High-speed directional molecular flow generating device and application thereof

Abstract

The invention relates to a high-speed directional molecular flow generating device and application thereof. The device comprises an air supply system, an ion source, a grid electrode assembly, a neutral pore plate and a charged particle swallowing device, the gas supply system is communicated with the gas inlet end of the ion source through a pipeline and provides neutral gas for the ion source; the ion source is used for ionizing the neutral gas into plasma, and the gas outlet end of the ion source is sequentially connected with the grid electrode assembly, the neutral pore plate and the charged particle swallowing device in series; the grid electrode assembly is used for extracting ions, accelerating ions and focusing ions; the neutral pore plate is grounded and is used for enabling passing ion beams to be subjected to an Auger process and converting ions into neutral molecules; and the charged particle swallowing device is used for absorbing unconverted ions and drift electrons. According to the invention, the complexity is low, the generated high-speed oriented molecular flow has good collimation, and an important experimental basis is provided for development and ground calibration of a space vacuum measuring instrument.

Description

Technical Field

[0001] The invention relates to the technical field of space vacuum measurement, and in particular to a high-speed directional molecular flow generating device and application thereof. Background Art

[0002] The execution of aerospace missions such as precise attitude and orbit control of spacecraft and analysis of planetary atmosphere can be achieved through in-situ measurement of gas molecules around spacecraft. However, the spacecraft is faced with a non-equilibrium high-speed directional molecular flow during operation. Unlike the equilibrium vacuum environment on the ground, the high-speed directional molecular flow exhibits anisotropy and unidirectional velocity characteristics. Its velocity distribution does not satisfy the Maxwell distribution law and cannot be measured by conventional means. At the same time, with the development of aerospace technology, the research and development of miniaturized space measurement instruments with light weight and low power consumption has become a new research hotspot. Therefore, the development of space high-speed directional molecular flow measurement and analysis instruments is of great significance. In the development of such measuring instruments, an indispensable prerequisite is to establish the calibration capability of space high-speed directional molecular flow in the laboratory so as to calibrate the measuring instrument and evaluate the measurement uncertainty. At present, many foreign studies have applied molecular beam technology to the calibration of space detection instruments. For example, the Return Flux Experiment (REFLEX) in the United States uses a calibration device equipped with an ion source, an electrostatic analyzer and a Mattauch-Herzog mass analyzer to calibrate it. Compared with foreign countries, China still has many deficiencies in the generation and calibration of low-energy molecular beams such as space directional molecular flow. For example, the calibration of the neutral particle analyzer equipped on my country's "Tianwen-1" Mars probe was led by the University of Bern in Switzerland. The difficulty in building a space high-speed directional molecular flow calibration test platform lies in the simulation of high-speed directional molecular flow.

[0003] The main methods of simulating high-speed directional molecular flow in the laboratory include molecular furnace, high-pressure expansion and atomic / molecular beam technology. Among them, the speed of high-speed directional beam generated by molecular furnace technology is usually less than 2km / s; the speed of high-speed directional molecular flow obtained by high-pressure expansion method can theoretically reach up to 9km / s, but the density of the beam is usually high, which is quite different from the actual flight environment of spacecraft; and molecular beam technology has long been used to simulate the directional flow environment of planetary atmosphere.

[0004] In summary, the molecular beam method is an effective way to simulate high-speed directional molecular flow in the laboratory. The idea of ​​"ionization-acceleration-neutralization-filtration" can be adopted to design a high-speed directional molecular flow generator based on an ion source. However, its principle for calibrating space measurement instruments and the speed and flux range of directional flow that it can simulate remain to be explored. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a high-speed directional molecular flow generating device and its application, which can simulate a directional molecular flow with high speed and low flux characteristics in a ground laboratory environment, and realize effective modulation of pressure by adjusting the beam speed and flux, thereby providing a calibration test basis for the research and development of space vacuum measuring instruments.

