A bidirectional synchronous high-speed imaging and diagnostic system for plasma oscillation in electric thrusters

Abstract

This invention proposes a bidirectional synchronous high-speed imaging and diagnostic system for electric thruster plasma oscillation. It comprises a vacuum chamber, an electric thruster, a vacuum chamber observation window, electric thruster plasma, a reflector assembly, a side-viewing optical path, a high-speed camera, a data processing system, and a high-speed camera's imaging range and a front-viewing optical path. The electric thruster, vacuum chamber observation window, and reflector assembly are bolted together inside the vacuum chamber. The electric thruster plasma is generated by the electric thruster and adheres to its outer surface. The side-viewing and front-viewing optical paths are formed by the reflector assembly. The high-speed camera is placed outside the vacuum chamber, with its imaging range directly facing the vacuum chamber observation window to capture the side-viewing and front-viewing optical paths. The electric thruster and its plasma are the subjects of the imaging. Compared to traditional bidirectional synchronous high-speed imaging, this invention establishes a bidirectional optical path to simultaneously introduce images of the side and front of the electric thruster into the lens of a single high-speed camera, requiring only a single high-speed camera. This reduces the financial and time costs of experiments and improves research efficiency.

Description

Technical Field

[0001] This invention belongs to the field of plasma diagnostics in electric propulsion technology, specifically a system for bidirectional synchronous high-speed imaging and diagnostics of plasma oscillations in electric thrusters. Background Technology

[0002] Compared to traditional chemical propulsion, space electric propulsion has been widely used in various on-orbit missions due to its advantages such as high specific impulse, long lifespan, and precisely adjustable thrust, including satellite position holding, orbit transfer, and deep space exploration. However, electric thrusters, such as Hall thrusters, contain 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 are closely related to their performance and lifespan, making them crucial for efficient and stable operation.

[0003] Experimental diagnostic methods for discharge instability within thrusters mainly include transient contact probe diagnostics and non-contact optical diagnostics. After decades of development, contact probe diagnostics are relatively complete, including saturation probes and Langmuir three-probe systems. Although contact probes have a relatively simple structure, they often can only measure a limited number of spatial points, providing limited information, and the invasive nature of the diagnostics interferes with the plasma atmosphere. Transient non-contact optical diagnostics for discharge instability diagnosis mainly include laser Thomson scattering and high-speed photography. While the former can obtain the dispersion relation of discharge instability, providing a deeper physical explanation, its system setup is too complex and it can only measure data from a single point, thus its use is limited. High-speed photography is relatively simple to operate; it can capture high-frame-rate plasma evolution videos like a regular camera, obtaining its spatiotemporal sequence. However, current high-speed imaging techniques for Hall thrusters, using a single camera, can only capture oscillations in a single direction at any given moment. This results in the inability to accurately identify the various modes of spoke oscillations from the side of the thruster, and the inability to accurately identify the modes of axial oscillations from the front. If a single camera captures images sequentially from different directions, the varying timing, phase, and reproducibility of operating conditions significantly increase the difficulty and uncertainty of oscillation analysis. Simultaneous triggering with two or more high-speed cameras is impractical due to their exorbitant price, often approaching a million dollars. Therefore, to achieve simultaneous imaging of oscillations in different directions of electric thrusters at a lower cost, it is necessary to develop a system for bidirectional synchronous high-speed imaging of plasma oscillations in electric thrusters. This system and method can be applied to bidirectional synchronous high-speed imaging of plasma oscillations in electric thrusters, exemplified by Hall thrusters.

[0004] Currently, common high-speed imaging and diagnostic systems for electric thruster plasma oscillations mainly include unidirectional imaging and bidirectional asynchronous imaging. Unidirectional imaging can only capture plasma oscillations in one direction, such as... Figure 1 As shown, however, the plasma of an electric thruster is very complex, including low-frequency and high-frequency oscillations in the axial and circumferential directions. High-speed photography from only one direction cannot fully describe the characteristics of plasma oscillations.

[0005] Currently common two-way asynchronous photography systems, such as Figure 2 As shown. Since only one high-speed camera can be used for the experiment, frontal and side videos of the thruster plasma will be acquired separately. Even though the operating parameters are kept constant during the experiment to ensure repeatable experimental phenomena, the measured oscillation modes and precise oscillation frequencies may vary depending on the experimental dataset.

