Diagnostic system and method for electric thruster beam plasma parameter characteristics

Abstract

The application provides a kind of electric thruster beam plasma parameter characteristic diagnostic system and method, it is related to plasma diagnostic field, the system includes vacuum chamber, for accommodating electric thruster and providing vacuum environment;Optical fiber signal acquisition module is set to the inside of vacuum chamber, for from multiple angles acquisition optical signal of the beam plasma generated by electric thruster;Image acquisition module is set to the outside of vacuum chamber, with optical fiber signal acquisition module light path connection, for receiving optical signal and converting into two-dimensional image time sequence;Data processing module is connected with communication with image acquisition module, for processing two-dimensional image time sequence, to reconstruct the four-dimensional distribution of the parameter of beam plasma.The application realizes low disturbance, low cost multi-parameter synchronous diagnosis by means of calibration optical fiber, light splitting filter and inversion process, improves efficiency and resolution.

Description

Technical Field

[0001] This application relates to the field of plasma diagnostics, and more specifically, to a diagnostic system and method for the characteristics of plasma parameters in an electric thruster beam. Background Technology

[0002] Space electric propulsion, with its advantages of high specific impulse and long lifespan, is widely used in missions such as satellite position holding and deep space exploration. The four-dimensional parameter evolution characteristics of the beam plasma directly determine the performance and reliability of the electric thruster, and its diagnosis is key to the optimal design of the thruster. Among existing diagnostic methods, contact probe arrays disturb the plasma, while non-contact solutions using multiple high-speed cameras are costly and limited by the observation window of the vacuum chamber. Fiber optic arrays and high-speed cameras for flame diagnostics are not suitable due to the characteristics of the electric thruster beam being cryogenic plasma and the diagnostic environment being high vacuum. As a result, there is currently a lack of low-disturbance, cost-effective four-dimensional diagnostic solutions. Summary of the Invention

[0003] The purpose of this application is to provide a diagnostic system and method for the characteristics of electric thruster beam plasma parameters, which solves the above-mentioned problems existing in the prior art and can realize low-disturbance, low-cost four-dimensional diagnosis of electric thruster beam plasma.

[0004] Firstly, a diagnostic system for the characteristics of beam plasma parameters in an electric thruster is provided, the system comprising:

[0005] A vacuum chamber is used to house the electric thruster and provide a vacuum environment.

[0006] An optical fiber signal acquisition module, located inside the vacuum chamber, is used to acquire optical signals of the beam plasma generated by the electric thruster from multiple angles.

[0007] An image acquisition module is located outside the vacuum chamber and is optically connected to the fiber optic signal acquisition module. It is used to receive the optical signal and convert it into a two-dimensional image time series.

[0008] The data processing module is communicatively connected to the image acquisition module and is used to process the time series of the two-dimensional image to reconstruct the four-dimensional distribution of the parameters of the beam plasma.

[0009] In one possible implementation, the fiber optic signal acquisition module includes:

[0010] The fiber bundle adjustment frame is configured to be positioned around the central axis of the electric thruster;

[0011] Multiple imaging fiber sub-bundles are mounted on the fiber bundle adjustment frame for acquiring the side optical signals of the beam plasma.

[0012] At least one calibration fiber sub-bundle is installed on the fiber bundle adjustment frame, and its entrance end is set in a preset geometric relationship with the entrance end of any imaging fiber sub-bundle.

[0013] The output ends of multiple imaging fiber sub-bundles and the calibration fiber sub-bundle are combined to form a fiber bundle, which is led out to the outside of the vacuum chamber via the through-chamber flange and connected to the image acquisition module.

[0014] In one possible implementation, the entrance end plane of the calibration fiber sub-bundle is perpendicular to the entrance end plane of the imaging fiber sub-bundle.

[0015] In one possible implementation, the system further includes a focus calibration module, which includes:

[0016] A film plate is disposed inside the vacuum chamber and located upstream of the outlet of the electric thruster;

[0017] The distance between the film plate and the entrance end of the calibration fiber sub-bundle is adjustable, and it is correlated with the distance between the entrance end of the imaging fiber sub-bundle and the central axis of the electric thruster. When the image acquisition module focuses the image of the film plate formed by the calibration fiber sub-bundle, it is equivalent to focusing the central axis of the electric thruster.

[0018] In one possible implementation, the image acquisition module includes:

[0019] The optical path module for splitting and filtering is connected to the optical fiber bundle and is used to split and filter the incident light according to a preset spectrum.

[0020] At least one high-speed camera is connected to the spectral filtering optical path module to capture optical signals and obtain two-dimensional image time series under different spectral bands.

[0021] In one possible implementation, the beam-splitting and filtering optical path module is a switchable module, comprising at least:

[0022] The first submodule is used for optical path transmission without beam splitting or filtering;

[0023] The second submodule is used to split the incident light into filtering channels with at least three different characteristic spectral bands.

[0024] Secondly, a diagnostic method for the characteristics of electric thruster beam plasma parameters is provided. This method is applied to a diagnostic system for the characteristics of electric thruster beam plasma parameters as described in the first aspect. The method may include:

[0025] Inside the vacuum chamber, a first distance is established between the imaging fiber sub-bundle and the central axis of the electric thruster, and based on the first distance, a second distance is established between the calibrated fiber sub-bundle and the film plate, such that the second distance is equal to the first distance;

[0026] After the electric thruster is ignited, the position of the imaging fiber sub-bundle is adjusted and the reference coefficient is calculated in real time. Based on the reference coefficient, the diagnostic position of the imaging fiber sub-bundle is determined.