[0006] To achieve the above-mentioned purpose, the present invention provides a high-speed directional molecular flow generating device, including a gas supply system, an ion source, a grid assembly, a neutralization orifice plate and a charged particle swallower;

[0007] The gas supply system is connected to the gas inlet end of the ion source through a pipeline to provide neutral gas to the ion source;

[0008] The ion source is used to ionize the neutral gas into plasma, and the gas outlet of the ion source is connected in series with the grid assembly, the neutralization orifice plate, and the charged particle eater in sequence;

[0009] The grid assembly is used to extract ions, accelerate ions, and focus ions;

[0010] The neutralization orifice plate is grounded and used to cause the ion beam passing through to undergo an Auger process, thereby converting the ions into neutral molecules;

[0011] The charged particle eater is used to absorb unconverted ions and drift electrons.

[0012] According to a technical solution of the present invention, the gas supply system includes a gas source, a gas source valve, a pressure stabilizing chamber, a fixed flow conductance orifice element and a vacuum valve;

[0013] The gas source, the pressure stabilizing chamber and the gas inlet end of the ion source are connected in sequence, the gas source valve is arranged on the connecting pipe between the gas source and the pressure stabilizing chamber, a vacuum gauge is installed on the pressure stabilizing chamber, and the fixed flow conductance orifice element and the vacuum valve are installed on the connecting pipe between the pressure stabilizing chamber and the ion source.

[0014] According to a technical solution of the present invention, the ion source, the neutralization orifice plate and the charged particle swallower are coaxially arranged in the same housing;

[0015] The grid assembly is mounted on the housing.

[0016] According to a technical solution of the present invention, the ion source includes a cathode, a magnet coil and an anode grid;

[0017] The chamber of the housing in which the ion source is installed is a discharge chamber, at the air inlet end of the cathode discharge chamber, the magnetic coil is sleeved on the outside of the discharge chamber, and the anode grid is installed inside the discharge chamber;

[0018] The cathode is coaxially arranged with the neutralization orifice plate and the charged particle swallower.

[0019] According to a technical solution of the present invention, the grid assembly includes a screen grid and an acceleration grid;

[0020] The screen grid and the accelerating grid are sequentially arranged at the gas outlet end of the ion source.

[0021] According to a technical solution of the present invention, the charged particle swallower includes two electrode plates arranged opposite to each other, and the two electrode plates are respectively connected to a positive voltage of 500V and a negative voltage of 500V.

[0022] According to a technical solution of the present invention, it also includes a beam measurement system for evaluating the density loss in the neutralization process of an ion beam, the beam measurement system includes a Faraday cup for measuring the flux of an ion beam formed through a grid assembly, a dual-channel picoammeter for measuring the current on the neutralization aperture and the charged particle eater, a dual-probe ion beam velocity measurement device for measuring the velocity of the ion beam, and a suspension-type micro-thrust measurement device for measuring the thrust generated by a high-speed directional molecular flow.

[0023] According to a technical solution of the present invention, the suspended sheet method micro-thrust measurement device comprises a capacitor, a low friction coefficient bearing and a circular metal sheet;

[0024] The inner ring of the low friction coefficient bearing is sleeved on a stationary fixed shaft;

[0025] The circular metal sheet is vertically connected to the side of the outer ring of the low-friction bearing through a rigid connecting piece. An electrode plate is rigidly connected to the other side of the outer ring of the low-friction bearing opposite to the circular metal sheet. The electrode plate and the circular metal sheet are located on the same straight line passing through the center of the low-friction bearing. The electrode plate is arranged between the two plates of the capacitor.

[0026] According to a technical solution of the present invention, the shell is connected to the ultra-high vacuum chamber through a flange interface.