[0006] The shortcomings and problems of the existing design are as follows:

[0007] 1. Unidirectional high-speed photography can only capture the unidirectional two-dimensional features of electric thruster plasma. Due to the high cost of high-speed cameras, high-speed photography experiments on electric thruster plasma generally only use a single high-speed camera for unidirectional high-speed photography. Currently, commonly used directions include axial and radial photography of the electric thruster. However, axial photography mainly captures circumferential plasma instabilities. Taking Hall thrusters as an example, it mainly captures the spoke oscillations of different modes, but the identification of axial instabilities is not clear enough. Similarly, radial photography mainly captures axial plasma instabilities. Taking Hall thrusters as an example, it mainly captures axial breathing patterns, but the identification of circumferential instabilities is not clear enough. Therefore, unidirectional high-speed photography can only capture the unidirectional two-dimensional features of electric thruster plasma, and cannot fully record features in other directions, thus failing to obtain a comprehensive understanding of the instability features of electric thruster plasma.

[0008] 2. Two-way asynchronous high-speed photography suffers from operational complexity, high time costs, and difficulties in reproducible operation. Like ordinary cameras, high-speed photography requires precise focusing to obtain a clear sequence of images of electric thruster discharge oscillations. While two-way asynchronous high-speed photography can capture the plasma instability characteristics of the electric thruster from two directions, each change in the high-speed camera's position necessitates refocusing with a film plate to obtain a clear image and prevent image distortion. Furthermore, since ground-based experiments with the electric thruster require a high-vacuum simulation system (vacuum chamber), each refocusing with a film plate necessitates opening and closing the chamber for venting and evacuation, significantly increasing operational complexity and time costs, thus extending the experimental cycle. Moreover, performing two separate shots from two directions cannot guarantee complete consistency in experimental conditions and oscillation phase.

[0009] 3. Existing two-way synchronous high-speed photography suffers from excessively high costs. Current experiments rarely employ two-way synchronous high-speed photography, primarily because it relies on the synchronized triggering of two high-speed cameras. The near-million-dollar cost of a single high-speed camera makes this approach impractical. Furthermore, the synchronization delay between multiple high-speed cameras is around 100 ns, which affects the analysis of experimental patterns and mechanisms.

[0010] Literature on unidirectional high-speed imaging and diagnostic system for plasma oscillations in electric thrusters:

[0011] [1]Liu D,Huffman R,Branam R,et al.200W Hall Thruster DischargeOscillations with Xe and Kr Propellant[C] / / 42nd AIAA Plasmadynamics andLasers Conference in conjunction with the 18th International Conference onMHD Energy Conversion(ICMHD).3738.

[0012] [2]Hall SJ,Jorns BA,Cusson SE,et al.Performance and high-speed characterization of a 100-kW nested Hall thruster[J].Journal of Propulsionand Power,2022,38(1):40-50.

[0013] Literature on bidirectional asynchronous high-speed imaging and diagnostic system for plasma oscillations in electric thrusters:

[0014] [3]Désangles V,Shcherbanev S,Charoy T,et al.Fast camera analysis ofplasma instabilities in Hall effect thrusters using a POD method underdifferent operating regimes[J].Atmosphere,2020,11(5):518. Summary of the Invention

[0015] This invention proposes a synchronous bidirectional high-speed imaging and diagnostic system for electric thruster plasma oscillation. It uses a combination of a plane mirror and a moving platform to build a bidirectional optical path to simultaneously introduce images of the side and front of the electric thruster into the lens of a single high-speed camera. Compared with unidirectional high-speed imaging, this invention can obtain the instability characteristics of electric thruster plasma in multiple directions and can simultaneously capture the bidirectional oscillation information of electric thruster plasma, thus addressing the aforementioned drawback 1.

[0016] This invention simultaneously presents a sequence of photographic images of the side and front of the electric thruster in a high-speed camera's imaging module, obtaining pseudo-three-dimensional features of the electric thruster's plasma instability and acquiring more information. Compared to bidirectional asynchronous high-speed photography, this invention can simultaneously capture the plasma instability features of the electric thruster from two directions, eliminating time and phase differences and ensuring that the images from different directions depict the same discharge oscillation phenomenon. This reduces random errors in the experiment, addressing the aforementioned drawback 2.

