooling detection.

[0085] See Figure 4 This is a simulation diagram of the pressure change of the mixed gas when detecting the composition of the negative pressure gas using this device. The simulation was performed using MATLAB software. It was assumed that the mixed gas had a pressure of 10 Pa and consisted of water vapor, carbon dioxide, nitrogen, oxygen, hydrogen, and helium. Water vapor, carbon dioxide, nitrogen, oxygen, and hydrogen each accounted for 18%, and helium accounted for 10%. The Clausius-Clapeyron equation was used to calculate the gas sublimation temperature in the simulation, while in the experiment, the sublimation temperature was determined based on changes in pressure and roughness. According to the calculations, the mixed gas pressure decreased significantly at temperatures of 193 K, 107 K, 43 K, 39 K, and 10.9 K, corresponding to the sublimation temperatures of water vapor, carbon dioxide, nitrogen, oxygen, and hydrogen, respectively. After hydrogen sublimation, the mixed gas pressure remained at 0.014 Pa, indicating the presence of helium, a non-solidifying gas, in the mixed gas.

[0086] See Figure 5 ,correspond Figure 4 The simulation calculations show the change in surface roughness. The initial surface roughness of the refrigerator's cold head was set to 0.2 μm based on actual conditions. The surface roughness of the cold head exhibited peak values ​​when the refrigerator cooled to 193 K, 107 K, 43 K, 39 K, and 10.9 K, respectively. Figure 4 It can determine the composition of water vapor, carbon dioxide, nitrogen, oxygen, and hydrogen. Since helium does not sublimate within the cooling range of the refrigerator, the helium composition needs to be determined in conjunction with the partial pressure of the remaining gas.

[0087] Ultimately, this invention provides a highly efficient gas composition detection method based on a cryogenic refrigerator, particularly suitable for rapid analysis of trace gases and gas composition under negative pressure environments. Employing a modular design, this invention integrates refrigeration, defrosting, gas flow, pressure, and temperature monitoring and control functions into a single structure, and achieves gas composition analysis across multiple temperature zones through a pressure-temperature feedback control system. Compared to existing technologies, this invention significantly improves cryogenic control accuracy, gas condensation detection sensitivity, and defrosting efficiency, meeting the gas composition detection needs under complex environments and providing an efficient and reliable technical solution for trace gas composition analysis under negative pressure.

[0088] It should be noted that all contents not described in detail in this specification are existing technologies known to those skilled in the art. The above embodiments are merely preferred technical solutions of the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and inventive concepts of the present invention within the scope of the technology disclosed in the present invention should be covered within the protection scope of the present invention.

Claims

1. A gas composition analysis device based on a cryogenic refrigerator, characterized in that, include: A sealed test chamber, which is connected to a gas valve system via piping; A cryogenic refrigerator for cooling the test chamber, wherein the cold head of the cryogenic refrigerator is located inside the test chamber; 3D profile measuring instrument for detecting surface roughness of cold heads; Pressure-temperature sensor module for detecting and testing indoor temperature and pressure; Frost removal device for removing frost from the surface of a cold head; The data processing and control module receives the roughness signal from the 3D profile measuring instrument, the temperature signal and pressure signal from the pressure-temperature sensor module, and outputs the gas composition detection results based on the received signals.

2. The gas composition analysis device based on a cryogenic refrigerator according to claim 1, characterized in that, The detection head of the 3D contour measuring instrument is located on the outer wall of the test chamber; the outer wall of the test chamber is provided with a transparent window corresponding to the detection head of the 3D contour measuring instrument.

3. The gas composition analysis device based on a cryogenic refrigerator according to claim 2, characterized in that, Also includes: A heating unit that heats the test chamber; A display module for displaying roughness signals and / or temperature signals and / or pressure signals; The cryogenic refrigeration unit is a GM refrigeration unit or other regenerative refrigeration unit.

4. The gas composition analysis device based on a cryogenic refrigerator according to claim 1, characterized in that, The frost removal device includes: A base that is fixed to the side wall of the test chamber; Telescopic mechanism fixed to the base; A defrosting head fixed to the top of the telescopic mechanism has a working position that contacts the surface of the cold head to perform defrosting operation after the telescopic mechanism is extended into position, and a standby position that moves away from the surface of the cold head after the telescopic mechanism is retracted.

5. A method for performing full-component gas analysis using the apparatus of claim 1, characterized in that, Includes the following steps: (1) After the test chamber is evacuated to the target vacuum state, stop evacuating and introduce the gas to be tested into the test chamber; (2) The low-temperature refrigerator cools the test chamber and detects the temperature and pressure of the test chamber. When the temperature drops to the corresponding target temperature, the 3D profile measuring instrument is turned on and the temperature is maintained for the set time to detect the surface roughness of the cold head of the low-temperature refrigerator. (3) If the surface roughness increase reaches the set value within the set time, then the target gas corresponding to the target temperature exists; otherwise, there is no target gas, and the detection result is output.

6. The method for performing full composition analysis of gas according to claim 5, characterized in that, When testing a gas system containing multiple components, after step (3) is completed, start the frost removal device to remove the frost layer on the surface of the current low-temperature refrigeration cold head until the roughness is lower than the set value; repeat steps (2) to (3) to test the next gas component.

7. The method for performing full composition analysis of gas according to claim 6, characterized in that, When testing a gas system containing multiple components, the target temperature for each component is determined based on the possible gas components. The temperature is then lowered to each target temperature in descending order to complete the testing of the corresponding gas components in sequence.

8. The method for performing full composition analysis of gas according to claim 5, characterized in that, The target temperature is the sublimation temperature of the target gas.

9. The method for performing full composition analysis of gas according to claim 5, characterized in that, After the test is completed, when the temperature is cooled to a certain target temperature, the pressure drop is measured while the surface roughness is being measured. By simultaneously judging the increase in surface roughness and the pressure drop, it is determined whether the target gas is present.

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