Electron beam field quasi-periodic reconstruction system and method for discharge oscillation of electric thruster

Abstract

The application provides a beam light field quasi-periodic reconstruction system and method for discharge oscillation of an electric thruster. The method comprises the following steps: spraying a beam plasma in a vacuum chamber after the electric thruster is started; monitoring and modulating a discharge current, sending an image acquisition trigger signal to a shooting and processing system, or modulating a voltage input into the electric thruster to obtain a modulated discharge current, and returning to the step of monitoring the discharge current of the electric thruster; based on the image acquisition trigger signal, the shooting and processing system acquires an image of the beam plasma, obtains a beam circumferential projection picture time sequence after a preset angle of rotation, processes the beam circumferential projection picture time sequence under different angles according to a three-dimensional tomographic reconstruction algorithm, and obtains a beam three-dimensional light field time sequence. The method realizes dynamic reconstruction of a beam three-dimensional light field time sequence with low cost and high synchronization accuracy.

Description

Technical Field

[0001] This application relates to the field of space electric propulsion technology, and more specifically, to a quasi-periodic reconstruction system and method for beam optical field of electric thruster discharge oscillation. Background Technology

[0002] Compared to traditional chemical propulsion, space electric propulsion, with its advantages of high specific impulse, long lifespan, and precisely adjustable thrust, has been widely used in various missions such as satellite position maintenance, orbit transfer, and deep space exploration. Hall thrusters are among the most widely used electric thrusters in the field of space electric propulsion; however, they suffer from various discharge instabilities, such as axial breathing oscillations and ion transit instabilities, and circumferential spoke oscillations and electron cyclotron drift instabilities. These instabilities are inherent in Hall thrusters, and their performance is closely related to the thruster's performance, efficiency, and lifespan, making them crucial for the stable operation of the entire electric propulsion system and even the satellite.

[0003] Existing diagnostic technologies are mainly divided into two categories: contact probes and non-contact optical diagnostics. Among them, high-speed cameras are the mainstream means of obtaining the spatiotemporal characteristics of discharge oscillations, including: Contact probe technology: physical probes such as saturation probes and Langmuir three-probes are used to directly penetrate the plasma beam to measure the time-series evolution data of parameters such as electron density and temperature. The advantage is that the structure is simple and can obtain time-analytical data of various plasma parameters; the disadvantage is that the spatial coverage is insufficient: it can only measure a limited number of spatial points and cannot reconstruct the full field distribution information. Non-contact optical diagnostic technology: the technology solution with high-speed cameras as the core is the closest existing technology, which mainly includes three implementation methods: (1) Unidirectional shooting mode: a single high-speed camera takes a time series of two-dimensional images of beam intensity integration from a fixed direction (such as axial or circumferential). The disadvantage is that it can only obtain oscillation information in a single direction (such as circumferential or axial) and cannot reflect the three-dimensional spatial effect. The integration of two-dimensional images masks the local microstructure, resulting in incomplete analysis of oscillation propagation path. (2) Bidirectional synchronous shooting mode: a single high-speed camera can simultaneously acquire images in two directions through a plane mirror group. The disadvantages are that the optical path debugging is complicated (the lens group angle needs to be accurate to the arcsecond level); the number of directions is limited (maximum two), and the three-dimensional reconstruction data is incomplete; the lens group introduces optical path errors, reducing the image alignment accuracy. (3) Multi-camera multi-directional shooting mode: deploy multiple high-speed cameras to cover different angles and obtain multi-directional image sequences. The disadvantages are that the price of a single device exceeds one million, and the cost of multiple systems increases exponentially; the trigger delay between devices is >1μs (typical oscillation period 10–100μs), which leads to "spatiotemporal tearing" in three-dimensional reconstruction; the calibration and maintenance of multiple devices is complicated and the practicality is low. Summary of the Invention

[0004] The purpose of this application is to provide a quasi-periodic beam optical field reconstruction system and method for electric thruster discharge oscillation, which ensures the quasi-periodicity of discharge through current monitoring and modulation. Combined with multi-angle rotation shooting and three-dimensional tomography reconstruction by a single high-speed camera, it realizes low-cost and high-synchronization-precision dynamic reconstruction of the beam three-dimensional optical field time series.

[0005] It achieves low-cost, nanosecond-level synchronous three-dimensional light field reconstruction supported by a single high-speed camera, breaking through the dimensional and cost limitations of traditional diagnostics and providing a feasible tool for the study of the three-dimensional propagation mechanism of discharge oscillation.

