CN201096521Y - Non-contact type plasma temperature and electron density measuring apparatus - Google Patents

Abstract

The utility model discloses a non-contact type plasma temperature and electron density measuring device. The measuring device is composed of a light guide window, a polymery conducting optical fiber, a photoelectric conversion device, a data acquisition system and a computer processing system, and the utility model adopts the design of four optical channels, and can simultaneously collect the spectral line information for computing the temperature and electron density, and can obtain voltage and current signals exerted on both ends of a semiconductor bridge through connecting with a multichannel oscillograph at the same time, and a high speed response circuit is adopted to quicken the response speed of the whole system, and the temporal resolution is high. The device adopts the non-contact measurement and has no interference to plasma, and provides a simple and effective real-time transient measuring method for detecting the plasma temperature and electron density. The measuring device is particularly suitable for the temperature measurement and small-sized plasma parameter measurement under severe conditions such as high temperature and high pressure combustion, poisonous combustion and explosion and detonation.

Description

Non-contact plasma temperature and electron density measurement device

a technical field

The utility model relates to a spectrum measuring device, in particular to a non-contact measuring device for measuring plasma temperature and electron density by using spectrum technology.

Two background technology

The semiconductor bridge (hereinafter referred to as SCB) plasma ignition technology is a new technology that has been developed rapidly in the past 20 years. Understanding the change law of plasma temperature and electron density during the action of SCB is very important for studying the mechanism of SCB ignition and detonation. Particularly important. However, due to the small space size of the SCB plasma itself, the short existence time, the large transient temperature change, and the ignition is completed under normal pressure, the requirements for the test technology are very strict, and the existing technology for the plasma test method, such as probe The transient diagnosis cannot be realized by the microwave method, the microwave method and the scattering method. The China Academy of Engineering Physics has developed a six-channel optical pyrometer that uses optical fibers to receive and transmit light energy to study the radiation properties of materials under impact loading, and has been continuously improved in the following ten years. The principle is to compare the radiance of the light source to be measured with the standard light source on the basis of Planck's thermal radiation theory to obtain the temperature of the source to be measured. This measurement method can only achieve a single temperature measurement for SCB plasma, and when measuring, in the derivation of the formula, the correction of the factor is involved, which not only increases the complexity of the operation, but also affects the accuracy of the result. In addition, it uses the measurement of the spectral radiation of each channel, and the small differences between the devices in the device (such as: optical filters and photomultiplier tubes) will bring large errors to the results. It is reported abroad that an optical multi-channel analyzer (OMA) is used to measure the SCB plasma temperature. It mainly obtains a beam of monochromatic light by grating, then measures the spectral radiation intensity, and obtains the plasma temperature according to the planck law. For example, D.A.Benson and others obtained the emission spectrum of SCB plasma at 180-700nm through OMA as early as 1987, and obtained the temperature range of the plasma from the analysis of the spectral lines. It can also be measured by measuring the propagation velocity of the plasma. Estimate the plasma temperature. These methods provide a feasible test method for the determination of the SCB plasma temperature, but the instrument can only obtain a spectral line at one wavelength each time, and is only suitable for a single temperature measurement. The equipment is expensive and has a large volume, which is not easy It is portable, and there are many optical parts, and the energy loss is large. Like other existing test methods, it cannot provide time-resolved plasma temperature and electron density measurement results at the same time. To measure the electron density, it is necessary to combine other methods such as the probe method for measurement. Therefore, it is difficult to meet the requirements of transient determination.

Three invention content

The purpose of this utility model is to provide a portable non-contact plasma temperature and electron density measuring device which utilizes the spectral information when the plasma is emitted to simultaneously measure its temperature and electron density in real time.

The purpose of this utility model is achieved through the following technical solutions, non-contact plasma temperature and electron density measuring device, which includes a light guide window, a conductive optical fiber, a data acquisition system and a computer processing system, the light guide window is located at the end of the conductive optical fiber The receiving port, the output end of the data acquisition system is connected to the input end of the computer processing system. It is characterized in that the conduction optical fiber adopts a one-in-multiple-out optical fiber, and each output end of the optical fiber is provided with filters of different wavelengths. selection, it should be ensured that there are at least two atomic spectral lines and one ion spectral line corresponding to the central wavelength of the filter, or at least two ion spectral lines and one atomic spectral line, and the corresponding different atoms formed after the filter Or the monochromatic light of the ion spectral line is converted by photomultiplier tubes equal to the number of filters, and then amplified by the current signal amplifier, and then input to the corresponding input terminal of the data acquisition system to provide calculation data for the computer processing system.

