CN117420083B - Online monitoring device and method for trace products of plasma erosion - Google Patents

Abstract

A plasma erosion trace product online monitoring device and method, relating to the field of plasma spectrum testing technology, solving the technical problem of "how to monitor the erosion trace products of plasma thruster components", the device comprises a metal shielding cover, and a first convex lens, a first reflector, a dichroic prism, a second convex lens, a grating and a second reflector arranged inside the metal shielding cover, and a photomultiplier tube and an analysis and processing device arranged outside the metal shielding cover; an incident light slit and an exit light slit are fixed on the side wall of the metal shielding cover, the exit light slit is connected to the photomultiplier tube, and the photomultiplier tube is connected to the analysis and processing device; the device and method design a spectrometer device to monitor the light intensity of the trace product spectral line, establish the relationship between the intensity of the trace material radiation spectral line and the light intensity signal fluctuation, so as to obtain the absolute density of the trace product, with high reliability and sensitive monitoring.

Description

A device and method for online monitoring of trace products of plasma erosion

Technical Field

The invention relates to the technical field of plasma spectrum testing.

Background technique

Plasma thruster is the core equipment of electric propulsion system. It plays an important role in satellite propulsion and attitude control. Its performance status directly determines the status of the propulsion system.

Traditional life assessment tests for plasma thrusters are costly and time-consuming, which is not conducive to rapid iteration and optimization of designs by engineering units. In fact, studies have shown that the main cause of life failure of plasma thrusters is component erosion. For example, hollow cathode emitter erosion and Hall thruster wall erosion lead to thruster failure. Therefore, monitoring trace products of erosion of plasma thruster components is an effective means to evaluate the life of plasma thrusters. The emission spectroscopy method has the characteristics of in-situ, immediate, and non-intrusive, and can be used to monitor trace products of erosion of plasma thruster components. In fact, the density of trace products of plasma erosion is several times lower than the density of the discharge working fluid of the thruster body, and it is necessary to design a spectrometer device to enable it to monitor trace products.

However, the signals measured by existing spectral measurement methods in other fields have the characteristics of strong signals, and do not involve the testing and analysis of weak signals of trace substances. Therefore, they are not suitable for the collection of trace weak signals in plasma thruster life assessment. If directly applied, there is a problem of not being able to measure trace product signals.

Therefore, how to solve the problem of monitoring trace corrosion products of plasma thruster components has become a technical problem that needs to be solved urgently in this field.

Summary of the invention

In order to solve the above technical problems, the present invention provides an online monitoring device and method for trace products of plasma erosion. The device is designed with a spectrometer to monitor the light intensity of the trace product spectral lines, establishes the relationship between the intensity of the trace substance radiation spectral lines and the light intensity signal fluctuation, so as to obtain the absolute density of the trace product, with high reliability and sensitive monitoring.

A plasma erosion trace product online monitoring device comprises a metal shield, and a first convex lens, a first reflector, a beam splitter, a second convex lens, a grating and a second reflector arranged inside the metal shield, and a photomultiplier tube and an analysis and processing device arranged outside the metal shield;

An incident light slit and an exit light slit are fixed on the side wall of the metal shield, the exit light slit is connected to the photomultiplier tube, and the photomultiplier tube is connected to the analysis and processing equipment; the first convex lens is arranged in the metal shield close to the incident light slit, and the first reflector is arranged corresponding to the first convex lens;

The plasma radiation light collected by the incident light slit passes through the first convex lens, the first reflector, the beam splitter, the second convex lens, the grating and the second reflector in sequence, and is incident on the photomultiplier tube through the exit light slit, and the photomultiplier tube transmits the acquired experimental light intensity information to the analysis and processing equipment;

The analysis and processing device includes the following modules:

Light intensity acquisition module, used to collect experimental light intensity information within the wavelength range of trace products;

A fluctuation error calculation module, used for calculating the fluctuation error caused by the experimental light intensity fluctuation based on the experimental light intensity;

A relationship building module, used to establish the relationship between the theoretical light intensity and the experimental light intensity;

A trace product density calculation module, used to calculate the density of the trace product based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity;

Wherein, the theoretical light intensity is expressed by the following formula:

Imodel=ε× _ne × _ni × _Qi ;

Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, _ne is the electron density, _ni is the trace product density, Qi _is the excitation rate coefficient, and Imodel represents the theoretical intensity of the trace product luminescence, that is, the theoretical light intensity.