[0017] Compared to traditional two-way synchronous high-speed photography, this invention constructs a two-way optical path to simultaneously introduce images of the side and front of the electric thruster into the lens of a single high-speed camera. Only a single high-speed camera is needed, which can reduce the financial and time costs of experiments and improve research efficiency.

[0018] To achieve the goal of bidirectional synchronous high-speed photography of electric thruster plasma instability, this invention designs a bidirectional high-speed imaging and diagnostic system for electric thruster plasma oscillation, mainly composed of a bidirectional plane mirror assembly, a moving platform assembly, and a high-speed camera. This scheme increases the dimensionality of data acquired through high-speed photography of electric thruster plasma oscillation, improves the time synchronization of bidirectional high-speed photography of electric thruster plasma oscillation, and reduces the cost of bidirectional high-speed photography of electric thruster plasma oscillation.

[0019] The overall structure of the invention is as follows Figure 3 As shown, the main structure consists of a vacuum chamber 1, an electric thruster 2, a vacuum chamber observation window 3, an electric thruster plasma 4, a reflector group 5, a side-viewing optical path 6, a high-speed camera 7, a data processing system 8, a high-speed camera shooting range 9, and a front-viewing optical path 10. This invention achieves bidirectional synchronous high-speed photography of the instability of the electric thruster plasma through the design of a bidirectional plane reflector group and a high-speed camera.

[0020] The electric thruster 2, vacuum chamber observation window 3, and reflector assembly 5 are bolted together inside the vacuum chamber 1. The electric thruster plasma 4 is generated by the electric thruster 2 and adheres to its outer side. The side-viewing optical path 6 and the front-viewing optical path 10 are formed by the reflector assembly 5. A high-speed camera 7 is placed outside the vacuum chamber 1, with its shooting range 9 directly facing the vacuum chamber observation window 3 to capture the side-viewing optical path 6 and the front-viewing optical path 10. The electric thruster 2 and the electric thruster plasma 4 are the objects being photographed; they can be of any type and structure, and this system can photograph and diagnose them. A typical structure of the electric thruster 2 includes a plasma generation module and an acceleration module, while a typical structure of the electric thruster plasma 4 is a cone-shaped or spherical plasma feather-like flow field.

[0021] This invention solves the problem of difficult bidirectional, synchronous, low-cost, and high-speed photography of plasma instabilities in electric thrusters. Vacuum chamber 1 is the experimental environment used to simulate a high-vacuum environment, typically providing 10... -3 Pressures below Pa. The electric thruster 2 generates thrust by ionizing and accelerating the working fluid using electrical energy. Researchers observe the oscillating electric thruster plasma 4 through the vacuum chamber observation window 3 using the naked eye or optical imaging equipment. Through the reflector group 5, light emitted from the side of the electric thruster plasma is reflected by the side-viewing optical path 6, and light emitted from the front is reflected by the front-viewing optical path 10, entering the high-speed camera's imaging range 9 of the high-speed camera 7. The images are received by the photosensitive element and finally transmitted to the data processing system 8 via signal lines, achieving the purpose of bidirectional synchronous high-speed photography of the electric thruster plasma oscillations.

