A slice-type high-precision steady-state plasma parameter measurement probe

Abstract

This invention relates to the field of ion detection technology, and particularly to a slice-type high-precision steady-state plasma parameter measurement probe. The system includes a housing, and a multi-mode slicing assembly, a collecting electrode, and a controller installed within the housing. The housing has a circular opening. The multi-mode slicing assembly includes a slicing turntable and multiple circumferentially arranged slices on the turntable. The slices and the circular opening are the same size. Rotating the turntable aligns different slices with the circular opening for measurement. A collecting electrode is located downstream of the ion flow in the multi-mode slicing assembly to collect current. The collecting electrode receives the current and outputs an electrical signal to the controller for recording. This solution enables automatic switching between multiple measurement modes of the probe system and possesses high precision, long lifespan, and structural reconfigurability to meet the plasma parameter measurement requirements under complex operating conditions in the plume regions of various types of thrusters in electric propulsion systems.

Description

Technical Field

[0001] This invention relates to the field of ion detection technology, and in particular to a slice-type high-precision steady-state plasma parameter measurement probe. Background Technology

[0002] In the current research and testing of electric propulsion systems, accurately measuring plasma parameters (including ion energy distribution and ion current density) in the plume region is of great significance for evaluating thruster performance, studying thruster-satellite interactions, and performing plume modeling. Therefore, plasma diagnostic tools such as RPA probes and Faraday probes are widely used.

[0003] Currently, mainstream RPA probes primarily utilize multi-layered metal grids, applying specific potentials between each grid. Electrons are filtered out by negatively biased grids, and the ion current is measured by gradually adjusting the gate potential, thus inverting the ion energy distribution function. However, its measurement range is limited by the fixed grid structure parameters, especially in regions with significant plasma density variations, leading to reduced signal-to-noise ratio and energy spectrum distortion. Another commonly used Faraday probe structure primarily uses an open metal collector, collecting ions and removing electrons. Ion current density is obtained by measuring the current generated when ions collide with the collector. However, it cannot provide detailed spectral information such as energy distribution, and different probe types are required for different operating modes, resulting in complex operation and low efficiency. Furthermore, existing RPA or Faraday probes typically employ fixed grid structures, lacking structural adjustment capabilities and compatibility with various thruster models and their measurement requirements under different operating conditions, lacking adaptability and scalability. Additionally, during long-term use, the grid of fixed probes is susceptible to physical erosion by high-energy ions, leading to changes in aperture size and decreased measurement accuracy. Frequent replacement of probe components increases experimental costs and maintenance complexity. Summary of the Invention

[0004] This invention provides a slice-type high-precision steady-state plasma parameter measurement probe, which overcomes the technical defects of existing plasma measurement probes such as simple structure, separate functions, poor measurement adaptability and limited service life. The device can realize automatic switching of multiple measurement modes and has high precision, long life and structural reconfigurability to meet the plasma parameter measurement needs of various types of thruster plume regions in electric propulsion systems under complex operating conditions.

[0005] This invention provides a slice-type high-precision steady-state plasma parameter measurement probe, including a housing, and a multi-mode slicing assembly, a collecting electrode, and a controller installed inside the housing; The outer casing has a circular opening. The multi-mode slicing assembly includes a slicing turntable and multiple embedded slices arranged circumferentially on the slicing turntable. The embedded slices include blind plate slices and low-pass, medium-pass, and high-pass slices with different aperture sizes and aperture spacings. The embedded slices and the circular opening are the same size. The slicing turntable is rotated to align different embedded slices with the circular opening for measurement. A collecting electrode for collecting current is provided downstream of the ion current of the multi-mode slicing assembly. The collecting electrode is used to receive the current and output an electrical signal to the controller for recording.

[0006] In one possible design, the plasma parameter measurement probe further includes a stepper motor connected to the slicing turntable for controlling the rotation of the slicing turntable, and a controller connected to the stepper motor for controlling the rotation angle of the stepper motor.

[0007] In one possible design, the plasma parameter measurement probe also includes a ground grid located upstream of the ion flow direction of the slice disk. The ground grid is used to attenuate the ion flux entering the analyzer and to shield other grid potentials.