[0027] The position of the film plate is adjusted according to the position change of the captured fiber sub-bundle to maintain the equality of the first distance and the second distance; the position change is determined by the initial safe position of the captured fiber sub-bundle and the diagnostic position;

[0028] The control image acquisition module focuses the adjusted film plate through the calibration fiber sub-bundle;

[0029] After the imaging fiber sub-bundle is in the diagnostic position and has completed focusing, the image acquisition module is triggered to acquire a two-dimensional image time series of the beam plasma at multiple angles.

[0030] The two-dimensional image time series is reconstructed by three-dimensional tomography and parameter inversion to determine the four-dimensional distribution of the parameters of the beam plasma.

[0031] In one possible implementation, determining the diagnostic location of the captured fiber sub-bundle based on the reference coefficient includes:

[0032] Move the captured fiber sub-bundle to a position where the reference coefficient is not less than the configured safety threshold, and determine the diagnostic position of the captured fiber sub-bundle;

[0033] The reference coefficient is the average ratio of the light intensity signals acquired by the shooting fiber sub-bundle and the calibration fiber sub-bundle.

[0034] In one possible implementation, triggering the image acquisition module includes:

[0035] The discharge current signal of the electric thruster is monitored by the configured trigger control module;

[0036] When the discharge current signal reaches the configured trigger value, a synchronous trigger signal is generated and sent to the image acquisition module.

[0037] In one possible implementation, the three-dimensional tomographic reconstruction and parameter inversion of the two-dimensional image time series includes:

[0038] When the two-dimensional image time series is a single spectral band, the four-dimensional distribution of light intensity parameters is obtained by inversion;

[0039] When the two-dimensional image time series contains at least two different feature spectral segments, the four-dimensional distribution of at least one parameter among electron temperature and ionization fraction is obtained by inversion based on the spectral segment ratio model.

[0040] This application provides a diagnostic system and method for the characteristics of beam plasma parameters of an electric thruster. The system includes a vacuum chamber for housing the electric thruster and providing a vacuum environment; an optical fiber signal acquisition module, located inside the vacuum chamber, for acquiring optical signals of the beam plasma generated by the electric thruster from multiple angles; an image acquisition module, located outside the vacuum chamber and optically connected to the optical fiber signal acquisition module, for receiving optical signals and converting them into a two-dimensional image time series; and a data processing module, communicatively connected to the image acquisition module, for processing the two-dimensional image time series to reconstruct the four-dimensional distribution of the beam plasma parameters. This application achieves low-disturbance, low-cost, multi-parameter synchronous diagnosis by utilizing calibration fibers, beam splitting filtering, and inversion processes, thereby improving efficiency and resolution. Attached Figure Description

[0041] 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.

[0042] Figure 1 A schematic diagram of the structure of a diagnostic system for the characteristics of electric thruster beam plasma parameters provided in an embodiment of this application;

[0043] Figure 2 This is a schematic diagram illustrating the imaging or calibration of fiber optic sub-bundles provided in an embodiment of this application.

[0044] Figure 3 A schematic diagram of the beam splitting and filtering optical path module provided in an embodiment of this application;

[0045] Figure 4 A schematic flowchart illustrating a diagnostic method for the characteristics of electric thruster beam plasma parameters provided in this application embodiment;

[0046] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application;

[0047] Figure reference numerals: 1-Electric thruster, 2-Vacuum chamber, 3-Power processing module, 4-Trigger control module, 5-Fiber optic bundle adjustment frame, 6-Film plate, 7-Imaging fiber sub-bundle, 8-Calibration fiber sub-bundle, 9-Through-chamber flange, 10-Fiber optic bundle combiner, 11-Brightness filtering optical path module, 12-High-speed camera, 13-Data processing module. Detailed Implementation

[0048] 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 of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0049] Traditional four-dimensional diagnostics of electric thruster beam plasma using probe arrays and multiple high-speed cameras suffers from plasma disturbance and high diagnostic costs. While flame four-dimensional diagnostics combines high-speed cameras with fiber optic arrays, offering a feasible approach, the electric thruster beam, being a cryogenic plasma, emits relatively weaker light compared to flame. Furthermore, due to the higher frequency of the dynamic behavior being diagnosed, the high-speed camera requires a higher frame rate, resulting in weaker beam light capture capability. The most direct approach is to bring the sub-bundles of the fiber optic array closer to the electric thruster beam to enhance the system's light-gathering capability. However, if the fiber sub-bundles are too close to the electric thruster beam, the plasma can easily erode the fiber and its components, even causing failure. The fiber sub-bundles can also interfere with the plasma atmosphere, leading to inaccurate diagnostics. In addition, electric thruster beam diagnostics require a high-vacuum simulation system (vacuum chamber). Therefore, repeatedly determining the position of the fiber sub-bundles at various angles and performing focusing calibration increases operational complexity and time costs (the vacuum chamber evacuation and degassing process is time-consuming).

[0050] Therefore, this application provides a diagnostic system and method for the characteristics of electric thruster beam plasma parameters, which solves the above-mentioned problems existing in the prior art and can realize low-disturbance, low-cost four-dimensional diagnosis of electric thruster beam plasma.