[0006] In a first aspect, a quasi-periodic reconstruction method for the beam optical field of electric thruster discharge oscillation is provided, applied to a quasi-periodic reconstruction system for the beam optical field of electric thruster discharge oscillation. The system includes: an electric thruster, a vacuum chamber, a vacuum chamber observation window, a monitoring and modulation system, and an imaging and processing system. The method may include:

[0007] After the electric thruster is activated, it ejects a beam of plasma into the vacuum chamber;

[0008] The monitoring and modulation system monitors the discharge current of the electric thruster and determines whether to modulate the voltage input to the electric thruster based on the monitoring results. Specifically, when the discharge current meets the quasi-periodic condition and reaches a preset current value, an image acquisition trigger signal is sent to the imaging and processing system. When the discharge current does not meet the quasi-periodic condition, the voltage input to the electric thruster is modulated to obtain a modulated discharge current, and the system returns to the execution step: monitoring the discharge current of the electric thruster.

[0009] Based on the image acquisition trigger signal, the imaging and processing system acquires images of the beam plasma corresponding to multiple preset angles of rotation of the central axis of the electric thruster, obtaining time series of circumferential projection images of the beam at different angles. Then, according to the three-dimensional tomography reconstruction algorithm, the time series of circumferential projection images of the beam at different angles are processed to obtain the time series of three-dimensional light intensity field of the beam.

[0010] In one possible implementation, the monitoring and modulation system includes a thruster power supply system, a current clamp, a discharge current monitoring and determination module, and an active modulation module;

[0011] The monitoring and modulation system monitors the discharge current of the electric thruster and determines, based on the monitoring results, whether to modulate the voltage input to the electric thruster, including:

[0012] The discharge current monitoring and determination module collects the discharge current of the electric thruster after startup through the current clamp; the discharge current monitoring and determination module monitors the discharge current to determine whether the discharge current meets the quasi-periodic condition;

[0013] If the conditions are met, the discharge current monitoring and determination module will output an image acquisition trigger signal to the imaging and processing system when it detects that the discharge current has reached the preset current value.

[0014] If the conditions are not met, the discharge current monitoring and determination module outputs a modulation signal to the active modulation module to instruct the active modulation module to modulate the input voltage to the electric thruster through the thruster power system. When the discharge current monitoring and determination module detects that the modulated discharge current meets the preset current condition, the discharge current monitoring and determination module checks whether the modulated discharge current reaches the preset current value. If it does, the discharge current monitoring and determination module outputs an image acquisition trigger signal to the imaging and processing system.

[0015] In one possible implementation, the shooting and processing system includes a function signal generator, a high-speed camera, a data processing system, and a rotating platform;

[0016] The time series of the three-dimensional light intensity field of the electric thruster beam was obtained, including:

[0017] After receiving the image acquisition trigger signal output by the discharge current monitoring and determination module, the function signal generator outputs a level trigger signal to the high-speed camera to trigger the high-speed camera to start.

[0018] A high-speed camera captures the time series of the circumferential projection image of the electric thruster's beam. After the rotating platform rotates around the central axis of the electric thruster by a preset angle, the time series of the circumferential projection image of the beam during the discharge cycle are obtained at different angles. The time series of the circumferential projection image of the beam collected at different angles are uploaded to the data processing system.

[0019] The data processing system processes the time series of the circumferential projection map of the beam collected at different angles according to the three-dimensional tomographic reconstruction algorithm to obtain the time series of the three-dimensional light intensity field of the electric thruster beam.

[0020] In one possible implementation, the preset current condition includes:

[0021] Quasi-periodic conditions are defined as follows: the repeatability of the discharge current for different periods is better than 10%.

[0022] The condition for consistent main frequency is that the corresponding oscillation main frequency values ​​obtained by performing Fourier processing on the modulated discharge current and the discharge current before modulation do not differ by more than ±10%, and no new oscillation main frequency is generated.

[0023] The time-average consistency condition is that the average value of the modulated discharge current and the discharge current before modulation on a second-scale time scale does not differ by more than ±10%.

[0024] In one possible implementation, the active modulation module modulates the input voltage to the electric thruster via the thruster power system, including:

[0025] The active modulation module changes the amplitude, frequency, and waveform of the input voltage to the electric thruster through the thruster power system.

[0026] Secondly, a quasi-periodic beam optical field reconstruction system for electric thruster discharge oscillation is provided, the system may include:

[0027] Electric thruster, vacuum chamber, vacuum chamber observation window, monitoring and modulation system, and imaging and processing system;

[0028] The electric thruster is placed inside the vacuum chamber, and the observation window of the vacuum chamber is located on top of the electric thruster inside the vacuum chamber, directly facing the beam region of the electric thruster;

[0029] The electric thruster is electrically connected to the monitoring and modulation system, and the monitoring and modulation system is electrically connected to the imaging and processing system.

