Time-of-flight mass spectrometry device for characterizing performance of electrospray thruster at different angles

Abstract

The invention discloses a time-of-flight mass spectrometry device for characterizing different-angle performance of an electrospray thruster, and belongs to the field of testing of emission performance of the electrospray thruster. The device comprises a flight time mass spectrum device, a thruster rotating system, a thruster, a power supply system and a data acquisition device. The time-of-flight mass spectrometry device comprises an electrostatic door device, a particle flight tube section and a collection device. The thruster device comprises an electrospray thruster, an electrospray thruster rotating system and a fixing device. The collecting device is a stainless steel round pipe with a flange, and an insulating spacer, a metal grid mesh and a collecting plate are placed in the round pipe. According to the invention, the wire mesh wraps the transmission line for transmitting the current signal on the collection plate, so that electromagnetic interference is reduced. The emission angle of the electrospray thruster is controlled through the electric rotating table outside the vacuum cabin, the rotating angle of the thruster is accurately controlled, plume velocities of the electrospray thruster at different angles are measured, and the thrust and specific impulse of the electrospray thruster at different angles are calculated through measured data.

Description

Technical Field

[0001] The invention belongs to the field of electrospray thruster launch performance testing and relates to a time-of-flight mass spectrometer for electrospray thruster performance characterization. Background Art

[0002] In recent years, electrospray thrusters have been widely used in micro-satellite space missions. Measuring electrospray thrusters is of great significance to improving the key performance of electrospray thrusters. TOF testing can obtain the type of emitted particles, thrust and specific impulse of electrospray thrusters, which are important indicators for evaluating the performance of electrospray thrusters. Through these parameters, it can be determined whether the performance of the thruster meets the requirements.

[0003] Time of flight (TOF) is an important method for measuring the speed of microscopic particles. This method measures the flight time of flying particles passing through a known distance, and thus calculates the particle flight speed. The TOF method can measure the velocity of the electrospray thruster plume, and the particle flight time is obtained through the electrical characteristics of the plume particles.

[0004] At present, the schemes for measuring the velocity of electrospray thruster plume have certain shortcomings:

[0005] (1) Excessive electromagnetic interference. Since the thrust generated by the electrospray thruster is small, fewer particles penetrate the grid, and some particles deflect to the tube wall. The current collected by the collection plate is very small. If the electromagnetic interference is too large, the measurement results will be inaccurate.

[0006] (2) High space requirements. Since the measurement method requires the particles to fly a certain distance, the overall size of the measurement device must meet the measurement requirements. Therefore, measuring the speed inside the vacuum chamber requires a large space, and it is not convenient to measure in a small vacuum chamber.

[0007] (3) The electrospray thruster performance characterization measurement system did not measure the electrospray thruster at different angles, but only performed TOF measurement in the positive direction of the electrospray thruster. Summary of the invention

[0008] Aiming at the characteristics of charged particles in the plume generated by the electrospray thruster, the main purpose of the present invention is to provide a time-of-flight mass spectrometer for characterizing the performance of the electrospray thruster at different angles, which can characterize the performance of the electrospray thruster and measure the plume velocity at different angles of the electrospray thruster. On this basis, the type of particles can be determined by the test results, and the thrust and specific impulse of the electrospray thruster at different angles can be calculated by the measurement data. The present invention also has the following advantages: ① Shielding of electromagnetic interference; ② Flange connection with the vacuum cabin can be performed outside the vacuum cabin; ③ The rotation of the electrospray thruster at different angles is achieved by an electric rotating table, which can accurately control the rotation angle of the thruster.

[0009] The objective of the present invention is achieved through the following technical solutions:

[0010] The invention discloses a time-of-flight mass spectrometer for characterizing the performance of an electrospray thruster at different angles, comprising a time-of-flight mass spectrometer, a thruster rotation system, a thruster, a power supply system and a data acquisition device.