[0051] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0052] Figure 1 This is a schematic diagram of a diagnostic system for the characteristics of electric thruster beam plasma parameters, provided as an embodiment of this application. Figure 1 As shown, the system may include:

[0053] A. Vacuum chamber 2, used to house the electric thruster 1 and provide a vacuum environment; specifically, vacuum chamber 2 provides the core vacuum diagnostic environment for the system of this application. Its internal space must meet the installation and operation requirements of the electric thruster 1, the fiber optic signal acquisition module, and the focusing calibration module, and have the ability to maintain a high vacuum level to match the generation and diagnostic conditions of the electric thruster's beam plasma. The electric thruster 1 is fixed to the platform inside the vacuum chamber 2 by a bracket. The central axis of the electric thruster 1 is parallel to the xy plane to ensure that the beam plasma is ejected in a preset direction.

[0054] B. Fiber optic signal acquisition module, located inside vacuum chamber 2, is used to acquire optical signals of the beam plasma generated by electric thruster 1 from multiple angles, providing the original signal source for subsequent image conversion and parameter inversion;

[0055] Furthermore, the fiber optic signal acquisition module includes:

[0056] B1. The fiber optic bundle adjustment frame 5 is configured to be positioned around the central axis of the electric thruster 1. Specifically, the fiber optic bundle adjustment frame 5 provides support for the installation and position adjustment of the imaging fiber sub-bundle 7 and the calibration fiber sub-bundle 8. Its specific structure is a vertical ring-shaped frame with multiple support arms (all support arms are 3D printed, and the ring-shaped frame has at least 9 support arm fixing interfaces pre-installed), equipped with frame guide rails, support arm guide rails, and a fiber optic bundle telescopic mechanism. This frame is configured to be positioned around the central axis of the electric thruster 1. By adjusting the xyz three-degree-of-freedom guide rails, the ring-shaped frame can be coaxially arranged with the electric thruster 1, and the frame plane is flush with the outlet plane of the electric thruster 1 in the negative x direction, ensuring that the acquisition field of view of the fiber sub-bundle can accurately cover the distribution area of ​​the beam plasma.

[0057] B2. Multiple imaging fiber sub-bundles 7 are mounted on the fiber bundle adjustment frame 5 to collect the side optical signals of the beam plasma. Specifically, the multiple imaging fiber sub-bundles 7 are evenly mounted on different arms of the fiber bundle adjustment frame 5. The specifications of each imaging fiber sub-bundle 7 are consistent, including the number of fibers and fiber lengths. Each imaging fiber sub-bundle is equipped with a matching fiber collimating lens at its front end to improve the efficiency and consistency of optical signal acquisition. The core function of the imaging fiber sub-bundles 7 is to collect the side optical signals of the beam plasma. Because they are distributed circumferentially along the ring frame, they can capture optical signals of the beam plasma from multiple angles, providing sufficient angular data support for subsequent 3D reconstruction.

[0058] B3. At least one calibration fiber sub-bundle 8 is installed on the fiber bundle adjustment frame 5, and its entrance end is set in a preset geometric relationship with the entrance end of any shooting fiber sub-bundle 7.

[0059] The entrance plane of the calibration fiber sub-bundle 8 is perpendicular to the entrance plane of the imaging fiber sub-bundle 7.

[0060] Specifically, the calibration fiber sub-bundle 8 is installed on one of the arms of the fiber bundle adjustment frame 5 (the other arms do not need to be installed). Its specifications are completely consistent with those of the imaging fiber sub-bundle 7, and its front end is also equipped with a fiber collimating lens. The entrance end of the calibration fiber sub-bundle 8 is set in a preset geometric relationship with the entrance end of any imaging fiber sub-bundle 7. Specifically, the planes of the entrance ends are perpendicular to each other and are tangent to the cylindrical structure of the other. This geometric layout ensures the correlation of the light signals collected by the two, providing a reliable basis for the subsequent calculation of the reference coefficient. The core functions of the calibration fiber sub-bundle 8 include two aspects: first, it works with the imaging fiber sub-bundle 7 to calculate the reference coefficient, providing a quantitative basis for the position adjustment of the imaging fiber sub-bundle 7; second, it works with the focusing calibration module to achieve disturbance-free focusing of the high-speed camera 12, avoiding the operational complexity and plasma disturbance problems caused by traditional focusing methods.

[0061] The output ends of multiple imaging fiber sub-bundles 7 and calibration fiber sub-bundles 8 are combined to form a fiber bundle 10, which is led out to the outside of the vacuum chamber 2 via the through-flanged flange 9 and connected to the image acquisition module. Specifically, the output ends of multiple imaging fiber sub-bundles 7 and calibration fiber sub-bundles 8 are combined to form a fiber bundle 10. The end of the fiber bundle 10 furthest from the fiber sub-bundles is led out to the outside of the vacuum chamber 2 via the through-flanged flange 9 and optically connected to the beam splitting and filtering optical path module 11 of the image acquisition module. The fiber bundle 10 can concentrate the optical signals acquired by multiple fiber sub-bundles, reduce signal loss, and reduce the complexity of the external optical path layout. The through-flanged flange 9 serves to seal and fix the fiber bundle, ensuring that the vacuum environment of the vacuum chamber 2 is not affected and ensuring the positional stability of the fiber bundle 10.

[0062] C. An image acquisition module, located outside the vacuum chamber 2, is optically connected to the fiber optic signal acquisition module and is used to receive optical signals and convert them into a two-dimensional image time series; further, the image acquisition module includes:

[0063] C1. The beam splitting and filtering optical path module 11 is connected to the optical fiber bundle 10 and is used to split and filter the incident light according to a preset spectrum. The beam splitting and filtering optical path module 11 is a switchable module and includes at least: a first sub-module for optical path transmission without beam splitting and filtering; and a second sub-module for splitting the incident light to at least three filtering channels with different characteristic spectrums.