Furthermore, the incident light slit width is 25 um.

Furthermore, the incident light slit is externally connected to an SMA connector, the SMA connector is connected to an optical fiber, the other side of the optical fiber is used to receive light radiated from the plasma region, and the optical fiber is a high-transmittance deep ultraviolet optical fiber with a core of 1000um.

Furthermore, the device also includes a grating angle control component, which is disposed on a side wall of the metal shielding cover adjacent to the side wall of the incident light slit, and the grating angle control component is connected to the grating.

An online monitoring method for trace products of plasma erosion, using the above device, comprises the following steps:

Collect experimental light intensity information within the wavelength range of trace products;

Calculating a fluctuation error caused by fluctuations in the experimental light intensity based on the experimental light intensity;

Establishing the relationship between the theoretical light intensity and the experimental light intensity;

Based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity, the density of the trace product is calculated.

Furthermore, when collecting experimental light intensity information within the wavelength range of trace products, a preset number of times is collected in a continuous time, and the preset number of times is 100 times.

Furthermore, the wavelength range of the trace product is: the wavelength center is 250nm and the range is 1nm.

Further, the density of the trace product is calculated by the following formula:

n _i =erro ² /(ε× _ne ×Q _i );

Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, _ne is the electron density, _ni is the trace product density, _Qi is the excitation rate coefficient, and erro is the fluctuation error.

Furthermore, ε is 0.01, and n _e is the electron density value measured by the probe of the hollow cathode device, which is 10 ¹¹ cm ^-3 ;

The excitation rate coefficient is expressed as follows:

_Qi = 2.56 × ^10-8 × _Te ^(0.193) × exp (-3.93/ _Te );

Here, Te _is the electron temperature value measured by the probe of the hollow cathode device, which is 3eV.

The device and method for online monitoring of trace products of plasma erosion provided by the present invention have at least the following beneficial effects:

(1) A spectrometer was designed to monitor the light intensity of the trace product spectrum. After the plasma radiation light enters the device, it is split twice by the beam splitter and grating, and then diverges and converges before being received by the photomultiplier tube. The measured spectral intensity is received multiple times in a continuous period of time, and the relationship between the intensity of the trace substance radiation spectrum and the light intensity signal fluctuation is established to obtain the absolute density of the trace product. Compared with traditional testing methods, this monitoring method has high reliability and sensitive monitoring.

(2) Receiving the measured spectral intensity multiple times in a continuous period of time can better measure the volatility of the trace product light intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a light path diagram of an embodiment of an online monitoring device for plasma erosion trace products provided by the present invention;

FIG2 is a flow chart of an embodiment of an online monitoring method for trace products of plasma erosion;

Figure numerals: 1-metal shielding cover, 2-incident light slit, 3-first convex lens, 4-first reflector, 5-beam splitter prism, 6-second convex lens, 7-grating, 8-second reflector, 9-exit light slit, 10-photomultiplier tube, 11-precision mechanical stepping control console.

Detailed ways

In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, but should not be construed as limitations on the present application.

In the description of the present application, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

In this application, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can be a direct connection or an indirect connection through an intermediate medium, it can also be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

Embodiment 1:

Referring to FIG. 1 , in some embodiments, there is provided an online monitoring device for trace products of plasma erosion, comprising a metal shield 1, and a first convex lens 3, a first reflector 4, a beam splitter prism 5, a second convex lens 6, a grating 7 and a second reflector 8 arranged inside the metal shield 1, and a photomultiplier tube 10 and an analysis and processing device arranged outside the metal shield 1;

An incident light slit 2 and an exit light slit 9 are fixed on the side wall of the metal shield 1. The exit light slit 9 is connected to the photomultiplier tube 10, and the photomultiplier tube 10 is connected to the analysis and processing equipment; the incident light slit 2 is used to collect plasma radiation light. The first convex lens 3 is arranged in the metal shield 1 close to the incident light slit 2, and the first reflector 4 is arranged corresponding to the first convex lens 3;

The incident light slit 2 is connected to an optical fiber with an SMA905 connector in front, and the other end of the optical fiber is placed in the monitored area to collect the light radiated by the plasma. The light then passes through the first convex lens 3, the first reflector 4, the beam splitter prism 5, the second convex lens 6, the grating 7 and the second reflector 8 in sequence from the incident light slit 2, and is incident on the photomultiplier tube 10 through the exit light slit 9. The photomultiplier tube 10 transmits the acquired experimental light intensity information to the analysis and processing equipment.

