Water and methane mixed gas preparation device and method for lunar mass spectrometer

Abstract

The application relates to the technical field of vacuum measurement, in particular to a water and methane mixed gas preparation device and method for a moon exploration mass spectrometer, which comprises a water gas preparation chamber, a water gas bottle, a pressure stabilizing chamber, a moon exploration mass spectrometer, a methane gas bottle and a gas extraction system, wherein: a metal container is arranged in the water gas preparation chamber; the water gas bottle is connected with the pressure stabilizing chamber through a first valve and connected with the water gas preparation chamber through a seventh valve; the methane gas bottle is connected with the pressure stabilizing chamber through a second valve; the pressure stabilizing chamber is connected with the moon exploration mass spectrometer through a fifth valve and a small hole; and the gas extraction system comprises a first gas extraction system, a second gas extraction system and a third gas extraction system. The standard water gas is prepared through a liquid nitrogen freezing and air extraction method, and the mixed gas configuration of methane and water gas is completed, so that the problems of water gas preparation and water and methane mixing under the water strong adsorption are solved.

Description

Technical Field

[0001] This application relates to the field of vacuum measurement technology, and more specifically, to a device and method for preparing a mixture of water and methane gas for a lunar exploration mass spectrometer. Background Technology

[0002] The mission requires in-situ water ice detection in the permanently shadowed region of the lunar south pole, targeting potential water or methane. Before the mission begins, a calibration experiment of the lunar mass spectrometer must be completed on the ground, which is crucial for evaluating its performance. The most important aspect of calibrating the lunar mass spectrometer is preparing a standard water vapor-methane mixture. However, water is a liquid at room temperature and pressure, and water vapor readily adsorbs onto surfaces, posing a significant challenge to preparing this mixture.

[0003] To obtain a mixture of methane and water vapor, pure water vapor needs to be prepared. Common methods for preparing water vapor include direct heating, carrier gas bubbling, and chemical reaction. However, direct heating produces water vapor containing dissolved gases; carrier gas bubbling results in water vapor contaminated by the carrier gas, affecting gas mixing; and chemical reaction requires more stringent experimental conditions and is inconvenient to operate. Therefore, a more convenient and contaminant-free method for preparing pure water vapor is needed.

[0004] In the vacuum field, obtaining a standard gas mixture typically requires an expansion method. This involves controlling gas expansion through valves in several vacuum chambers of known volume, and measuring the pressure after equilibrium is reached. However, the gases used in this expansion method are typically those with weak adsorption properties, such as nitrogen, argon, and carbon dioxide, where the number of gas molecules does not decrease during expansion. Water vapor, however, has strong adsorption properties. If water vapor is expanded using this method, a large number of water molecules will be adsorbed onto the inner surface of the vacuum chamber during expansion, no longer existing in gaseous form. Therefore, a method is needed to prepare a water vapor-methane standard gas mixture without altering the vacuum chamber.

[0005] In addition, to obtain a standard water-air flow rate, it is necessary to first measure the conductance of water molecules through the orifice. Currently, the main methods for measuring conductance are the fixed volume method and the fixed conductance method. The fixed volume method can calculate the conductance value of water molecules by measuring the rate of increase of the test chamber pressure and under the condition of knowing the test chamber volume. However, it is applicable to the condition of large air intake. When the air intake is very small, the fixed volume method has a large error in measuring the conductance of water-air. The fixed conductance method is also not suitable for measuring the conductance of water-air flow because the equilibrium time required when measuring small conductance is long. Summary of the Invention

[0006] This application provides a device and method for preparing a water-methane mixed gas for a lunar exploration mass spectrometer, which solves the problems of water gas preparation and mixing water and methane under the strong adsorption of water.