[0011] The time-of-flight mass spectrometer comprises an electrostatic gate device, a particle flight pipe section and a collecting device; the electrostatic gate device is a stainless steel round tube with a flange, and an insulating gasket, a metal grid and a metal gasket with a central circular hole are placed inside the round tube, and different sizes of the central circular hole can change the particle entry flow rate; the electrostatic gate is horizontally connected to the particle flight pipe section through a flange; both ends of the particle flight pipe section are provided with flanges; the collecting device is horizontally connected to the particle flight pipe section through another flange; the collecting device is a stainless steel round tube with a flange, and an insulating gasket, a metal grid and a collecting plate are placed inside the round tube; the thruster rotation system comprises a thruster system, an electric rotating platform and a fixing device; the fixing device is a transfer plate and a z-axis lifting platform; the thruster system comprises an electrospray thruster and a thruster housing; and the electric rotating disk is connected to an external control system through a control line.

[0012] The thruster device comprises an electrospray thruster, an electrospray thruster rotating system and a fixing device.

[0013] The power supply system comprises a voltage-adjustable high-voltage direct current power supply and a high-voltage pulse power supply.

[0014] The data acquisition device includes a current amplifier and an oscilloscope.

[0015] Furthermore, the electrostatic gate device includes a stainless steel round tube with a flange, an insulating gasket, a metal grid and a circular metal gasket. The metal grid is placed on the insulating gasket groove, and the notch on the metal grid coincides with the protrusion of the insulating gasket; the insulating gasket, metal grid and metal gasket are inside the round tube, the metal gasket is at the tube mouth, followed by the insulating gasket and metal grid in sequence, there are four insulating gaskets and three metal grids in total, the insulating gaskets, metal grids and metal gaskets are tightly fitted, and are connected and fixed to the round tube with bolts; the adapter plate is used to connect and fix the z-axis lifting platform and the electric rotating platform, and is installed between the electric rotating platform and the z-axis lifting platform.

[0016] Furthermore, the collecting device comprises a stainless steel round tube with a flange, an insulating gasket, a metal grid, a collecting plate, a disc flange and a spring; the metal grid and the collecting plate are placed on the groove of the insulating gasket, and the notches on the metal grid and the collecting plate coincide with the protrusions of the insulating gasket; the insulating gasket, the grid and the collecting plate are placed at the pipe mouth in sequence; the electrostatic door has a total of three insulating gaskets, one grid and one collecting plate; the spring is placed between the disc flange and the last insulating gasket and contacts the two; the thruster housing can fix the thruster at the center position of the z-axis lifting platform.

[0017] Furthermore, the flange sizes of the electrostatic gate device, the particle flight tube section and the collection device are the same and are connected by bolts; the adapter plate has different threaded holes for connecting and fixing the z-axis lifting platform and the electric rotating platform; the thruster shell material is metal, and there are screw holes on both sides for fixing the thruster to the center position of the z-axis lifting platform.

[0018] Furthermore, there are sealing rings between the electrostatic gate device, the particle flight pipe section and the collection device flange.

[0019] Furthermore, the insulating gasket, the metal grid and the circular metal gasket with a central circular hole in the electrostatic gate device are all provided with four evenly distributed circular holes for bolt connection.

[0020] Furthermore, a round hole is provided on the wall of the stainless steel round tube with flange of the electrostatic door device for inserting a high-voltage connector.

[0021] Furthermore, a circular hole is provided at the center of the metal gasket in the electrostatic door device, and the circular hole is used to adapt to and replace metal gaskets with different circular hole sizes.

