阅读说明：本技术 一种基于直流电源的脉冲等离子体生成系统 (Pulse plasma generating system based on direct-current power supply ) 是由 何寿杰 赵建勋 李金浩 包慧玲 李庆 于 2021-01-13 设计创作，主要内容包括：本发明涉及一种基于直流电源的脉冲等离子体生成系统,其结构包括真空室、直流电源、光电倍增管和示波器,真空室外接电容薄膜式绝对压强变送器,内置有阴极不锈钢针和阳极钼片,在真空室的侧壁上设置有位置相对的两个观察窗；示波器连接两个电压信号探头,其中一个电压信号探头与阴极不锈钢针电连接,另一个电压信号探头与阳极钼片电连接,用于显示施加在阴极不锈钢针和阳极钼片上的电压波形,并对真空室内生成的脉冲等离子体进行定性和定量分析。本发明输入电源结构简单,通过控制实验电路以及相关环境参数的变化,可实现输入端为直流电源的条件下在针板放电空间中生成稳定的脉冲等离子体。(The invention relates to a pulse plasma generating system based on a direct-current power supply, which structurally comprises a vacuum chamber, the direct-current power supply, a photomultiplier and an oscilloscope, wherein the vacuum chamber is externally connected with a capacitive film absolute pressure transmitter, a cathode stainless steel needle and an anode molybdenum sheet are arranged in the vacuum chamber, and two observation windows which are opposite in position are arranged on the side wall of the vacuum chamber; the oscilloscope is connected with two voltage signal probes, wherein one voltage signal probe is electrically connected with the cathode stainless steel needle, and the other voltage signal probe is electrically connected with the anode molybdenum sheet and is used for displaying voltage waveforms applied to the cathode stainless steel needle and the anode molybdenum sheet and carrying out qualitative and quantitative analysis on the pulse plasma generated in the vacuum chamber. The input power supply has simple structure, and can generate stable pulse plasma in the needle plate discharge space under the condition that the input end is the direct current power supply by controlling the experimental circuit and the change of relevant environmental parameters.)

1. A pulsed plasma generation system based on a dc power supply, comprising:

the vacuum chamber is a closed shell in a vacuum state, is externally connected with a capacitance film type absolute pressure transmitter and is internally provided with a cathode stainless steel needle and an anode molybdenum sheet which are used as needle plate discharge electrodes, the cathode stainless steel needle is opposite to the anode molybdenum sheet from top to bottom, and two observation windows which are opposite in position are arranged on the side wall of the vacuum chamber;

the negative pole of the DC power supply passes through a current-limiting resistor R₁Is electrically connected with the cathode stainless steel needle, the anode of the cathode stainless steel needle is grounded, and the anode of the cathode stainless steel needle is measured by a resistance R₂Is electrically connected with the anode molybdenum sheet;

the photomultiplier is arranged on the outer side of an observation window beside the vacuum chamber and is used for collecting a pulse plasma optical signal generated in the vacuum chamber; and

the oscilloscope is used for displaying voltage waveforms applied to the cathode stainless steel needle and the anode molybdenum sheet and carrying out qualitative and quantitative analysis on the pulse plasma generated in the vacuum chamber; and two voltage signal probes are connected on the oscilloscope, wherein one voltage signal probe is electrically connected with the cathode stainless steel needle, and the other voltage signal probe is electrically connected with the anode molybdenum sheet.

2. The pulsed plasma generation system of claim 1, wherein said vacuum chamber comprises a cylinder with an open top and a top cover covering the top of the cylinder, said capacitive membrane absolute pressure transducer is connected to said cylinder through a pipe, and a gas inlet, a gas outlet, an anode port and a cathode port are further connected to the sidewall of said cylinder.

3. The pulsed plasma generation system of claim 2, wherein a rough vacuum trim valve and a fine vacuum trim valve are provided on the piping connecting the capacitive diaphragm absolute pressure transmitter.

4. A pulsed plasma generation system according to claim 1, 2 or 3, wherein said cathode stainless steel needle and said anode molybdenum sheet are respectively disposed on a discharge electrode holder, two mica sheets are disposed on said discharge electrode holder in opposite positions, said cathode stainless steel needle vertically penetrates and is fixed on the central hole of one of the mica sheets, and said anode molybdenum sheet is disposed in the middle of the surface of the other mica sheet opposite to the cathode stainless steel needle.