[0030] In one possible implementation, the monitoring and modulation system includes: a thruster power supply system, a current clamp, a discharge current monitoring and determination module, and an active modulation module;

[0031] The output of the thruster power system is electrically connected to the electric thruster via a current clamp. The input of the discharge current monitoring and determination module is electrically connected to the current clamp. One end of the active modulation module is electrically connected to the input of the thruster power system. The other end of the active modulation module is electrically connected to one output of the discharge current monitoring and determination module. The other output of the discharge current monitoring and determination module is electrically connected to the imaging and processing system.

[0032] In one possible implementation, the shooting and processing system includes: a function signal generator, a high-speed camera, a data processing system, and a rotating platform;

[0033] The electric thruster is placed on the rotating platform inside the vacuum chamber; the high-speed camera is placed at the observation window of the vacuum chamber.

[0034] The input terminal of the function signal generator is electrically connected to the monitoring and modulation system, the output terminal of the function signal generator is electrically connected to the input terminal of the high-speed camera, and the input terminal of the high-speed camera is electrically connected to the input terminal of the data processing system.

[0035] In one possible implementation, the central axis of the electric thruster is located at the center of the field of view of the high-speed camera, and the shooting direction of the high-speed camera is perpendicular to the central axis of the electric thruster.

[0036] In one possible implementation, the shooting and processing system further includes: a narrowband filter array, which comprises different narrowband filters;

[0037] The narrowband filter array is configured to be mounted in front of the camera lens of the high-speed camera, so that the camera lens of the high-speed camera can be paired with any narrowband filter.

[0038] This application provides a quasi-periodic beam field reconstruction system and method for electric thruster discharge oscillation. This method is applied to a quasi-periodic beam optical field reconstruction system for electric thruster discharge oscillation. The system includes an electric thruster, a vacuum chamber, a vacuum chamber observation window, a monitoring and modulation system, and an image acquisition and processing system. The method includes: after the electric thruster starts, it ejects a beam plasma into the vacuum chamber; the monitoring and modulation system monitors the discharge current of the electric thruster and determines whether to modulate the input voltage based on the monitoring results; when the discharge current meets the quasi-periodic condition and reaches a preset current value, it sends an image acquisition trigger signal to the image acquisition and processing system; when the discharge current does not meet the quasi-periodic condition, it modulates the input voltage of the electric thruster to obtain the modulated discharge current and returns to the execution step: monitoring the discharge current of the electric thruster; based on the image acquisition trigger signal, the image acquisition and processing system acquires images of the beam plasma corresponding to multiple preset angles of rotation of the electric thruster's central axis, obtaining time series of circumferential projection images of the beam at different angles, and processes these time series of circumferential projection images of the beam at different angles according to a three-dimensional tomographic reconstruction algorithm to obtain the three-dimensional beam intensity field time series of the electric thruster. This method ensures the quasi-periodicity of discharge through current monitoring and modulation, and combines multi-angle rotation shooting with three-dimensional tomography reconstruction using a single high-speed camera to achieve low-cost, high-synchronization-precision dynamic reconstruction of the time sequence of the beam's three-dimensional optical field. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A schematic diagram of a beam optical field quasi-periodic reconstruction system for electric thruster discharge oscillation provided in this application embodiment;

[0041] Figure 2 A schematic diagram of another beam optical field quasi-periodic reconstruction system for electric thruster discharge oscillation provided in this application embodiment;

[0042] Figure 3 A flowchart illustrating a quasi-periodic reconstruction method for beam optical field of electric thruster discharge oscillation provided in an embodiment of this application;

[0043] Figure 4 This document provides a time series of a three-dimensional beam intensity field within a single discharge cycle, as well as a schematic diagram of the discharge current waveform at each angle at the start of the image capture, for embodiments of this application. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art. Words such as "comprising" or "including" mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects. Words such as "connection," "coupled," or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0045] This application ensures that the electric thruster operates in a state where the discharge current exhibits quasi-periodic characteristics (the repeatability of discharge currents in different periods is better than 10%) by constructing a quasi-periodic beam optical field reconstruction system for electric thruster discharge oscillation. By selecting an appropriate current trigger value and delay trigger time, the system will trigger the electric thruster beam multi-angle synchronous triggering and imaging system when the electric thruster is in the same discharge state, causing it to rotate the electric thruster and trigger a high-speed camera to take pictures at different circumferential angles, thereby obtaining the time series of two-dimensional beam intensity integral maps from multiple angles. Through three-dimensional reconstruction, the time series of three-dimensional beam intensity field can be further obtained, and then the oscillation propagation characteristics in different directions can be analyzed.