The utility model is mainly established based on the atomic emission spectrum theory. According to the theory of atomic emission spectroscopy, when an excited atom transitions from a high energy level to a low energy level, it will radiate energy in the form of light, resulting in a specific atomic spectrum. Under certain conditions, the radiation intensity and temperature of the same kind of atoms or ion spectral lines conform to the Boltzmann equation, which provides a theoretical basis for plasma temperature measurement; Combining with the Saha equation of the equilibrium composition, the plasma electron density can be calculated. According to the above principles, the working principle of the utility model is: during measurement, the light guide window of the conductive fiber is placed at a certain distance to align with the measured plasma, and when the measured body generates plasma discharge, the light guide window receives the plasma The light generated when the body interacts, and the light is divided into multiple equal beams through the conductive fiber, part of the light is used to calculate the plasma temperature, and the other part of the light is used to calculate the electron density of the plasma; due to the The wavelengths are different, so when each light beam passes through the filters with different wavelengths, monochromatic light corresponding to different atomic or ion spectral lines is formed. The signal amplifier amplifies and adjusts it, and turns the relatively weak electrical signal after the response of the photomultiplier tube into a stronger electrical signal, which is collected by the acquisition card or oscilloscope of the data acquisition system, and finally the acquisition card or oscilloscope is processed by the computer processing system. The collected electrical signals are calculated to obtain the temperature and electron density of the plasma. In order to meet the necessary conditions for the measurement of plasma temperature and electron density, when selecting filters of different wavelengths, it should be ensured that there are at least two atomic spectral lines and one ion spectral line or at least two ion spectral lines corresponding to the central wavelength of the filter. In this way, when the system calculates the plasma temperature, the computer processing system can select the electrical signal data corresponding to at least two atomic spectral lines or two ion spectral lines through the data acquisition system, and then according to the boltzmann formula Calculate the plasma temperature; and when calculating the plasma electron density, the computer processing system selects the electrical signal data corresponding to at least one atomic spectral line and one ion spectral line through the data acquisition system, and calculates according to the boltzmann-saha equation. Obtain the plasma electron density.

Compared with the prior art, the utility model has the remarkable advantages that: 1. The temperature and the electron density of the plasma are measured by the spectral line relative intensity method, wherein, it is based on the ratio of the light intensity of the spectral line whose wavelength is very close to that to be measured. The functional relationship between the gas temperature and the degree of ionization to obtain the temperature and electron density respectively can greatly reduce the uncertainty of the measurement results of the optical device of the instrument, and the derivation of the formula does not involve a correction factor, as long as the transition of the spectral line is known The probability, the statistical weight of the excited state and the energy of the excited state are enough, thereby improving the accuracy of the measurement; 2. The response speed of the whole system is fast and the time resolution is high. It can measure the small-sized plasma with a high time resolution of 10 ns Real-time measurement of the temperature distribution and electron density variation law in the generation process to realize real-time transient analysis of plasma parameters; 3. The utility model adopts multiple optical channel designs, which can simultaneously collect spectra for calculating temperature and electron density Line information, compared with OMA instruments, does not require gratings or prism beam splitters, reduces the loss of light energy, improves light sensitivity, and the system is low in cost, small in size, easy to carry, and easy to operate. 4. Using optical fiber Conduction, no need to contact the flame, no interference to the plasma, provides a simple and effective real-time transient measurement method for the diagnosis of plasma temperature and electron density. It is especially suitable for temperature measurement and small-scale plasma parameter measurement under harsh conditions such as high temperature and high pressure combustion, toxic combustion, explosion and detonation.

Concrete structure of the present utility model is provided by following accompanying drawing and embodiment.

Four drawings

The accompanying drawing is a schematic diagram of the structure and principle of the non-contact plasma temperature and electron density measuring device according to the utility model.

Five specific implementation methods

Below in conjunction with the accompanying drawings, taking the measurement of semiconductor bridge (SCB) plasma as an example, the specific structure of the utility model will be further described in detail.

Referring to the accompanying drawings, according to the non-contact plasma temperature and electron density measuring device manufactured by the utility model, the light guide window 1 adopts a white sapphire window, the conductive optical fiber 2 adopts a one-in and four-out optical fiber, and the bottom of the white sapphire window 1 is processed into a circular platform Type embedded in the guide fiber 2, the filter 3 set at the output port of the guide fiber 2 is composed of four interference filters 8, 9, 10, 11, and their wavelengths are 510.5nm, 521.8nm, 390.55nm and 413.09nm, corresponding to three atomic spectral lines and an ion spectral line; photomultiplier tube 4 and a current signal amplifier 5 are set on the exit light paths of four interference filters 8, 9, 10, 11, and photomultiplier tube 4 is composed of Four of the same model 12, 13, 14, and 15 are composed. After the light is converted into an electrical signal, it is input into the data acquisition system 6. The data acquisition system 6 adopts a LeCroyLT374 four-channel high-speed dynamic storage oscilloscope, which is a high-precision data acquisition system. The time resolution is as high as 10 ns. The four channels of the oscilloscope receive the signal data of the intensity of the four spectral lines of the plasma spectrum after photoelectric conversion, and the output is connected to the computer processing system 7 .

