Modeling methods, apparatus, design methods and systems for gas flow behavior

Abstract

This invention discloses a method, apparatus, design method, and system for modeling gas flow behavior. The modeling method includes: acquiring partition information of multiple zones in the vacuum system of a mass spectrometer; establishing a gas flow regime model for each zone based on the partition information; establishing an effective pumping velocity model for each zone based on the partition information and the gas flow regime models for each zone; and combining the effective pumping velocity models of each zone to obtain a gas flow behavior model in the vacuum system of the mass spectrometer. This modeling method can accurately model the gas flow behavior of the tubing in the vacuum system of a mass spectrometer.

Description

Technical Field

[0001] Specifically, this invention relates to a method for modeling gas flow behavior in a mass spectrometer vacuum system, a design method for a mass spectrometer vacuum system, a modeling device for gas flow behavior in a mass spectrometer vacuum system, a design system for a mass spectrometer vacuum system, and a mass spectrometer vacuum system. Background Technology

[0002] A thermal ionization mass spectrometer (TIMS) mainly consists of an ion source, a magnetic field mass analyzer, a detector system, a vacuum system, a measurement and control system, and a software system.

[0003] The vacuum system is a key component of the thermal ionization mass spectrometer. A high vacuum environment is fundamental to the operation of the thermal ionization mass spectrometer. A good vacuum system can create a long mean free path for ions and a chemically clean environment, avoiding ion optical contamination and signal loss caused by collisions between charged ions and background gases and various lenses.

[0004] However, due to the complexity of gas flow in the tubing of a vacuum system, current mass spectrometers are unable to accurately model and calculate the complex flow patterns of gas in the vacuum tubing when designing the vacuum system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a modeling method, apparatus, design method and system for gas flow behavior. This modeling method can accurately model the gas flow behavior of the pipeline in the vacuum system of a mass spectrometer.

[0006] According to an embodiment of a first aspect of the present invention, a method for modeling gas flow behavior in a vacuum system of a mass spectrometer is provided, wherein the vacuum system of the mass spectrometer has multiple partitions that are sequentially connected. The method includes the following steps:

[0007] Obtain partition information for multiple zones in the vacuum system of the mass spectrometer;

[0008] Based on the partition information, gas flow models for each partition are established.

[0009] Based on the partition information and the gas flow pattern model of each partition, an effective pumping speed model for each partition is established.

[0010] By combining the effective pumping rate models of each partition, a gas flow behavior model in the vacuum system of the mass spectrometer is obtained.

[0011] Preferably, the partitioning information includes gas characteristic parameters, geometric parameters, and pumping speed characteristic parameters;

[0012] The gas characteristic parameters include: gas viscosity η, gas density ρ, gas flow rate v, and gas pressure p;

[0013] The geometric parameters include: the equivalent diameter d of the cross-section of the partitioned pipe;

[0014] The pumping speed characteristic parameters include: pump inlet air pressure, air pressure inside the zone, volumetric flow rate at the pump inlet, and leakage rate inside the zone.

[0015] Preferably, the step of: establishing a gas flow pattern model for each partition based on the partition information, includes:

[0016] Based on the gas characteristic parameters and geometric parameters, the airflow state in each zone is analyzed;

[0017] Based on the airflow conditions in each zone, gas flow patterns models for each zone are established.

[0018] Preferably, the step of: establishing a gas flow pattern model for each zone based on the airflow state in each zone, including:

[0019] In sequence, determine whether the airflow state in each zone is the first flow state or the second flow state:

[0020] When the airflow state in the partition is the first flow state, the gas flow state model adopts the Reynolds number expression, and the first flow state is the turbulent state;

[0021] When the airflow state in the partition is the second flow state, the gas flow state model adopts the Knudsen number expression, and the second flow state is viscous flow, molecular flow or transitional flow state.

[0022] Preferably, the Reynolds number is expressed as:

[0023]

[0024] In the formula, Re is the Reynolds number; η is the gas viscosity; ρ is the gas density; and v is the gas velocity.

[0025] The Knudsen number is expressed as follows:

[0026]

[0027] In the formula, Kn is the Knudsen number; v is the gas velocity; η is the gas viscosity; p is the gas pressure; and d is the equivalent diameter of the cross-section of the partitioned pipe.

[0028] Preferably, the effective pumping speed model includes:

[0029] Q = P·S eff ·F(Kn)

[0030] F(Kn) = 1 + α·Kn

[0031] S eff =S0·(1-β·f(Re))

[0032] Q=P·S0·(1-β·f(Re))·(1+α·Kn)

[0033] In the formula, Q is the leakage rate within the partition; P is the pressure within the system; S eff For effective pumping speed; F(Kn) is a correction term dependent on Knudsen number; α is the slip correction coefficient; S0 is the nominal pumping speed of the pump; β is the transition flow correction coefficient; f(Re) is a correction function related to Reynolds number.

[0034] Preferably, the effective pumping speed model further includes:

[0035]

[0036] Δp=p 真空腔 -p 泵入口 =p c -p in

[0037]

[0038] In the formula, p in p is the pump inlet air pressure value. c S represents the internal air pressure value of the zone; S represents the pumping speed; S eff For effective pumping speed; This is the volumetric flow rate at the pump inlet.

[0039] According to a second aspect of the present invention, a method for designing a vacuum system for a mass spectrometer is provided, comprising the following steps:

[0040] Obtain the pump model database and the vacuum requirement values ​​for each zone in the mass spectrometer vacuum system;

[0041] Based on the above modeling method for gas flow behavior, a model of gas flow behavior in the vacuum system of a mass spectrometer is obtained.

[0042] Based on the vacuum requirement and the gas flow behavior model, the pumps for each section of the mass spectrometer are selected.

[0043] Preferably, the step of selecting a pump for the mass spectrometer based on the pump model database, the vacuum requirement value, and the gas flow behavior model specifically includes:

[0044] Based on the vacuum requirement value of the target zone, select a pump that meets the first preset condition from the pump model database;

[0045] Based on the gas flow behavior model, the effective pumping speed of the pump is obtained;

[0046] Based on the effective pumping speed of the pump, select the pump that meets the second preset condition from the pumps that meet the first preset condition, and thus obtain the target pump model.

[0047] Repeat the above steps until the pump selection for all zones is completed.

[0048] Preferably, the first preset condition is: the maximum vacuum degree of the pump is less than or equal to the pump utilization rate multiplied by the vacuum degree requirement value, or the pump has a minimum residual pressure;

[0049] The second preset condition is: the pump's rated pumping speed is greater than or equal to the effective pumping speed.

[0050] According to a third aspect of the present invention, a modeling apparatus for gas flow behavior in a mass spectrometer vacuum system is provided, comprising: a first acquisition unit, a first modeling unit, a second modeling unit, and a first processing unit; the first acquisition unit is configured to acquire partition information of multiple partitions in the vacuum system of the mass spectrometer; the first modeling unit is electrically connected to the first acquisition unit and is configured to establish gas flow regime models for each partition based on the partition information; the second modeling unit is electrically connected to both the first acquisition unit and the first modeling unit and is configured to establish effective pumping rate models for each partition based on the partition information and the gas flow regime models for each partition; the first processing unit is electrically connected to the second modeling unit and is configured to combine the effective pumping rate models of each partition to obtain a gas flow behavior model in the mass spectrometer vacuum system.

[0051] Preferably, the first processing unit includes an analysis module and an execution module. The analysis module is used to analyze the airflow state in each partition based on the gas characteristic parameters and geometric parameters in the partition information. The execution module is used to establish a gas flow state analysis model for each partition based on the airflow state in each partition.

[0052] According to an embodiment of a fourth aspect of the present invention, a design system for a mass spectrometer vacuum system is provided, comprising: a second acquisition unit, a second processing unit, and a gas flow behavior modeling device for the mass spectrometer vacuum system; the second acquisition unit is used to acquire a pump model database and vacuum requirement values ​​for each partition of the mass spectrometer vacuum system; the gas flow behavior modeling device for the mass spectrometer vacuum system is used to establish a gas flow behavior model for the mass spectrometer vacuum system; the second processing unit is electrically connected to the second acquisition unit and the gas flow behavior modeling device for the mass spectrometer vacuum system, respectively, and is used to select pumps for each partition of the mass spectrometer based on the pump model database, the vacuum requirement values, and the gas flow behavior model.