[0027] According to one aspect of the present invention, an application of a high-speed directional molecular flow generating device as described in any one of the above technical solutions is proposed for calibrating a space vacuum measuring instrument.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention proposes a high-speed directional molecular flow generating device and its application. The gas supply system provides a stable flow of neutral gas into the ion source. The neutral gas is ionized into plasma in the ion source. The ions therein are pulled out by the grid assembly and accelerated to the desired state to form an ion beam. Then the ion beam passes through the neutralization orifice plate to undergo an Auger process to be converted into a high-speed directional molecular flow. After entering the charged particle eater, the unneutralized ions in the high-speed directional molecular flow will be deflected under the action of the electric field and hit the electrode plate of the charged particle eater. In this way, a collimated and pure high-speed directional molecular flow can be obtained at the outlet. In this process, the beam measurement system can perform in-situ measurements of the characteristic parameters of the beam, such as velocity, flux, etc., so as to quantitatively analyze the pressure of the high-speed directional molecular flow.

[0030] The directional molecular flow generating device of the present invention can provide a high-speed directional molecular flow with a speed not less than 7 km / s, and the pressure of the high-speed directional molecular flow can be continuously adjusted within a certain pressure range, which meets the on-orbit operation space environment of most spacecraft.

[0031] The directional molecular flow generating device of the present invention has the characteristics of low complexity, and the generated high-speed directional molecular flow has good collimation, which provides an important experimental basis for the development of space vacuum measuring instruments and ground calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic diagram schematically shows the structure of a high-speed directional molecular flow generating device in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a charged particle swallower in one embodiment of the present invention is shown;

[0035] Figure 3 A schematic diagram showing the principle of forming an ion beam flow by a grid assembly in one embodiment of the present invention;

[0036] Figure 4 The figure schematically shows the principle diagram of measuring molecular flow conductivity using the constant volume method in one embodiment of the present invention.

[0037] Reference numerals:

[0038] 1. Gas supply system; 2. Ion source; 3. Grid assembly; 4. Faraday cup; 5. Dual-channel picoammeter; 6. Dual-probe ion beam velocity measurement device; 7. Neutralization orifice plate; 8. Charged particle eater; 9. Flange interface; 10. Suspension plate method micro-thrust measurement device;

[0039] 101. gas source; 102. source valve; 103. pressure stabilizing chamber; 104. vacuum gauge; 105. fixed flow conductance orifice element; 106. vacuum valve;

[0040] 201, cathode; 202, magnetic coil; 203, anode grid;

[0041] 301, screen grid; 302, acceleration grid;

[0042] 1001. capacitor; 1002. low friction coefficient bearing; 1003. round metal sheet. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the present invention provides a high-speed directional molecular flow generating device, comprising a gas supply system 1, an ion source 2, a grid assembly 3, a neutralization orifice plate 7 and a charged particle swallower 8;

[0045] The gas supply system 1 is connected to the gas inlet end of the ion source 2 through a pipeline to provide neutral gas to the ion source 2;

[0046] The ion source 2 is used to ionize the neutral gas into plasma, and the gas outlet of the ion source 2 is connected in series with the grid assembly 3, the neutralization orifice plate 7, and the charged particle eater 8 in sequence;

[0047] The grid assembly 3 is used to extract ions, accelerate ions, and focus ions;

[0048] The neutralization orifice plate 7 is grounded and used to cause the passing ion beam to undergo an Auger process, thereby converting the ions into neutral molecules;

[0049] The charged particle eater 8 is used to absorb the unconverted ions and drift electrons.

[0050] In the present invention, the gas supply system 1 provides a stable flow of neutral gas to the ion source 2. The neutral gas is ionized in the ion source 2 to become a plasma. The ions therein are pulled out by the grid assembly 3 and accelerated to the desired state to form an ion beam. Then, the ion beam passes through the neutralization orifice plate 7 and undergoes an Auger process to be transformed into a high-speed directional molecular flow. After entering the charged particle eater 8, the unneutralized ions in the high-speed directional molecular flow will be deflected under the action of the electric field and hit the plate of the charged particle eater 8. In this way, a collimated and pure high-speed directional molecular flow can be obtained at the outlet. In this process, the beam measurement system can perform in-situ measurements of the characteristic parameters of the beam, such as velocity, flux, etc., so as to quantitatively analyze the pressure of the high-speed directional molecular flow.

