Device and method for measuring adaptation coefficient of rarefied gas momentum

Abstract

The invention provides a rarefied gas momentum adaptation coefficient measurement device and method.The device comprises an ion beam generation system, a vacuum environment simulation system and a parameter measurement system.Ion beams are generated through a microwave method, a vacuum chamber simulates real rarefied gas conditions, and an ion beam impacts a test sample piece to simulate interaction between rarefied gas and the surface of an aircraft; a momentum adaptation coefficient is calculated through aerodynamic force based on an object plane reflection model theory, and measurement of micro aerodynamic force is converted into geometric displacement measurement based on a laser displacement sensor. The rarefied gas condition under the real flight condition is simulated, the ion beam impact test sample piece is generated by using the microwave method, the interaction between the rarefied gas and the surface of the aircraft in the real flight process is simulated, the measurement of micro aerodynamic force is converted into geometric displacement measurement, and the measurement accuracy is improved. The structure for measuring geometric displacement through an optical method is simpler, and the measurement precision is higher; through different cross beam suspension modes, a tangential momentum adaptation coefficient and a normal momentum adaptation coefficient can be measured respectively.

Description

Technical Field

[0001] This invention relates to the field of aerospace experimental technology, and in particular to a device and method for measuring the momentum adaptation coefficient of rarefied gases. Background Technology

[0002] The momentum fit coefficient is a key concept in rarefied gas dynamics and micro / nano-scale fluid mechanics, primarily used to describe the momentum exchange process during collisions between gas molecules and solid surfaces. When gas molecules collide with a solid surface, some undergo diffuse reflection, fitting into the solid surface, while others undergo specular reflection, reflecting off at the same angle. The momentum fit coefficient represents the proportion of the momentum of the diffusely reflected molecules to the incident momentum. When the momentum fit coefficient is 0, complete specular reflection occurs; when the momentum fit coefficient is 1, complete diffuse reflection occurs; in reality, the momentum fit coefficient lies between these two values. The momentum fit coefficient is further classified according to the direction of the collision into normal momentum fit coefficient and tangential momentum fit coefficient.

[0003] The momentum fitness coefficient plays a crucial role in the theoretical modeling, numerical simulation, and engineering applications of rarefied gas dynamics. In rarefied gas flows with high Knudsen numbers, the traditional Navier-Stokes equations fail, and collisions between gas molecules and walls dominate the flow behavior. The momentum fitness coefficient is critical in constructing slip boundary conditions; a small momentum fitness coefficient results in high slip velocities, with the gas experiencing almost no resistance from wall friction; conversely, a large momentum fitness coefficient leads to low slip velocities, making the gas more susceptible to wall drag. When modifying temperature jump boundary conditions in heat transfer models, both the momentum fitness coefficient and the thermal fitness coefficient influence the temperature distribution. In the design of low-Earth orbit satellites and novel upper-atmosphere spacecraft, the aerodynamic lift and drag of spacecraft flying in rarefied gases are strongly correlated with the momentum fitness coefficient. A low momentum fitness coefficient on the spacecraft surface can effectively reduce drag and improve the lift-to-drag ratio.

[0004] Therefore, the measurement of the momentum adaptation coefficient is of great significance, but because the aerodynamic force generated by rarefied gases is very small, for a distance of 1m... 2 The flat plate, at an angle of attack of 30°, an orbital altitude of 200 km, and a momentum adaptation factor of 0.85, produced an aerodynamic lift of 1 mN. However, at an altitude of 300 km, the aerodynamic lift decreased to only 0.05 mN. In the experimental simulation, the area of ​​the test specimen was much smaller than 1 m². 2Its aerodynamic lift is only on the order of μN, making the measurement of such a tiny force extremely difficult. Currently, methods for measuring momentum fitness include the rotating cylinder method, the sound velocity method, the magnetic levitation rotor method, the microchannel method, and the rotating disk method. These methods are all indirect, transforming momentum fitness measurement into the measurement of parameters such as frictional torque, sound velocity, mass flow rate, and angular velocity. This requires establishing a physical model relating the momentum fitness to these parameters, and the correctness of these physical models lacks sufficient verification, thus the accuracy of indirect methods is insufficient. In contrast, the ion beam method is a direct measurement method. The aerodynamic force generated by the interaction of the ion beam with the object surface can simulate the real flight environment. The measurement principle is based on the definition of momentum fitness and does not rely on complex theoretical models. Therefore, the ion beam method has an inherent advantage in measuring momentum fitness. Summary of the Invention

[0005] The purpose of this invention is to provide a device and method for measuring the momentum adaptation coefficient of rarefied gases, so as to solve the above-mentioned technical problems.