5. The pulsed plasma generating system according to claim 4, wherein the tip of the cathode stainless steel needle is aligned with the center of the anode molybdenum sheet.

Technical Field

The invention relates to a gas discharge plasma generating device, in particular to a pulse plasma generating system based on a direct-current power supply.

Background

With the deep development of gas discharge in the field of generating plasma, the gas discharge plasma technology plays more and more important roles in the fields of spectral analysis, surface treatment, material preparation, environmental management and the like, continuous plasma cannot be generated spontaneously in nature, and the mode of artificially generating plasma mainly adopts gas discharge, namely gas ionization. Therefore, as an emerging field in scientific research, plasma generation has been a focus of research by scholars in various countries.

The plasma has high energy activity, in recent years, with the appearance of pulse plasma, the gas discharge plasma technology is gradually applied to various fields of human production and life, and irregular bright spots can not appear in the generation process of the pulse plasma. But the generating conditions are complex and are easily interfered by the external environment. Especially, the power supply generating pulse has complex structure and higher energy consumption in the operation process, part of teams use a direct current power supply to connect a direct current conversion device to generate periodic pulse voltage, the power supply needs to be modified, and the power supply has large volume, complex process and high price, so that the technical difficulty of research and development is caused, and the cost performance is low.

The existing generation technology for generating pulse plasma is basically generated by ionizing gas by an alternating-current high-voltage power supply and a composite high-voltage power supply, such as: the pulse power supply formed by alternating conversion between direct current and direct current, the direct current power supply connected with the alternating current-direct current conversion device to generate pulse current, the direct current power supply and the resonant circuit generating circuit for multiplying voltage. The power supply needs to be modified, the principle is that the pulse power supply drives the generation of the pulse plasma, but the pulse power supply is difficult in research and development technology and low in cost performance, and the application development of the pulse plasma is hindered.

Disclosure of Invention

The invention aims to provide a pulse plasma generating system based on a direct current power supply, which aims to solve the problem that pulse plasma is difficult to generate under the direct current power supply.

The invention is realized by the following steps: a pulsed plasma generation system based on a dc power supply, comprising:

the vacuum chamber is a closed shell in a vacuum state, is externally connected with a capacitance film type absolute pressure transmitter and is internally provided with a cathode stainless steel needle and an anode molybdenum sheet which are used as needle plate discharge electrodes, the cathode stainless steel needle is opposite to the anode molybdenum sheet from top to bottom, and two observation windows which are opposite in position are arranged on the side wall of the vacuum chamber;

the negative pole of the DC power supply passes through a current-limiting resistor R₁Is electrically connected with the cathode stainless steel needle, the anode of the cathode stainless steel needle is grounded, and the anode of the cathode stainless steel needle is measured by a resistance R₂Is electrically connected with the anode molybdenum sheet;

the photomultiplier is arranged on the outer side of an observation window beside the vacuum chamber and is used for collecting a pulse plasma optical signal generated in the vacuum chamber; and

the oscilloscope is used for displaying voltage waveforms applied to the cathode stainless steel needle and the anode molybdenum sheet and carrying out qualitative and quantitative analysis on the pulse plasma generated in the vacuum chamber; and two voltage signal probes are connected on the oscilloscope, wherein one voltage signal probe is electrically connected with the cathode stainless steel needle, and the other voltage signal probe is electrically connected with the anode molybdenum sheet.

The vacuum chamber comprises a cylinder body with an open top and an upper cover covering the upper opening of the cylinder body, the capacitance film absolute pressure transmitter is connected to the cylinder body through a pipeline, and the side wall of the cylinder body is further connected with an air inlet, an air outlet, an anode interface and a cathode interface.