[0051] The directional molecular flow generating device of the present invention can provide a high-speed directional molecular flow with a speed not less than 7 km / s, and the pressure of the high-speed directional molecular flow can be continuously adjusted within a certain pressure range, which meets the on-orbit operation space environment of most spacecraft.

[0052] The directional molecular flow generating device of the present invention has the characteristics of low complexity, and the generated high-speed directional molecular flow has good collimation, which provides an important experimental basis for the development of space vacuum measuring instruments and ground calibration.

[0053] In some embodiments of the present invention, the gas supply system 1 includes a gas source 101, a gas source valve 102, a pressure stabilizing chamber 103, a fixed flow conductance orifice element 105 and a vacuum valve 106;

[0054] The gas source 101, the pressure stabilizing chamber 103 and the gas inlet end of the ion source 2 are connected in sequence, the gas source valve 102 is arranged on the connecting pipe between the gas source 101 and the pressure stabilizing chamber 103, a vacuum gauge 104 is installed on the pressure stabilizing chamber 103, and a fixed flow conductance orifice element 105 and a vacuum valve 106 are installed on the connecting pipe between the pressure stabilizing chamber 103 and the ion source 2.

[0055] The gas source 101 serves as the source of gas supply and provides the required neutral gas for the entire device. The gas source valve 102 accurately controls the on-off of the gas flow from the gas source 101 to the pressure stabilizing chamber 103 to ensure the controllability of the gas supply. The pressure stabilizing chamber 103 plays a key role in stabilizing the pressure during the gas transmission process. The vacuum gauge 104 installed therein monitors the pressure changes in real time to ensure the stability of the gas pressure entering the ion source 2. The fixed flow conductance orifice element 105 and the vacuum valve 106 cooperate with each other to accurately adjust the gas flow and pressure entering the ion source 2. This structural design can provide the ion source 2 with a neutral gas with a stable flow and pressure, so that the ionization process in the ion source 2 is carried out stably, thereby ensuring the stability and consistency of the plasma generated subsequently, and laying the foundation for generating high-quality high-speed directional molecular flow.

[0056] Among them, the fixed conductance small hole element 105 is a precisely machined circular thin-walled small hole, which is a customized element. In the field of vacuum technology, fixed conductance elements are conventional elements, and the calculation and test methods of conductance values ​​have corresponding standards. For the fixed conductance small hole element 105, the following method can be used to complete the calculation and test of the conductance value of the small hole under molecular flow conditions.

[0057] For pores with larger size and regular shape, the conductance value under molecular flow conditions can be calculated by theoretical formula. After accurately measuring the thickness and diameter of the pore, the conductance value of the pore can be obtained.

[0058]

[0059] In the formula

[0060] A0 - area of ​​the small hole, m 2 ;

[0061] T - gas thermodynamic temperature, K;

[0062] M - molecular weight of gas, g / mol;

[0063] R - molar gas constant, taken as 8.314 J / (mol·K);

[0064] K1 - Clausing correction coefficient for cylindrical holes, which corrects the hole thickness d;

[0065] K2 - beam effect correction factor;

[0066] K3 - free path correction coefficient;

[0067] K4 - Conical hole correction factor.

[0068] For conductance elements with smaller conductance values, their pore diameters are in the μm range, which are difficult to obtain through conventional mechanical processing methods. They require complex processes such as laser drilling combined with multiple coatings. The shapes of the holes in the actual pore elements are irregular and cannot be calculated using the ideal pore conductance formula, so they can only be obtained through experimental testing. The constant volume method is generally used for testing, and the specific method is as follows: a certain pressure of gas is filled into a vacuum chamber of known volume, and the vacuum chamber is evacuated only through the conductance element. The pressure in the vacuum chamber decays continuously over time, and the conductance value of the conductance element can be calculated by measuring the volume of the constant volume chamber, the initial pressure and the final pressure of the constant volume chamber, and the interval time between the initial pressure and the final pressure. The measurement principle of the constant volume method is as follows. Figure 4 As shown,

[0069] The flow conductance value can be calculated using the following formula:

[0070]

[0071] in,

[0072] V—volume of constant volume chamber, m 3 ;

[0073] t—pumping time, s;

[0074] P—pressure value in the constant volume chamber after the air is pumped out for time t, Pa;

[0075] P0—Pressure value in the constant volume chamber when the vacuum starts, Pa.