[0006] This invention provides a device for measuring the momentum adaptation coefficient of rarefied gases, comprising an ion beam generation system, a vacuum environment simulation system, and a parameter measurement system. The ion beam generation system consists of a microwave source, a compressed gas cylinder, and an electromagnetic coil. The vacuum environment simulation system consists of a vacuum chamber, a vacuum gauge, and vacuum equipment. The parameter measurement system consists of a test sample, a laser displacement sensor, an ion energy probe, and a microammeter. The electromagnetic coil is wound and sleeved outside the vacuum chamber and connected to the microwave source. The compressed gas cylinder is connected to the interior of the vacuum chamber for gas supply. The vacuum gauge and the ion energy probe are installed inside the vacuum chamber. The vacuum chamber is connected to the vacuum equipment. The test sample is suspended inside the vacuum chamber and equipped with a laser displacement sensor corresponding to the test sample. The microammeter is connected to the test sample to measure the current value generated by the ion beam acting on the test sample.

[0007] This invention also provides a method for measuring the momentum adaptation coefficient of rarefied gases. This method utilizes a rarefied gas momentum adaptation coefficient measuring device. First, the test sample is dusted. The arrangement of the test sample is selected according to the requirement of measuring normal or tangential force, and it is installed in a vacuum chamber. Then, the vacuum chamber is sealed, and after the test sample is completely stationary, its position is measured using a laser displacement sensor. Next, the cooling water pump is turned on to start cooling water circulation, and the mechanical pump is turned on to evacuate air from the vacuum chamber. When the pressure in the vacuum chamber drops below 10 Pa, the molecular pump is turned on to continue evacuating the remaining air until the pressure in the vacuum chamber drops to 10 Pa. -3Pa; then turn on the microwave source and electromagnetic coil power supply, open the compressed gas cylinder valve to introduce oxygen, and the microwave ionizes the oxygen under the action of the magnetic field to generate an oxygen ion beam. The oxygen ion beam strikes the test sample, causing it to swing. The swing displacement distance is measured using a laser displacement sensor, the current value of the test sample is measured using a microammeter, and the energy of the ion beam is measured using an ion energy probe. The momentum adaptation coefficient can be calculated based on the measurement results. Finally, the valves and power supply in the system are closed according to the principle of opening first and then closing, and the test ends.

[0008] This invention utilizes a vacuum chamber to simulate rarefied gas conditions under real flight conditions. It uses a microwave method to generate ion beam impact test specimens, simulating the interaction between rarefied gas and the aircraft surface during actual flight. This addresses the problem of insufficient verification of the correctness of physical models establishing the correlation between momentum adaptation coefficient and measurement parameters in traditional indirect measurement methods, resulting in more realistic and reliable measurement results. Furthermore, this invention transforms the measurement of minute aerodynamic forces into geometric displacement measurement. Measuring geometric displacement using optical methods simplifies the structure and increases measurement accuracy. By employing different beam suspension methods, both tangential and normal momentum adaptation coefficients can be measured separately. Attached Figure Description

[0009] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of the rarefied gas momentum adaptation coefficient measuring device of the present invention;

[0011] Figure 2 This is a schematic diagram illustrating the theoretical principle of momentum adaptation coefficient measurement in this invention.

[0012] Figure 3 This is a schematic diagram of the ion beam aerodynamic measurement principle of the present invention;

[0013] Figure 4 This is a schematic diagram of the arrangement of the ion beam aerodynamic measurement device of the present invention;

[0014] Figure 5 This is a flowchart of the method for measuring the momentum adaptation coefficient of rarefied gases according to the present invention.

[0015] Explanation of reference numerals in the attached figures:

[0016] In the diagram: 1-Microwave source, 2-Waveguide circulator, 3-Compressed gas cylinder, 4-Electromagnetic coil, 5-Cooling water pump, 6-Vacuum chamber, 7-Vacuum gauge, 8-Mechanical pump, 9-Molecular pump, 10-Observation window, 11-Test sample, 12-Hanging rope, 13-Crossbeam, 14-Laser displacement sensor, 15-Ion energy probe, 16-Microamplitude meter; Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying 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 limiting this invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] Example 1

[0021] like Figures 1-5 As shown:

[0022] A device for measuring the momentum adaptation coefficient of rarefied gases includes an ion beam generation system, a vacuum environment simulation system, and a parameter measurement system.