[0008] In one possible design, the plasma parameter measurement probe also includes a retardation grid disposed between the slicing disk and the collecting electrode, connected to a variable negative pressure.

[0009] In one possible design, the plasma parameter measurement probe further includes an insulator disposed between the mosaic slice, the retardation gate, and the collecting electrode.

[0010] In one possible design, the plasma parameter measurement probe includes two low-pass slices, two medium-pass slices, and two high-pass slices of the same type, positioned on the same diameter of the slice turntable.

[0011] In one possible design, the blind plate slices are positioned at 0° and 180°, the low-pass slices are positioned at 45° and 225°, the mid-pass slices are positioned at 90° and 270°, and the high-pass slices are positioned at 135° and 315°.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Expanded the measurement range and improved the signal-to-noise ratio. Traditional RPA probes, due to their fixed negative bias gate aperture, are limited by the oscillation characteristics of the plasma in the plume region and the Debye length, resulting in a narrow measurement range. Furthermore, when the bias gate aperture is unsuitable, problems such as excessive ion loss or insufficient electron filtering may occur. This invention, by configuring gate slices with various structural parameters, achieves automatic switching of the appropriate gate structure according to different plume densities and energy characteristics, balancing electron suppression and ion transmission, and effectively improving the signal-to-noise ratio.

[0013] 2. Significantly extends probe lifespan and improves repeatability and stability. With a redundant backup gate slice design and a rotation switching mechanism, the probe can be switched to an undamaged backup slice after being ion-eroded, avoiding the high cost and high risk of frequent opening of the chamber for replacement and manual maintenance.

[0014] 3. Improved the flexibility and efficiency of multi-parameter measurement. Integrating the dual functions of RPA and Faraday probe, this device enables a single unit to acquire high-precision ion energy distribution and accurately measure ion current density, avoiding the cumbersome operation and error accumulation associated with changing multiple devices. The use of a stepper motor for precise turntable angle control allows for rapid switching of measurement modes outside the chamber, significantly shortening the testing cycle and improving experimental efficiency.

[0015] 4. Strong compatibility with engineering applications, facilitating widespread adoption. The modular design and flexible configuration of this invention enable it to be compatible with different types of ion thrusters and Hall thrusters, adapting to various plume conditions and exhibiting excellent versatility and scalability. Its simple structure facilitates its adoption in research institutions and industrial applications, meeting the demands of commercial aerospace and deep space exploration for high-precision, high-reliability measurement equipment.

[0016] In summary, this invention not only overcomes the shortcomings of existing technologies in terms of measurement range, accuracy, service life, and operational efficiency, but also significantly improves the overall performance and engineering application value of plasma parameter measurement for ion thrusters through systematic structural design and functional integration, and has broad prospects for promotion and practical application significance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the structure of a slicing turntable provided by the present invention; Figure 2This is a schematic diagram of a slice-type high-precision steady-state plasma parameter measurement probe structure provided by the present invention.

[0019] In the picture: 1-Slicing turntable; 2-Outer shell; 3-Grounding grid; 4-Insulator; 5-Restriction grid; 6-Collector; 7-Controller; 8-Stepper motor. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0022] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0023] Although existing RPA probes and Faraday probes are widely used in plasma parameter measurement, they still have the following technical defects and application limitations when facing practical testing requirements such as multi-condition operation, high-energy particle environment, and long-term operation: 1. Limited measurement modes and low functional integration. Currently, RPA probes and Faraday probes are typically used as independent devices, each capable of measuring only one type of parameter. For example, RPA probes are primarily used to acquire ion energy distribution information, while Faraday probes are used to measure ion current density. Due to the differences in structure and working principle between the two types of probes, functional switching cannot be achieved easily. If a change in measurement type is required during testing, the probe itself often needs to be replaced, which is complex, inefficient, and detrimental to continuous measurement and data consistency.

[0024] 2. The fixed structure limits the measurement range and adaptability. The grid structure parameters of an RPA probe (including the diameter, thickness, and arrangement of the grid apertures) directly determine its electron suppression capability and ion transmittance. In high-density plasma plumes, if the grid aperture size is too small, ions are prone to collisions or deflection during passage, leading to a decrease in the detection current and a drop in the signal-to-noise ratio. Conversely, if the grid aperture is too large, the electron filtering effect is insufficient, generating background current interference and distorting the measured energy distribution. Since these structural parameters are fixed once fabricated, they are difficult to adapt to the needs of different thruster models or operating conditions. Probes must be customized for each test scenario, increasing costs and lacking versatility.