[0064] Specifically, the beam splitting and filtering optical path module 11 is optically connected to the end of the fiber bundle 10 furthest from the vacuum chamber 2. Its core function is to split and filter the incident optical signal according to a preset spectral band to adapt to different diagnostic needs. For example... Figure 3As shown, the beam splitting and filtering optical path module is a switchable module with a stable optical cage structure, including at least a first sub-module and a second sub-module, which can be flexibly switched according to diagnostic needs.

[0065] The first submodule is a non-splitter and non-filter submodule, which is used for non-splitter and non-filter optical path transmission. It is suitable for diagnostic scenarios where only the four-dimensional oscillation propagation characteristics of the beam plasma optical field need to be obtained. In this case, the optical signal is directly transmitted to the high-speed camera 12 through this submodule to ensure the integrity of the signal and the transmission efficiency.

[0066] The second submodule is a multi-channel beam splitting and filtering confocal submodule, used to split the incident light into at least three filtering channels with different characteristic spectral bands, adapting to diagnostic scenarios that require the acquisition of multiple types of plasma parameters such as electron temperature and ionization fraction. In a specific embodiment, this submodule includes three beam splitting channels, two of which have a splitting ratio of 25% and are respectively equipped with narrowband filters with center wavelengths of 805nm and 845nm (both with a bandwidth of 20nm), and one channel with a splitting ratio of 50% is equipped with a filter with a center wavelength of 485nm (with a bandwidth of 10nm). After processing by this submodule, optical signals in three spectral bands—785-825nm, 825-865nm, and 485-495nm—can be obtained, providing a spectral basis for multi-parameter inversion.

[0067] C2. At least one high-speed camera 12 is connected to the spectral filtering optical path module 11 to capture the optical signal after spectral filtering and obtain a two-dimensional image time series under different spectral bands.

[0068] Specifically, the high-speed camera 12 is optically connected to the output of the beam-splitting and filtering optical path module 11 to capture the optical signal after beam splitting and filtering, thereby obtaining two-dimensional image time series in different spectral bands. The frame rate of the high-speed camera 12 is determined based on the dominant oscillation frequency of the plasma under study, and is usually set to twice or more than the dominant oscillation frequency to ensure that the dynamic behavior of plasma at frequencies of 10 kHz and above can be fully captured, thus compensating for the insufficient frame rate in traditional flame diagnosis.

[0069] The high-speed camera 12 is communicatively connected to the data processing module 13, and the captured two-dimensional image time series can be transmitted to the data processing module 13 in real time for subsequent processing. At the same time, the high-speed camera 12 is also signal-connected to the trigger control module 4, which can synchronously start shooting when the discharge current of the electric thruster 1 reaches the preset trigger value, ensuring the correspondence between the two-dimensional image time series and the discharge waveform of the electric thruster, and improving the accuracy of parameter inversion.

[0070] D. The system also includes a focus calibration module, which includes:

[0071] Film plate 6 is movably disposed inside vacuum chamber 2 and located upstream of the outlet of electric thruster 1;

[0072] The distance between the film plate 6 and the entrance end of the calibration fiber sub-bundle 8 is adjustable, and it is correlated with the distance between the entrance end of the imaging fiber sub-bundle 7 and the central axis of the electric thruster 1. This allows the image acquisition module to focus on the image of the film plate 6 formed by the calibration fiber sub-bundle 8, which is equivalent to focusing on the central axis of the electric thruster 1. Figure 2 As shown, Figure 2 A schematic diagram for photographing or calibrating fiber sub-bundles.

[0073] Specifically, the focusing calibration module is used to achieve undisturbed focusing of the high-speed camera 12, avoiding the increased time cost and plasma disturbance problems caused by traditional focusing methods. This module includes the film plate 6 and the matching guide rail.

[0074] The film plate 6 is movably mounted inside the vacuum chamber 2 via a matching guide rail, and is located upstream of the outlet of the electric thruster 1. This mounting position avoids disturbance of the beam plasma by the film plate 6, while ensuring that the calibration fiber sub-bundle 8 can clearly capture its image. The distance between the film plate 6 and the inlet end of the calibration fiber sub-bundle 8 is adjustable, and this distance is fixedly correlated with the distance between the inlet end of the imaging fiber sub-bundle 7 and the central axis of the electric thruster 1, that is, the two always remain equal.

[0075] Furthermore, during initial calibration, the distance M between the imaging fiber sub-bundle 7 and the central axis of the electric thruster 1 is recorded. The position of the film plate 6 is adjusted so that its distance from the inlet end of the calibration fiber sub-bundle 8 is also M. When the imaging fiber sub-bundle 7 is adjusted and moved a distance N, the film plate 6 is moved a distance MN synchronously to ensure that the two distances are always equal. This correlation means that when focusing the image on the film plate 6 formed by the calibration fiber sub-bundle 8 through the image acquisition module, it is equivalent to focusing on the central axis of the electric thruster 1. There is no need to open the chamber to adjust the position of the film plate 6, which greatly reduces the operation time cost and avoids additional disturbance of the plasma by the film plate 6.

[0076] The matching guide rail provides guidance and support for the movement of the film plate 6, ensuring the movement accuracy of the film plate 6, thereby guaranteeing the accuracy of the distance correlation and ensuring the focusing accuracy.