The pulse plasma generating system of the invention takes a direct current power supply as an input end, and utilizes a vacuum chamber, a cathode stainless steel needle and an anode molybdenum sheet to directly generate plasma with pulse characteristics. The input power supply of the invention has simple structure, and can realize the generation of stable pulse plasma in the needle plate discharge space in the vacuum chamber by controlling the circuit of the generation system and controlling the change of relevant environmental parameters. The pulse plasma generating system of the invention utilizes the needle plate discharge electrode in the vacuum chamber to generate pulse plasma under the condition of controlling relevant parameters such as the air pressure of working gas, the magnitude of discharge current and the like and under the condition that the input end is a negative high-voltage direct-current power supply. By adjusting parameters such as voltage of a direct current power supply at an input end, gas pressure in the vacuum chamber, the distance between the cathode stainless steel needle and the anode molybdenum sheet, the needle point curvature radius of the cathode stainless steel needle and the like, the frequency of the pulse plasma, the output pulse voltage and current value and plasma parameters of a discharge space can be further changed.

Drawings

FIG. 1 is a schematic diagram of a pulsed plasma generation system of the present invention.

Fig. 2 is a schematic view of the structure of the vacuum chamber.

Fig. 3 is a schematic view of the structure of the needle plate discharge electrode.

Figure 4a is a graph of current and voltage pulse waveforms for a pulsed plasma in air at an average current of 25 mua.

FIG. 4b is a graph of average current in air versus frequency for an average current of 25 μ A.

FIG. 5 is a waveform diagram of plasma current and optical signal at an average current of 25 μ A.

In the figure: 1. the device comprises a direct current power supply, 2, a current-limiting resistor, 3, a vacuum chamber, 4, an observation window, 5, a cathode stainless steel needle, 6, an anode molybdenum sheet, 7, a photomultiplier, 8, an oscilloscope, 9, a measuring resistor, 10, an ammeter, 11, a mica sheet, 12, a flange, 13, an upper cover, 14, an air inlet, 15, an anode interface, 16, a coarse vacuum fine-tuning valve, 17, a fine vacuum fine-tuning valve, 18, a capacitance film type absolute pressure transmitter, 19, an air outlet, 20, a cathode interface, 21, a discharge electrode support and V, wherein the cathode interface is arranged on the direct current power supply, the cathode interface is arranged₁、V₂Two voltage signal probes of an oscilloscope.

Detailed Description

As shown in FIG. 1, the pulsed plasma generation system of the present invention comprises a vacuum chamber 3, a DC power supply 1, a photomultiplier tube 7, and an oscilloscope 8. The vacuum chamber 3 is a vacuum closed shell, is externally connected with a capacitance film absolute pressure transmitter 18, is internally provided with a cathode stainless steel needle 5 and an anode molybdenum sheet 6 which are used as needle plate discharge electrodes, the upper and lower positions of the cathode stainless steel needle 5 and the anode molybdenum sheet 6 are opposite, and two observation windows 4 which are opposite in position are arranged on the side wall of the vacuum chamber 3 and are used for observing the generation process of plasma. The negative pole of the DC power supply 1 is electrically connected with the cathode stainless steel needle 5 through the current-limiting resistor 2, and the DC power supply 1One path of the anode is grounded, and the other path is electrically connected with the anode molybdenum sheet 6 through the measuring resistor 9. The photomultiplier tube 7 is arranged outside an observation window 4 beside the vacuum chamber 3 and is used for collecting a pulsed plasma light signal generated in the vacuum chamber. The oscilloscope 8 is used for displaying the voltage waveforms applied to the cathode stainless steel needle 5 and the anode molybdenum sheet 6, and performing qualitative and quantitative analysis on the pulsed plasma generated in the vacuum chamber. The oscilloscope 8 is connected with two voltage signal probes (V)₁、V₂) Wherein the voltage signal probe V₁A voltage signal probe V electrically connected with the cathode stainless steel needle 5₂Is electrically connected with the anode molybdenum sheet 6. An ammeter 10 is connected to the connecting lead of the direct current power supply 1 and the anode molybdenum sheet 6 for detecting the discharge current.

As shown in fig. 2, the vacuum chamber 3 includes a cylinder with an open top and an upper cover 13 fixed to an upper opening of the cylinder through a flange 12, a capacitive membrane absolute pressure transmitter 18 is connected to the cylinder through a pipeline, and an air inlet 14, an air outlet 19, an anode interface 15 and a cathode interface 20 are further connected to a sidewall of the cylinder. A rough vacuum fine adjustment valve 16 and a fine vacuum fine adjustment valve 17 are also arranged on a pipeline connected with the capacitance film type absolute pressure transmitter 18.