[0022] Beneficial effects:

[0023] 1. The time-of-flight mass spectrometer device for characterizing the performance of electrospray thrusters at different angles disclosed in the present invention, the electrostatic gate device is fixedly connected to the vacuum chamber and the particle flight pipe section through a flange, the round tube extends into the vacuum chamber, and there are four bolt holes on the flange. The three flanges are connected and fixed by bolts and nuts, and the collecting device is also fixedly connected to the particle flight pipe section through a flange. The high-voltage connector on the electrostatic gate device is connected to the pulse power supply outside the vacuum chamber through a shielded wire, the metal grid is connected to the round tube through a wire and grounded, the collecting plate in the collecting device is connected to the vacuum connector on the flange cover plate, and the vacuum connector is connected to the data acquisition device through a shielded wire. The data acquisition device includes a current amplifier and an oscilloscope. Shielded wires are used between the vacuum connector and the data acquisition device to prevent electromagnetic interference. The high-voltage connector at the tail of the thruster is connected to the high-voltage DC power supply outside the vacuum chamber, and the extraction pole is grounded. The shell material of the present invention is metal, and the transmission line for transmitting the current signal on the collecting plate is wrapped with a metal wire mesh to reduce electromagnetic interference. When the thruster is not launched, the electromagnetic interference image on the oscilloscope is significantly weakened compared with the previous solution.

[0024] 2. The time-of-flight mass spectrometer disclosed in the present invention is used for characterizing the performance of an electrospray thruster at different angles. The electrostatic door is flange-connected to the vacuum chamber outside the vacuum chamber, and can complete the measurement of the electrospray thruster plume velocity under limited space conditions, reduce the space requirement for the vacuum chamber body, and enhance the time resolution of the measurement signal of the time-of-flight mass spectrometer.

[0025] 3. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles disclosed in the present invention fixes the metal grid through the depression on the insulating gasket, thereby ensuring that the central circular holes of the three metal grids can be aligned, and the particles can pass through the metal grids to reach the collection plate. There are evenly distributed circular holes on the insulating gasket and the metal gasket, and the round tube, the insulating gasket, the metal gasket and the grid are fixed together by bolts. A pulsed high voltage is applied to the middle grid through the high-voltage connector on the circular hole to form an electrostatic field around it. The central arrangement can ensure that the mesh is not shielded and ensure that the thruster plume reaches the collection plate normally.

[0026] 4. The time-of-flight mass spectrometer disclosed in the present invention is used for characterizing the performance of an electrospray thruster at different angles. The launch angle of the electrospray thruster is controlled by an electric rotating table outside the vacuum chamber, and the rotation angle of the thruster is precisely controlled, thereby realizing the measurement of the plume velocity of the electrospray thruster at different angles. This expands the dimension of measuring the working performance of the thruster and can measure the working ability of the thruster in different angular directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the connection of various parts of a TOF device (time-of-flight mass spectrometer, the same below);

[0028] FIG. 2( a ), FIG. 2( b ) and FIG. 2( c ) are schematic internal views of an electrostatic gate device, a particle flight tube section and a collection device in a TOF device of the present invention, respectively;

[0029] Figure 3 It is a measurement schematic diagram of a specific embodiment of the present invention;

[0030] Figure 4 Schematic diagram of the collector plate current waveform obtained in the positive voltage mode;

[0031] Figure 5 Schematic diagram of the collector plate current waveform obtained under negative voltage mode;

[0032] Figure 6 It is a schematic diagram of thruster specific impulse (thrust) / launch angle curve;

[0033] Figure 7 This is a schematic diagram of the connection between the TOF device and the vacuum chamber;

[0034] Figure 8 The electromagnetic interference image at the plate was not collected using a TOF device;

[0035] Fig. 9 Using a TOF device to collect electromagnetic interference images at the plate;

[0036] Fig.10 It is the thruster rotation system in the present invention.

[0037] Among them, 1-electrostatic gate device, 1a-stainless steel round tube with flange, 1b-insulating gasket, 1c-metal grid, 1d-circular metal gasket, 2-particle flight tube section, 3-collecting device, 3a-stainless steel round tube with flange, 3b-insulating gasket, 3c-metal grid, 3d-collecting plate, 3e-flange cover, 4-TOF device, 5-thruster, 6-power supply system, 7-data acquisition device, 8-vacuum cabin, 9-thruster system. DETAILED DESCRIPTION

[0038] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0039] Embodiment 1:

[0040] The time-of-flight mass spectrometer for characterizing the performance of an electrospray thruster at different angles disclosed in this embodiment measures the plume generated by the ionic liquid electrospray thruster 5, the output range of the external DC power supply is 0-3500V, the plume duration is in the microsecond range, the maximum current can reach tens of microamperes, and the plume path is 600-800mm. The main components of the plume are charged particles and neutral particles with different speeds.