[0023] The ion beam generation system consists of a microwave source 1, a waveguide circulator 2, a compressed gas cylinder 3, an electromagnetic coil 4, and a cooling water pump 5.

[0024] The vacuum environment simulation system consists of a vacuum chamber 6, a vacuum gauge 7, a mechanical pump 8, a molecular pump 9, and an observation window 10.

[0025] The parameter measurement system consists of a test specimen 11, a hanging rope 12, a crossbeam 13, a laser displacement sensor 14, an ion energy probe 15, and a microammeter 16.

[0026] Vacuum chamber 6 is a closed space. Electromagnetic coil 4 is wound around the outside of vacuum chamber 6. Electromagnetic coil 4 is connected to microwave source 1 through waveguide circulator 2. Microwave source 1 generates microwaves, which are output unidirectionally through waveguide circulator 2. Compressed gas cylinder 3 is connected to the inside of vacuum chamber 7 and provides compressed oxygen to the inside of vacuum chamber 7.

[0027] Coil 4 generates a uniform magnetic field in the horizontal direction. Microwaves are coupled with the magnetic field to discharge. Oxygen molecules absorb energy and ionize to generate oxygen ions. The oxygen ions are accelerated to form an ion beam under the action of electromagnetic field and air pressure.

[0028] Cooling water channels are provided on the microwave source 1 and the waveguide circulator 2. A cooling coil connected to the cooling water channels is installed on the electromagnetic coil 4. The cooling water channels and the cooling coil are connected to a water cooling system via a cooling water pump 5. The cooling water pump 5 provides circulating cooling water to cool the microwave source 1, the waveguide circulator 2, and the electromagnetic coil 4.

[0029] In this embodiment, the water cooling system includes a terminal device (such as a chiller) that provides cooling capacity, which is connected to the cooling water pump 5 and is responsible for cooling the circulated water (e.g., through a heat exchanger, a cooling fan, etc.).

[0030] The cooling system's circulation path is as follows: Cooling water pump 5 pumps the cooling medium from the terminal equipment, sequentially sending it into the cooling water channels of microwave source 1 and waveguide circulator 2, then into the cooling coil of electromagnetic coil 4. After absorbing heat, the medium flows back to the terminal equipment for cooling, completing the cycle. Microwave source 1 and waveguide circulator 2 generate a large amount of heat during high-frequency microwave emission, and electromagnetic coil 4 generates a magnetic field. The cooling system removes this heat through continuous circulation of cooling water, preventing component performance degradation, accelerated aging, or burnout due to high temperatures, ensuring the long-term stable operation of the ion beam generation system.

[0031] Mechanical pump 8 and molecular pump 9 are connected in series. Molecular pump 9 is connected to vacuum chamber 6. Mechanical pump 8 evacuates vacuum chamber 6 to a low vacuum level (below 10 Pa), and molecular pump 9 continues to evacuate vacuum chamber 6 to a high vacuum level (10 Pa). -3 The vacuum gauge 7 measures the vacuum level in the vacuum chamber 6, and the observation window 10 made of quartz glass provides an observation window for the experimental measurement.

[0032] A crossbeam 13 is installed on the top surface of the vacuum chamber 6. The test sample 11 is suspended on the crossbeam 13 by a hanging rope 12. The ion beam impacts the test sample 11 and generates a force, causing the test sample 11 to swing. The laser displacement sensor 14 emits a laser beam that shines on the test sample 11. After reflection, it is received by the receiving device of the laser displacement sensor 14. The angle of deflection of the test sample 11 under the force is very small, and the angle of the laser beam reflected back is also very small. The movement of the test sample 11 can be approximated as a one-dimensional displacement.

[0033] The distance traveled by the test specimen 11 is calculated by measuring the time variation of the laser beam's round trip. Then, the magnitude of the force acting on it is calculated based on this distance. The ion energy probe 15 measures the effective energy of the ion beam, and the microammeter 16 measures the current generated by the ion beam acting on the test specimen 11. Finally, the momentum fit coefficient of the test specimen 11 can be calculated based on the surface reflection model theory.