[0077] E. Data processing module 13, which is connected to the image acquisition module, is used to process the time series of two-dimensional images to reconstruct the four-dimensional distribution of the parameters of the beam plasma.

[0078] Specifically, the data processing module 13 is connected to the high-speed camera 12 of the image acquisition module. Its core function is to process the time series of two-dimensional images captured by the high-speed camera 12, including image noise correction, three-dimensional tomographic reconstruction and parameter inversion, and finally reconstruct the four-dimensional distribution of the parameters of the beam plasma.

[0079] The data processing module 13 first uses the average light intensity captured by the calibrated fiber sub-bundle 8 as environmental noise to correct the noise in the two-dimensional image time series and improve image quality. Then, it uses three-dimensional tomographic reconstruction algorithms such as filtered back projection algorithm or algebraic reconstruction method to process the two-dimensional image time series at different angles and in different spectral bands to obtain the three-dimensional light field time series of the beam plasma in different spectral bands. Finally, based on the preset spectral band ratio model, the three-dimensional light field data is substituted into the spectral band ratio model point by point to solve for the three-dimensional spatial distribution and temporal evolution characteristics of plasma parameters such as electron temperature and ionization fraction, thus completing the four-dimensional diagnosis.

[0080] This application provides a diagnostic system for the beam plasma parameter characteristics of an electric thruster. The system includes a vacuum chamber for housing the electric thruster and providing a vacuum environment; a fiber optic signal acquisition module, located inside the vacuum chamber, for acquiring optical signals of the beam plasma generated by the electric thruster from multiple angles; an image acquisition module, located outside the vacuum chamber and optically connected to the fiber optic signal acquisition module, for receiving the optical signals and converting them into a two-dimensional image time series; and a data processing module, communicatively connected to the image acquisition module, for processing the two-dimensional image time series to reconstruct the four-dimensional distribution of the beam plasma parameters. This application achieves low-disturbance, low-cost, multi-parameter synchronous diagnosis by utilizing beam splitting filtering and inversion processes, improving efficiency and resolution.

[0081] Figure 4 This is a schematic flowchart illustrating a method for diagnosing the characteristics of electric thruster beam plasma parameters, provided in an embodiment of this application. Figure 4 As shown, this method is applied to a diagnostic system for the characteristics of beam plasma parameters in an electric thruster. The method may include:

[0082] Step S410: Inside the vacuum chamber, establish a first distance between the imaging fiber sub-bundle and the central axis of the electric thruster, and based on the first distance, establish a second distance between the calibrated fiber sub-bundle and the film plate, so that the second distance is equal to the first distance.

[0083] Specifically, the first distance M is defined as the vertical distance from the entrance plane of the imaging fiber sub-bundle to the central axis of the electric thruster. Through the xyz three-degree-of-freedom guide rails of the fiber bundle adjustment frame, all imaging fiber sub-bundles are adjusted to the initial safe position (1. In the x direction, the edge of the light-receiving field of view of the imaging fiber sub-bundle 7 is flush with the exit plane of the electric thruster; 2. In the z direction, after the electric thruster is started, the fiber sub-bundle will not be directly eroded and damaged by the beam plasma). The first distance M is measured and recorded using a laser rangefinder.

[0084] Based on the first distance M, adjust the position of the film plate in the focusing calibration module so that the vertical distance from the entrance end plane of the calibration fiber sub-bundle to the film plate (defined as the second distance) is equal to the first distance M;

[0085] The initial position of the film plate is fixed, and the relative position of the shooting fiber sub-bundle and the calibration fiber sub-bundle is locked by the positioning scale of the fiber bundle adjustment frame. This ensures that the geometric relationship of the two entry end planes being perpendicular and tangent (the entry end planes are perpendicular and tangent to each other's cylinders) remains unchanged, laying the foundation for subsequent distance correlation adjustment.

[0086] Step S420: After the electric thruster is ignited, adjust the position of the imaging fiber sub-bundle and calculate the reference coefficient in real time. Based on the reference coefficient, determine the diagnostic position of the imaging fiber sub-bundle.

[0087] The diagnostic location of the captured fiber sub-bundle is determined based on the reference coefficient, including:

[0088] Move the captured fiber sub-bundle to a position where the reference coefficient is not less than the configured safety threshold to determine the diagnostic position of the captured fiber sub-bundle;

[0089] The reference factor is the average ratio of the light intensity signals acquired by photographing the fiber sub-bundle and the calibrated fiber sub-bundle.

[0090] Specifically, the vacuum pumping system of the vacuum chamber is activated to bring the vacuum level inside the chamber up to the working vacuum environment of the electric thruster. Then, the power supply module controls the power supply to the electric thruster, triggering the electric thruster to ignite and generate a beam of plasma.

[0091] The position of the shooting fiber sub-bundle is gradually adjusted along the direction close to the central axis of the electric thruster (usually towards the negative z direction) by using the support arm guide rail of the fiber bundle adjustment frame (for coarse adjustment of the fiber sub-bundle in the z direction) and the fiber bundle telescopic mechanism (for fine adjustment of the fiber sub-bundle in the x and z directions). During the adjustment process, the light intensity signals of the shooting fiber sub-bundle and the calibration fiber sub-bundle are collected in real time.