[0041] like Figure 1 As shown, the time-of-flight mass spectrometer device disclosed in this embodiment is used for characterizing the performance of an electrospray thruster at different angles, which includes an electrostatic gate device 1, a particle flight tube section 2 and a collection device 3.

[0042] As shown in FIG2 , it is a schematic diagram of the connection relationship between the electrostatic gate device, the particle flight tube section and the collection device in the TOF device.

[0043] The device structure of the electrostatic gate device 1 is shown in Figure 2 (a), wherein the stainless steel round tube 1a with flange is welded together with the flange. There is an insulating gasket inside the round tube, and a metal grid is in the middle. A circular hole is opened on the wall of the insulating gasket round tube. The high-voltage connector is connected to the metal grid in the middle through the circular hole. The front and rear metal grids are grounded. There is a circular metal gasket in front of the grid, and the middle circular hole can limit the plume diffusion angle. In this embodiment, the metal grid is fixed by the depression on the insulating gasket, so as to ensure that the central circular holes of the three metal grids can be aligned, and the particles can pass through the metal grid to reach the collection plate. There are evenly distributed circular holes on the insulating gasket and the metal gasket, and the round tube, insulating gasket, metal gasket and grid are fixed together by bolts. The pulsed high voltage is applied to the middle grid through the high-voltage connector on the circular hole to form an electrostatic field around it.

[0044] Both ends of the particle flight tube section 2 are provided with flanges, and the middle is a round tube. The device structure of the collecting device 3 is shown in FIG2(c), wherein the stainless steel round tube 3a with flange is welded with the flange. There is an insulating gasket inside the round tube, and a metal grid and a collecting plate are provided in the middle. The metal grid and the collecting plate are connected to two high-voltage connectors on the flange cover plate through wires. In this embodiment, the metal grid and the collecting plate are fixed by the depression on the insulating gasket, and there are evenly distributed round holes on the insulating gasket, and the insulating gasket and the grid are fixed together by bolts.

[0045] The electrostatic gate device 1 is fixedly connected to the vacuum chamber 8 and the particle flight pipe section 2 through a flange. The round tube extends into the vacuum chamber. There are four bolt holes on the flange. The three flanges are connected and fixed by bolts and nuts. The collecting device 3 is also fixedly connected to the particle flight pipe section through a flange. The high-voltage connector on the electrostatic gate device is connected to the pulse power supply outside the vacuum chamber through a shielded wire. The metal grid is connected to the round tube through a wire and grounded. The collecting plate in the collecting device is connected to the vacuum connector on the flange cover. The vacuum connector is connected to the data acquisition device through a shielded wire. The data acquisition device includes a current amplifier and an oscilloscope. Shielded wires are used between the vacuum connector and the data acquisition device to prevent electromagnetic interference. The high-voltage connector at the tail of the thruster is connected to the high-voltage DC power supply outside the vacuum chamber, and the extraction pole is grounded.

[0046] The TOF test principle is: when the electrostatic gate does not apply pulse high voltage, the charged particles in the plume generated by the thruster can reach the collection plate. At this time, a pulse high voltage is applied, and the charged particles cannot pass through the electrostatic gate, while the charged particles with different speeds that have passed will reach the collection plate one after another, thus obtaining a current image that decreases from the maximum value to zero, such as Figure 4 and Figure 5 As shown, after obtaining the image, the launch mode, thrust and specific impulse of the thruster are obtained according to formulas (4) to (6).