[0007] To achieve the above objectives, this application provides a device for preparing a water-methane mixture for a lunar mass spectrometer, comprising a water vapor preparation chamber, a water vapor cylinder, a pressure stabilizing chamber, a lunar mass spectrometer, a methane cylinder, and a pumping system. The water vapor preparation chamber contains a metal container. One end of the water vapor cylinder is connected to the pressure stabilizing chamber via a first valve, and the other end is connected to the water vapor preparation chamber via a seventh valve. The methane cylinder is connected to the pressure stabilizing chamber via a second valve. The pressure stabilizing chamber is connected to the lunar mass spectrometer via a fifth valve and a small orifice. The pumping system includes a first pumping system, a second pumping system, and a third pumping system. The first pumping system is connected to the lunar mass spectrometer and provides the necessary vacuum environment for its operation. The second pumping system is connected to the pressure stabilizing chamber and purifies it. The third pumping system is connected to the water vapor preparation chamber and prepares high-purity water vapor.

[0008] Furthermore, the first pumping system includes a first molecular pump and a first dry pump, wherein: the first molecular pump is connected to the lunar mass spectrometer via an adapter; and the first dry pump is connected to the first molecular pump via a sixth valve.

[0009] Furthermore, the second pumping system includes a second molecular pump and a second dry pump, wherein: the second molecular pump is connected to the pressure stabilizing chamber through a third valve; and the second dry pump is connected to the second molecular pump through a fourth valve.

[0010] Furthermore, the third pumping system includes a third molecular pump and a third dry pump, wherein: the third molecular pump is connected to the water-gas preparation chamber through an eighth valve; and the third dry pump is connected to the third molecular pump through a ninth valve.

[0011] Furthermore, the voltage stabilizing chamber is also connected to a capacitive thin-film vacuum gauge.

[0012] Furthermore, the metal container contained pure ice water.

[0013] In addition, this application also provides a method for preparing a water-methane mixed gas mixture using a lunar mass spectrometer for ground calibration tests, comprising the following steps: Step 1: Close all valves and orifices; Step 2: Open the small hole, the sixth valve, the third valve, the first valve, and the fourth valve; Step 3: Start the first dry pump and the second dry pump. When the pressure is appropriate, start the first molecular pump and the second molecular pump to evacuate the water gas cylinder, the pressure stabilizing chamber, and the lunar exploration mass spectrometer to initially extract the gas. Step 4: Bake the entire device to remove gas. The baking temperature is raised from room temperature to the highest temperature at a uniform rate and maintained for more than 48 hours. Then, it is gradually reduced back to room temperature at a uniform rate. Step 5: After baking, close the first and third valves to ensure that the background vacuum level in the water vapor cylinder, lunar mass spectrometer, and pressure stabilization chamber reaches 10. -7 Pa level; Step 6: Prepare standard water vapor. Place the metal container containing frozen water in the water vapor preparation chamber, open the eighth and ninth valves, turn on the third dry pump, and evacuate the water vapor preparation chamber to remove the atmospheric components from the water vapor preparation chamber and the metal container. What remains in the metal container is pure water ice. Step 7: Open the seventh valve to introduce water vapor from the water vapor preparation chamber into the water vapor cylinder; Step 8: Open the second valve and slowly introduce methane into the pressure stabilizing chamber through the methane cylinder. Measure the methane pressure p using a capacitive thin-film vacuum gauge. 甲烷 ; Step 9: Open the first valve to introduce water vapor into the pressure stabilizing chamber, and let the water vapor in the pressure stabilizing chamber stand still for 1 hour; Step 10: After the mixture of water vapor and methane has been left to stand for 1 hour, the pressure p of the water vapor and methane can be measured using a capacitive thin-film vacuum gauge. 水+甲烷 Thus, the pressure p of the water vapor can be calculated. 水 ; Step 11: Calculate the conductance of the mixture of water vapor and methane through the orifice using the formula; Step 12: Open the fifth valve and the small hole, and introduce the measured mixture of water vapor and methane into the lunar mass spectrometer through the small hole to complete the calibration test of the lunar mass spectrometer.

[0014] Furthermore, in step 10, the pressure of the water vapor is calculated using the following formula: p 水 =p 水+甲烷 -p 甲烷 ; Where, p 水 p is the pressure of water vapor. 水+甲烷 p is the mixing pressure of water vapor and methane. 甲烷 The pressure of methane.

[0015] Furthermore, in step 11, the mixing ratio of water vapor and methane mixture is: k = p 水 / p 甲烷 ; Where k is the mixing ratio of water vapor and methane, p 水 p is the pressure of water vapor. 甲烷 The pressure of methane.