[0053] According to a fifth aspect of the present invention, a mass spectrometer vacuum system is provided, comprising: an ion source region, an analysis region, a detector region, an oil-free rotary vane vacuum pump, a turbomolecular pump, and an ion sputtering pump; wherein the ion source region, the analysis region, and the detector region are sequentially connected, the oil-free rotary vane vacuum pump and the turbomolecular pump are both connected to the ion source region, and the ion sputtering pump is connected to the analysis region; wherein the oil-free rotary vane vacuum pump, the turbomolecular pump, and the ion sputtering pump are selected using the design method of the mass spectrometer vacuum system described above.

[0054] The gas flow behavior modeling method in this invention is used to model the gas flow behavior of a mass spectrometer vacuum system. By describing the gas flow state of each zone in the vacuum system separately, a gas flow regime model for each zone is established. This local modeling method can take into account the differences in flow regime characteristics between zones. Then, by establishing an effective pumping speed model, the impact of different zones on the overall vacuum system performance can be effectively analyzed. Finally, the gas flow regime models and effective pumping speed models of each zone are combined to describe the gas flow behavior in the entire vacuum system. The gas flow behavior model established based on this method can simulate and evaluate the gas behavior inside the vacuum system, summarize the gas behavior in the vacuum system, especially the flow in the transition region between pumps, and optimize the calculation of relevant parameters of gas flow behavior between zones. This provides a design reference for the design of mass spectrometer vacuum systems, especially for pump selection. Therefore, this method can accurately model the gas flow behavior of the pipelines in a mass spectrometer vacuum system. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the structure of the mass spectrometer vacuum system in some embodiments of the present invention;

[0056] Figure 2 This is a schematic diagram of the structure of a vacuum isolation valve in some embodiments of the present invention;

[0057] Figure 3 This is a schematic diagram of the sealing structure between the detector cavity and the cavity cover in some embodiments of the present invention;

[0058] Figure 4 This is a schematic diagram of a gas flow path model in some embodiments of the present invention.

[0059] In the diagram: 1-Oil-free rotary vane vacuum pump, 2-Turbomolecular pump, 3-Ion sputtering pump, 4-Vacuum isolation valve, 5-Vacuum sensor, 6-Sealing flange, 7-Seal, 8-Vacuum chamber, 9-Slide valve rod, 10-Slide valve bellows, 11-Guide sleeve, 12-Ion source, 13-Magnetic field mass analyzer, 14-Detector system, 15-Detector chamber, 16-Detector chamber cover, 17-Sealing ring. Detailed Implementation

[0060] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0061] In the description of this invention, it should be noted that the terms "upper", "lower", "upstream", "downstream", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of the description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0062] In the description of this invention, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] First, it should be noted that thermal ionization mass spectrometry (TIMS) possesses advantages such as high sensitivity, high selectivity, high resolution, adaptability, traceability, and a wide elemental coverage, making it widely used in the field of nuclear fuel reprocessing analysis. TMS demonstrates superior performance in specific analytical tasks such as radioactive isotope analysis, nuclear waste management, nuclear fuel cycle analysis, nuclear fuel quality control, and radioactive waste management.

[0065] Typically, a thermal ionization mass spectrometer (TIMS) mainly consists of an ion source (12), a magnetic field mass analyzer (13), a detector system (14), a vacuum system, and a measurement, control, and software system. Among these, the vacuum system is a crucial component. A high-vacuum environment is fundamental to the operation of a TIMS; a good vacuum system creates a long mean free path for ions and a chemically clean environment, avoiding ion optical contamination and signal loss caused by collisions between charged ions and background gases and various lenses.

[0066] To facilitate understanding of this invention, the structure of the thermal ionization mass spectrometer is first described: The vacuum system of the thermal ionization mass spectrometer includes a vacuum cavity comprising an ion source 12, a magnetic field mass analyzer 13, and a detector system 14. The ion source 12 has an internal cavity (referred to as the ionization region). In the ionization region, the sample is coated onto the surface of a high-melting-point metal strip and placed into the ion source. Under vacuum conditions, the sample is heated and evaporated by adjusting the current intensity flowing through the metal strip. Some neutral particles ionize during the evaporation process. The magnetic field mass analyzer 13 has an internal curved channel containing a magnetic field. The ionization region is connected to this curved channel. Charged ions generated in the ionization region are accelerated into the curved channel, where the magnetic field causes the charged ions to be subjected to a Lorentz force. Due to the different mass and charge ratios of different charged ions, under the influence of the Lorentz force, different charged ions exhibit different motion paths, resulting in different degrees of deflection of the ions in the magnetic field, thereby achieving mass separation. The detector system 14 has a receiving cavity (i.e., detector cavity 15) inside, which is connected to one end of the curved channel relative to the ionization region, for capturing ions passing through the analysis region and converting them into a measurable signal.

[0067] In other words, a mass spectrometer has multiple zones: an ion source zone, an analysis zone, and a detector zone. These zones are sequentially connected, as shown in the diagram. Figure 1 As shown. More specifically, the ion source region is the ionization region inside the ion source 12; the analysis region is the curved channel inside the magnetic field mass analyzer 13; and the detector region is the receiving cavity (i.e., detector cavity 15) inside the detector system 14.

[0068] The mass spectrometer's vacuum system also includes: an oil-free rotary vane vacuum pump 1, a turbomolecular pump 2, and an ion sputtering pump 3. Both the oil-free rotary vane vacuum pump 1 and the turbomolecular pump 2 are connected to the ion source region. The oil-free rotary vane vacuum pump 1 is used for pre-evacuation of the sample introduction system. The turbomolecular pump 2 is used to maintain a high vacuum in the ion source 12 and for pre-evacuation after vacuum loss in the analysis chamber. The ion sputtering pump 3 is used to ensure that the analysis region reaches an ultra-high vacuum.

[0069] It's easy to understand that mass spectrometry requires high vacuum conditions because gas molecules interfere with ion generation and transport. Lowering the gas pressure reduces the number of gas molecules, thereby increasing the free path of ions and preventing collisions with the gas. However, the vacuum requirements vary between different sections of a mass spectrometer's vacuum system, leading to highly complex gas flow patterns.

[0070] Current mass spectrometers often lack accurate modeling and calculation of complex gas flow patterns within vacuum pipelines, particularly in the transition region between pumps, during vacuum system design. After the pumps responsible for vacuum extraction are installed, issues frequently arise such as failure to achieve an ideal gradient vacuum or slow extraction speeds. Consequently, mass spectrometers designed by some domestic and international manufacturers frequently require redesign or adjustments after installation to address performance problems caused by inaccurate vacuum system design. This phenomenon largely stems from insufficient consideration of the complexity of the vacuum system during the design phase. A lack of detailed gas flow model calculations can lead to inappropriate selection of parameters such as pump location, layout, and pipe diameter within the vacuum system, thereby affecting the overall system performance.

[0071] In summary, the quality of the vacuum system plays a decisive role in ionization efficiency, ion transport, background noise, and instrument stability. To improve the design accuracy of the vacuum system, more refined gas flow dynamics analysis must be introduced in the early stages of the design process to ensure that the gas flow behavior between components is optimized. This approach not only reduces the need for subsequent adjustments but also contributes to the continuous advancement of mass spectrometry technology.

[0072] Example 1

[0073] Please see Figure 1 This invention discloses a method for modeling gas flow behavior in a vacuum system of a mass spectrometer. The vacuum system of the mass spectrometer has multiple partitions that are connected sequentially. The method includes the following steps:

[0074] Obtain partition information for multiple zones in the vacuum system of the mass spectrometer;

[0075] Based on the partition information, gas flow models for each partition are established.

[0076] Based on the zoning information and the gas flow pattern model of each zoning, an effective pumping speed model for each zoning is established.

[0077] By combining the effective pumping rate models of each partition, a gas flow behavior model in the vacuum system of the mass spectrometer is obtained.

[0078] It should be noted that the method in this embodiment can be executed using a software module. This method, by independently modeling each partition of the mass spectrometer vacuum system, can more accurately describe the gas flow behavior of each partition. This local modeling method can consider the differences in flow characteristics between partitions, improving the reliability of the overall model. Then, by establishing an effective pumping speed model, the impact of different partitions on the overall vacuum system performance can be effectively analyzed.