[0047] The principle of variable angle TOF test is: control the thruster launch angle α through the rotating table to change the thruster plume launch angle. At this time, a pulse high voltage is applied to the electrostatic gate to make the different charged particles passing through reach the collecting plate one after another, and a current image corresponding to different angles is obtained, and the maximum value is reduced to zero. After obtaining the image, the thruster launch mode, thrust and specific impulse can be obtained according to formulas (4) to (6). By calculating the working plume characteristics of the thruster at different angles, the specific impulse (thrust) / launch angle curve can be fitted with the launch angle as the independent variable and the key performance parameters such as specific impulse and thrust as the dependent variables, and the thruster working performance at different angles can be predicted based on this curve.

[0048]

[0049] Where m, v, q are the mass, velocity and charge of the charged particle, respectively, and U is the emission voltage. In the TOF test, the flying speed of the charged particle is

[0050]

[0051] Where L is the distance between the collector and the electrostatic gate, and t is the flight time of the charged particle. In the TOF curve, the charge of the charged particle can be obtained by integrating the current I(t):

[0052]

[0053] Among them, t0 is the initial time of TOF, t TOF is the time when the current signal decreases to 0, and I(t) is the current that changes with time in TOF. The mass flow rate of the propellant can be calculated from equations (1) to (3): for

[0054]

[0055] According to the momentum theorem T TOF t=mv and (3) we get

[0056]

[0057] Where T TOFis the thrust calculated from the TOF curve. According to the definition of specific impulse,

[0058]

[0059] In this embodiment, an ionic liquid electrospray thruster is selected to verify the basic function of the TOF device. By applying a pulse voltage and collecting current data on the collection plate, the speed of the plume generated by the electrospray thruster is measured.

[0060] Figure 7 The basic size of the medium vacuum chamber is 50cm×60cm. When conducting TOF experiments inside this vacuum chamber, a certain distance is required between each device. The internal length is not enough to place each device in the TOF experiment. Therefore, the TOF device 4 needs to be connected to the vacuum chamber through the vacuum chamber external flange to conduct TOF experiments so that the flight distance reaches 0.8m to test the performance of the ionic liquid electrospray thruster.

[0061] Before the formal experimental test, the electromagnetic interference signals at the collecting plate without using the TOF device 4 and with using the TOF device 4 were measured, and the oscilloscope images were obtained respectively. Figure 8 and Fig. 9 As shown, it can be concluded from the image that the use of the TOF device can significantly reduce electromagnetic interference.

[0062] The measurement process of the time-of-flight mass spectrometer for characterizing the performance of the electrospray thruster at different angles disclosed in this embodiment is as follows: a positive voltage is applied to the electrospray thruster 5 until the electrospray thruster 5 successfully launches a plume and the voltage is stopped from being increased when the thruster is working stably. At the same time, the current amplifier in the data acquisition device 7 is turned on and adjusted to a suitable gear, and whether there is current on the oscilloscope is observed. Then, a pulse voltage is applied to the electrostatic gate device 1, and the current image change on the oscilloscope is observed. Then, the voltage is reduced to zero and switched to a negative voltage, and the above steps are repeated.

[0063] The thruster launch angle is controlled by the rotating table in the thruster system 9, so that the thruster 4 rotates 5° in the clockwise direction. When the thruster 4 is working stably, the current amplifier is turned on and adjusted to the L position with a magnification of 10. 6 times, observe whether there is current on the oscilloscope, apply pulse high voltage to the electrostatic gate device 1, observe the change of the current image on the oscilloscope, then rotate the thruster 4 5° clockwise again, and repeat the above steps, where the thruster rotation angle range is -45° to +45°.

[0064] The time and current data of the collecting plate 3d collected by the data acquisition device 7 are obtained as follows: Figure 4 and Figure 5The image is obtained by calculating according to the formula, combining the distance of the device plume flight path, and obtaining the speed of charged particles in the plume, and obtaining the working thrust and specific impulse of the thruster 4 according to the above formula. By calculating the working plume characteristics of the thruster at different angles, the specific impulse (thrust) / launch angle curve can be fitted with the launch angle as the independent variable and the key performance parameters such as specific impulse and thrust as the dependent variables, and the working performance of the thruster at different angles can be predicted based on the curve, such as Figure 6 shown.