[0046] Figure 1 This is a schematic diagram of the structure of the beam optical field quasi-periodic reconstruction system for electric thruster discharge oscillation provided in the embodiments of this application. The system may include: electric thruster 1, vacuum chamber 2, vacuum chamber observation window 3, monitoring and modulation system 100, and imaging and processing system 200.

[0047] The electric thruster 1 is placed inside the vacuum chamber 2.

[0048] Vacuum chamber 2 is the enclosed environment for the experiment, used to provide the high vacuum required for the operation of electric thruster 1 (e.g., better than 10 ... The vacuum chamber 2 employs a rigid cavity design with excellent sealing performance. This, combined with a vacuum pumping system (containing necessary supporting structures), maintains a high internal vacuum, meeting the environmental requirements for beam plasma generation and stable discharge of the electric thruster 1, and preventing air molecules from interfering with plasma characteristics and diagnostic results. The vacuum chamber 2 has no additional obstructions inside, ensuring the beam plasma propagation path remains undisturbed, while also providing ample field of view for multi-angle imaging.

[0049] The vacuum chamber observation window 3 is located on the wall of the vacuum chamber 2 (preferably the top of the vacuum chamber 2) and has high light transmittance to facilitate optical observation. The vacuum chamber observation window 3 serves as the only channel for optical imaging and its position corresponds precisely to the arrangement of the imaging and processing system 200. That is, the vacuum chamber observation window 3 faces the beam area of ​​the electric thruster 1, while maintaining the airtightness of the chamber to ensure a high vacuum environment.

[0050] The monitoring and modulation system 100 is electrically connected to the electric thruster 1 and is used to monitor and modulate the discharge current.

[0051] The imaging and processing system 200 is electrically connected to the monitoring and modulation system 100 to trigger image acquisition and data processing for three-dimensional reconstruction of beam images captured synchronously from multiple angles.

[0052] like Figure 2 As shown, the monitoring and modulation system 100 may include: a thruster power supply system 4, a current clamp 5, a discharge current monitoring and determination module 6, and an active modulation module 8. Wherein:

[0053] The thruster power system 4 provides operating voltage and current to the electric thruster 1. The output terminal of the thruster power system 4 is connected in series with the discharge circuit of the electric thruster 1 through the current clamp 5.

[0054] The current clamp 5 (such as a Hall effect current sensor) is used to collect the discharge current signal of the electric thruster 1 in a non-contact manner. The output end of the current clamp 5 is electrically connected to the input end of the discharge current monitoring and judgment module 6.

[0055] The discharge current monitoring and determination module 6 (such as a digital signal processing system based on FPGA or microprocessor) is used to monitor the current waveform of the discharge current output by the current clamp 5 in real time and determine whether the current waveform meets the quasi-periodicity condition (specific conditions are described later).

[0056] One end of the active modulation module 8 (such as a programmable power modulator) is electrically connected to the input terminal of the thruster power system 4, and the other end of the active modulation module 8 is electrically connected to one output terminal of the discharge current monitoring and determination module 6. When the discharge current does not meet the conditions, the discharge current monitoring and determination module 6 outputs a modulation signal to the active modulation module 8. The active modulation module 8 modulates the input voltage of the thruster power system 4 (e.g., by changing the amplitude, frequency, or waveform) to achieve active modulation of the discharge current. The other output terminal of the discharge current monitoring and determination module 6 is electrically connected to the imaging and processing system 200, and is used to output an image acquisition trigger signal when the discharge current meets the conditions.

[0057] like Figure 2 As shown, the imaging and processing system 200 may include: a function signal generator 7, a high-speed camera 9, a data processing system 10, and a rotating platform 12. Wherein:

[0058] The electric thruster 1 is fixed on the rotating platform 12 (such as a rotary table driven by a stepper motor). The rotating platform 12 can rotate precisely around the central axis of the electric thruster 1 by a preset angle (for example, rotating 20 degrees each time, covering a 360-degree range).

[0059] A high-speed camera 9 (such as a Phantom high-speed camera) is placed outside the vacuum chamber observation window 3, and is aimed at the beam region of the electric thruster 1 through the vacuum chamber observation window 3. The shooting direction of the high-speed camera 9 is perpendicular to the central axis of the electric thruster 1, and the central axis of the electric thruster 1 is located at the center of the field of view of the high-speed camera 9 to ensure that the image is distortion-free.

[0060] The input terminal of the function signal generator 7 is electrically connected to the output terminal of the discharge current monitoring and determination module 6 in the monitoring and modulation system 100, and is used to receive the image acquisition trigger signal; the output terminal of the function signal generator 7 is electrically connected to the input terminal of the high-speed camera 9, and can output a high / low level trigger signal with a set delay time (the delay time is usually adjustable from 0 to 100 ms, with an accuracy of ns).