[0079] Specifically, pumping speed refers to the amount of gas that a vacuum pump can remove per unit time. Pumping speed is directly related to the gas flow and pressure distribution of the vacuum system. By analyzing the pumping speed of each zone, the role of each zone in the overall vacuum system and its impact on system performance can be quantitatively analyzed. Changes in pumping speed reflect the actual operating state of each zone. Furthermore, gas flow resistance exists during gas flow. Due to the behavior of gas flow resistance, the effective pumping speed of the pump is usually not equal to the actual pumping speed. Therefore, this method also considers the behavior of gas flow resistance, thus establishing an effective pumping speed model. In simulating gas movement, for complex mass spectrometers, the relationship between gas flow and flow resistance can be equivalent to the relationship between current and resistance. Based on the connection method between pipes, the flow resistance can be calculated similarly to series and parallel resistors.

[0080] By analyzing the gas flow regime and effective pumping speed of each zone, and then tying their equations together, a model of the overall gas flow behavior of the system is obtained. This model is useful for describing the complex gas flow behavior in the pipeline of the vacuum system and provides a valid basis for the design of the subsequent vacuum system.

[0081] In summary, the modeling method for gas flow behavior in the vacuum system of a mass spectrometer can accurately model the gas flow in the pipeline of the vacuum system of a mass spectrometer.

[0082] Specifically, the zoning information includes gas characteristic parameters, geometric parameters, and pumping speed characteristic parameters. Gas characteristic parameters include: gas viscosity η, gas density ρ, gas velocity v, and gas pressure p. Geometric parameters include: equivalent diameter d of the zoning pipe cross-section. Pumping speed characteristic parameters include: pump inlet gas pressure, internal zoning gas pressure, pump inlet volumetric flow rate, and leakage rate within the zoning. All of these parameters can be obtained through actual measurement.

[0083] Furthermore, in this embodiment, the above step of establishing a gas flow pattern model for each partition based on the partition information includes:

[0084] Based on the gas characteristic parameters and geometric parameters in the zoning information, the airflow state in each zone is analyzed. It should be noted that existing simulation software can be used in the step of analyzing the airflow state in each zone. Specifically, a finite element model is established based on the gas characteristic parameters and geometric parameters, such as... Figure 4 As shown, the airflow state of each zone is obtained by solving the problem using simulation software (e.g., moflow, FLUNET).

[0085] Then, based on the airflow state in each zone, a gas flow model for each zone is established. Generally, the flow state of gas can be divided into turbulent flow, viscous flow, molecular flow, and the transitional flow state between them (i.e., the transitional state between viscous flow and molecular flow, or Knudsen flow).

[0086] Specifically, the airflow state in each zone is sequentially determined to be either the first flow state or the second flow state:

[0087] When the airflow state in the partition is the first flow state, the gas flow state model adopts the Reynolds number expression, and the first flow state is the turbulent state.

[0088] When the airflow state in the partition is the second flow state, the gas flow state model adopts the Knudsen number expression. The second flow state is viscous flow, molecular flow, or transitional flow state.

[0089] The Reynolds number expression is:

[0090]

[0091] In the formula, Re is the Reynolds number; η is the gas viscosity; ρ is the gas density; v is the gas velocity; and d is the equivalent diameter of the pipe cross-section. When Re > 4000, it is turbulent flow; when Re < 2300, it is viscous flow.

[0092] The expression for Knudsen numbers is:

[0093]

[0094] In the formula, Kn is the Knudsen number; v is the gas velocity; η is the gas viscosity; p is the gas pressure; and d is the equivalent diameter of the cross-section of the partitioned pipe. When Kn > 0.5, it is molecular flow; when Kn < 0.01, it is viscous flow; and when 0.01 < Kn < 0.5, it is a transition state.

[0095] Specifically, in simulation software, the initial flow state of the gas in the partition can be considered as turbulent. Then, relevant parameters such as gas viscosity η, gas density ρ, gas velocity v, gas pressure p, and the equivalent diameter d of the partition's pipe cross-section are substituted into the Reynolds number expression. Based on the calculation results, the flow regime of the Reynolds number is determined. When Re > 4000, the airflow state in the target partition can be determined as the first flow regime (turbulent); when Re < 4000, the airflow state in the target partition can be determined as the second flow regime (molecular flow, viscous flow, and transitional flow). Then, by calculating the Knudsen number, the airflow in the second flow regime in the partition can be further classified into molecular flow, viscous flow, or transitional flow.

[0096] For the airflow in the first flow state, the Reynolds number expression is used to establish the gas flow model; for the airflow in the second flow state, the Knudsen number expression is used. The advantage of this approach is that by establishing the gas flow model using parameters such as gas viscosity η, gas density ρ, gas velocity v, gas pressure p, and the equivalent diameter d of the cross-section of the partitioned pipe, it can more accurately classify gases in microscale or low-pressure environments and effectively incorporate the changes in the physical properties of different gases, making it suitable for dynamic models.

[0097] Effective pumping speed models include:

[0098] Q = P·S eff ·F(Kn)

[0099] F(Kn) = 1 + α·Kn

[0100] S eff =S0·(1-β·f(Re))

[0101] Q=P·S0·(1-β·f(Re))·(1+α·Kn)

[0102] In the formula, Q is the leakage rate within the partition; P is the pressure within the system; S eff For effective pumping speed; F(Kn) is a correction term dependent on Knudsen number; α is the slip correction coefficient; S0 is the nominal pumping speed of the pump; β is the transition flow correction coefficient; f(Re) is a correction function related to Reynolds number.

[0103] Specifically, the simulation of the vacuum system of a mass spectrometer involves several key factors, including leak rate, effective pumping speed, gas flow model, and flow regime transition (such as from turbulent to molecular flow).

[0104] Leakage rate (Q) and effective pumping speed (S) eff The relationship between the two is a core issue in the simulation of a mass spectrometer vacuum system. The leak rate represents the rate at which gas enters the system, while the pumping rate represents the system's ability to remove gas. The balance between the two determines the system's vacuum level.

[0105] Q = P·S eff

[0106] Where:

[0107] Q is the leak rate, P is the pressure inside the system, and S eff is the effective pumping speed. Here, P is the统称of the internal air pressure values p of each partition c .

[0108] In this embodiment, a model applicable to a mass spectrometer that combines a gas flow model is proposed, and this model is applicable to the simulation of gas transition states:

[0109] (1) Relationship between Knudsen number and leak rate

[0110] Under transitional flow and slip flow conditions (0.01 < Kn < 10), the relationship between the leak rate and pressure of the system is no longer linear, and the slip effect of the gas and the transitional characteristics of molecular motion need to be considered. The leak rate formula is improved by introducing the Knudsen extension model.

[0111] In a high-vacuum system, as the Knudsen number increases, the gas transitions from continuous flow to molecular flow, and the leak rate model must consider this transitional process. By introducing the Knudsen number correction term F(Kn), the new leak rate formula can be expressed as:

[0112] Q = P·S eff ·F(Kn)

[0113] Where F(Kn) is a correction term dependent on the Knudsen number, reflecting the change in leak rate under different flow states. It can be defined as:

[0114] F(Kn) = 1 + α·Kn

[0115] α is the slip correction coefficient; when Kn → 0, F(Kn) ≈ 1, representing the leak rate in continuous flow; when Kn → ∞, F(Kn) increases, indicating that the leak rate effect in dilute gas flow gradually strengthens.

[0116] The correction of F(Kn) here means quantifying the influence of the leak rate on the gas system in the cavity. Specifically, when the Knudsen number approaches 0, the gas is continuous and sufficient. If there is a leak point at this time, when calculating the effective pumping speed S eff , that is to say, an effective pumping speed can be directly corresponding to the leak rate, and the gas leaking into the system can be easily pumped away directly by the pump. When Kn → ∞, F(Kn) increases, indicating that the leak rate of the dilute gas flow has a very large impact on the gas. When calculating the effective pumping speed , it shows that the gas molecules leaking into the system are difficult to be directly pumped away by the pump in this case.

[0117] In the second flow state, when Kn > 0.5, it is a molecular flow; when Kn < 0.01, it is a viscous flow; and when 0.01 < Kn < 0.5, it is a transition state. In other words, from viscous flow to molecular flow, the influence of the Knudsen number correction coefficient becomes increasingly significant.