When the plasma discharge is generated by the semiconductor bridge (SCB) plasma 16, the light passes through the white sapphire light guide window 1 and is led out by a conductive optical fiber 2 with one input and four outputs, and is divided into four equal bundles, and enters the corresponding wavelength at the same time The optical filter 3 is used to filter the light, and then through the photoelectric conversion device composed of four photomultiplier tubes 4 of the same type and a current signal amplifier 5, the light is converted into an electrical signal, and then input into the data acquisition system 6, and the computer Processing system 7 selects two atomic spectral lines of Cu510.5nm and 521.8nm to calculate the plasma temperature according to the relative intensity method of spectral lines, and selects the atomic spectral line of Si at 390.55nm and the primary ionization ion The spectral line 413.09nm is used to calculate the electron density of the plasma. At these two pairs of spectral lines, the self-absorption effect is small, so that there is no large interference on the spectral intensity. At the same time, when selecting these two spectral lines, due to the small interval between spectral lines, the influence of spectral radiance, spectral transmittance, etc. on spectral measurement can be ignored. The relatively small uncertainty allows for a higher level of test accuracy and precision.

When calculating the plasma temperature, the following boltzmann formula is used:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; )</span>\text{<span class="notranslate"> -ln</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="g"\; filenames="S2007200445674E00011.png"\; state="\{\{state\}\}">g</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}$

Among them, I _λ1 and I _λ2 are the intensities of two spectral lines whose wavelengths are λ ₁ and λ ₂ respectively, A ₁ and A ₂ are the transition probabilities of the two spectral lines respectively, and g ₁ and g ₂ are the two spectral lines respectively The statistical weight of the excited state, E ₁ and E ₂ are the excited state energies of the two spectral lines, k is the Boltzmann constant, and T is the excitation temperature.

When calculating the electron density, the following boltzmann-saha formula is used:

${\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; twenty\; one</span>}}_{<span\; class="notranslate">\; +</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; g</span>}}_{<span\; class="notranslate">\; +</span>}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{<span\; class="notranslate">\; +</span>}}{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}\mathrm{<span\; class="notranslate">\; kT</span>}}{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;h</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{<span\; class="notranslate">\; +</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; ion</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; kT</span>}}<span\; class="notranslate">\; )</span>$

Among them, _ne is the electron density of the plasma, λ is the wavelength of the spectral line, g is the statistical weight of the upper energy level of the spectral line, A is the transition probability, I is the relative emission intensity, E ₊ is the excitation potential of the primary ionized ion spectral line, E ₀ is the excitation potential of the atomic spectral line, E _ion is the primary ionization potential of the atom, k is the Boltzmann constant, and T is the electron temperature of the SCB plasma.

In the utility model, if the data acquisition system 6 adopts an oscilloscope more than eight channels, the voltage and current signals on the SCB can be collected simultaneously, and these data are input to the computer processing system, and further processing can be performed on the semiconductor bridge (SCB) plasma. analysis processing.

Claims (2)

1, a kind of contactless plasma temperature and electron density measurement device, it comprises leaded light window [1], conduction optical fiber [2], data acquisition system (DAS) [6] and computer processing system [7], leaded light window [1] is positioned at the receiving port of conduction optical fiber [2], the input end of the output termination computer processing system [7] of data acquisition system (DAS) [6], it is characterized in that conducting optical fiber [2] adopts one to advance to have more standard optical fiber, be provided with the optical filter [8] of different wave length at each output terminal of optical fiber, [9], [10], [11], the selection of each optical filter, should guarantee to have corresponding with its centre wavelength at least two atomic spectral lines and ion line or at least two ion lines and an atomic spectral line, mating plate [8] after filtration, [9], [10], [11] the corresponding with it not homoatomic of back formation or the monochromatic light of ion line, again respectively through being positioned at optical filter [8], [9], [10], [11] photomultiplier on the emitting light path [12], [13], [14], [15] conversion, after amplifying by current signal amplifier [5] at last, the corresponding input end of input data acquisition system (DAS) [6] is for computer processing system [7] provides computational data.

2, according to described contactless plasma temperature of claim 1 and electron density measurement device, it is characterized in that conducting optical fiber [2] and be into four and go out standard optical fiber, optical filter [8], [9], [10], corresponding three atomic spectral lines of [11] centre wavelength and ion line or three ion lines and an atomic spectral line.

Images