[0022] To enable a single high-speed camera to simultaneously capture the oscillations of the electric thruster plasma in different directions while ensuring approximately equal optical path lengths across different optical paths, this invention designs a high-precision, modular mirror assembly 5. The original image object is composed of a front calibration film plate 504 and a side calibration film plate 502. The front original image direction 501 and the side original image direction 503 represent the original image directions in two different directions, respectively. The film plates are used to calibrate the optical path and the high-speed camera, preventing distortion in the captured images. Replacing the front calibration film plate 504 and the side calibration film plate 502 with the electric thruster 2 allows for bidirectional synchronous high-speed imaging of the electric thruster plasma instability. The side original image direction 503 is imaged as a side mirror direction 507 via the side optical path (plane mirrors 506 and 509), and the front original image direction 501 is imaged as a front mirror direction 508 via the front optical path (plane mirror 511). Displacement platforms 505, 510, and 512 are used to adjust the position of the plane mirrors. To prevent plasma from eroding the mirror surface, plane mirrors generally use a dielectric film. The final optical path difference between the side and front optical paths is approximately within 5cm, ensuring that both the side and front images are simultaneously within the focal length of the high-speed camera's lens, resulting in a clear image. Based on the speed of light being 2.998 × 10⁻⁶... 8 Calculations using m / s show that the time difference between imaging via the side optical path and the front optical path does not exceed 5cm ÷ 2.998 × 10 8 m / s = 1.67 × 10 -10 s = 0.167 ns, indicating that the side optical path and the front optical path have excellent time synchronization under clear imaging conditions. The base platform 513 is used to support all the above components, including the side calibration film plate 502, the front calibration film plate 504, the displacement platform 505, the plane mirror 506, the plane mirror 509, the displacement platform 510, the plane mirror 511, and the displacement platform 512.

[0023] Traditional high-speed photography of electric thruster plasma instabilities has almost entirely neglected the simultaneous capture of instability characteristics in different directions. Existing research almost entirely focuses on unidirectional capture of electric thruster plasma instabilities. Even when high-speed photography considering different directions of electric thruster plasma instabilities is employed, each instability is analyzed and studied independently. Therefore, there has long been no need for bidirectional synchronous high-speed photography of electric thruster plasma instabilities. However, in recent years, with the deepening of research, it has been discovered that oscillations in different directions of electric thruster plasma exhibit strong coupling relationships, necessitating a scheme for bidirectional synchronous high-speed photography of electric thruster plasma instabilities to investigate the internal coupling mechanism.

[0024] Traditional high-speed imaging optical paths for electric thruster plasma instability do not consider whether the optical path lengths of optical paths in different directions are consistent, making it difficult to guarantee the clarity of images from different directions. The inconsistent optical path lengths of optical paths arranged according to conventional thinking mean that, during high-speed imaging, at most one optical path can be imaged at the focal point of the high-speed camera lens, making it impossible to simultaneously and clearly capture the plasma instability characteristics of electric thrusters from different directions.

[0025] The beneficial effects of this invention compared to the prior art are as follows:

[0026] 1. The bidirectional synchronous high-speed imaging and diagnostic system for electric thruster plasma oscillations designed in this invention can achieve synchronous high-speed imaging of electric thruster plasma oscillations in different directions. By utilizing a plane mirror assembly and a displacement platform, side and front optical paths are constructed, and images of electric thruster plasma oscillations in different directions are introduced into the same high-speed camera with approximately the same optical path, achieving synchronous high-speed imaging of electric thruster plasma oscillations in different directions. This allows for the study of the coupling mechanism of electric thruster plasma oscillations in different directions.

[0027] 2. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system designed in this invention can achieve high-definition, high-synchronization bidirectional synchronous high-speed imaging. By adjusting the two optical paths to be close in optical path length, the oscillation images of the electric thruster plasma in both directions can be clearly captured; and at this time, the optical path difference between the two optical paths is small, and the imaging time difference is on the order of 0.1 ns, which has excellent time synchronization.

[0028] 3. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system designed in this invention can reduce the high costs associated with multiple high-speed cameras. By using a single high-speed camera to complete bidirectional synchronous high-speed imaging, the cost of a second high-speed camera is reduced by nearly a million dollars. This method can also be extended to other fields requiring bidirectional synchronous high-speed imaging, such as bidirectional synchronous high-speed imaging of flame combustion. Attached Figure Description

[0029] Figure 1 This refers to Liu's literature on the unidirectional high-speed imaging and diagnostic system for plasma oscillations in electric thrusters.

[0030] Figure 2 This is a bidirectional asynchronous high-speed imaging and diagnostic system for plasma oscillations in electric thrusters, as described in Désangles's literature.

[0031] Figure 3 This is a schematic diagram of the overall structure of the present invention.

[0032] Figure 4 This is a schematic diagram of the reflector assembly.

[0033] Figure 5 This is a schematic diagram of the bidirectional synchronous imaging results of the plasma oscillation characteristics of an electric thruster.