[0076] In some embodiments of the present invention, the ion source 2, the neutralization orifice plate 7 and the charged particle eater 8 are coaxially arranged in the same housing;

[0077] The grid assembly 3 is mounted on the housing.

[0078] The ion source 2, the neutralization orifice plate 7 and the charged particle swallower 8 are coaxially arranged, so that the ions can be efficiently transmitted along the same axis from generation to conversion into neutral molecules and removal of impurities, reducing collisions and energy losses during ion movement, and effectively improving the transmission efficiency and collimation of the ion beam. The grid assembly 3 is installed on the shell, with a relatively fixed position and a tight connection with the ion source 2, which can more stably extract, accelerate and focus the ions, ensure the quality and directionality of the ion beam, and thus facilitate the formation of a high-speed directional and energy-concentrated molecular flow, while facilitating the overall assembly and maintenance of the device and enhancing the mechanical stability of the device.

[0079] In some embodiments of the present invention, the ion source 2 includes a cathode 201, a magnet coil 202 and an anode grid 203;

[0080] The chamber of the housing in which the ion source 2 is installed is a discharge chamber, the cathode 201 is at the air inlet end of the discharge chamber, the magnetic coil 202 is sleeved on the outside of the discharge chamber, and the anode grid 203 is installed inside the discharge chamber;

[0081] The cathode 201 is coaxially arranged with the neutralization orifice plate 7 and the charged particle swallower 8 .

[0082] The ion source 2 mentioned in the present device adopts the principle of hot cathode electron bombardment atomic discharge to obtain plasma. A structure of a hot emission cathode 201 and an anode grid 203 is arranged in the discharge chamber. The cathode 201 is located at the air inlet end to emit electrons, and the magnetic coil 202 generates a magnetic field outside the chamber, which increases the probability of collision between electrons and atoms, thereby greatly improving the gas ionization efficiency. The anode grid 203 is installed inside the chamber to form an electric field with the cathode 201, further promoting gas ionization, and can efficiently ionize neutral gas into plasma, providing sufficient ion sources for the subsequent generation of high-speed directional molecular flow, achieving a strong ion beam output at a lower energy consumption, and ensuring the performance and efficiency of the device.

[0083] In addition, the outer shell of the discharge chamber is grounded, and the anode grid 203 is connected to an external adjustable high voltage source through a ceramic insulation lead-out terminal.

[0084] In some embodiments of the present invention, the grid assembly 3 includes a screen grid 301 and an acceleration grid 302;

[0085] The screen grid 301 and the acceleration grid 302 are sequentially arranged at the gas outlet end of the ion source 2 .

[0086] The screen grid 301 and the acceleration grid 302 are sequentially arranged at the gas outlet of the ion source 2, and the electric field formed between the two is used to orderly operate the ions. The screen grid 301 first extracts the ions, and the acceleration grid 302 then accelerates and focuses the ions, so that the ions obtain sufficient energy and good directionality, forming a high-speed and collimated ion beam, so that the energy and direction of the ion beam can be accurately controlled, providing key power and direction guarantee for the subsequent conversion of the ion beam into a high-speed directional molecular flow, thereby improving the quality and performance of the high-speed directional molecular flow generated by the entire device.

[0087] Since there is plasma inside the discharge chamber, a crescent-shaped sheath emission surface is formed at a single small hole of the screen grid 301, such as Figure 3 As shown, the emission surface is the emission surface of the ions.

[0088] like Figure 2 As shown, in some embodiments of the present invention, the charged particle eater 8 includes two electrode plates arranged opposite to each other, and the electrode plates can be in the form of two symmetrical semi-cylindrical structures, and the two electrode plates are respectively connected to a positive voltage of 500V and a negative voltage of 500V.