[0016] Furthermore, in step 11, the conductance of the water vapor and methane mixture passing through the orifice is calculated using the following formula: Where C0' is the conductance of the water vapor and methane mixture through the orifice, t1 is the time Δp of the pressure change of the lunar mass spectrometer when a standard gas is introduced and the inlet pressure is P1; t2 is the time Δp of the pressure change of the lunar mass spectrometer when a methane and water mixture with a ratio of k is introduced and the inlet pressure is P2; P1 is the inlet pressure of the standard gas; P2 is the inlet pressure of the methane and water mixture; Δp is from 0.1 Pa to 1 Pa; and C0 is the known orifice conductance under standard gas conditions.

[0017] The apparatus and method for preparing a water-methane mixture for a lunar mass spectrometer provided in this application have the following advantages: This application prepares standard water gas using liquid nitrogen cryogenic evacuation and completes the preparation of a mixed gas of methane and water gas, solving the problems of water gas preparation and mixing water and methane under strong water adsorption. At the same time, the conductance of the binary mixed gas through the small hole is calculated by formula derivation, which is used to estimate the flow rate of the mixed gas entering the lunar exploration mass spectrometer and complete the ground calibration of the lunar exploration mass spectrometer. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings: Figure 1 This is a schematic diagram of the apparatus for preparing a water and methane mixed gas for a lunar mass spectrometer according to an embodiment of this application; In the diagram: 1-Water gas cylinder, 2-First valve, 3-Pressure stabilizing chamber, 4-Capacitive thin-film vacuum gauge, 5-Fifth valve, 6-Orifice, 7-Lunar exploration mass spectrometer, 8-Adapter, 9-First molecular pump, 10-Sixth valve, 11-First dry pump, 12-Third valve, 13-Second molecular pump, 14-Second dry pump, 15-Fourth valve, 16-Methane cylinder, 17-Second valve, 18-Water gas preparation chamber, 19-Seventh valve, 20-Eighth valve, 21-Third molecular pump, 22-Ninth valve, 23-Third dry pump, 24-Metal container. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0022] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] In addition, the term "multiple" should mean two or more.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] like Figure 1As shown, this application provides a device for preparing a water and methane mixture for a lunar mass spectrometer, including a water vapor preparation chamber 18, a water vapor cylinder 1, a pressure stabilizing chamber 3, a lunar mass spectrometer 7, a methane cylinder 16, and a pumping system. The water vapor preparation chamber 18 contains a metal container 24. One end of the water vapor cylinder 1 is connected to the pressure stabilizing chamber 3 via a first valve 2, and the other end is connected to the water vapor preparation chamber 18 via a seventh valve 19. The methane cylinder 16 is connected to the pressure stabilizing chamber 3 via a second valve 17. The pressure stabilizing chamber 3 is connected to the lunar mass spectrometer 7 via a fifth valve 5 and a small orifice 6. The pumping system includes a first pumping system, a second pumping system, and a third pumping system. The first pumping system is connected to the lunar mass spectrometer 7 and provides the vacuum environment required for its operation. The second pumping system is connected to the pressure stabilizing chamber 3 and is used to evacuate and purify the pressure stabilizing chamber 3. The third pumping system is connected to the water vapor preparation chamber 18 and is used to prepare high-purity water vapor.

[0026] Specifically, since water is in a liquid state at room temperature and pressure, water vapor is easily adsorbed onto the surface of objects, making it impossible to obtain an accurate water-methane mixture using conventional expansion methods. However, the water-methane mixture preparation device for the lunar exploration mass spectrometer provided in this application uses liquid nitrogen cryogenic evacuation to prepare high-purity water vapor, which is then mixed with methane gas introduced earlier to form a water-methane mixture. The mixture is then introduced into the lunar exploration mass spectrometer 7 through orifice 6. The flow rate of the mixture entering the lunar exploration mass spectrometer 7 is calculated based on the conductance formula of orifice 6, thereby calibrating the lunar exploration mass spectrometer 7.