[0025] 3. The structure is not replaceable, and its service life is limited. Under prolonged high-energy ion beam bombardment, the grid material of RPA probes is prone to physical erosion and thermal deformation, causing changes in the size and distribution of the grid apertures. This leads to the probe gradually deviating from its design state, thereby reducing measurement accuracy and repeatability. Furthermore, most existing probes employ a non-replaceable integral grid structure, requiring complete replacement once damaged. This is particularly problematic when operating within a vacuum chamber, necessitating repeated opening and closing of the chamber, severely impacting experimental efficiency and increasing maintenance costs.

[0026] 4. Lack of backup redundancy and configuration flexibility Traditional probe structure designs are typically customized for specific tasks, lacking redundancy across multiple measurement modes and modularity. If gate damage or failure occurs during testing, it cannot be replaced or switched immediately, severely impacting data integrity and experimental progress.

[0027] In summary, existing RPAs and Faraday probes have significant shortcomings in terms of functional integration, measurement flexibility, service life, and adaptability, making it difficult to meet the urgent needs of electric propulsion systems for high-precision, multi-mode, and long-term plasma parameter measurements. Therefore, there is an urgent need for a new probe device with strong structural innovation, high functional integration, and flexible configuration and switching capabilities to improve the adaptability, efficiency, and reliability of measurements.

[0028] To solve the above technical problems, such as Figure 1 and Figure 2As shown, this embodiment of the invention provides a slice-type high-precision steady-state plasma parameter measurement probe, including a housing 2, and a multi-mode slicing assembly, a collecting electrode 6, and a controller 7 (PCB) installed inside the housing 2. The outer casing 2 is provided with a circular opening. The multi-mode slicing assembly includes a slicing turntable 1 (repulsion grid) and multiple embedded slices arranged circumferentially on the slicing turntable 1. The embedded slices include blind plate slices and low-pass slices, medium-pass slices and high-pass slices with different aperture sizes and aperture spacings. The embedded slices and the circular opening are the same size. The slicing turntable 1 is rotated so that different embedded slices are aligned with the circular opening for measurement. A collecting electrode 6 is provided downstream of the ion current of the multi-mode slicing assembly for collecting current. The collecting electrode 6 is used to receive the current and output an electrical signal to the controller 7 for recording.

[0029] This invention is based on the principles of ion energy blocking and ion current collection. By setting various types of negative bias gate slices, it controls the entry of particles with different energies in the plasma into the probe, and coordinates with the blocking gate 5 to regulate the kinetic energy of the ions, thereby achieving ion energy spectrum measurement. A rotary switching mechanism driven by a stepper motor 8 is introduced, which can automatically switch between multiple measurement modes and achieve a seamless transition between RPA mode and Faraday probe mode.

[0030] By configuring eight different gate slices on the turntable, the probe can quickly switch between low-density, medium-density, and high-density ion energy measurement modes and Faraday probe mode, which is compatible with the testing requirements of different thruster models and plume parameter scenarios, significantly improving the applicability and measurement range of the probe.

[0031] The innovative design employs a stepper motor and a rotary chip replacement mechanism, allowing for precise replacement of the gate chip based on angle positioning. This overcomes the limitations of traditional RPA probes, which require manual opening and replacement, effectively improving operational convenience and system reliability. It also avoids issues such as poor repeatability and performance degradation caused by gate erosion.

[0032] Each operating mode is equipped with redundant slicing sites, which can quickly activate backup slices after a set of slices is damaged, extending the effective lifespan of the probes; at the same time, the gate structure parameters can be flexibly configured according to different application scenarios, supporting extended function design and improving the adaptability and engineering reconfigurability of the device.

[0033] All slices are pre-set with optimized aperture and geometry to adapt to different plasma oscillation characteristics and Debye lengths in the plume region, achieving a balance between electron suppression and ion permeability, thereby obtaining current-voltage characteristic curves and ion energy distributions with higher signal-to-noise ratios, ensuring the accuracy, repeatability and stability of measurement data.