[0061] The output of the high-speed camera 9 is electrically connected to the data processing system 10 (such as a computer workstation running MATLAB or custom reconstruction software) to upload the time series of the circumferential projection map of the beam at a certain angle within a single discharge cycle. Before the high-speed camera 9 operates, the shooting range 11 of the high-speed camera 9 needs to be calibrated using a film plate to correct optical distortion and ensure image accuracy.

[0062] The rotating platform 12 is communicatively / electrically connected to the data processing system 10. After the high-speed camera 9 completes the capture of an image sequence at a certain angle, it uploads the data to the data processing system 10. Once the data processing system 10 confirms that the data has been received, it generates a rotation command. This command may be executed via a separate platform controller (not shown separately in the figure) or directly by the motor of the rotating platform 12 driven by the data processing system 10.

[0063] This system achieves low-cost, nanosecond-level synchronous 3D light field reconstruction supported by a single high-speed camera, breaking through the dimensional and cost limitations of traditional diagnostics and providing a feasible tool for studying the 3D propagation mechanism of discharge oscillations. Simultaneously, through a closed-loop design of intelligent monitoring-modulation-triggering-reconstruction, the system upgrades the traditional high-cost, low-dimensional diagnostic paradigm into an economical, high-precision, and fully 3D dynamic analysis tool.

[0064] Figure 3 This is a flowchart illustrating a quasi-periodic reconstruction method for the beam optical field of an electric thruster discharge oscillation, provided as an embodiment of this application. Figure 3 As shown, the method may include:

[0065] Step S310: After the electric thruster is started, a beam of plasma is ejected from the vacuum chamber.

[0066] The electric thruster 1 is powered by the thruster power system 4, which enables it to start up and eject a beam of plasma into the vacuum chamber 2. The current clamp 5 collects the discharge current signal in real time and transmits it to the discharge current monitoring and judgment module 6.

[0067] Step S320: The monitoring and modulation system monitors the discharge current of the electric thruster after startup, and determines whether to modulate the voltage of the input electric thruster based on the monitoring results, so as to send an image acquisition trigger signal to the imaging and processing system.

[0068] In specific implementation, the monitoring and modulation system 100 collects the discharge current of the electric thruster 1 after startup and monitors the discharge current. When the discharge current reaches the preset current value, it sends an image acquisition trigger signal to the image acquisition and processing system 200. When the discharge current does not reach the preset current value, it modulates the voltage input to the electric thruster to obtain the modulated discharge current and returns to the execution step: monitoring the discharge current of the electric thruster 1.

[0069] Specifically, the discharge current monitoring and determination module 6 collects the discharge current of the electric thruster 1 after startup through the current clamp 5; the discharge current monitoring and determination module 6 monitors the discharge current to determine whether the discharge current meets the quasi-periodic condition.

[0070] If the conditions are met, the discharge current monitoring and judgment module 6 will output an image acquisition trigger signal to the shooting and processing system 200 when it detects that the discharge current has reached the preset current value.

[0071] If the conditions are not met (e.g., waveform irregularity, poor periodicity), the discharge current monitoring and judgment module 6 outputs a modulation signal to the active modulation module 8 to instruct the active modulation module 8 to modulate the input voltage to the electric thruster 1 through the thruster power system 4. The modulation method may include changing the voltage amplitude, frequency, and waveform. The modulation frequency must be set to N times (N≥1) of the discharge oscillation main frequency to be diagnosed (or the least common multiple of its multiple types of oscillation main frequencies) to ensure modulation effectiveness. During the modulation process, the discharge current monitoring and judgment module 6 continuously monitors the modulated discharge current. That is, when the discharge current monitoring and judgment module 6 detects that the modulated discharge current meets the preset current condition, the discharge current monitoring and judgment module 6 checks whether the modulated discharge current has reached the preset current value. If it has, the discharge current monitoring and judgment module 6 outputs an image acquisition trigger signal to the imaging and processing system 200.

[0072] The preset current conditions may include:

[0073] Quasi-periodic conditions are defined as follows: the repeatability of the discharge current for different periods is better than 10%.

[0074] The condition for consistent main frequency is that the corresponding oscillation main frequency values ​​obtained by performing Fourier processing on the modulated discharge current and the discharge current before modulation do not differ by more than ±10%, and no new oscillation main frequency is generated.

[0075] The time-average consistency condition is that the average value of the modulated discharge current and the discharge current before modulation on a second-scale time scale does not differ by more than ±10%.

[0076] The system ensures the comparability of data from different periods by satisfying three conditions (quasi-periodicity, consistency of main frequency, and consistency of time average).