[0027] More specifically, the water vapor preparation chamber 18 is used to prepare high-purity water vapor. Liquid water is frozen into water ice using a liquid nitrogen freezing and evacuation method, and dissolved air and other impurities are removed under vacuum to obtain a pure water vapor source. The water vapor cylinder 1 receives the pure water vapor from the water vapor preparation chamber 18 and serves as a temporary storage container. During subsequent mixed gas preparation, water vapor is supplied to the pressure stabilizing chamber 3 as needed. The pressure stabilizing chamber 3 is the core chamber for gas mixing and pressure stabilization. It receives methane gas from the methane cylinder 16 and water vapor from the water vapor cylinder 1, ensuring thorough mixing and stabilization of the water vapor and methane under constant temperature (50±5℃). This ensures accurate gas ratios and provides a stable gas source environment for subsequent supply of the mixed gas to the lunar mass spectrometer 7 through the orifice 6. The methane cylinder 16 provides a pure methane gas source. Orifice 6 is a standard element with known flow conductance, and its mass discrimination effect has little impact on changes in the injection ratio. It is primarily used to precisely control the rate at which gas enters the lunar mass spectrometer 7 in the form of molecular flow. Subsequent measurement data can be used to calculate the actual gas flow rate entering the lunar mass spectrometer 7. The lunar mass spectrometer 7 is the target instrument being calibrated. In ground calibration tests, a mixture of water vapor and methane in known proportions is introduced, and its response signal is used to calibrate the instrument's detection sensitivity and accuracy. In subsequent actual exploration missions, it can detect water or methane that may be present on the lunar surface.

[0028] Furthermore, the first evacuation system includes a first molecular pump 9 and a first dry pump 11, wherein: the first molecular pump 9 is connected to the lunar mass spectrometer 7 via an adapter 8; the first dry pump 11 is connected to the first molecular pump 9 via a sixth valve 10. Since the lunar mass spectrometer 7 must operate under ultra-high vacuum to avoid residual gas interfering with the detection signal, the first evacuation system is used to establish and maintain the high vacuum or ultra-high vacuum environment required for the operation of the lunar mass spectrometer 7. The first dry pump 11 starts first, evacuating the mass spectrometer and connected pipelines from atmospheric pressure to a lower vacuum level, typically in the range of 0.1 Pa - 100 Pa, creating preconditions for the molecular pump to start; the first molecular pump 9 starts after the dry pump establishes the pre-vacuum, raising the vacuum level inside the lunar mass spectrometer 7 to the required 10 Pa for operation. -7 The Pa level or even higher. The first molecular pump 9 can effectively remove gases such as nitrogen, oxygen, and argon, creating an extremely clean and stable high-vacuum analytical environment for the lunar exploration mass spectrometer 7.

[0029] Furthermore, the second evacuation system includes a second molecular pump 13 and a second dry pump 14, wherein: the second molecular pump 13 is connected to the pressure stabilizing chamber 3 via a third valve 12; the second dry pump 14 is connected to the second molecular pump 13 via a fourth valve 15. The second evacuation system performs vacuuming and purification of the pressure stabilizing chamber 3 and related pipelines. Before the experiment begins, the second dry pump 14 performs rough evacuation of the pressure stabilizing chamber 3, water vapor cylinder 1, methane pipeline, etc., removing most of the gas; the second molecular pump 13, in conjunction with the baking step, evacuates the pressure stabilizing chamber 3 and other containers to a high vacuum during the baking heating process, forcefully removing water vapor, air, and other impurities adsorbed on the inner walls, reducing the background of the apparatus, and preventing the release of gases adsorbed on the walls during subsequent experiments that could contaminate the mixed gas or affect pressure measurements.

[0030] Furthermore, the third evacuation system includes a third molecular pump 21 and a third dry pump 23, wherein: the third molecular pump 21 is connected to the water vapor preparation chamber 18 via an eighth valve 20; the third dry pump 23 is connected to the third molecular pump 21 via a ninth valve 22. The third evacuation system is used to implement the liquid nitrogen cryogenic evacuation method to prepare high-purity water vapor. The third dry pump 23 performs initial evacuation of the water vapor preparation chamber 18 after it has been filled with chilled water, removing most of the air; when the water is in a frozen solid state (water ice), the third molecular pump 21 efficiently and for a long time removes impurity gases (such as N2, O2, CO2, etc. dissolved in water ice) from the water vapor preparation chamber 18 and the metal container 24. Because the vapor pressure of water ice is extremely low at this time, the molecular pump can selectively remove the impurity gases, while leaving the pure water molecules in the solid ice.