[0034] Figure 2 This is a schematic diagram illustrating the theoretical principle of momentum adaptation coefficient measurement. The ion beam is positioned at a certain angle θ. i When ions act on the surface of an object, some undergo diffuse reflection, reflecting out at any angle, while others undergo specular reflection, reflecting out at the same angle θ. i It is reflected away. Assume the momentum of the incident ion beam is decomposed into normal momentum P. i and tangential momentum τ i The momentum of specular reflection is decomposed into normal momentum P. r and tangential momentum τ r The momentum of diffuse reflection is P. s Then the normal momentum fitness coefficient σ′ and the tangential momentum fitness coefficient σ are defined as follows:

[0035] σ′=(p i -p r ) / (p i -p s )

[0036] σ=(τ i -τ r ) / τ i

[0037] Therefore, σ can be considered as the proportion of diffuse reflection ions among all ions, while 1-σ is the proportion of specular reflection. When σ = 1, the ion beam is entirely diffusely reflected on the object surface, and momentum is completely absorbed, resulting in complete adaptation. When σ = 0, the ion beam is entirely specularly reflected on the object surface, and there is no momentum exchange.

[0038] The ion beam acting on the test sample 11 generated a normal force F. N and tangential force F T Normal force FN It can be represented as:

[0039] F N =Msinθ i +0.667σ′M+(1-σ′)Msinθ i

[0040] Where M is the incident momentum of the ion beam, the first term represents the normal component of the incident momentum of the ion beam, the second term represents the momentum of the diffuse reflection ions, 0.667 represents the average value of the normal component, and the third term represents the momentum of the specular reflection ions.

[0041] Tangential force F T It can be represented as:

[0042] F T =Mcosθ i -(1-σ)Mcosθ i =σMcosθ i

[0043] Let the incident momentum of a single ion be mv, where m is the ion mass and v is the ion velocity. Then the incident momentum M of the ion beam can be calculated using the following formula:

[0044]

[0045] Where Q is the charge, e is the unit charge, and I is the current generated by the ion beam, which can be measured using a microammeter. The ion velocity can be calculated using the kinetic energy formula. The ion beam energy E can be calculated and measured using the ion energy probe 15.

[0046] Therefore, the normal force F acting on the test specimen 11 is measured by experiment. N and tangential force F T The ion beam energy E, the generated current I, and the incident angle of the ion beam can be expressed by the following formula:

[0047]

[0048] The normal momentum adaptation coefficient σ′ and the tangential momentum adaptation coefficient σ are calculated respectively.

[0049] Figure 3 This is a schematic diagram illustrating the principle of ion beam aerodynamic measurement. The ion beam acts on the test sample 11, generating aerodynamic force that causes the test sample 11 to oscillate. Assuming the mass of the test sample 11 is m, the length of the hanging rope 12 is L, the aerodynamic force generated by the ion beam is F, the displacement of the test sample 11 is Δx, and the oscillation angle of the hanging rope 12 is θ, Δx can be measured by the laser displacement sensor 14. Therefore, the aerodynamic force is:

[0050] F=mgtanθ≈mgΔx / L

[0051] The mass of test sample 11 is ~0.1g, the length of hanging rope 12 is ~0.1m, and the accuracy of laser displacement sensor 14 can reach ~0.1μm. Therefore, the accuracy of ion beam aerodynamic measurement can reach ~10. -9 N.

[0052] Figure 4 The diagram shows the arrangement of the ion beam aerodynamic measurement device. The left diagram shows the arrangement of the tangential force measurement device, where the endpoints of the test sample 11 are suspended from two crossbeams 13 by two hanging ropes 12, restricting the movement of the test sample 11 in the normal direction so that only the tangential force can be measured. The right diagram shows the arrangement of the normal force measurement device, where the two endpoints of the test sample 11 are suspended from both sides of the crossbeam 14 by hanging ropes 12, restricting the movement of the test sample 11 in the tangential direction so that only the normal force can be measured.