[0089] The two electrode plates of the charged particle eater 8 are respectively connected to a positive voltage of 500V and a negative voltage of 500V. Under the action of a strong electric field, it can effectively attract and capture ions that have not been converted into neutral molecules and electrons drifting from the discharge chamber, thereby ensuring that the high-speed directional molecular flow at the outlet contains almost no charged particle impurities, improving the purity of the molecular flow, and avoiding the interference of charged particles on subsequent measurements and applications, thereby improving the quality of the high-speed directional molecular flow output by the device and ensuring its accuracy and reliability in the calibration of space vacuum measuring instruments.

[0090] In some embodiments of the present invention, a beam measurement system for evaluating the density loss in the ion beam neutralization process is also included. The beam measurement system includes a Faraday cup 4, a dual-channel picoammeter 5, a dual-probe ion beam velocity measurement device 6, and a suspended plate method micro-thrust measurement device 10.

[0091] The Faraday cup 4 measures the flux of the ion beam formed by the grid assembly 3 by collecting the current generated by the ions, providing basic data for calculating the relevant parameters of the ion beam, and playing a key basic role in analyzing the properties of high-speed directional molecular flows and calibrating space vacuum measuring instruments.

[0092] The dual-channel picoammeter 5 monitors the current on the neutralization orifice plate 7 and the charged particle eater 8, which can reflect the flow of ions and electrons in these two components, assist in analyzing the neutralization process of the ion beam and the treatment effect of charged particles, and help to gain a deeper understanding of the physical process inside the device and optimize the device performance.

[0093] The dual-probe ion beam velocity measurement device 6 is based on the time-of-flight method and accurately measures the velocity of the ion beam, providing key parameters for evaluating the performance of high-speed directional molecular flow and is one of the important bases for accurately calibrating space vacuum measurement instruments.

[0094] The suspended sheet method micro-thrust measurement device 10 is used to measure the thrust generated by the high-speed directional molecular flow, provide data support for optimizing the neutralization process of the device, ensure that the high-speed directional molecular flow generated by the device meets the calibration requirements, and improve the calibration accuracy.

[0095] In some embodiments of the present invention, the suspended sheet method micro-thrust measurement device 10 includes a capacitor 1001, a low friction coefficient bearing 1002 and a circular metal sheet 1003;

[0096] The inner ring of the low-friction bearing 1002 is sleeved on a fixed shaft. It can be understood that the fixed shaft is fixed, and there is no relative rotation between the inner ring of the low-friction bearing 1002 and the fixed shaft, while the outer ring of the low-friction bearing 1002 rotates based on the inner ring.

[0097] The circular metal sheet 1003 is vertically connected to the side of the outer ring of the low-friction bearing 1002 through a rigid connector. An electrode plate is rigidly connected to the other side of the outer ring of the low-friction bearing 1002 opposite to the circular metal sheet 1003 to form a pendulum-like structure. The electrode plate and the circular metal sheet 1003 are located on the same straight line passing through the center of the low-friction bearing 1002, and the electrode plate is arranged between the two plates of the capacitor 1001.

[0098] When the high-speed directional molecular flow impacts the circular metal sheet 1003, due to the effect of the low-friction bearing 1002, the impact force of the molecular flow can be effectively transmitted to the electrode plate, causing it to deflect and displace. The electrode plate is located between the two plates of the capacitor 1001, and its deflection causes a differential change in the capacitor 1001. By measuring this capacitance change, the thrust generated by the molecular flow can be accurately calculated, and the tiny thrust generated by the high-speed directional molecular flow can be measured with high sensitivity, providing a reliable basis for accurately evaluating the density loss in the neutralization process of the ion beam, and further providing a key data reference for optimizing the neutralization process of the device and improving the overall performance, ensuring that the high-speed directional molecular flow generated by the device meets the calibration requirements, and improving the calibration accuracy of the space vacuum measurement instrument.

[0099] In some embodiments of the present invention, the housing is connected to the ultra-high vacuum chamber via a flange interface 9 .