[0118] The correction factors α and β here are usually estimated using DSMC (Direct Monte Carlo Simulation) or CFD (Computational Fluid Dynamics), and sometimes determined using empirical formulas or experiments. Since these factors usually only need to be roughly estimated, they will not be discussed in detail here.

[0119] (2) Relationship between Reynolds number and pumping speed

[0120] The Reynolds number describes the flow pattern of gas in a pipe and primarily affects the effective pumping rate. The effective pumping rate of the system can be adjusted according to different Reynolds number ranges as follows:

[0121] S eff =S0·(1-β·f(Re))

[0122] in:

[0123] S0 is the nominal pumping speed of the pump; β is the transition flow correction coefficient; f(Re) is a correction function related to the Reynolds number, which can be determined based on experiments or numerical simulations.

[0124] When the mass spectrometer starts to be evacuated from atmospheric conditions, f(Re) = 0; as the gas is gradually pumped away, the gas flow rate decreases, the viscosity effect increases, the pumping speed decreases, and f(Re) gradually increases.

[0125] (3) A comprehensive model combining Knudsen number and Reynolds number

[0126] By combining the Knudsen number with the Reynolds number, a more comprehensive leak rate-pumping rate model can be obtained:

[0127] Q=P·S0·(1-β·f(Re))·(1+α·Kn)

[0128] The correction coefficients in this model can be determined based on experiments or numerical simulations. For large mass spectrometers or more complex mass spectrometer vacuum systems, the parameters in this model are usually calculated first using experimental measurement methods, component-level simulation methods, or experimental-simulation combined methods, and then the entire vacuum system is simulated as a whole.

[0129] Furthermore, the effective pumping rate model also includes:

[0130]

[0131] Δp=p 真空腔 -p 泵入口 =pc -p in

[0132]

[0133] In the formula, p in p is the pump inlet air pressure value. c S represents the internal air pressure value of the zone; S represents the pumping speed; S eff For effective pumping speed; This is the volumetric flow rate at the pump inlet.

[0134] Here, the pressure difference Δp is intended to indicate that when simulating and setting the pumping speed (i.e., pump selection), the selection of the pumping location and the setting of the pumping speed must satisfy the pressure difference Δp = p. 真空腔 -p 泵入口 >0 or higher than a certain threshold, so that the gas can overcome the flow resistance and be finally extracted from the cavity to the pump.

[0135] In this application, the gas inflow rate is directly used as the basis. The effective pumping speed is calculated using pressure difference to reflect the dynamic behavior of the gas, emphasizing the flow characteristics of the gas in the system and making it suitable for more complex flow conditions. In other words, the pumping speed calculation model proposed in this application is more suitable for calculating the effective pumping speed under complex conditions.

[0136] It's important to note that the effective pumping speed model here refers specifically to the pump itself. The focus here is on how to derive the pump's volumetric flow rate value after assessing the gas within the chamber. These formulas will be used in practical designs to calculate the simulated pump's volume, pressure requirements, etc. Since simulation software typically only displays chamber pressure, surface pressure, and cross-sectional pressure values ​​during the simulation process, this part of the model is used for checking or adjusting these values. Furthermore, when material leakage rate measurement experiments haven't been conducted, this part of the model is usually used for simulation calculations to estimate the approximate pump modeling requirements. With sufficient parameters available, using only the above pumping speed model is sufficient.

[0137] In summary, this application proposes a modeling method for gas flow behavior in a mass spectrometer vacuum system. This method can be applied to the design and implementation of vacuum systems in thermal ionization mass spectrometers, and is particularly suitable for describing complex gas flow states within a vacuum system. This method can help optimize the implementation of gradient vacuum and improve vacuum extraction speed.

[0138] In other words, this method simulates and evaluates the behavior of gases inside a vacuum system, summarizes the behavior of gases in a vacuum system, especially the flow in the transition region between pumps, optimizes the calculation of gas flow resistance between pipes and between pipes and pumps, and provides a certain design reference for the vacuum systems of other mass spectrometers.

[0139] Example 2

[0140] Please see Figure 1 The present invention also discloses a design method for a vacuum system of a mass spectrometer, comprising the following steps:

[0141] Obtain the pump model database and the vacuum requirement values ​​for each zone in the mass spectrometer vacuum system;

[0142] Based on the gas flow behavior modeling method in Example 1, a gas flow behavior model in the mass spectrometer vacuum system is obtained;

[0143] Based on the pump model database, vacuum requirements, and gas flow behavior models, pumps for each section of the mass spectrometer are selected.

[0144] It should be noted that the pump model database can be a database built by staff based on the existing pump equipment on the market. It includes the pump model and the maximum vacuum, minimum residual pressure, pump utilization rate and rated pumping speed for each model.

[0145] Specifically, in the vacuum system of a thermal ionization mass spectrometer, the zones include the ion source zone, the analysis zone, and the detector zone. The ion source 12 and the ion lens zone (i.e., the ion source zone) require a high vacuum, typically around 10. -6 Up to 10 -9 Within the mbar range. The ion source region has specific vacuum requirements, such as rapid evacuation and recovery speeds, stability, and adequate vacuum monitoring. Additionally, the vacuum requirements for the analysis and detector regions are typically around 10 mbar. -8 Up to 10 -10 mbar falls within the ultra-high vacuum range. To further illustrate, the vacuum requirement for the ion source region of a vacuum system is 2 × 10⁻⁶ mbar. -8 mbar; the required vacuum level in the analysis zone is 7 × 10⁻⁶ mbar. -9 mbar, the required vacuum level in the detector area is 2×10⁻⁶ mbar. -9 .

[0146] Then, based on the pump model database, vacuum requirements, and gas flow behavior models, the pumps for each section of the mass spectrometer are selected, specifically including:

[0147] Based on the vacuum requirement value of the target zone, select a pump that meets the first preset condition from the pump model database;

[0148] The effective pumping speed of the pump is obtained based on the gas flow behavior model;

[0149] Based on the pump's effective pumping speed, select the pump that meets the second preset condition from the pumps that meet the first preset condition; this yields the target pump model. Repeat the above steps until the pump selection for all zones is completed.

[0150] Specifically, the first preset condition is: the pump's maximum vacuum degree is less than or equal to the pump's utilization rate multiplied by the pump's vacuum parameters, or the pump has a minimum residual pressure. The second preset condition is: the pump's rated pumping speed is greater than or equal to the effective pumping speed.

[0151] In other words, the pump selected for this vacuum system should meet two conditions:

[0152] 1) The first preset condition is:

[0153] P max ≤K×P

[0154] Among them, P max Where K is the pump's maximum vacuum; K is the pump's utilization rate; and P is the required vacuum level of the pump (i.e., the required vacuum level for the zone). K is generally chosen to be no more than 0.5. If this condition is not met, then a pump with minimum residual pressure must be selected.

[0155] It should be noted that the pump's maximum vacuum degree P max In essence, it refers to the lowest air pressure value that the pump can achieve in a given zone during operation; the vacuum requirement value P is the lowest air pressure value required for that zone; in other words, the higher the vacuum level, the lower the air pressure value. The pump utilization rate K is a parameter less than 0.5, therefore, K serves as a coefficient for the vacuum requirement value P. The pump utilization rate K can range from 0.1 to 0.4, for example: 0.1, 0.2, 0.3, or 0.4.

[0156] 2) The second preset condition is:

[0157] S R ≥S

[0158] That is, the rated pumping speed of the selected vacuum pump must be greater than or equal to the calculated value of the vacuum pump pumping speed. Wherein, S R S is the pump's rated pumping speed, and S is the pump's effective pumping speed.

[0159] Taking the analysis zone as an example, the pump selection steps are explained: the vacuum requirement for the analysis zone is 10. -8 When K is set to 0.4, the maximum vacuum level of the pump must be less than or equal to 4 × 10⁻⁴. -9 Filter from the pump model database to find all pumps with a maximum vacuum of 4×10⁻⁶. -9The pump model is determined first, and then, from the pump models that meet the first preset condition, the pump model with a rated pumping speed greater than the effective pumping speed is selected as the target pump model, thus completing the pump selection for the analysis area. The pump selection process for the ion source area and detector area is similar and will not be described in detail here.