[0034] The labels in the diagram are explained as follows:

[0035] Vacuum chamber 1, electric thruster 2, vacuum chamber observation window 3

[0036] Electric thruster plasma 4 Reflector group 5 Side-viewing optical path 6

[0037] 7 High-speed camera 8 Data processing system 9 High-speed camera shooting range

[0038] Facing the light path 10

[0039] Frontal image direction 501; Side calibration film plate 502; Side image direction 503

[0040] Front calibration film plate 504, displacement platform 505, plane mirror 506

[0041] Side mirror orientation 507, Front mirror orientation 508, Plane mirror 509

[0042] Displacement platform 510, Plane mirror 511, Displacement platform 512

[0043] Base platform 513 Detailed Implementation

[0044] The key feature of this invention is the design and implementation of a bidirectional synchronous imaging optical path for the plasma oscillation characteristics of electric thrusters. Alternatives are as follows:

[0045] The purpose of the optical path of this invention is to make the optical path lengths of the two optical paths close (<5cm). Therefore, depending on the specific experimental setup, any arrangement that yields a similar optical path can be used instead, such as the side optical path or the front optical path undergoing more turns, or the mirrors in the side optical path and the front optical path not being placed at a 45° angle.

[0046] This invention is applicable to bidirectional synchronous imaging diagnosis of plasma oscillation characteristics of electric thrusters. To ensure clear imaging of the two optical paths by the photosensitive module of the high-speed camera, the total optical path difference between the two optical paths is between 1 and 10 cm, and the diameter of the plane mirror is between 1 and 20 cm.

[0047] The system's operation process:

[0048] Vacuum chamber 1, under the operation of mechanical pumps and cryogenic pumps, reaches the working pressure of the electric thruster, typically 1×10⁻⁶. -5 Pa ~ 1×10 -2Pa. The electric thruster 2, as the research object, is generally an ion thruster, Hall thruster, or other electric thruster with significant plasma and plume generation. It uses electrical energy to ionize an inert gas working medium (argon, krypton, xenon) to generate electric thruster plasma 4, which is then accelerated to form thrust. The plasma density is 1 × 10⁻⁶ Pa. 13 m -3 ~1×10 19 m -3 The vacuum chamber observation window 3 is generally made of quartz glass and is typically 10cm to 50cm in size. The reflector group 5 is used to reflect and image the plasma 4 from the electric thruster.

[0049] Before photographing the electric thruster plasma 4, the reflector assembly 5 needs to be calibrated, such as... Figure 4 As shown. Calibration uses a side calibration film plate 502 and a front calibration film plate 504. The front original image direction 501 is reflected by the plane mirror 511 to form the front mirror direction 508, which is the frontal viewing optical path 10. The side original image direction 503 is reflected by the plane mirrors 506 and 509 to form the side mirror direction 507, which is the side viewing optical path 6. The plane mirrors in the above optical paths are all 45° to ensure that the optical path lengths of the two optical paths are approximately equal. The plane mirrors use a dielectric film to enhance their corrosion resistance in the plasma environment. Their diameter is between 1 and 20 cm to ensure that a complete plasma image can be observed and that the optical paths between the plane mirrors do not interfere with each other. The displacement platforms 505, 510, and 512 are used to adjust the relative position and angle of the plane mirrors to control the optical path. When the film plate appears as a regular rectangle in the high-speed camera, it indicates that the optical path calibration is complete. At this point, replacing the side calibration film plate 502 and the front calibration film plate 504 with the electric thruster 2 and the electric thruster plasma 4 allows for bidirectional synchronous imaging of the electric thruster plasma oscillation characteristics. A schematic diagram of the imaging results is shown below. Figure 5 As shown, the side view and the front view have similar clarity; both are clear images.

[0050] The optical path lengths of the side-view optical path 6 and the front-view optical path 10 are between 1m and 5m to meet the focal length range of the high-speed camera 7 lens and the limitations of the experimental environment. The maximum shooting frame rate of the high-speed camera 7 is over 200,000 frames per second. The difference in optical path length between the side-view optical path 6 and the front-view optical path 10 is within 1 to 10cm to ensure that both the side and front images are within the shooting range 9 of the high-speed camera and are simultaneously clear images. The data processing system 8 is connected to the high-speed camera 7 via a high-speed transmission network cable and uses post-processing programs such as C and Python to analyze and process the captured image sequences.