The analysis and processing device includes the following modules:

Light intensity acquisition module, used to collect experimental light intensity information within the wavelength range of trace products;

A fluctuation error calculation module, used for calculating the fluctuation error caused by the experimental light intensity fluctuation based on the experimental light intensity;

A relationship building module, used to establish the relationship between the theoretical light intensity and the experimental light intensity;

The trace product density calculation module is used to calculate the density of the trace product based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity.

Preferably, the normal direction of the first reflector 4 forms an angle of 45 degrees with the incident light beam from the first convex lens 3 .

Preferably, the incident light slit 2 has a width of 25um, and the incident light slit 2 is externally connected to an SMA connector, and the SMA connector is used to insert an optical fiber, and the other side of the optical fiber is used to receive light radiated from the plasma region, and the optical fiber is a high-transmittance deep ultraviolet optical fiber with a core of 1000um. It should be noted that the size of the slit will affect the resolution and luminous flux. Generally speaking, the smaller the slit, the higher the resolution, but the smaller the luminous flux. A small optical channel will reduce the signal strength and make it difficult for the device to measure. Therefore, in order to take into account both resolution and luminous flux, a size of 25um was selected.

The device further comprises a grating 7 angle control component, wherein the grating 7 angle control component is disposed on a side wall of the metal shielding cover 1 adjacent to the side wall of the incident light slit 2 , and the grating 7 angle control component is connected to the grating 7 .

Preferably, the angle control component of the grating 7 is a precision mechanical stepping control platform 11 , and the precision mechanical stepping control platform 11 is connected to the grating 7 for controlling the angle of the grating 7 .

During operation, the light beam collected by the incident light slit 2 propagates to the first convex lens 3, which converges the optical fiber and converts it into parallel light; then it is incident on the first reflector 4, and the propagation direction of the light beam changes by 90 degrees through the triangular first reflector 4, and is incident on the beam splitter prism 5, and the light beam is dispersed by the beam splitter prism 5, and the function of the beam splitter prism 5 is to decompose the complex light into monochromatic light, and then it is incident on the second convex lens 6, and the second convex lens 6 converges the light beam; the light beam is converged by the second convex lens 6 and incident on the grating 7 for splitting, and the light beam split twice by the beam splitter prism 5 and the grating 7 is further propagated to the second reflector 8; the light beam is received by the exit light slit 9, and is incident on the detector of the photomultiplier tube 10, and is converted into an electrical signal that can be analyzed and processed. The wavelength band of the light received by the photomultiplier tube 10 is related to the deflection angle of the grating 7, and the deflection angle of the grating 7 can be controlled by the precision mechanical stepping control table 11. At this point, the light radiated by the plasma is received by the photomultiplier tube 10 after splitting.

The above is a general description of the monitoring device. Now, combined with specific application scenarios, taking the monitoring of B atomic spectral lines of trace products of emitter erosion in aerospace electric propulsion hollow cathode equipment as an example, the implementation of the aforementioned device and the application of the method are further explained.

The typical wavelengths of the B atoms of the erosion products of the hollow cathode equipment of aerospace electric propulsion are 249.68nm and 249.77nm. Therefore, the spectrometer system needs to extract the spectrum line in the region with a wavelength center of 250nm and a range of 1nm. The above purpose can be achieved by adjusting the precision mechanical stepping control table 11 to control the angle of the grating 7.