[0092] The average value of the ratio of the light intensity of each fiber in the fiber matrix of the captured fiber sub-bundle and the calibrated fiber sub-bundle is determined as the reference coefficient K;

[0093] If only the four-dimensional oscillation characteristics of the beam plasma optical field are required, a safety threshold of 2 is set based on the beam plasma light intensity characteristics and diagnostic accuracy requirements. If parameters such as electron temperature and ionization fraction need to be retrieved, a safety threshold of 10 is set. The reference coefficient is lower than the safety threshold as the limit position to avoid fiber damage and plasma disturbance. When the reference coefficient K stably reaches the safety threshold, the position adjustment of the fiber sub-bundle is stopped. The position of the fiber sub-bundle at this time is the diagnostic position.

[0094] Step S430: Adjust the position of the film plate according to the position change of the shooting fiber sub-bundle to maintain the first distance and the second distance being equal.

[0095] Specifically, determine the total movement distance N (usually along the negative z-direction) of the imaging fiber sub-bundle from the initial safe position (the position corresponding to the first distance M) to the diagnostic position. This movement distance is the position change, i.e., N = first distance M - diagnostic position M', where M is the vertical distance from the imaging fiber sub-bundle to the central axis of the electric thruster during the initial calibration, and M' is the corresponding distance at the diagnostic position.

[0096] The film plate is moved along a direction close to the calibration fiber sub-bundle (usually in the negative x direction), and the moving distance is strictly equal to the position change N. After adjustment, the second distance from the inlet plane of the calibration fiber sub-bundle to the film plate becomes M'=MN, ensuring that the second distance always remains equal to the first distance, continuing the equivalent correlation established in the initial calibration.

[0097] During the adjustment process, the actual position of the film plate is fed back in real time by the laser displacement sensor built into the vacuum chamber. Combined with the PID control algorithm, the movement deviation is corrected, ultimately ensuring that the equality error between the first distance and the second distance is ≤ ±0.1mm. This design avoids the operation of repeatedly evacuating and venting the vacuum chamber to adjust the film plate, greatly reducing time costs, while providing a precise position reference for subsequent undisturbed focusing.

[0098] Step S440: Control the image acquisition module to focus the adjusted film plate through the calibration fiber sub-bundle.

[0099] Specifically, the beam splitting and filtering optical path module is switched to the first sub-module, which uses a fully transparent optical lens group to ensure that the optical signal of the film plate transmitted by the calibration fiber sub-bundle is transmitted to the high-speed camera without loss or deflection, thus eliminating the interference of the beam splitting / filtering link on the focusing accuracy.

[0100] Activate the autofocus function of the high-speed camera, capture the image of the film plate through the calibrated fiber sub-bundle, and gradually adjust the lens focal length of the high-speed camera until the details of the film plate (black and white squares with defined side lengths) in the image are clearly distinguishable, thus completing the focus calibration.

[0101] Since the film plate is fixed upstream of the electric thruster's outlet and does not intersect with the beam plasma jet path, it will not cause disturbance to the beam. At the same time, the equivalent relationship between the second distance and the first distance allows the focusing accuracy of the film plate to be directly mapped to the focusing accuracy of the electric thruster's central axis, eliminating the need to extend the focusing element into the beam region and completely solving the plasma disturbance problem caused by traditional focusing methods.

[0102] Step S450: After the fiber sub-bundle is in the diagnostic position and focusing is completed, the image acquisition module is triggered to acquire a two-dimensional image time series of the beam plasma from multiple angles.

[0103] The discharge current signal of the electric thruster is monitored by a trigger control module.

[0104] When the discharge current signal reaches the configured trigger value, a synchronous trigger signal is generated and sent to the image acquisition module.

[0105] Specifically, if the diagnostic target is to obtain multiple parameters such as electron temperature and ionization fraction, and the reference coefficient is ≥10, the beam splitting and filtering optical path module needs to be switched to the second sub-module. This module uses a dual-path narrowband filter with a splitting ratio of 25% (center wavelength 805nm / 845nm, bandwidth 20nm) and a single-path filter with a splitting ratio of 50% (center wavelength 485nm, bandwidth 10nm) to split the incident light into three characteristic spectral bands: 785-825nm, 825-865nm, and 475-495nm. After switching, the distance linkage adjustment in step S430 and the focus calibration in this step need to be repeated to ensure the synchronization and sharpness of multi-spectral imaging.

[0106] The discharge current signal of the electric thruster is acquired in real time by a trigger control module. Based on the rated operating parameters of the electric thruster, a current trigger threshold is set (deviation from the rated operating current ≤ ±5%). This triggering mechanism is used to establish the correspondence between the discharge current waveform and the time series of optical images, clarifying the relationship between the dynamic behavior of the beam plasma and the operating state of the electric thruster.

[0107] When the discharge current signal reaches the preset trigger threshold, the trigger control module generates a synchronous trigger signal, driving the high-speed camera to start shooting. The shooting parameters strictly adhere to the following requirements:

[0108] In some embodiments, the frequency of the plasma oscillation under study is adaptively set according to the main frequency of the beam plasma, and is not less than twice the main frequency; a two-dimensional integral image time series of the beam plasma under multiple angles is generated, with an image resolution of not less than 1024×1024 pixels; the time is set to 1-10s according to diagnostic requirements, and the image data is transmitted in real time to the high-speed storage unit of the data processing module through a gigabit Ethernet interface during the acquisition process to ensure no data loss; relying on the ring skeleton layout of the fiber bundle adjustment frame, optical signals within a 360-degree range are simultaneously acquired through multiple shooting fiber sub-bundles, and the output ends of the shooting fiber sub-bundles are combined by fiber bundles and led out of the vacuum chamber through the chamber flange to provide complete projection data support for three-dimensional tomographic reconstruction.