[0077] Step S330: The imaging and processing system, based on the image acquisition trigger signal, performs image acquisition on the beam plasma corresponding to multiple preset angles of rotation of the central axis of the electric thruster, obtains the time series of the circumferential projection map of the beam at different angles, and processes the time series of the circumferential projection map of the beam at different angles according to the three-dimensional tomographic reconstruction algorithm to obtain the time series of the three-dimensional light intensity field of the beam.

[0078] Here, different angles refer to the different angles obtained by rotating around the central axis of the electric thruster 1 multiple times by preset angles.

[0079] The shooting and processing system 200 includes a function signal generator 7, a high-speed camera 9, a data processing system 10, and a rotating platform 12.

[0080] After receiving the image acquisition trigger signal output by the discharge current monitoring and judgment module 6, the function signal generator 7 outputs a level trigger level to the high-speed camera 9 after a user-configurable precise delay (used to compensate for optical or circuit delays, or to specify the start of shooting from a specific moment within the discharge cycle) to trigger the high-speed camera 9.

[0081] Once triggered, the high-speed camera 9 begins capturing images at a preset frame rate. This preset frame rate should be determined based on the dominant frequency of the discharge oscillation to be studied, typically twice or more of the dominant frequency, to satisfy the Nyquist sampling theorem and ensure that oscillation details can be captured. The high-speed camera 9 continuously captures images, recording the time series of the beam circumferential projection map of the electric thruster 1 during one or more discharge cycles. After capturing the images, the time series image data is uploaded to the data processing system 10 for temporary storage.

[0082] After the rotating platform 12 rotates around the central axis of the electric thruster 1 by a preset angle, the above-mentioned monitoring, modulation, shooting and data uploading process is repeated until the time series of the circumferential projection map of the beam collected at different angles is obtained; the time series of the circumferential projection map of the beam collected at different angles is uploaded to the data processing system 10; the rotation angle can be arbitrarily adjusted and selected each time, such as taking 18 shots at 20-degree intervals within a 360-degree range.

[0083] Since each shot is triggered by the same discharge current signal at the same phase point, it ensures that the time series of images acquired at different angles are strictly synchronized in time, that is, each frame of the image at each angle corresponds to the same moment in the discharge cycle.

[0084] The data processing system 10 can process the time series of the circumferential projection map of the beam collected at different angles through three-dimensional tomographic reconstruction algorithms such as filtered back projection or algebraic reconstruction to obtain the time series of the three-dimensional light intensity field of the electric thruster beam.

[0085] Furthermore, the data processing system 10 can perform two-point power spectral density and other processing on the three-dimensional optical field time series of the electric thruster beam to obtain the three-dimensional propagation characteristics of oscillation in different directions and other physical information.

[0086] This application achieves multi-angle shooting (e.g., 18 angles covering 360°) by rotating a platform (preset angle such as 20°), and combines it with a three-dimensional tomography algorithm (e.g., filtered back projection) to convert traditional two-dimensional integral images into three-dimensional light intensity field time series, thereby improving the full-dimensional diagnostic capability.

[0087] The current modulation module automatically maintains quasi-periodicity (repeatability error <10%), avoiding manual intervention; the rotating platform is integrated into the vacuum chamber, allowing for angle adjustment without repeatedly breaking the vacuum.

[0088] Experiments show that the implementation was carried out using the breathing oscillation of a Hall thruster as an example. The electric thruster operated under quasi-periodic conditions, with a discharge current frequency of approximately 20 kHz. The rotation angle interval was set to 20 degrees, rotating once every 20 degrees within a 360-degree range, capturing a total of 18 angles. The high-speed camera frame rate was set to 200 kHz, and the delay time was adjusted to align with the start of the discharge cycle. The implementation results are as follows... Figure 4 As shown, the time series of the three-dimensional light intensity field of the beam during a single discharge cycle, as well as the discharge current waveforms at various angles at the start of the image capture, demonstrate that the system successfully reconstructed the three-dimensional light intensity field and revealed the three-dimensional propagation characteristics of the oscillation.

[0089] Figure 4 The upper nine-square grid is the core output of this application's system, presenting the complete spatiotemporal evolution sequence of the beam field within a single discharge cycle of the Hall thruster through three-dimensional tomographic reconstruction technology. Each sub-graph represents a three-dimensional axial-radial section of the optical field at a specific moment, with the time sequence strictly following the arrangement from left to right and from top to bottom (T1 to T9), achieving a time resolution at the microsecond level.