The light radiated by the plasma enters the spectrometer system through optical fiber light guidance. One end of the optical fiber is fixed in the vacuum tank through a fiber coupler to monitor the light-emitting area of the electric propulsion hollow cathode device, and the other end is fixed on the through-vacuum fiber feedthrough flange. An optical fiber is used outside the vacuum tank, one side of the optical fiber is connected to the through-vacuum fiber feedthrough flange, and the other side is screwed on the SMA interface of the spectrometer entrance slit. Preferably, the optical fiber selects a high-transmittance deep ultraviolet optical fiber with a core of 1000um. It should be noted that the wavelength position of the signal of the trace product is the ultraviolet signal. If a non-ultraviolet optical fiber is used, the signal will be reduced due to the optical fiber, which will cause the already weak signal to lose part, and the signal will be weaker and difficult to measure. The core of 1000um can increase the light flux, so as to improve the signal-to-noise ratio of the signal.

At this point, the complex light radiated by the plasma of the electric propulsion hollow cathode device is processed by the spectrometer system and detected and received by the photomultiplier tube 10. The photomultiplier tube 10 is controlled to achieve continuous time acquisition. Preferably, the plasma hollow cathode device is continuously collected 100 times under one working condition to measure the volatility of the light intensity of the trace product.

Embodiment 2:

Referring to FIG. 2 , in some embodiments, a method for online monitoring of trace products of plasma erosion is provided, using the above-mentioned device, comprising the following steps:

S1. Collecting experimental light intensity information within the wavelength range of trace products;

S2. calculating a fluctuation error caused by fluctuations in the experimental light intensity based on the experimental light intensity;

S3, establishing the relationship between the theoretical light intensity and the experimental light intensity;

S4. Calculate the density of the trace product based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity.

Specifically, in step S1, when collecting experimental light intensity information within the wavelength range of trace products, a preset number of times is collected in a continuous time, and the preset number of times is 100 times.

During the collection process, the experimental light intensity information within the wavelength range of the trace product is collected by adjusting the angle of the grating 7. The wavelength range of the trace product is: the wavelength center is 250nm, and the range is 1nm.

In step S3, the theoretical light intensity is expressed by the following formula:

Imodel=ε× _ne × _ni × _Qi ;

Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, _ne is the electron density, _ni is the trace product density, _Qi is the excitation rate coefficient, and Imodel represents the theoretical intensity of the trace product luminescence, that is, the theoretical light intensity.

In step S4, the density of the trace product is calculated by the following formula:

n _i =erro ² /(ε× _ne ×Q _i );

Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, _ne is the electron density, _ni is the trace product density, and _Qi is the excitation rate coefficient.

As a preferred implementation, ε is 0.01, and n _e is the electron density value measured by the probe of the hollow cathode device, which is 10 ¹¹ cm ^-3 ;

The excitation rate coefficient is expressed as follows:

_Qi = 2.56 × ^10-8 × _Te ^(0.193) × exp (-3.93/ _Te );

Here, Te _is the electron temperature value measured by the probe of the hollow cathode device, which is 3eV.

The specific derivation and calculation process is as follows:

The trace product spectrum was identified and its intensity was recorded as I _i (i=1-100).

The error caused by the experimental light intensity fluctuation is expressed by the following formula:

erro=(I _i -I _i ')/I _i ',i=1-100;

Among them, I _i ' is the average value of multiple experimental acquisitions, and erro is the error caused by experimental light intensity fluctuations.

The theoretical luminescence intensity of the trace product is calculated as follows:

I _model =ε×n _e ×n _i ×Q _i ;

Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, which is determined by the geometric optical relationship between the optical fiber and the radiated light, _ne is the electron density, _ni is the trace product density, _Qi is the excitation rate coefficient, and _Imodel represents the theoretical intensity of the trace product luminescence.

In this embodiment, ε is 0.01, ne _is the electron density value measured by the hollow cathode device probe, which is 10 ¹¹ cm ^-3 , Te _is the electron temperature value measured by the hollow cathode device probe, which is 3 eV. _Qi is 2.56×10 ^-8 × _Te ^(0.193) ×exp(-3.93/ _Te ).

The relationship between the experimental light intensity fluctuation and the absolute intensity of the experimental light intensity is:

erro = 1./sqrt(I _model );

erro = _{1./sqrt(ε×ne×ni×Qi ) ;}

erro=(I _i -I _i ')/I _i ', i=1-100;

The density of the trace product is expressed as follows:

n _i =erro ² /(ε× _ne ×Q _i ).