[0031] Furthermore, the pressure stabilizing chamber 3 is also connected to a capacitive thin-film vacuum gauge 4. The capacitive thin-film vacuum gauge 4 obtains the pressure of the gas in the pressure stabilizing chamber 3 by measuring the change in capacitance. Its measurement results are not affected by the type of gas, and its measurement range is suitable for calibrating the lunar exploration mass spectrometer 7.

[0032] Furthermore, the metal container 24 stores pure ice water. First, the metal container 24 is immersed in liquid nitrogen for cooling, and liquid water is dripped into the metal container 24 to freeze the liquid water inside the metal container 24; then, the metal container 24 containing frozen water is placed in the water vapor preparation chamber 18, and the water vapor preparation chamber 18 is evacuated to remove the atmospheric components from the water vapor preparation chamber 18 and the metal container 24; finally, what remains in the metal container 24 is pure water ice.

[0033] Furthermore, this application also provides a method for preparing a water-methane mixed gas mixture using a lunar mass spectrometer for ground calibration experiments. This method primarily involves preparing pure water gas and a standard water-methane mixed gas mixture, and then using a formula to derive and calculate the conductance of the binary mixed gas passing through orifice 6, thereby calculating the flow rate of the mixed gas entering the mass spectrometer and completing the calibration of the lunar mass spectrometer 7. The specific steps include: Step 1: Close all valves and orifice 6; Step 2: Open small hole 6, sixth valve 10, third valve 12, first valve 2, and fourth valve 15; Step 3: Start the first dry pump 11 and the second dry pump 14. When the pressure is appropriate, start the first molecular pump 9 and the second molecular pump 13 to evacuate the water gas cylinder 1, the pressure stabilizing chamber 3, and the lunar exploration mass spectrometer 7 to initially extract the gas. Step 4: Bake the entire device to remove gas. The baking temperature is raised from room temperature to the highest temperature at a uniform rate and maintained for more than 48 hours. Then, it is gradually reduced back to room temperature at a uniform rate. Step 5: After baking, close the first valve 2 and the third valve 12 to ensure that the background vacuum in the water vapor cylinder 1, the lunar mass spectrometer 7, and the pressure stabilizing chamber 3 reaches 10. -7 Pa level; Step 6: Prepare standard water vapor. Place the metal container 24 containing chilled water into the water vapor preparation chamber 18, open the eighth valve 20 and the ninth valve 22, and turn on the third dry pump 23 to evacuate the water vapor preparation chamber 18, removing the atmospheric components from the water vapor preparation chamber 18 and the metal container 24. What remains in the metal container 24 is pure water ice. During the evacuation process, pay attention to the evacuation time to avoid depleting the water source. Step 7: Open the seventh valve 19 to introduce the water vapor in the water vapor preparation chamber 18 into the water vapor cylinder 1; Step 8: Open the second valve 17 and slowly introduce methane into the pressure stabilizing chamber 3 through the methane cylinder 16. Use the capacitive thin-film vacuum gauge 4 to measure the pressure p of the methane. 甲烷 ; Step 9: Open the first valve 2, introduce water vapor into the pressure stabilizing chamber 3, and let the water vapor in the pressure stabilizing chamber 3 remain still and stable for 1 hour, controlling the temperature of the pressure stabilizing chamber 3 to be 50±5℃; Step 10: After the mixture of water vapor and methane has been left to stand for 1 hour, the pressure p of the water vapor and methane can be measured using a capacitive thin-film vacuum gauge 4. 水+甲烷 To ensure that its value is less than 1000 Pa, the pressure p of the water vapor can be calculated using the following formula. 水 : p 水 =p 水+甲烷 -p 甲烷 ; where p 水 p is the pressure of water vapor. 水+甲烷 p is the mixing pressure of water vapor and methane. 甲烷 The pressure of methane.