As shown in FIG. 3, the cathode stainless steel needle 5 and the anode molybdenum sheet 6 are respectively arranged on the discharge electrode support 21, two square mica sheets 11 with opposite positions are arranged on the discharge electrode support 21, and the cathode stainless steel needle 5 with the curvature radius of 50-500 μm vertically penetrates through and is fixed on the central hole position of the left mica sheet 11 through an insulating sealant to be used as the cathode of the needle plate discharge unit. And a circular anode molybdenum sheet 6 is adhered to the right end surface of the right mica sheet 11, is opposite to the cathode stainless steel needle 5, and serves as an anode of the needle plate discharge unit. The needle point of the cathode stainless steel needle 5 is aligned with the center of the anode molybdenum sheet 6. The needle tail of the cathode stainless steel needle 5 and the back of the anode molybdenum sheet 6 are respectively connected with leads which are respectively connected to an anode interface 15 and a cathode interface 20 of the vacuum chamber 3 so as to be connected with the anode and the cathode of the direct current power supply 1. Thereby forming a needle plate discharge electrode structure. The needle plate discharge electrode is put into and fixed in the vacuum chamber 3, and the cathode stainless steel needle 5 and the anode molybdenum sheet 6 are at the upper and lower opposite positions.

Before operation, working gas required by an experimental environment is filled into the vacuum chamber 3 through the air inlet 14, air is extracted through the air outlet 19, air is filled into the reaction vacuum chamber 3 through the rough vacuum fine-tuning valve 16 and the fine vacuum fine-tuning valve 17, the gas pressure in the vacuum chamber reaches a numerical value required by the experiment, and the air pressure data is read through the capacitive thin film absolute pressure transmitter 18. After standing still for a certain period of time, the reaction environment in the vacuum chamber 3 is made stable. After the operation starts, the direct current power supply 1 is switched on, and the output direct current voltage is finely adjusted (the voltage lifting step length is 1V), so that the phenomenon that the cathode emits light to the anode space and the light emission is gradually enhanced occurs in the needle plate discharge space. When the discharge current reaches the stage of tens of microamperes to a few milliamperes, pulse plasma is generated in the space of the needle plate discharge electrode.

In order to further verify the properties of the pulsed plasma, the plasma parameters were further analyzed using waveform data derived by oscilloscope 8. First, the voltage signal of the discharge circuit is placed in the voltage signal probe (V) of the oscilloscope in the pulsed plasma generation system₁、V₂) The collected pulse signals are converted into data information and sent to a computer, and the pulse properties of the plasmas in the needle plate discharge space at different stages can be obtained through the analysis of computer software. Through analysis, the properties of the pulsed plasmas generated by the needle plate discharge electrodes under different curvature radiuses are similar, and only the frequency of the pulses is slightly different. As can be seen from fig. 4a, p = 2Torr, R in air₁ Voltage-current waveform diagram of pulsed plasma with average current of 25 μ a generated under the condition of = 2M Ω, r = 0.1mm, the peak value of voltage is 455.4V, and the minimum value is 347V; the peak value of the current is 496 μ A, the minimum value is 4 μ A; the current pulse has a rising edge of about 9.6 mus, a falling edge of about 33.2 mus, and a latency of about 250 mus. A periodic pulsed signal may be displayed at the output of oscilloscope 8, with both current and voltage exhibiting periodic pulsed characteristics, indicating that a pulsed plasma has been generated. Frequency of pulsed plasma with current conditionsAs can be seen from fig. 4b, as the average current rises, the frequency of the pulses rises.

Fig. 5 shows the time evolution of the self-pulsed light signal measured from the vertical electrode gap with a photomultiplier tube. As can be seen from fig. 5, the current and the optical signal have a good correspondence. When the discharge current is small, the optical signal is extremely weak. When the discharge breaks down, the current rises rapidly, and the light intensity in the discharge space rises steeply. When the current reaches a peak value, the optical signal also reaches a maximum value. Then, as the current decreases, the light intensity gradually decreases. It can be seen that the rising edge time of the light emission intensity is shorter than the decay time of the light emission, which corresponds to the current variation trend. Since the light emission intensity is directly related to the excited-state particle density, which is directly related to plasma parameters such as electron density, the result also proves that the plasma generated in the discharge space exhibits a periodic pulse property.