The plasma erosion trace product online monitoring device and method provided in the present embodiment are designed with a spectrometer device to monitor the trace product spectral line light intensity. After the plasma radiation light enters the interior of the device, it is split twice by a beam splitter prism and a grating and diverged and converged before being received by a photomultiplier tube. The measured spectral intensity is received multiple times in a continuous time, and a relationship between the trace substance radiation spectral line intensity and the light intensity signal fluctuation is established to obtain the trace product absolute density. Compared with the traditional testing method, the monitoring method has high reliability and sensitive monitoring. The measured spectral intensity is received multiple times in a continuous time, which can better measure the volatility of the trace product light intensity.

Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (5)

1. An online monitoring device for trace products of plasma erosion, characterized in that it comprises a metal shield, and a first convex lens, a first reflector, a beam splitter, a second convex lens, a grating and a second reflector arranged inside the metal shield, and a photomultiplier tube and an analysis and processing device arranged outside the metal shield; An incident light slit and an outgoing light slit are fixed on the side wall of the metal shield, the outgoing light slit is connected to the photomultiplier tube, and the photomultiplier tube is connected to the analysis and processing equipment; The plasma radiation light collected by the incident light slit passes through the first convex lens, the first reflector, the beam splitter, the second convex lens, the grating and the second reflector in sequence, and is incident on the photomultiplier tube through the exit light slit, and the photomultiplier tube transmits the acquired experimental light intensity information to the analysis and processing equipment; The analysis and processing device includes the following modules: Light intensity acquisition module, used to collect experimental light intensity information within the wavelength range of trace products; A fluctuation error calculation module, used for calculating the fluctuation error caused by the experimental light intensity fluctuation based on the experimental light intensity; A relationship building module, used to establish the relationship between the theoretical light intensity and the experimental light intensity; A trace product density calculation module, used to calculate the density of the trace product based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity; Wherein, the theoretical light intensity is expressed by the following formula: Imodel=ε× _ne × _ni × _Qi ; Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, _ne is the electron density, _ni is the trace product density, Qi _is the excitation rate coefficient, and Imodel represents the theoretical intensity of the trace product luminescence, that is, the theoretical light intensity; When collecting experimental light intensity information within the wavelength range of trace products, a preset number of times is collected in a continuous time, and the preset number of times is 100 times; The wavelength range of the trace product is: the wavelength center is 250nm, and the range is 1nm; The density of the trace product is calculated by the following formula: n _i =erro ² /(ε× _ne ×Q _i ); Among them, ε is the proportion of light radiated by the plasma received by the incident light slit, ne _is the electron density, _ni is the trace product density, _Qi is the excitation rate coefficient, and erro is the fluctuation error; ε is 0.01, and n _e is the electron density value measured by the probe of the hollow cathode device, which is 10 ¹¹ cm ^-3 ; The excitation rate coefficient is expressed as follows: _Qi = 2.56 × ^10-8 × _Te ^(0.193) × exp (-3.93/ _Te ); Here, Te _is the electron temperature value measured by the probe of the hollow cathode device, which is 3eV. 2. The device according to claim 1, characterized in that the width of the incident light slit is 25 um. 3. The device according to claim 1 is characterized in that the incident light slit is externally connected to an SMA connector, the SMA connector is connected to an optical fiber, the other side of the optical fiber is used to receive light radiated from the plasma area, and the optical fiber is a high-transmittance deep ultraviolet optical fiber with a core of 1000um. 4. The device according to claim 1 is characterized in that the device also includes a grating angle adjustment component, the grating angle adjustment component is arranged on the side wall of the metal shielding cover adjacent to the side wall of the incident light slit, and the grating angle adjustment component is connected to the grating. 5. A method for online monitoring of trace products of plasma erosion, characterized in that it is applied to the device as claimed in any one of claims 1 to 4, comprising the following steps: Collect experimental light intensity within the wavelength range of trace products; Calculating a fluctuation error caused by fluctuations in the experimental light intensity based on the experimental light intensity; Establishing the relationship between the theoretical light intensity and the experimental light intensity; Based on the fluctuation error and the relationship between the theoretical light intensity and the experimental light intensity, the density of the trace product is calculated.