[0100] According to one aspect of the present invention, an application of a high-speed directional molecular flow generating device as described in any one of the above technical solutions is proposed for calibrating a space vacuum measuring instrument.

[0101] During the occurrence of high-speed directional molecular flow, the flux of the ion beam measured by Faraday cup 4 is Φ i The dual-probe ion beam velocity measurement device 6 measures the ion beam velocity v based on the time-of-flight method. i The multi-channel picoammeter 5 measures the currents on the neutralization plate 7 and the charged particle eater 8 as I n and I a According to the suspension method, the micro-thrust measuring device 10 can measure the thrust generated by the high-speed directional molecular flow in the axial direction, and calculate the flux loss factor α and the speed loss factor η caused by the neutralization process on the ion beam, and further calculate the neutralization efficiency γ of the ion beam. According to the beam parameters, the pressure of the high-speed directional molecular flow near the outlet axis can be calculated, and the space vacuum measuring instrument can be calibrated based on this.

[0102] The detailed principle of using high-speed directional molecular flow for calibration of space vacuum measuring instruments is as follows.

[0103] The gas molecules in the space environment are normal to the spacecraft wall. The pressure generated on the plane is:

[0104]

[0105] For the high-speed directional molecular flow generation module, a large-aperture ion source can be selected, so the influence of the edge divergence effect of the beam on the beam flux near the axis can be ignored. Moreover, for a high-speed directional molecular beam, its thermal motion velocity is much smaller than the volume velocity, and its velocity distribution function curve should be a Boltzmann distribution with a very narrow pulse width, so the volume velocity can be used for approximate equivalence to reduce the process of statistical integration and averaging of the velocity of particles near the beam axis. Then, equation (3) can be rewritten as:

[0106] p=2nmv 2 (4)

[0107] Where n is the number density of the neutral beam near the axis (m -3 ), m is the mass of the particle (kg), and v is the volume velocity of the neutral beam (m / s).

[0108] Taking into account the density and velocity losses caused by the ion neutralization process, the density loss factor and velocity loss factor of the ion beam after passing through the neutralization orifice are α and η respectively, and the neutralization efficiency of the ion beam is γ. The calibration principle formula can be rewritten as follows:

[0109]

[0110] Among them, n i is the number density near the ion beam axis (m -3 ), v i is the volume velocity of the ion beam (m / s). The mass of ions is almost the same as that of neutral particles, so m remains unchanged.

[0111] The velocity of the ion beam is measured based on the time-of-flight method:

[0112]

[0113] Where L is the distance between the two probes of the time-of-flight method (m), and Δt is the time difference between the signals measured by the two probes (s).

[0114] The number density n near the ion beam axis i The flux Φ near the ion beam axis i m -2 s -1 Divided by the beam velocity v i get.

[0115]

[0116] And Φ i The current I that can be measured by the Faraday cup i According to the definition of current, 1A is equal to 6.25×10 18 The current of a single charge passing through the cross section. So the flux of the ion beam can be calculated by the following formula:

[0117]

[0118] Where A is the effective measurement area of ​​the Faraday cup (m 2 ).

[0119] In summary, the pressure expression of the neutral beam output by the high-speed directional molecular flow generation module can be derived as follows:

[0120] p=2φ i mv i αηγ (9)

[0121]

[0122] Formulas (9) and (10) are the basis for using the high-speed directional molecular flow to calibrate space vacuum measuring instruments.

[0123] Parts of the present invention that are not described in detail belong to the well-known technology in the art.

[0124] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0125] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0126] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-speed directional molecular flow generating device, characterized in that: It comprises a gas supply system (1), an ion source (2), a grid assembly (3), a neutralization orifice plate (7) and a charged particle eater (8); The gas supply system (1) is connected to the gas inlet end of the ion source (2) through a pipeline to provide neutral gas to the ion source (2); The ion source (2) is used to ionize the neutral gas into plasma, and the gas outlet end of the ion source (2) is connected in series with the grid assembly (3), the neutralization orifice plate (7), and the charged particle eater (8) in sequence; The grid assembly (3) is used to extract ions, accelerate ions, and focus ions; The neutralization orifice plate (7) is grounded and is used to cause the passing ion beam to undergo an Auger process, thereby converting the ions into neutral molecules; The charged particle eater (8) is used to absorb unconverted ions and drifting electrons.