Claims

1. A bidirectional synchronous high-speed imaging and diagnostic system for plasma oscillation in an electric thruster, characterized in that: It consists of a vacuum chamber, an electric thruster, a vacuum chamber observation window, an electric thruster plasma, a reflector assembly, a side-viewing optical path, a high-speed camera, a data processing system, and the high-speed camera's shooting range and front-viewing optical path; Among these, The electric thruster, vacuum chamber observation window, and reflector assembly are bolted together inside the vacuum chamber. The electric thruster plasma is generated by the electric thruster and adheres to the outside of the electric thruster. The side-view and front-view optical paths are formed by the reflector assembly. A high-speed camera is placed outside the vacuum chamber, with its shooting range facing the vacuum chamber observation window to capture the side-view and front-view optical paths. The electric thruster and its plasma are the subjects of the photograph. The reflector assembly consists of a front calibration film plate and a side calibration film plate. The front original image direction and the side original image direction represent the original image directions in two directions, respectively. The film plate is used to calibrate the optical path and the high-speed camera to prevent distortion of the captured image. By replacing the front calibration film plate and the side calibration film plate with an electric thruster, bidirectional synchronous high-speed photography of the plasma instability of the electric thruster can be performed.

2. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: The objects to be photographed can be any type and structure of electric thruster and electric thruster plasma, and can be photographed and diagnosed.

3. A bidirectional synchronous high-speed imaging and diagnostic system for plasma oscillation of an electric thruster according to claim 1 or 2, characterized in that: The structure of an electric thruster includes a plasma generation module and an acceleration module. The plasma structure of the electric thruster is a cone-shaped or spherical plasma feather-shaped flow field.

4. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: The side original image direction is imaged as a side mirror direction through the side optical path, i.e., the plane mirror and the plane mirror image. The front original image direction is imaged as a front mirror direction through the front optical path, i.e., the plane mirror image. The displacement platform is used to adjust the position of the plane mirror.

5. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: The plane mirror uses a dielectric film, and the optical path difference between the side optical path and the front optical path is within 5 cm, ensuring that the side mirror and the front mirror are simultaneously at the focal length of the high-speed camera lens, presenting a clear image.

6. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: The base platform is used to support all the above components, including the side calibration film plate, the front calibration film plate, the displacement platform, and the plane mirror.

7. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: To ensure clear imaging of the two optical paths to the high-speed camera's photosensitive module, the total optical path difference between the two optical paths is between 1 and 10 cm, and the diameter of the plane mirror is between 1 and 20 cm.

8. The electric thruster plasma oscillation bidirectional synchronous high-speed imaging and diagnostic system according to claim 1, characterized in that: The optical path lengths of the side-view and front-view optical paths are between 1 m and 5 m to meet the focal length range of the high-speed camera lens and the limitations of the experimental environment; the maximum shooting frame rate of the high-speed camera is over 200,000 frames; the difference in optical path length between the side-view and front-view optical paths is within 1 to 10 cm to ensure that both the side and front images are within the shooting range of the high-speed camera and are both clear images; the data processing system is connected to the high-speed camera via a high-speed transmission network cable and uses C and Python processing programs to complete the analysis and processing of the captured image sequence.

9. The operation process of the bidirectional synchronous high-speed imaging and diagnostic system for plasma oscillation of an electric thruster according to claim 1, characterized in that: The vacuum chamber, powered by mechanical and cryogenic pumps, reaches the operating pressure of the electric thruster, which is 1×10⁻⁶. -5 Pa ~ 1×10 -2 Pa; The electric thrusters studied include ion thrusters, Hall thrusters, and electric thrusters with significant plumes. They generate thruster plasma by ionizing the inert gas working fluid with electrical energy and then accelerate it to form thrust. The plasma density is 1×10⁻⁶. 13 m -3 ~1×10 19 m -3 The vacuum chamber observation window is made of quartz glass and measures between 10 cm and 50 cm in size. The reflector group is used to image the plasma reflected from the electric thruster.

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