[0034] The mixing ratio of water vapor and methane is: k = p 水 / p 甲烷 Where k is the mixing ratio of water vapor and methane, and p 水 p is the pressure of water vapor.甲烷 The pressure of methane.

[0035] Step 11: Calculate the conductance of the water vapor and methane mixture through orifice 6 using the following formula: Where C0' is the conductance of the water vapor and methane mixture through orifice 6, t1 is the time Δp of the pressure change of the lunar mass spectrometer 7 when a standard gas is introduced and the inlet pressure is P1; t2 is the time Δp of the pressure change of the lunar mass spectrometer 7 when a methane and water mixture with a ratio of k is introduced and the inlet pressure is P2; P1 is the inlet pressure of the standard gas; P2 is the inlet pressure of the methane and water mixture; Δp is from 0.1 Pa to 1 Pa; C0 is the known conductance of orifice 6 under standard gas conditions; Step 12: Open the fifth valve 5 and the small hole 6, and introduce the measured mixture of water vapor and methane into the lunar mass spectrometer 7 through the small hole 6 to complete the calibration test of the lunar mass spectrometer 7.

[0036] Specifically, the method of preparing a water-methane mixed gas using a lunar mass spectrometer provided in this application can not only prepare a standard water-methane standard binary mixed gas, but also calculate the conductance of the binary mixed gas when passing through the orifice 6 through formula derivation, calculate the flow rate of the mixed gas entering the lunar mass spectrometer 7, and complete the calibration of the lunar mass spectrometer 7. This effectively eliminates the influence of water adsorption on the accuracy of the mixed gas preparation and can obtain an accurate water-methane binary standard mixed gas.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A device for preparing a water and methane mixed gas mixture for a lunar exploration mass spectrometer, characterized in that, It includes a water vapor preparation chamber, water vapor cylinders, a pressure stabilizing chamber, a lunar exploration mass spectrometer, methane cylinders, and a gas extraction system, among which: The interior of the water vapor preparation chamber is equipped with a metal container; The metal container contains pure ice water; The water vapor preparation chamber is used to prepare high-purity water vapor. Liquid water is frozen into water ice by liquid nitrogen freezing and evacuation, and dissolved air and other impurity gases are removed in a vacuum environment to obtain a pure water vapor source. One end of the water vapor cylinder is connected to the pressure stabilizing chamber via a first valve, and the other end is connected to the water vapor preparation chamber via a seventh valve; The methane cylinder is connected to the pressure stabilizing chamber via a second valve; The pressure stabilizing chamber is connected to the lunar mass spectrometer via a fifth valve and a small orifice; The water vapor cylinder is used to receive pure water vapor from the water vapor preparation chamber and serves as a temporary storage container for the water vapor. During the subsequent preparation of mixed gas, water vapor is supplied to the pressure stabilizing chamber as needed. The pressure stabilizing chamber is used to ensure that the water vapor and methane are fully mixed and stabilized under constant temperature conditions. The air extraction system includes a first air extraction system, a second air extraction system, and a third air extraction system; The first pumping system is connected to the lunar mass spectrometer and is used to provide the vacuum environment required for the lunar mass spectrometer to operate. The second vacuum system is connected to the pressure stabilizing chamber and is used to evacuate and purify the pressure stabilizing chamber; The third air extraction system is connected to the water vapor preparation chamber and is used to prepare high-purity water vapor.

2. The apparatus for preparing a water and methane mixed gas for a lunar mass spectrometer according to claim 1, characterized in that, The first pumping system includes a first molecular pump and a first dry pump, wherein: The first molecular pump is connected to the lunar mass spectrometer via an adapter; The first dry pump is connected to the first molecular pump via a sixth valve.

3. The apparatus for preparing a water and methane mixed gas for a lunar mass spectrometer according to claim 2, characterized in that, The second pumping system includes a second molecular pump and a second dry pump, wherein: The second molecular pump is connected to the pressure stabilizing chamber via a third valve; The second dry pump is connected to the second molecular pump via a fourth valve.