[0090] From time T1 to time T9, the three-dimensional light field of the Hall thruster beam plasma generally shows a process of changing from dark to bright and then back to dark. This indicates that the thruster is dominated by typical axial breathing oscillation at this time. With the periodic process of a large number of electrons colliding with and ionizing neutral atoms and being consumed and propellant replenished, the thruster beam plasma exhibits oscillating behavior similar to "breathing" in the axial direction, and manifests as a global feature in three-dimensional space.

[0091] Between T4 and T6, the bright ring structure in the three-dimensional light intensity field of the beam plasma exhibits circumferential non-uniformity, which represents axial spoke oscillation, also caused by the thruster ionization process.

[0092] The two oscillations are coupled together in three-dimensional space, making them difficult to identify simultaneously using traditional diagnostic methods.

[0093] Figure 4 The image below shows the correspondence between the trigger time and the phase of the discharge current for 18 shooting angles (one point every 20 degrees within a 360-degree range). The horizontal axis represents time, and the vertical axis represents the amplitude of the discharge current.

[0094] The curve characteristics indicate that the discharge current exhibits quasi-periodic oscillations, with a waveform approximating a damped sine curve and a period of approximately 40 μs (frequency 25 kHz, typical breathing oscillation characteristics). Furthermore, the discharge current curves measured at different shooting angles satisfy the quasi-periodic condition (periodic repeatability error <10%).

[0095] Each circle in the diagram represents a trigger shooting moment, corresponding to the nine time points (T1-T9) in the upper nine-square grid. All circles are strictly aligned with the same phase points on the current curve (e.g., T1 is always at a trough, T5 is at a peak), proving that the time synchronization error of multi-angle shooting is <100ns. The circle positions are determined by the function signal generator based on a preset current threshold (e.g., the current value corresponding to the peak is ≥I). o Automatic triggering avoids delays caused by manual intervention. Nine points are evenly distributed throughout the oscillation cycle, completely capturing the entire process of light field evolution.

[0096] Furthermore, the imaging and processing system 200 may also include a narrowband filter array; this narrowband filter array may include different narrowband filters; the narrowband filter array is configured to be selectively mounted in front of the imaging lens of the high-speed camera, so that the imaging lens of the high-speed camera can be paired with any narrowband filter. That is, by changing different narrowband filters, the high-speed camera can acquire a sequence of two-dimensional projection images of the beam plasma under different characteristic spectral bands. In other words, the imaging and processing system can also use different narrowband filters paired with the high-speed camera to obtain the evolution results of the three-dimensional light field over time under different spectral bands, which can be used for further plasma parameter inversion, such as electron temperature and electron density. The relationship between light intensity in different spectral bands and plasma parameters is as follows:

[0097]

[0098] in, For characteristic spectral line intensity, For electron temperature, For electron density, This is the correction factor for ion valence state.

[0099] Those skilled in the art will understand that the embodiments in this application can be provided as methods, systems, or computer program products. Therefore, the embodiments in this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the embodiments in this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0100] This application describes embodiments of methods, apparatus (systems), and computer program products according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0101] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0102] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0103] Although preferred embodiments have been described in this application, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of this application.

[0104] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the claims in this application and their equivalents, then this application also intends to include these modifications and variations.

Claims

1. A method for quasi-periodic reconstruction of the beam optical field of an electric thruster discharge oscillation, characterized in that, A quasi-periodic beam field reconstruction system for discharge oscillations in an electric thruster, the system comprising: an electric thruster, a vacuum chamber, a vacuum chamber observation window, a monitoring and modulation system, and an imaging and processing system, the method comprising: After the electric thruster is activated, it ejects a beam of plasma into the vacuum chamber; The monitoring and modulation system monitors the discharge current of the electric thruster and determines whether to modulate the voltage input to the electric thruster based on the monitoring results. When the discharge current meets the quasi-periodic condition and reaches a preset current value, it sends an image acquisition trigger signal to the imaging and processing system. When the discharge current does not meet the quasi-periodic condition, it modulates the voltage input to the electric thruster to obtain the modulated discharge current and returns to the execution step: monitoring the discharge current of the electric thruster. Based on the image acquisition trigger signal, the imaging and processing system acquires images of the beam plasma corresponding to multiple preset angles of rotation of the central axis of the electric thruster, obtaining time series of circumferential projection images of the beam at different angles. Then, according to the three-dimensional tomography reconstruction algorithm, the time series of circumferential projection images of the beam at different angles are processed to obtain the time series of three-dimensional light intensity field of the beam.