[0053] Figure 5 The flowchart illustrates the method for measuring the momentum adaptation coefficient of rarefied gases. First, the test sample 11 undergoes dust removal treatment. The method is then selected based on the requirement to measure either the normal force or the tangential force. Figure 3 The sample 11 is installed inside vacuum chamber 6 using the following installation method. Vacuum chamber 6 is then sealed, and after the sample 11 comes to a complete stop, its position is measured using laser displacement sensor 14. Cooling water pump 5 is then turned on to initiate cooling water circulation, and mechanical pump 8 is activated to evacuate air from vacuum chamber 6. When the pressure in the vacuum chamber drops below 10 Pa, molecular pump 9 is activated to continue evacuating the remaining air until the pressure in the vacuum chamber drops to 10 Pa. -3 Pa; then turn on the power supply of microwave source 1 and electromagnetic coil 4, open the valve of compressed gas cylinder 3 to introduce oxygen, and the microwave ionizes the oxygen under the action of the magnetic field to generate an oxygen ion beam. The oxygen ion beam hits the test specimen 11, causing it to swing. The swing displacement distance is measured using laser displacement sensor 14, the current value of test specimen 11 is measured using microammeter 16, and the energy of the ion beam is measured using ion energy probe 15. The momentum adaptation coefficient can be calculated based on the measurement results; finally, the valves and power supply in the system are closed according to the principle of opening first and then closing, and the test ends.

[0054] This invention utilizes a vacuum chamber to simulate rarefied gas conditions under real flight conditions. It uses a microwave method to generate ion beam impact test specimens, simulating the interaction between rarefied gas and the aircraft surface during actual flight. The simulation process does not rely on theoretical model assumptions, whereas traditional indirect measurement methods require establishing a physical model relating momentum adaptation coefficients to measurement parameters, and the correctness of these physical models lacks sufficient verification. Therefore, the measurement results of this invention are more realistic and reliable. This invention transforms the measurement of minute aerodynamic forces into geometric displacement measurement, using optical methods to measure geometric displacement. Compared to measurement sensors, this method has a simpler structure and higher measurement accuracy. Existing technologies typically only measure the tangential momentum adaptation coefficient; this invention, through different beam suspension methods, can measure both the tangential and normal momentum adaptation coefficients separately.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring the momentum adaptation coefficient of rarefied gases, characterized in that: The system includes an ion beam generation system, a vacuum environment simulation system, and a parameter measurement system. The ion beam generation system consists of a microwave source, a compressed gas cylinder, and an electromagnetic coil. The vacuum environment simulation system consists of a vacuum chamber, a vacuum gauge, and vacuum equipment. The parameter measurement system consists of a test sample, a laser displacement sensor, an ion energy probe, and a microammeter. The electromagnetic coil is wound and sleeved on the outside of the vacuum chamber and is connected to the microwave source. The compressed gas cylinder is connected to the inside of the vacuum chamber for gas supply. The vacuum gauge and ion energy probe are installed inside the vacuum chamber. The vacuum chamber is connected to the vacuum equipment. The test sample is suspended inside the vacuum chamber and equipped with a laser displacement sensor corresponding to the test sample. The microammeter is connected to the test sample to measure the current value generated by the ion beam acting on the test sample.

2. The device for measuring the momentum adaptation coefficient of rarefied gas according to claim 1, characterized in that: The microwave source is connected to the electromagnetic coil via a waveguide circulator.

3. The device for measuring the momentum adaptation coefficient of rarefied gas according to claim 2, characterized in that: The microwave source and the waveguide circulator are provided with cooling water channels, and the electromagnetic coil is equipped with a cooling coil that communicates with the cooling water channels. The cooling water channels and the cooling coil are connected to the cooling system through a cooling water pump.

4. The device for measuring the momentum adaptation coefficient of rarefied gas according to claim 1, characterized in that: The vacuum equipment includes a mechanical pump and a molecular pump connected in series. The molecular pump is connected to the vacuum chamber. The mechanical pump evacuates air from the vacuum chamber to a low vacuum level, and the molecular pump evacuates the vacuum chamber to a high vacuum level.

5. The device for measuring the momentum adaptation coefficient of rarefied gas according to claim 1, characterized in that: The vacuum chamber is equipped with an observation window that provides an observation position.

6. The device for measuring the momentum adaptation coefficient of rarefied gas according to claim 1, characterized in that: A crossbeam is installed on the top surface of the vacuum chamber, and the test specimen is suspended on the crossbeam by a rope.