2. The high-speed directional molecular flow generating device according to claim 1, characterized in that: The gas supply system (1) comprises a gas source (101), a gas source valve (102), a pressure stabilizing chamber (103), a fixed flow conductance orifice element (105) and a vacuum valve (106); The gas source (101), the pressure stabilizing chamber (103) and the gas inlet end of the ion source (2) are connected in sequence; the gas source valve (102) is arranged on the connecting pipe between the gas source (101) and the pressure stabilizing chamber (103); a vacuum gauge (104) is installed on the pressure stabilizing chamber (103); and the fixed flow conductance orifice element (105) and the vacuum valve (106) are installed on the connecting pipe between the pressure stabilizing chamber (103) and the ion source (2).

3. The high-speed directional molecular flow generating device according to claim 1, characterized in that: The ion source (2), the neutralization orifice plate (7) and the charged particle swallower (8) are coaxially arranged in the same housing; The grid assembly (3) is mounted on the shell.

4. The high-speed directional molecular flow generating device according to claim 3, characterized in that: The ion source (2) comprises a cathode (201), a magnetic coil (202) and an anode grid (203); The chamber of the housing in which the ion source (2) is installed is a discharge chamber, the cathode (201) is at the air inlet end of the discharge chamber, the magnetic coil (202) is sleeved on the outside of the discharge chamber, and the anode grid (203) is installed inside the discharge chamber; The cathode (201), the neutralization orifice plate (7), and the charged particle eater (8) are coaxially arranged.

5. The high-speed directional molecular flow generating device according to claim 3, characterized in that: The grid assembly (3) comprises a screen grid (301) and an accelerating grid (302); The screen grid (301) and the accelerating grid (302) are sequentially arranged at the gas outlet end of the ion source (2).

6. The high-speed directional molecular flow generating device according to claim 1, characterized in that: The charged particle swallower (8) comprises two electrode plates arranged opposite to each other, and the two electrode plates are respectively connected to a positive voltage of 500V and a negative voltage of 500V.

7. The high-speed directional molecular flow generating device according to claim 1, characterized in that: The invention also comprises a beam current measurement system for evaluating the density loss in the neutralization process of an ion beam, wherein the beam current measurement system comprises a Faraday cup (4) for measuring the flux of an ion beam formed by a grid assembly (3), a dual-channel picoammeter (5) for measuring the current on the neutralization aperture plate (7) and the charged particle eater (8), a dual-probe ion beam current velocity measurement device (6) for measuring the velocity of the ion beam, and a suspension-type micro-thrust measurement device (10) for measuring the thrust generated by a high-speed directional molecular flow.

8. The high-speed directional molecular flow generating device according to claim 7, characterized in that: The suspended sheet method micro-thrust measurement device (10) comprises a capacitor (1001), a low-friction coefficient bearing (1002) and a circular metal sheet (1003); The inner ring of the low friction coefficient bearing (1002) is sleeved on a stationary fixed shaft; The circular metal sheet (1003) is vertically connected to the side of the outer ring of the low-friction bearing (1002) through a rigid connector, and an electrode plate is rigidly connected to the other side of the outer ring of the low-friction bearing (1002) opposite to the circular metal sheet (1003). The electrode plate and the circular metal sheet (1003) are located on the same straight line passing through the center of the low-friction bearing (1002), and the electrode plate is arranged between the two plates of the capacitor (1001).

9. The high-speed directional molecular flow generating device according to claim 3, characterized in that: The shell is connected to the ultra-high vacuum chamber via a flange interface (9).

10. An application of a high-speed directional molecular flow generating device as claimed in any one of claims 1 to 9, characterized in that: Used to calibrate space vacuum measuring instruments.

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