[0109] Furthermore, the electric thruster is provided with a stable power supply by the power processing module, ensuring the continuity and stability of the beam plasma generation process and providing a consistent diagnostic target for image acquisition.

[0110] Step S460: Perform three-dimensional tomography reconstruction and parameter inversion on the two-dimensional image time series to determine the four-dimensional distribution of the parameters of the beam plasma.

[0111] Three-dimensional tomographic reconstruction and parameter inversion of two-dimensional image time series include:

[0112] When the time series of a two-dimensional image is a single spectral band, the four-dimensional distribution of light intensity parameters is obtained by inversion;

[0113] When a two-dimensional image time series contains at least two different feature spectral bands, the four-dimensional distribution of at least one parameter among electron temperature and ionization fraction can be obtained by inversion based on the spectral band ratio model.

[0114] Specifically, based on filtered back-projection algorithms or algebraic reconstruction methods, three-dimensional tomographic reconstruction is performed on the time series of two-dimensional images from different angles and spectral bands. During the reconstruction process, fan-beam correction is first applied to the projected images at each angle to unify the detector pixel size; then, the projection data is processed using a filtering function; finally, the filtered projection data is back-projected along the ray direction to a three-dimensional voxel space, and by accumulating the projection values ​​of each voxel, a three-dimensional optical field time series of the beam plasma in each spectral band is generated.

[0115] Subsequently, if the two-dimensional image time series is a single spectral band, the four-dimensional distribution of the beam plasma light intensity parameters (three-dimensional spatial distribution + time evolution characteristics) can be directly inverted based on the three-dimensional light field time series, which can be used to analyze the plasma oscillation propagation behavior.

[0116] If a two-dimensional image time series contains at least two different feature spectral bands, then the preset spectral band ratio model is invoked, and the parameters are solved on a voxel-by-voxel basis:

[0117] Electron temperature inversion: Using the intensity ratio of the 785-825nm spectral band (corresponding to an 805nm filter) to the 825-865nm spectral band (corresponding to an 845nm filter), the electron temperature is calculated using the following formula. :

[0118]

[0119] in, For characteristic spectral line intensity, This is the correction factor for ion valence state.

[0120] This formula can be used to solve for the three-dimensional spatial distribution and temporal evolution characteristics of electron temperature.

[0121] Based on the electron temperature obtained above, and using the intensity ratio of the 825-865nm spectral band (corresponding to an 845nm filter) to the 475-495nm spectral band (corresponding to a 485nm filter), the ionization fraction is calculated using the following formula. :

[0122]

[0123] This method integrates the three-dimensional spatial distribution data of parameters such as light intensity, electron temperature, and ionization fraction with the evolution sequence in the time dimension to form a complete four-dimensional distribution of the parameters of the beam plasma. It can be output in a visual form such as three-dimensional cloud map and time evolution curve, providing direct data support for the optimization of electric thruster operating conditions.

[0124] This step solves the problem of undisturbed focusing inside the vacuum chamber through a distance linkage mechanism, ensures the correlation between the image and the working status of the electric thruster through synchronous triggering of the trigger control module, and achieves high-precision four-dimensional diagnosis of multiple types of parameters through the spectral band ratio model.

[0125] In some embodiments, the plasma multi-band inversion model in this application, taking Xe as an example, is also applicable to electric thrusters using other inert gases as working fluids, but the corresponding spectral bands of the filter need to be adjusted.

[0126] This application also provides an electronic device, such as... Figure 5 As shown, it includes a processor 510, a communication interface 520, a memory 530, and a communication bus 540, wherein the processor 510, the communication interface 520, and the memory 530 communicate with each other through the communication bus 540.

[0127] Memory 530 is used to store computer programs;

[0128] When the processor 510 executes the program stored in the memory 530, it performs the following steps:

[0129] Inside the vacuum chamber, a first distance is established between the imaging fiber sub-bundle and the central axis of the electric thruster, and based on the first distance, a second distance is established between the calibrated fiber sub-bundle and the film plate, such that the second distance is equal to the first distance;

[0130] After the electric thruster is ignited, the position of the imaging fiber sub-bundle is adjusted and the reference coefficient is calculated in real time. Based on the reference coefficient, the diagnostic position of the imaging fiber sub-bundle is determined.

[0131] The position of the film plate is adjusted according to the position change of the captured fiber sub-bundle to maintain the equality of the first distance and the second distance; the position change is determined by the initial safe position of the captured fiber sub-bundle and the diagnostic position;

[0132] The control image acquisition module focuses the adjusted film plate through the calibration fiber sub-bundle;

[0133] After the imaging fiber sub-bundle is in the diagnostic position and has completed focusing, the image acquisition module is triggered to acquire a two-dimensional image time series of the beam plasma at multiple angles.

[0134] The two-dimensional image time series is reconstructed by three-dimensional tomography and parameter inversion to determine the four-dimensional distribution of the parameters of the beam plasma.

[0135] The communication bus mentioned above can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in the diagram, but this does not mean that there is only one bus or one type of bus.

[0136] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0137] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0138] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0139] The implementation methods and beneficial effects of the various components of the electronic device in the above embodiments for solving the problem can be found in [reference needed]. Figure 4 The steps in the illustrated embodiments are used to implement the electronic device. Therefore, the specific working process and beneficial effects of the electronic device provided in this application will not be repeated here.

[0140] In another embodiment provided in this application, a computer-readable storage medium is also provided, which stores instructions that, when executed on a computer, cause the computer to perform a diagnostic method for the characteristics of electric thruster beam plasma as described in any of the above embodiments.