[0160] In summary, the design method of the mass spectrometer vacuum system in this embodiment, based on the simulation of gas flow behavior, studied the performance influencing factors of each component in the vacuum system, such as the type, layout, and number of pumps, and used more efficient and compact vacuum pump technology to optimize the realization of gradient vacuum and improve vacuum extraction speed and stability.

[0161] Example 3

[0162] This embodiment presents a specific example of a design method for a mass spectrometer vacuum system.

[0163] In the process of designing the vacuum system for a mass spectrometer, the first step is to summarize and model the flow patterns of the gas in the vacuum pipeline.

[0164] The following is a detailed explanation of the simulation process for the gas molecule motion behavior and pump selection in this vacuum system:

[0165] The design process of the vacuum system of the intrinsic spectrometer can be realized using existing simulation software (such as fluid simulation software such as moflow and FLUNET).

[0166] 1. Based on the actual thermal ionization mass spectrometer design scheme, establish a high-precision three-dimensional model and a gas flow path model, such as... Figure 4 As shown, a geometric model of the vacuum system of the thermal ionization mass spectrometer is established and then imported into the simulation software.

[0167] 2. In the gas molecule motion simulation software, set relevant parameters (i.e., initial solution parameters), including: pump position (i.e., initial pump setting position), pump extraction speed (i.e., initial pump setting speed), gas leakage rate at each flange, material desorption parameters, etc. Simultaneously, call the gas flow behavior model established in Example 1 through the simulation software. The gas flow behavior model is described as follows:

[0168] The vacuum chamber 8 of a thermal ionization mass spectrometer has different vacuum requirements for different regions depending on their function. Therefore, the type, number, and layout of the pumps must ensure that the entire mass spectrometer maintains a gradient-stable vacuum environment. The ion source 12 and the ion lens region require high vacuum, typically around 10. -6 Up to 10 -9 The vacuum level is within the range of mbar. Furthermore, the ion source region has specific requirements for vacuum, such as rapid evacuation and recovery speed, stability, and adequate vacuum monitoring. The vacuum level in the analysis and detector regions is typically around 10 mbar.-7 Up to 10 - 9 mbar is in the ultra-high vacuum range.

[0169] Furthermore, when selecting the pump placement location for this vacuum system, it is necessary to simulate and evaluate the gas behavior inside the system. Generally, gas flow states can be categorized into turbulent flow, viscous flow, molecular flow, and transitional flow states between them. In turbulent flow, frictional force (gas viscosity η), mass inertia (proportional to gas density ρ), flow velocity v, and cross-sectional area d are used for evaluation. The evaluation formula is as follows:

[0170]

[0171] Where Re is the Reynolds number, when Re > 4000 it is turbulent flow; when Re < 2300 it is viscous flow.

[0172] Viscous flow and molecular flow, as well as their transition states, are simulated using the Knudsen number. The Knudsen number is expressed as follows:

[0173]

[0174] Where p is pressure, Kn is Knudsen number, Kn > 0.5 is molecular flow, Kn < 0.01 is viscous flow, and 0.01 < Kn < 0.5 is transition state.

[0175] Furthermore, when the vacuum container is evacuated by the vacuum pump, the volume of gas flowing through the pump inlet per unit time (the volumetric flow rate at the pump inlet) is the pumping speed S, and the expression for the pumping speed is:

[0176]

[0177] Where S is the pumping speed, usually expressed in volume units (such as cubic meters per second), representing the volume of gas flowing into the system per unit time. The volumetric flow rate at the gas inlet represents the volume of gas passing through the inlet per unit time.

[0178] During the vacuuming process, gas flows out of the chamber, through the pipe, and towards the pump, requiring a pressure difference. The expression for the pressure difference is as follows:

[0179] Δp=p 真空腔 -p 泵入口 =p c -p in

[0180] This flow process involves gas flow resistance. Due to this resistance, the effective pumping speed of the pump is usually not equal to S; therefore, S needs to be multiplied by a correction factor. The expression for the effective pumping speed is as follows:

[0181]

[0182] In simulating gas movement, for complex mass spectrometers, the relationship between gas flow and flow resistance can be equivalent to the relationship between current and resistance. Depending on the connection method between pipes, the flow resistance can be calculated similarly to that of resistors in series or parallel.

[0183] It should also be noted that during the simulation, the flow resistance of a portion of the volume or wall surface may sometimes need to be defined. In other words, during the simulation, it may be necessary to define the wall friction force so that the software can calculate the gas flow resistance.

[0184] 1. Darcy-Wiesbach equation

[0185] This equation is used to calculate the pressure loss (ΔP) in the pipeline:

[0186]

[0187] in:

[0188] ΔP is the pressure loss (Pa);

[0189] f is the Darcy friction factor, which depends on the Reynolds number (Re) and the relative roughness of the pipe;

[0190] L is the pipe length (m);

[0191] D is the inner diameter of the pipe (m);

[0192] ρ is the density of the gas (kg / m3);

[0193] v is the gas velocity (m / s).

[0194] 2. Calculation of Darcy friction factor f

[0195] The calculation of the friction factor depends on the type of flow:

[0196] For laminar flow (when Reynolds number Re < 2000), the friction factor f can be directly calculated using the following formula:

[0197]

[0198] In turbulent flow (Re>4000), the friction factor f can be calculated using the Colebrook-White equation or the approximate Swamee-Jain equation, which is related to the pipe roughness and Reynolds number.

[0199] The Swamee-Jain equation is a commonly used approximation formula:

[0200]

[0201] in:

[0202] ∈ is the roughness (m) of the inner wall of the pipe. For stainless steel pipes, the roughness is usually around 0.0015 mm.

[0203] 3. Select the mass spectrometer wall surface where the pressure needs to be observed or create a cross section in the model to calculate the flux. Set the mesh generation method according to the finite element method and set the pressure observation direction of the cross section.

[0204] 4. Run the simulation software. The simulation software solves the gas flow behavior model based on the above solution parameters, and obtains and records the real-time wall pressure heat map, cross-sectional pressure curve, and gas molecule motion behavior inside the model.

[0205] 5. Set the pressure threshold to stop the simulation, record the time elapsed from the start to the end of the simulation, and evaluate the stability, effectiveness, and responsiveness of the vacuum system of the model.

[0206] This concludes the initial solution calculation process. The next iteration calculation will then be performed based on the relevant parameters obtained from the solution.

[0207] 6. The subsequent iterative calculation process is as follows: First, adjust the position of the pump in the model and reselect the pump (i.e., adjust parameters such as pumping speed). Then, input the results back into the simulation software for calculation to obtain the real-time wall pressure heat map, cross-sectional pressure curve, and gas molecule motion behavior inside the model after iteration. Observe the trends of the heat map and curve changes, compare the time elapsed from the start of the simulation to the end of the simulation, analyze the differences in the vacuum system under different models, and select the optimal model scheme.

[0208] Furthermore, the pump selected for this vacuum system should meet two conditions:

[0209] 1) The first preset condition is:

[0210] P max ≤K×P

[0211] Among them, P max Where K is the pump's maximum vacuum; K is the pump's utilization rate; and P is the pump's actual required vacuum. K is generally chosen to be no more than 0.5. If this condition is not met, then a pump with minimal residual pressure must be selected.

[0212] 2) The second preset condition is:

[0213] S R ≥S

[0214] In other words, the rated pumping speed of the selected vacuum pump must be greater than or equal to the calculated vacuum pump pumping speed.

[0215] Example 4

[0216] The present invention also discloses a modeling device for gas flow behavior in a vacuum system of a mass spectrometer, comprising: a first acquisition unit, a first modeling unit, a second modeling unit, and a model unit.

[0217] The system comprises the following components: a first acquisition unit, used to acquire partition information of multiple zones within the vacuum system of the mass spectrometer; a first processing unit, electrically connected to the first acquisition unit, used to establish gas flow regime models for each zone based on the partition information; a second modeling unit, electrically connected to both the first acquisition unit and the first modeling unit, used to establish effective pumping rate models for each zone based on the partition information and the gas flow regime models for each zone; and a first processing unit, electrically connected to the second modeling unit, used to combine the effective pumping rate models of each zone to obtain a gas flow behavior model within the vacuum system of the mass spectrometer.

[0218] It should be noted that this device is used to execute the modeling method for gas flow behavior in the mass spectrometer vacuum system of Example 1. This device can be implemented using software modules. The first acquisition unit can be a database module; after obtaining partition information for multiple zones in the vacuum system, the operator uploads this partition information to the database. The first modeling unit is electrically connected to the first acquisition unit and can access the partition information in the database.