[0065] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles, characterized in that: It includes a time-of-flight mass spectrometer, a thruster rotation system, a thruster, a power supply system, and a data acquisition device; The time-of-flight mass spectrometer comprises an electrostatic gate device, a particle flight tube section and a collecting device; the electrostatic gate device is a stainless steel round tube with a flange, and an insulating gasket, a metal grid and a metal gasket with a central circular hole are placed inside the round tube, and the size of the different central circular holes can change the particle inlet flow rate; the electrostatic gate is horizontally connected to the particle flight tube section through a flange; both ends of the particle flight tube section are provided with flanges; the collecting device is horizontally connected to the particle flight tube section through another flange; the collecting device is a stainless steel round tube with a flange, and an insulating gasket, a metal grid and a collecting plate are placed inside the round tube; the thruster rotation system comprises a thruster system, an electric rotating table and a fixing device; the fixing device is a transfer plate and a z-axis lifting table; the thruster system comprises an electrospray thruster and a thruster housing; the electric rotating disk is connected to an external control system through a control line; The thruster device comprises an electrospray thruster, an electrospray thruster rotation system and a fixing device; The power supply system includes a voltage-adjustable high-voltage DC power supply and a high-voltage pulse power supply; The data acquisition device includes a current amplifier and an oscilloscope.

2. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles according to claim 1, characterized in that: The electrostatic door device comprises a stainless steel round tube with a flange, an insulating gasket, a metal grid and a round metal gasket, wherein the metal grid is placed on the groove of the insulating gasket, and the notch on the metal grid coincides with the protrusion of the insulating gasket; The insulating gasket, metal grid and metal gasket are inside the round tube, the metal gasket is at the tube mouth, followed by the insulating gasket and metal grid in sequence. There are four insulating gaskets and three metal grids in total. The insulating gaskets, metal grids and metal gaskets fit tightly and are fixed to the round tube with bolts; the adapter plate is used to connect and fix the z-axis lifting platform and the electric rotating platform, and is installed between the electric rotating platform and the z-axis lifting platform.

3. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles according to claim 1, characterized in that: The collecting device comprises a stainless steel round tube with a flange, an insulating gasket, a metal grid, a collecting plate, a disc flange and a spring. The metal grid and the collecting plate are placed on the groove of the insulating gasket, and the notches on the metal grid and the collecting plate coincide with the protrusions of the insulating gasket. The insulating gasket, the grid and the collecting plate are placed at the pipe mouth in sequence. The electrostatic gate grid has three insulating gaskets, one grid and one collecting plate. The spring is placed between the disc flange and the last insulating gasket and contacts the two. The thruster housing can fix the thruster at the center of the z-axis lifting platform.

4. The time-of-flight mass spectrometer for characterizing the performance of an electrospray thruster at different angles according to claim 1, 2 or 3, characterized in that: The flange sizes of the electrostatic gate device, the particle flight tube section and the collection device are the same and are connected by bolts; the adapter plate is provided with different threaded holes for connecting and fixing the z-axis lifting platform and the electric rotating platform; the thruster housing is provided with screw holes on both sides for fixing the thruster at the center position of the z-axis lifting platform.

5. The time-of-flight mass spectrometer for characterizing the performance of an electrospray thruster at different angles according to claim 1, 2 or 3, characterized in that: There are sealing rings between the electrostatic door device, the particle flight pipe section and the flange of the collection device.

6. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles according to claim 1 or 2, characterized in that: The insulating gasket, the metal grid and the circular metal gasket with a central circular hole in the electrostatic gate device are all provided with four evenly distributed circular holes for bolt connection.

7. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles according to claim 1 or 2, characterized in that: The stainless steel round tube with flange of the electrostatic door device has a round hole on its wall for inserting a high-voltage connector.

8. The time-of-flight mass spectrometer for characterizing the performance of electrospray thrusters at different angles according to claim 1 or 2, characterized in that: The center of the metal gasket in the electrostatic door device is provided with a circular hole, and the circular hole is used to adapt to and replace the metal gaskets with different circular hole sizes.

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