[0141] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute a diagnostic method for the characteristics of electric thruster beam plasma as described in any of the above embodiments.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected," "coupled," or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0147] 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 embodiments in this application are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments in this application.

[0148] 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 embodiments of this application and their equivalents, then these modifications and variations are also intended to be included in the embodiments of this application.

Claims

1. A diagnostic system for the characteristics of beam plasma parameters in an electric thruster, characterized in that, The system comprises: a vacuum chamber for accommodating an electric thruster and providing a vacuum environment; an optical fiber signal acquisition module arranged inside the vacuum chamber and configured to acquire optical signals of beam plasma generated by the electric thruster from multiple angles; an image acquisition module arranged outside the vacuum chamber and connected with the optical fiber signal acquisition module in an optical path, configured to receive the optical signals and convert them into a two-dimensional image time sequence; a data processing module in communication connection with the image acquisition module, configured to process the two-dimensional image time sequence to reconstruct a four-dimensional distribution of parameters of the beam plasma. The optical fiber signal acquisition module comprises: an optical fiber bundle adjusting frame configured to be arranged around a central axis of the electric thruster; a plurality of shooting optical fiber sub-beams mounted on the optical fiber bundle adjusting frame and configured to acquire side optical signals of the beam plasma; at least one calibration optical fiber sub-beam mounted on the optical fiber bundle adjusting frame, an inlet end of which is arranged in a preset geometric relationship with an inlet end of any shooting optical fiber sub-beam; output ends of the plurality of shooting optical fiber sub-beams and the calibration optical fiber sub-beam are merged to form an optical fiber bundle, which is led out to the outside of the vacuum chamber through a chamber flange and connected with the image acquisition module; the inlet end plane of the calibration optical fiber sub-beam is perpendicular to the inlet end plane of the shooting optical fiber sub-beam; The system further comprises a focusing calibration module, which comprises: a film plate arranged inside the vacuum chamber and located upstream of an outlet of the electric thruster; wherein the distance between the film plate and the inlet end of the calibration optical fiber sub-beam is adjustable and is in a correlation relationship with the distance between the inlet end of the shooting optical fiber sub-beam and the central axis of the electric thruster, and when focusing on the image of the film plate formed by the calibration optical fiber sub-beam through the image acquisition module, it is equivalent to focusing on the central axis of the electric thruster.

2. The system of claim 1, wherein, The image acquisition module comprises: a light splitting and filtering light path module connected with the optical fiber bundle and configured to split and filter incident light according to a preset spectral range; at least one high-speed camera connected with the light splitting and filtering light path module and configured to shoot optical signals to obtain two-dimensional image time sequences under different spectral ranges.

3. The system of claim 2, wherein, The light splitting and filtering light path module is a switchable module, which at least comprises: a first sub-module for conducting light without splitting and filtering; a second sub-module for splitting incident light into at least three filtering channels of different characteristic spectral ranges.

4. A method of diagnosing beam plasma parameter characteristics of an electric thruster, characterized by, The method is applied to the diagnostic system for diagnosing the beam plasma parameter characteristics of the electric thruster according to any one of claims 1-3, and the method comprises: in the vacuum chamber, establishing a first distance between the shooting optical fiber sub-beam and the central axis of the electric thruster, and based on the first distance, establishing a second distance between the calibration optical fiber sub-beam and the film plate, so that the second distance is equal to the first distance; after the electric thruster is ignited, adjusting the position of the shooting optical fiber sub-beam and calculating a reference coefficient in real time, and determining a diagnostic position of the shooting optical fiber sub-beam according to the reference coefficient. According to the position change amount of the shooting optical fiber sub-beam, the position of the film plate is adjusted to maintain the equality of the first distance and the second distance; the position change amount is determined according to the initial safe position and the diagnostic position of the shooting optical fiber sub-beam; The image acquisition module is controlled to focus on the adjusted film plate through the calibration optical fiber sub-beam; After the shooting optical fiber sub-beam is at the diagnostic position and the focusing is completed, the image acquisition module is triggered to collect a two-dimensional image time sequence of the multi-angle beam plasma; The two-dimensional image time sequence is subjected to three-dimensional tomographic reconstruction and parameter inversion to determine the four-dimensional distribution of the parameters of the beam plasma.

5. The method of claim 4, wherein, According to the reference coefficient, the diagnostic position of the shooting optical fiber sub-beam is determined, including: The shooting optical fiber sub-beam is moved to a position where the reference coefficient is not less than a configured safety threshold to determine the diagnostic position of the shooting optical fiber sub-beam; The reference coefficient is the average ratio of the light intensity signals collected by the shooting optical fiber sub-beam and the calibration optical fiber sub-beam.

6. The method of claim 4, wherein, Triggering the image acquisition module includes: The discharge current signal of the electric thruster is monitored through a configured trigger control module; When the discharge current signal reaches a configured trigger value, a synchronous trigger signal is generated to the image acquisition module.

7. The method of claim 4, wherein, The three-dimensional tomographic reconstruction and parameter inversion of the two-dimensional image time sequence includes: When the two-dimensional image time sequence is a single spectral segment, the four-dimensional distribution of the light intensity parameter is obtained by inversion; When the two-dimensional image time sequence contains at least two different characteristic spectral segments, based on a spectral segment ratio model, the four-dimensional distribution of at least one parameter of the electron temperature and the ionization fraction is obtained by inversion.

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