[0219] Specifically, the second modeling unit includes an analysis module and an execution module. The analysis module is used to analyze the airflow state in each zone based on the gas characteristic parameters and geometric parameters in the zone information. The execution module is used to establish a gas flow pattern model for each zone based on the airflow state in each zone.

[0220] In summary, this modeling device can simulate and evaluate the behavior of gases inside a vacuum system, summarize the behavior of gases in a vacuum system, especially the flow in the transition region between pumps, optimize the calculation of gas flow resistance between pipes and between pipes and pumps, and provide certain design references for the design of vacuum systems for mass spectrometers.

[0221] Example 5

[0222] The present invention also discloses a design system for a mass spectrometer vacuum system, comprising: a second acquisition unit, a second processing unit, and a modeling device for gas flow behavior in the mass spectrometer vacuum system of Example 4.

[0223] The second acquisition unit is used to acquire a pump model database and the vacuum requirement values ​​for each zone in the mass spectrometer vacuum system. The modeling device is used to establish a gas flow behavior model in the mass spectrometer vacuum system, specifically, to obtain the gas flow behavior model in the mass spectrometer vacuum system according to the gas flow behavior modeling method in Example 1. The second processing unit is electrically connected to both the second acquisition unit and the modeling device, and is used to select pumps for each zone in the mass spectrometer based on the pump model database, vacuum requirement values, and gas flow behavior model.

[0224] It should be noted that this system is used to execute the design method of the mass spectrometer vacuum system in Example 2. This system can be implemented using software modules. The second acquisition unit can be a database module containing a pump model database and a vacuum requirement value database. The pump models selected by the operator are uploaded to this database module to form the pump model database. This pump model database also stores the vacuum requirement values ​​for each zone. For example, the vacuum requirement value for the ion source zone is 10. -6 The vacuum level requirement for the analysis and detector areas is 10. -8 .

[0225] By employing the modeling apparatus described in Example 4 to perform the modeling method for gas flow behavior, the calculation of gas flow resistance between pipes and between pipes and pumps is optimized, providing a certain design reference for the design of the vacuum system of the mass spectrometer.

[0226] Then, the second processing unit can be a computer software module used to select the pump in the mass spectrometer based on the pump model database, vacuum requirements, and gas flow behavior model.

[0227] In summary, the design of the vacuum system for the intrinsic spectrometer was based on the simulation of gas flow behavior. The study investigated the performance influencing factors of each component in the vacuum system, such as the type, layout, and number of pumps, thereby achieving better pump selection, optimizing the implementation of gradient vacuum, and improving vacuum extraction speed and stability.

[0228] Example 6

[0229] The present invention also discloses a mass spectrometer vacuum system, comprising: an ion source region, an analysis region, a detector region, an oil-free rotary vane vacuum pump 1, a turbomolecular pump 2, and an ion sputtering pump 3.

[0230] The ion source region, analysis region, and detector region are sequentially connected. Both the oil-free rotary vane vacuum pump 1 and the turbomolecular pump 2 are connected to the ion source region, and the ion sputtering pump 3 is connected to the analysis region. The oil-free rotary vane vacuum pump 1, turbomolecular pump 2, and ion sputtering pump 3 were selected using the design method for the mass spectrometer vacuum system in Example 2.

[0231] Specifically, the vacuum system consists of a vacuum chamber 8, an oil-free rotary vane vacuum pump 1, a turbomolecular pump 2, an ion sputtering pump 3, a vacuum isolation valve 4, a vacuum sensor 5, a sealing flange 6, and a seal 7 (which can be a copper gasket or a silver wire seal; typically, a copper gasket is used for the seal of component 7, but using a silver wire seal instead of a copper gasket can achieve a lower leakage rate).

[0232] The selection and placement of each pump must meet the requirement that the vacuum of the 12-chamber ion source be better than 5 × 10⁻⁶. -6 Pa(5×10 -8 mbar), the analytical chamber is better than 3×10 -7 Pa(3×10 -9 mbar).

[0233] Specifically, the oil-free rotary vane vacuum pump 1 is used for pre-vacuuming in the sample introduction system. When the pump is started, the vacuum is usually poor and the gas flow in the vacuum chamber 8 is turbulent. Therefore, the pump needs to be placed at the very front to quickly complete the transition to viscous flow using a high pumping speed.

[0234] The turbomolecular pump 2 is used to maintain a high vacuum in the sample introduction system and ion source 12, and is also used for vacuum pre-evacuation after the analysis chamber is emptied. The pump is positioned near the oil-free rotary vane vacuum pump 1, where the gas flows in a viscous manner. This position ensures that the probability of gas flow collision is reduced, flow resistance is decreased, and the transition to molecular flow is completed quickly.

[0235] Ion sputtering pump 3 is used to ensure a high vacuum in the analysis region. This device is based on the absorption of gas by a cathode material (titanium) during high-voltage discharge within a magnetic field. The pump is positioned near the turbomolecular pump 2, and multiple pumps can be added in the middle and rear sections as needed when the cavity is large. In this invention, the gas molecule flow behavior and vacuum requirements within the cavity are comprehensively calculated and simulated. Two ion sputtering pumps 3 are selected, located between the vacuum isolation valve and the flying flat tube, and between the flying flat tube and the detector cavity 15, respectively.

[0236] Vacuum isolation valve 4 can disconnect and isolate the ion source 12 chamber from the high vacuum area of ​​the analysis chamber. This ensures the cleanliness and dryness of the high vacuum area of ​​the analysis system during cleaning, maintenance, and sample replacement of the ion source 12.

[0237] The ion sputtering pump, valves, and other components can withstand high-temperature baking treatment at 250℃ to 300℃.

[0238] Vacuum sensors 5 are installed on the pump's suction pipe, the ion source 12 chamber, and the ion flight pipeline. The vacuum sensor 5 connected to the pump's suction pipe is used to monitor the pre-vacuum pressure in real time and to determine whether the turbomolecular pump 2 can be activated. The vacuum sensor 5 connected to the ion source 12 chamber is used to monitor whether the vacuum isolation valve can be opened after sample change and whether the lens high pressure can be activated. The vacuum sensor 5 connected to the ion flight pipeline is used to determine the cleanliness of the ion flight path during sample measurement.

[0239] During the initial assembly and vacuuming process of the thermal ionization mass spectrometer, a baking process was implemented. Heating tape was wrapped around the exterior of the chamber for baking, using the high temperature to expel gases desorbed from the material surface, gases diffusing from the material interior to the surface, and gases permeating into the vacuum through the chamber walls. The oil-free rotary vane vacuum pump 1 and turbomolecular pump 2 were activated for evacuation, while the baking function of the ion sputtering pump 3 was used simultaneously.

[0240] The following will provide a further explanation of each part of this vacuum system:

[0241] like Figure 1 As shown, this embodiment provides a vacuum system design and implementation method for a thermal ionization mass spectrometer, including: a vacuum chamber 8, an oil-free rotary vane vacuum pump 1, a turbomolecular pump 2, an ion sputtering pump 3, a vacuum isolation valve 4, a vacuum sensor 5, a sealing flange 6, and a sealing element 7 (which can be a sealing copper gasket or a sealing silver wire).

[0242] Oil-free rotary vane vacuum pump 1 is used for pre-vacuuming in the sample introduction system. The selected oil-free rotary vane vacuum pump 1 has a maximum pressure of 0.67 Pa and a pumping rate of 200 L / min. Turbomolecular pump 2 is used to maintain a high vacuum in ion source 12 and for pre-vacuuming after vacuum breaking in the analysis chamber. Turbomolecular pump 2 has a pumping rate of 255 L / s and a maximum pressure of 1 × 10⁻⁶ Pa. -10 mbar, rotation speed 60000 r / min. Ion sputtering pump 3 is used to ensure high vacuum in the analysis zone. The operating speed of ion sputtering pump 3 is approximately 160 L / s (at 1×10 mbar). -6 The welded housing of ion sputtering pump 3 is made of stainless steel, forming a sealed volume. The nominal diameter of its inlet pipe flange is 100 mm. A connecting pipe with a nominal flange diameter of 16 mm is welded to the housing for connecting to the high-pressure vacuum input. The anode voltage of ion sputtering pump 3 can be selected by the user as 3kV, 5kV, or 7kV. Ion sputtering pump 3 itself can be baked at ≤300℃. After pre-evacuation using an oil-free vacuum pump and turbomolecular pump 2, ion sputtering pump 3 reaches the start-up condition. At this time, ion sputtering pump 3 is turned on to absorb the remaining gas inside the pipeline. Ion sputtering pump 3 can ensure that the pressure in the analysis chamber does not exceed 3 × 10⁻⁶. -7 Pa(3×10-9 mbar).