[0034] This probe system is highly adaptable and easy to deploy, suitable for both ground-based vacuum laboratory testing environments and potential applications in plasma diagnostics for future space platforms. Its modular, low-cost, and highly reliable design meets the urgent needs of commercial aerospace and electric propulsion R&D institutions for long-term reliable operation and functional reuse of testing equipment.

[0035] In this embodiment, the outer shell 2 adopts a robust cylindrical design to support the electrodes at each stage, the stepper motor 8 mechanism, and the slicing turntable 1 assembly, while also providing protection, dustproofing, heat conduction, and support functions. An airflow channel is provided at the opening of the outer shell 2 to accommodate the natural inflow of plasma from a vacuum chamber or space plasma environment.

[0036] In this embodiment, the blind plate slice is equivalent to a Faraday probe. When the plasma plume reaches the FP collector 6, electrons are repelled and ions are collected. The ion current density is calculated by sampling the resistor. J i : In the formula: V is the sampling voltage; R is the sampling resistance; A is the effective collection area of ​​the collecting electrode 6.

[0037] The main design parameters are the dimensions of collector electrode 6, the distance between collector electrode 6 and the shielding cylinder, and the dimensions of the shielding cylinder. The dimensions of collector electrode 6 are determined by the plume plasma density, manufacturing process, and current sampling resolution. The distance between collector electrode 6 and the shielding cylinder... λ D It is related to the Debye length of the electron: Where ε0, k B 、e、T e and n e These represent the dielectric constant, Boltzmann constant, elementary charge, average electron temperature, and electron density, respectively.

[0038] In RPA mode: The main design parameters are grid spacing and mesh diameter.

[0039] The inter-grid distance x can be determined using the relationship derived by Hutchinson: Grid hole diameter:

[0040] The gate aperture s and the gate aperture spacing d can be determined using the range of values ​​proposed by Sakai at the highest resolution: In some embodiments of the present invention, the plasma parameter measurement probe further includes a stepper motor 8, which is connected to the slicing turntable 1 and is used to control the rotation of the slicing turntable 1. A controller 7 is connected to the stepper motor 8 and is used to control the rotation angle of the stepper motor 8.

[0041] In this embodiment, the rotating disk is driven to precisely control the slicing angle; automatic switching of working modes is achieved, and remote control and program settings are supported. The stepper motor 8 is the core driving device for realizing the rotatable slicing gate mechanism of this invention. The motor shaft is coaxially connected to a circular rotating disk configured inside the probe, and multiple negatively biased gate slices are evenly distributed on the rotating disk. The rotation of the motor controls the angle of the rotating disk, thereby enabling rapid and precise switching of the gate slices between different measurement modes.

[0042] In some embodiments of the present invention, the plasma parameter measurement probe further includes a ground grid 3, which is located upstream of the ion flow direction of the slice turntable 1. The ground grid 3 is used to attenuate the ion flux entering the analyzer and to shield other grid potentials.

[0043] In some embodiments of the present invention, the plasma parameter measurement probe further includes a retardation gate 5, which is disposed between the slicing turntable 1 and the collecting electrode 6 and connected to a variable negative voltage. The variable negative voltage is applied to adjust the ion energy threshold entering the collecting electrode 6, thereby achieving segmented scanning of the ion energy spectrum.

[0044] In some embodiments of the present invention, the plasma parameter measurement probe further includes an insulator 4 disposed between the mosaic slice, the retardation gate 5, and the collecting electrode 6. The insulator 4 provides structural support while preventing short circuits, ensuring long-term operational stability.

[0045] In some embodiments of the present invention, the plasma parameter measurement probe includes two low-pass slices, two medium-pass slices, and two high-pass slices, with slices of the same type positioned on the same diameter of the slicing turntable 1.

[0046] In some embodiments of the present invention, the blind plate slices are set at 0° and 180° positions, the low-pass slices are set at 45° and 225° positions, the mid-pass slices are set at 90° and 270° positions, and the high-pass slices are set at 135° and 315° positions.