2. The method as described in claim 1, characterized in that, The monitoring and modulation system includes a thruster power supply system, a current clamp, a discharge current monitoring and determination module, and an active modulation module. The monitoring and modulation system monitors the discharge current of the electric thruster and determines, based on the monitoring results, whether to modulate the voltage input to the electric thruster, including: The discharge current monitoring and determination module collects the discharge current of the electric thruster after startup through the current clamp; the discharge current monitoring and determination module monitors the discharge current to determine whether the discharge current meets the quasi-periodic condition; If the conditions are met, the discharge current monitoring and determination module will output an image acquisition trigger signal to the imaging and processing system when it detects that the discharge current has reached the preset current value. If the conditions are not met, the discharge current monitoring and determination module outputs a modulation signal to the active modulation module to instruct the active modulation module to modulate the input voltage to the electric thruster through the thruster power system. When the discharge current monitoring and determination module detects that the modulated discharge current meets the preset current condition, the discharge current monitoring and determination module checks whether the modulated discharge current reaches the preset current value. If it does, the discharge current monitoring and determination module outputs an image acquisition trigger signal to the imaging and processing system.

3. The method as described in claim 2, characterized in that, The shooting and processing system includes a function signal generator, a high-speed camera, a data processing system, and a rotating platform; The time series of the three-dimensional light intensity field of the electric thruster beam was obtained, including: After receiving the image acquisition trigger signal output by the discharge current monitoring and determination module, the function signal generator outputs a level trigger signal to the high-speed camera to trigger the high-speed camera to start. A high-speed camera captures the time series of the circumferential projection image of the electric thruster's beam. After the rotating platform rotates around the central axis of the electric thruster by a preset angle, the time series of the circumferential projection image of the beam during the discharge cycle are obtained at different angles. The time series of the circumferential projection image of the beam collected at different angles are uploaded to the data processing system. The data processing system processes the time series of the circumferential projection map of the beam collected at different angles according to the three-dimensional tomographic reconstruction algorithm to obtain the time series of the three-dimensional light intensity field of the electric thruster beam.

4. The method as described in claim 2, characterized in that, The preset current conditions include: Quasi-periodic conditions are defined as follows: the repeatability of the discharge current for different periods is better than 10%. The condition for consistent main frequency is that the corresponding oscillation main frequency values ​​obtained by performing Fourier processing on the modulated discharge current and the discharge current before modulation do not differ by more than ±10%, and no new oscillation main frequency is generated. The time-average consistency condition is that the average value of the modulated discharge current and the discharge current before modulation on a second-scale time scale does not differ by more than ±10%.

5. The method as described in claim 2, characterized in that, The active modulation module modulates the input voltage to the electric thruster via the thruster power system, including: The active modulation module changes the amplitude, frequency, and waveform of the input voltage to the electric thruster through the thruster power system.

6. A quasi-periodic beam field reconstruction system for performing the beam field quasi-periodic reconstruction method for electric thruster discharge oscillation according to any one of claims 1-5, characterized in that, The system includes: an electric thruster, a vacuum chamber, a vacuum chamber observation window, a monitoring and modulation system, and an image capture and processing system; The electric thruster is placed inside the vacuum chamber, and the observation window of the vacuum chamber is located on top of the electric thruster inside the vacuum chamber, directly facing the beam region of the electric thruster; The electric thruster is electrically connected to the monitoring and modulation system, and the monitoring and modulation system is electrically connected to the imaging and processing system.

7. The system as described in claim 6, characterized in that, The monitoring and modulation system includes: a thruster power supply system, a current clamp, a discharge current monitoring and determination module, and an active modulation module; The output of the thruster power system is electrically connected to the electric thruster via a current clamp. The input of the discharge current monitoring and determination module is electrically connected to the current clamp. One end of the active modulation module is electrically connected to the input of the thruster power system. The other end of the active modulation module is electrically connected to one output of the discharge current monitoring and determination module. The other output of the discharge current monitoring and determination module is electrically connected to the imaging and processing system.

8. The system as described in claim 6, characterized in that, The shooting and processing system includes: a function signal generator, a high-speed camera, a data processing system, and a rotating platform; The electric thruster is placed on the rotating platform inside the vacuum chamber; the high-speed camera is placed at the observation window of the vacuum chamber. The input terminal of the function signal generator is electrically connected to the monitoring and modulation system, the output terminal of the function signal generator is electrically connected to the input terminal of the high-speed camera, and the input terminal of the high-speed camera is electrically connected to the input terminal of the data processing system.

9. The system as described in claim 8, characterized in that, The central axis of the electric thruster is located at the center of the field of view of the high-speed camera, and the shooting direction of the high-speed camera is perpendicular to the central axis of the electric thruster.

10. The system as described in claim 8, characterized in that, The shooting and processing system also includes: a narrowband filter group, which includes different narrowband filters; The narrowband filter array is configured to be mounted in front of the camera lens of the high-speed camera, so that the camera lens of the high-speed camera can be paired with any narrowband filter.

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