[0243] like Figure 2 As shown, in this embodiment, the vacuum isolation valve 4 consists of a slide valve connecting rod 9, a slide valve bellows 10, a guide sleeve 11, a sealing ring 17, and other accessories. It is sealed between the ion source 12 cavity and the flight tube of the thermal ionization mass spectrometer via a sealing flange 6. It is used to isolate the high vacuum region of the ion source 12 and ion lens from the ultra-high vacuum region of the analyzer and detector.

[0244] Among them, the slide valve connecting rod 9 is used to connect to the external push rod and to control the movement of the valve.

[0245] The slide valve bellows 10 provides a flexible seal during valve movement and allows for a degree of deformation to accommodate the valve's motion. The slide valve bellows 10 is typically made of a soft, elastic metallic material, such as stainless steel. When the valve is closed, the slide valve bellows 10 provides an effective seal to prevent gas leakage. Since the valve requires some movement during opening and closing, the bellows structure of the slide valve bellows 10 allows it to accommodate this movement. The slide valve bellows 10 also absorbs vibrations and shocks caused by airflow or other motions, helping to prevent damage to the valve and other components. During the cavitation process in the ion source 12 chamber, the pressure difference with the downstream end of the mass spectrometer may be significant; the structural design of the slide valve bellows 10 enables it to withstand these pressure differences.

[0246] The primary function of the guide sleeve 11 is to ensure that the valve moves along the correct trajectory when opening and closing. This helps maintain the stability and accuracy of the valve, ensures proper alignment of the sealing surfaces, and prevents leakage. Simultaneously, the guide sleeve 11 is made of a low-friction material to reduce friction during valve movement. This helps extend the valve's lifespan and ensures smooth operation.

[0247] The sealing ring 17 is used to provide a seal when the valve is closed, preventing gas leakage. The sealing ring 17 fills the gap between the valve and the valve seat, ensuring a tight seal. The sealing ring 17 used in mass spectrometers typically needs to be temperature-resistant, corrosion-resistant, radiation-resistant, maintain elasticity, have a long service life, and provide good sealing performance.

[0248] The ion flight tube utilizes a one-piece die-casting technology. Commercially available thermal ionization mass spectrometers typically use welding techniques for their flight tubes, which often result in connection points that can be potential sources of leakage in the vacuum system. One-piece die-casting creates a seamless, more uniform, and continuous structure, reducing potential leakage points and improving overall strength. Furthermore, it produces a more uniform surface and a smaller internal volume, contributing to improved sealing. Using a single material for die casting completely eliminates the welding problems between different materials, significantly improving the material compatibility and long-term stability of the vacuum system.

[0249] Furthermore, in this embodiment, the detector cavity 15 and the detector cavity cover 16 are sealed with silver wire. Silver has good plasticity and ductility, its coefficient of thermal expansion is not much different from that of stainless steel, and it is cost-effective and easy to weld, making it a good sealing material. In larger or non-standard flange seals, the leakage rate after assembly using silver wire is much lower than other sealing methods.

[0250] The Faraday cup moving device within detector cavity 15 is controlled by a slide rail, with its controller located inside the cavity. Internal placement of the controller reduces the airtightness requirements of external connections, thereby lowering the risk of gas leakage. Furthermore, in a vacuum environment, heat conduction and convection are virtually eliminated, resulting in more stable temperature control and contributing to the stable operation of the controller.

[0251] Vacuum sensors 5 are installed on the pump's suction pipe, the ion source 12 chamber, and the ion flight pipeline. The vacuum sensor 5 connected to the pump's suction pipe is used to monitor the pre-vacuum pressure in real time and to determine whether the turbomolecular pump 2 can be activated. The vacuum sensor 5 connected to the ion source 12 chamber is used to monitor whether the vacuum isolation valve can be opened after sample change and whether the lens high pressure can be activated. The vacuum sensor 5 connected to the ion flight pipeline is used to determine the cleanliness of the ion flight path during sample measurement.

[0252] The following will describe the operation procedure of this vacuum system in detail:

[0253] 1. Vacuum system operation procedure:

[0254] Confirm that all connections on the instrument are correct and that the seals are secure.

[0255] Turn on the oil-free rotary vane vacuum pump 1 to evacuate ion source chamber 12 to a primary vacuum;

[0256] When the vacuum sensor 5 connected to the pump extraction pipe shows a vacuum of <10Pa, start the turbomolecular pump 2.

[0257] The vacuum sensor 5 connected to the ion source 12 chamber shows a vacuum < 1 × 10⁻⁶. -4After Pa, the vacuum sensor 5 connected to the ion flight pipeline is activated.

[0258] Vacuum sensor 5 connected to the ion flight pipeline shows a vacuum < 1 × 10⁻⁶. -4 After Pa, turn on the ion pump and select the high-pressure setting according to the actual situation.

[0259] 2. Operation procedure for the vacuum system of the 12-chamber ion source (maintenance and sample change process):

[0260] Close the vacuum isolation valve

[0261] Confirm that all connections on the instrument are correct and that the seals are secure.

[0262] Turn off turbomolecular pump 2;

[0263] After the turbomolecular pump 2 reaches 0 speed, turn off the oil-free rotary vane vacuum pump 1 and vent the gas.

[0264] Open ion source chamber 12 to complete sample change.

[0265] Turn off the ion source chamber 12 and confirm that all connections of the instrument are correct and the seals are good.

[0266] Turn on the oil-free rotary vane vacuum pump 1 to evacuate ion source chamber 12 to a primary vacuum;

[0267] When the vacuum sensor 5 connected to the pump extraction pipe shows a vacuum of <10Pa, start the turbomolecular pump 2.

[0268] Once the vacuum sensor 5 connected to the ion source 12 chamber displays a vacuum of <1×10-4Pa, the vacuum isolation valve is opened.

[0269] 3. Baking program:

[0270] Before baking the vacuum system, the entire instrument must be assembled and powered on, and a preliminary vacuum test must be performed using a molecular pump, with the vacuum not exceeding 5 × 10⁻⁶. -4 Pa.

[0271] Before baking, remove the analysis electromagnet, wrap the vacuum chamber 8, flight pipe and connecting flange with aluminum foil, turn on the molecular pump and oil-free rotary vane vacuum pump 1, and turn off the ion pump.

[0272] The baking process utilizes multiple sets of self-temperature-controlled, high-quality insulating heating tapes wrapped around the chambers and flight tubes. The chambers from detector 15 to ion source 12 are sequentially heated and baked, with the baking temperature set according to the specific temperature requirements of each component. The ion pump baking mode is also activated. The detector baking temperature is 100℃, the flight tube baking temperature is 130℃, and the ion source 12 chamber baking temperature is 110℃. The overall baking time is 24 hours, continuing until the vacuum level no longer decreases.

[0273] After baking, gradually cool down from ion source chamber 12 to receiver chamber (30 minutes apart), turn off the ion pump baking mode, and remove the heating belt and aluminum foil.

[0274] Maintain the evacuation of the molecular pump and ion pump for at least 12 hours and record the vacuum level of the vacuum chamber.

[0275] The following is a detailed explanation of the simulation process for the gas molecule motion behavior and pump selection in this vacuum system:

[0276] 1. Based on the actual thermal ionization mass spectrometer design scheme, establish a high-precision three-dimensional model and a gas flow path model.

[0277] 2. In the gas molecule motion simulation software, set relevant parameters, including: pump position, pump extraction speed, gas leakage rate at each flange, material desorption parameters, etc.

[0278] 3. Select the mass spectrometer wall surface where the pressure needs to be observed or create a cross section in the model to calculate the flux. Set the mesh generation method according to the finite element method and set the pressure observation direction of the cross section.

[0279] 4. Run the simulation software to obtain and record real-time wall pressure heat map, cross-sectional pressure curve, and gas molecule motion behavior inside the model.