4. The apparatus for preparing a water and methane mixed gas for a lunar mass spectrometer according to claim 3, characterized in that, The third pumping system includes a third molecular pump and a third dry pump, wherein: The third molecular pump is connected to the water vapor preparation chamber via the eighth valve; The third dry pump is connected to the third molecular pump via the ninth valve.

5. The apparatus for preparing a water and methane mixed gas for a lunar mass spectrometer according to claim 4, characterized in that, The voltage stabilizing chamber is also connected to a capacitive thin-film vacuum gauge.

6. A method for preparing a water-methane mixed gas using the lunar exploration mass spectrometer according to claim 5, characterized in that, For ground calibration testing, the following steps are included: Step 1: Close all valves and orifices; Step 2: Open the small hole, the sixth valve, the third valve, the first valve, and the fourth valve; Step 3: Start the first dry pump and the second dry pump. When the pressure is appropriate, start the first molecular pump and the second molecular pump to evacuate the water gas cylinder, the pressure stabilizing chamber, and the lunar exploration mass spectrometer to initially extract the gas. Step 4: Bake the entire device to remove gas. The baking temperature is raised from room temperature to the highest temperature at a uniform rate and maintained for more than 48 hours. Then, it is gradually reduced back to room temperature at a uniform rate. Step 5: After baking, close the first and third valves to ensure that the background vacuum level in the water vapor cylinder, lunar mass spectrometer, and pressure stabilization chamber reaches 10. -7 Pa level; Step 6: Prepare standard water vapor. Place the metal container containing frozen water in the water vapor preparation chamber, open the eighth and ninth valves, turn on the third dry pump, and evacuate the water vapor preparation chamber to remove the atmospheric components from the water vapor preparation chamber and the metal container. What remains in the metal container is pure water ice. Step 7: Open the seventh valve to introduce water vapor from the water vapor preparation chamber into the water vapor cylinder; Step 8: Open the second valve and slowly introduce methane into the pressure stabilizing chamber through the methane cylinder. Measure the methane pressure p using a capacitive thin-film vacuum gauge. 甲烷 ; Step 9: Open the first valve to introduce water vapor into the pressure stabilizing chamber, and let the water vapor in the pressure stabilizing chamber stand still for 1 hour; Step 10: After the mixture of water vapor and methane has been left to stand for 1 hour, the pressure p of the water vapor and methane can be measured using a capacitive thin-film vacuum gauge. 水+甲烷 Thus, the pressure p of the water vapor can be calculated. 水 ; Step 11: Calculate the conductance of the mixture of water vapor and methane through the orifice using the formula; Step 12: Open the fifth valve and the small hole, and introduce the measured mixture of water vapor and methane into the lunar mass spectrometer through the small hole to complete the calibration test of the lunar mass spectrometer.

7. The method for preparing a water-methane mixed gas using a lunar mass spectrometer according to claim 6, characterized in that, In step 10, the pressure of the water vapor is calculated using the following formula: p 水 =p 水+甲烷 -p 甲烷 ; Where, p 水 p is the pressure of water vapor. 水+甲烷 p is the mixing pressure of water vapor and methane. 甲烷 The pressure of methane.

8. The method for preparing a water-methane mixed gas using a lunar mass spectrometer according to claim 7, characterized in that, In step 11, the mixing ratio of water vapor and methane mixture is: k=p 水 / p 甲烷 ; Where k is the mixing ratio of water vapor and methane, p 水 p is the pressure of water vapor. 甲烷 The pressure of methane.

9. The method for preparing a water-methane mixed gas using a lunar mass spectrometer according to claim 8, characterized in that, In step 11, the conductance of the water vapor and methane mixture passing through the orifice is calculated using the following formula: ， Wherein, C0' is the conductance of the water vapor and methane mixture through the orifice, t1 is the time Δp of the pressure change of the lunar mass spectrometer when a standard gas is introduced and the inlet pressure is P1; t2 is the time Δp of the pressure change of the lunar mass spectrometer when a methane and water mixture with a ratio of k is introduced and the inlet pressure is P2; P1 is the inlet pressure of the standard gas; P2 is the inlet pressure of the methane and water mixture; Δp is from 0.1 Pa to 1 Pa; and C0 is the known orifice conductance under standard gas conditions.

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