7. A method for measuring the momentum adaptation coefficient of a rarefied gas, characterized in that: This method utilizes the rarefied gas momentum adaptation coefficient measuring device described in claims 1-6. First, the test sample is dusted. The arrangement of the test sample is selected according to the requirement of measuring normal or tangential force, and it is installed inside a vacuum chamber. Then, the vacuum chamber is sealed, and after the test sample is completely stationary, its position is measured using a laser displacement sensor. Next, the cooling water pump is turned on to start cooling water circulation, and the mechanical pump is turned on to evacuate air from the vacuum chamber. When the pressure in the vacuum chamber drops below 10 Pa, the molecular pump is turned on to continue evacuating the remaining air until the pressure in the vacuum chamber drops to 10 Pa. -3 Pa; then turn on the microwave source and electromagnetic coil power supply, open the compressed gas cylinder valve to introduce oxygen, and the microwave ionizes the oxygen under the action of the magnetic field to generate an oxygen ion beam. The oxygen ion beam strikes the test sample, causing it to swing. The swing displacement distance is measured using a laser displacement sensor, the current value of the test sample is measured using a microammeter, and the energy of the ion beam is measured using an ion energy probe. The momentum adaptation coefficient can be calculated based on the measurement results. Finally, the valves and power supply in the system are closed according to the principle of opening first and then closing, and the test ends.

8. The method for measuring the momentum adaptation coefficient of rarefied gases according to claim 7, characterized in that: The test specimen is arranged using a beam suspension method. When measuring the tangential force, the end points of the test specimen are suspended from two beams by two ropes, which restricts the movement of the test specimen in the normal direction so that only the tangential force can be measured. When measuring the normal force, the two end points of the test specimen are suspended from both sides of the beam by ropes, which restricts the movement of the test specimen in the tangential direction so that only the normal force can be measured.

9. The method for measuring the momentum adaptation coefficient of rarefied gases according to claim 7, characterized in that: Based on the momentum adaptation coefficient obtained from the surface reflection model theory, the ion beam is positioned at a certain angle θ. i When ions act on the surface of an object, some undergo diffuse reflection, reflecting out at any angle, while others undergo specular reflection, reflecting out at the same angle θ. i Reflected out; assuming the momentum of the incident ion beam is decomposed into normal momentum P. i and tangential momentum τ i The momentum of specular reflection is decomposed into normal momentum Pr and tangential momentum τ. r The momentum of diffuse reflection is P. s Then the normal momentum fitness coefficient σ′ and the tangential momentum fitness coefficient σ are defined as follows: σ′=(p i -p r ) / (p i -p s ) σ=(τ i -t r ) / t i The ion beam generates a normal force F on the test sample. N and tangential force F T Normal force F N It can be represented as: F N =Msinθ i +0.667σ′M+(1-σ′)Msinθ i Where M is the incident momentum of the ion beam, the first term represents the normal component of the incident momentum of the ion beam, the second term represents the momentum of the diffuse reflection ions, 0.667 represents the average value of the normal component, and the third term represents the momentum of the specular reflection ions. Tangential force F T It can be represented as: F T =M cosθ i -(1-σ)M cosθ i =σM cosθ i Let the incident momentum of a single ion be , m be the ion mass, and v be the ion velocity. Then the incident momentum M of the ion beam can be calculated using the following formula: Where Q is the charge, e is the unit charge, and I is the current generated by the ion beam, which can be measured using a microammeter; the ion velocity is obtained using the kinetic energy formula. The calculation is performed, and the ion beam energy E can be obtained by measuring the ion energy probe. Therefore, the normal force F acting on the test specimen is measured experimentally. N and tangential force F T The ion beam energy E, the generated current I, and the incident angle of the ion beam can be expressed by the following formula: The normal momentum adaptation coefficient σ′ and the tangential momentum adaptation coefficient σ are calculated respectively.

10. The method for measuring the momentum adaptation coefficient of rarefied gases according to claim 7, characterized in that: Based on the measurement of aerodynamic force using a laser displacement sensor, an ion beam acts on the test sample to generate aerodynamic force, causing the test sample to oscillate. Assuming the mass of the test sample is m, the length of the hanging rope is L, the aerodynamic force generated by the ion beam is F, the displacement of the test sample is Δx, and the oscillation angle of the hanging rope is θ, Δx can be measured using a laser displacement sensor. Therefore, the aerodynamic force is: F=mgtanθ≈mgΔx / L The mass of the test sample is ~0.1g, the length of the hanging rope is ~0.1m, and the accuracy of the laser displacement sensor can reach ~0.1μm. Therefore, the accuracy of the ion beam aerodynamic measurement can reach ~10. -9 N.

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