[0280] 5. Set the pressure threshold to stop the simulation, record the time elapsed from the start to the end of the simulation, and evaluate the stability, effectiveness, and responsiveness of the vacuum system of the model.

[0281] 6. Among them, the software simulation calculation can obtain the heat map of the relationship between wall pressure and pumping time, the curve of the relationship between the average interface pressure and pumping time, the ideal ultimate vacuum value, and the pumping time required to reach the ideal ultimate vacuum value.

[0282] 7. Adjust parameters such as the pump position and pumping speed in the model, observe the heat map and curve change trends, compare the time elapsed from the start of the simulation to the end of the simulation, analyze the differences in the vacuum system under different models, and select the optimal model scheme.

[0283] This vacuum system has the following advantages:

[0284] 1. Based on the simulation of gas flow behavior, this system studies the performance influencing factors of various components in the vacuum system, such as the type, layout, and number of pumps. It uses more efficient and compact vacuum pump technology to optimize the realization of gradient vacuum and improve vacuum extraction speed and stability.

[0285] 2. During the manufacturing and installation of components, this vacuum system employs special casting and sealing technologies, which improves the sealing performance of the vacuum system, effectively reduces potential leakage points, reduces the need for routine maintenance, and improves the stability of later use.

[0286] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for modeling gas flow behavior in a vacuum system of a mass spectrometer, characterized in that, The vacuum system of the mass spectrometer has multiple partitions, which are connected sequentially. The method includes the following steps: Obtain partition information for multiple zones in the vacuum system of the mass spectrometer; Based on the partition information, gas flow models for each partition are established. Based on the partition information and the gas flow pattern model of each partition, an effective pumping speed model for each partition is established. The effective pumping speed model includes: ; In the formula, The leakage rate within the partition; For the pressure within the system; For effective pumping speed; It is a Knudsen number; For the correction term that depends on the Knudsen number; This is the slip correction factor; This refers to the pump's nominal pumping speed. It is the transition flow correction factor; A correction function related to the Reynolds number; Furthermore, the effective pumping speed model also includes: ； In the formula, This refers to the air pressure at the pump inlet. S represents the internal air pressure value of the zone; S represents the pumping speed. For effective pumping speed; This is the volumetric flow rate at the pump inlet; By combining the effective pumping rate models of each partition, a gas flow behavior model in the vacuum system of the mass spectrometer is obtained.

2. The method according to claim 1, characterized in that, The partitioning information includes gas characteristic parameters, geometric parameters, and pumping speed characteristic parameters; The gas characteristic parameters include: gas viscosity. Gas density Gas flow rate air pressure value ; The geometric parameters include: the equivalent diameter of the cross-section of the partitioned pipe. ; The pumping speed characteristic parameters include: pump inlet air pressure, air pressure inside the zone, volumetric flow rate at the pump inlet, and leakage rate inside the zone.

3. The method according to claim 2, characterized in that, The steps include: establishing gas flow patterns for each partition based on the partition information, including: Based on the gas characteristic parameters and geometric parameters in the zoning information, the airflow state in each zoning zone is analyzed; Based on the airflow conditions in each zone, gas flow patterns models for each zone are established.

4. The method according to claim 3, characterized in that, The steps include: establishing gas flow pattern models for each zone based on the airflow conditions in each zone, including: In sequence, determine whether the airflow state in each zone is the first flow state or the second flow state: When the airflow state in the partition is the first flow state, the gas flow state model adopts the Reynolds number expression, and the first flow state is the turbulent state; When the airflow state in the partition is the second flow state, the gas flow state model adopts the Knudsen number expression, and the second flow state is viscous flow, molecular flow or transitional flow state.

5. The method according to claim 4, characterized in that, The Reynolds number is expressed as follows: In the formula, Re is the Reynolds number; For gas viscosity; The density of the gas; This refers to the gas flow rate; The Knudsen number is expressed as follows: In the formula, It is a Knudsen number; This refers to the gas flow rate; For gas viscosity; This refers to the air pressure value. The equivalent diameter of the cross-section of the zonal pipe.

6. A design method for a vacuum system of a mass spectrometer, characterized in that, Includes the following steps: Obtain the pump model database and the vacuum requirement values ​​for each zone in the mass spectrometer vacuum system; The gas flow behavior modeling method according to any one of claims 1-5 is used to obtain a gas flow behavior model in the vacuum system of a mass spectrometer. Based on the pump model database, the vacuum requirement value, and the gas flow behavior model, the pumps for each section of the mass spectrometer are selected.

7. The method according to claim 6, characterized in that, The steps include: selecting pumps for each section of the mass spectrometer based on the pump model database, the vacuum requirement value, and the gas flow behavior model; specifically, this includes: Based on the vacuum requirement value of the target zone, select a pump that meets the first preset condition from the pump model database; Based on the gas flow behavior model, the effective pumping speed of the pump is obtained; Based on the effective pumping speed of the pump, select the pump that meets the second preset condition from the pumps that meet the first preset condition, and thus obtain the target pump model. Repeat the above steps until the pump selection for all zones is completed.

8. The method according to claim 7, characterized in that, The first preset condition is: the maximum vacuum degree of the pump is less than or equal to the pump utilization rate multiplied by the vacuum degree requirement value, or the pump has a minimum residual pressure; The second preset condition is: the pump's rated pumping speed is greater than or equal to the effective pumping speed.

9. A modeling device for gas flow behavior in a vacuum system of a mass spectrometer, characterized in that, include: The system comprises a first acquisition unit, a first modeling unit, a second modeling unit, and a first processing unit; The first acquisition unit is used to acquire partition information of multiple partitions in the vacuum system of the mass spectrometer; The first modeling unit is electrically connected to the first acquisition unit and is used to establish gas flow models for each partition according to the partition information. The second modeling unit is electrically connected to the first acquisition unit and the first modeling unit, respectively, and is used to establish an effective pumping speed model for each partition based on the partition information and the gas flow pattern model of each partition. The effective pumping speed model includes: ; In the formula, The leakage rate within the partition; For the pressure within the system; For effective pumping speed; It is a Knudsen number; For the correction term that depends on the Knudsen number; This is the slip correction factor; This refers to the pump's nominal pumping speed. It is the transition flow correction factor; A correction function related to the Reynolds number; Furthermore, the effective pumping speed model also includes: ； In the formula, This refers to the air pressure at the pump inlet. S represents the internal air pressure value of the zone; S represents the pumping speed. For effective pumping speed; This is the volumetric flow rate at the pump inlet; The first processing unit is electrically connected to the second modeling unit and is used to combine the effective pumping speed models of each partition to obtain a gas flow behavior model in the vacuum system of the mass spectrometer.

10. The apparatus according to claim 9, characterized in that, The first processing unit includes an analysis module and an execution module. The analysis module is used to analyze the airflow state in each zone based on the gas characteristic parameters and geometric parameters in the zone information. The execution module is used to establish a gas flow pattern model for each zone based on the airflow state in each zone.

11. A design system for a vacuum system of a mass spectrometer, characterized in that, include: The second acquisition unit, the second processing unit, and the modeling device for gas flow behavior in the vacuum system of the mass spectrometer as described in claim 9 or 10; The second acquisition unit is used to acquire the pump model database and the vacuum requirement values ​​of each partition in the mass spectrometer vacuum system; The modeling device for gas flow behavior in the vacuum system of the mass spectrometer is used to establish a model of gas flow behavior in the vacuum system of the mass spectrometer. The second processing unit is electrically connected to the second acquisition unit and the gas flow behavior modeling device in the vacuum system of the mass spectrometer, respectively, and is used to select pumps for each section of the mass spectrometer according to the pump model database, the vacuum requirement value and the gas flow behavior model.

12. A vacuum system for a mass spectrometer, characterized in that, include: Ion source region, analysis region, detector region, oil-free rotary vane vacuum pump, turbomolecular pump and ion sputtering pump; The ion source region, the analysis region, and the detector region are connected in sequence. The oil-free rotary vane vacuum pump and the turbomolecular pump are both connected to the ion source region, and the ion sputtering pump is connected to the analysis region. The oil-free rotary vane vacuum pump, the turbomolecular pump, and the ion sputtering pump are selected using the design method of the mass spectrometer vacuum system according to any one of claims 6-8.

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