[0047] Specifically, the slicing turntable 1 has multiple mounting positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

[0048] Multiple types of gate slices: Level 1 – Faraday Probe Mode: Blind plates are installed at 0° and 180° positions. When the negative bias gate is rotated to these two angles, the probe obtains a high-precision ion current through the bias gate, and its working principle is the same as that of the Faraday probe. Level 2—Low-Density Ion Energy Measurement Mode: Low-pass slices are installed at 45° and 225° positions. When measuring high-density plume parameters, rotating the negative bias grid to these two angles can achieve efficient suppression of electron current. High-precision ion energy distribution information is obtained after passing through the hindrance grid 5. The two slices serve as backups for each other, which can increase the service life. Level 3 – Medium-Density Ion Energy Measurement Mode: Install the through-slice at 90° and 270° positions. When measuring medium-density plume parameters, rotating the negative bias grid to these two angles enables high-precision measurement of ion energy distribution. The two slices serve as backups for each other, increasing their lifespan. Level 4 – Medium-Density Ion Energy Measurement Mode: High-pass slices are installed at 135° and 315°. When measuring low-density plume parameters, rotating the negative bias grid to these two angles enables high-precision measurement of ion energy distribution. The two slices serve as backups for each other, increasing their lifespan.

[0049] Work process 1) Mode initialization phase Power is supplied to the probe, and the system's main control circuit, stepper motor driver, and data acquisition module are powered on and enter standby mode. According to the test task, the measurement mode combination corresponding to each slice position is preset, and the required slices are installed at the designated positions on the rotating turntable.

[0050] 2) Mode switching control stage During the experiment, based on the density characteristics of the plume region to be measured, the stepper motor 8 was controlled by command to precisely rotate the turntable angle so that the target slice was rotated to the negative bias grid position, thereby realizing the measurement mode switch. When the slice was precisely aligned with the measurement position, the control system immediately stopped the motor power supply.

[0051] 3) Plasma parameter measurement stage Based on the current slice structure (blind plate, low-pass, medium-pass, or high-pass), select the appropriate bias voltage and blocking voltage; the measurement system acquires current, voltage, or power signals according to the selected mode.

[0052] 4) Data Analysis Phase Using measurement data, parameters such as ion energy distribution and current density are calculated.

[0053] 5) End Phase After the measurement task is completed, the control system sends a motor zeroing command to reset the turntable to its initial angle.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sliced high precision steady state plasma parameter measurement probe, characterized in that, Includes a housing, and a multi-mode slicing assembly, a collection electrode, and a controller mounted within the housing; The outer shell is provided with a circular opening. The multi-mode slicing assembly includes a slicing turntable and a plurality of embedded slices arranged circumferentially on the slicing turntable. The slicing turntable is a repulsion grid. The embedded slices include blind plate slices and low-pass, medium-pass, and high-pass slices with different aperture sizes and aperture spacings. The embedded slices and the circular opening are the same size. The slicing turntable is rotated to align different embedded slices with the circular opening for measurement. A collecting electrode for collecting current is provided downstream of the ion current of the multi-mode slicing assembly. The collecting electrode is used to receive the current and output an electrical signal to the controller for recording.

2. The plasma parameter measurement probe of claim 1, wherein, It also includes a stepper motor, which is connected to the slicing turntable and is used to control the rotation of the slicing turntable. The controller is connected to the stepper motor and is used to control the rotation angle of the stepper motor.

3. The plasma parameter measurement probe of claim 1, wherein, It also includes a grounding grid located upstream of the ion flow direction of the slice turntable. The grounding grid is used to attenuate the ion flux entering the analyzer and to shield other grid potentials.

4. The plasma parameter measurement probe according to claim 1, characterized in that, It also includes a blocking gate, which is disposed between the slicing turntable and the collecting electrode and connected to a variable negative pressure.

5. The plasma parameter measurement probe according to claim 4, characterized in that, It also includes an insulator disposed between the etched slice, the blocking gate, and the collecting electrode.

6. The plasma parameter measurement probe according to claim 1, characterized in that, The low-pass slice, the mid-pass slice, and the high-pass slice each consist of two slices, and slices of the same type are positioned on the same diameter of the slice turntable.

7. The plasma parameter measurement probe according to claim 6, characterized in that, The blind plate slices are set at 0° and 180° positions, the low-pass slices are set at 45° and 225° positions, the mid-pass slices are set at 90° and 270° positions, and the high-pass slices are set at 135° and 315° positions.

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