Study of Intense Electron Beams Produced by High-Voltage Pulsed Glow Discharges

We report the generation of high-current-density (20 A/cm2) pulsed electron beams from high-voltage (48-100 kV) glow discharges using cathodes 7.5 cm in diameter. The pulse duration was determined by the energy of the pulse generator and varied between 0.2 ?s and several microseconds, depending on the discharge current. The largest electron beam current (900 A) was obtained with an oxidized aluminum cathode in a helium-oxygen atmosphere. An oxidized magnesium cathode produced similar results, and a molybdenum cathode operated at considerably lower currents. A small-diameter (<1 mm) well-collimated beam of energetic electrons of very high current density (>1 kA/cm2) was also observed to develop in the center of the discharge. Electrostatic probe measurements show that the negative glow plasma density and the electron beam current have a similar spatial distribution. Electron temperatures of 1-1.5 eV were measured at 7 cm from the cathode. The plasma density (8.5 · 1011 cm-3 at 450 A) was found to depend linearly on the discharge current. In discharges at high currents a denser and higher temperature plasma region was observed to develop at approximately 20 cm from the cathode. We have modeled the process of electron beam generation and predicted the energy distribution of the electron beam. More than 95 percent of the electron beam energy is calculated to be within 10 percent of that corresponding to the discharge voltage.     

Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.     

Pulsed corona discharge driven by Marx generator: Diagnostics and optimization for NOx treatment

A compact, repetitive Marx generator with an external trigger is constructed and coupled with a wire-to-plate corona reactor for a positive pulsed corona discharge studies. The reactor resistance and capacitance behavior during the pulse was observed. It was found that the reactor's capacitance increases three times during the pulse due to the streamer propagation from anode to grounded electrode. Using the time development of the capacitance and resistance during the pulse and the reactor inter-electrode distance, the streamer velocity has been calculated to be 1 × 10⁶ m/s, for system arrangement presented in this work. As an indicator of chemical activity of pulsed corona, ozone production was measured. Emission spectroscopy measurements in the UV region were performed to detect species that appear in the discharge and to determine vibrational and rotational temperatures, which are found to be 3200 K and 340 K respectively. As a measure of pollution control potential of the constructed pulsed corona system, NO oxidation efficiency was investigated and compared with results presented in literature. It was shown that pulsed corona systems with significantly longer pulse durations are competitive with several times shorter pulse duration systems, which implies that chemical efficiency of secondary streamers is comparable with efficiency of primary streamers.     

Electromagnetic radiation sources based on a low-inductive extended z-discharge

Model sources of electromagnetic radiation based on a low-inductive extended z-discharge are studied experimentally and numerically. The discharge is initiated by a high-voltage pulse generator through a long transmission line. It is shown that using a sliding discharge traveling wave, one can provide electrical breakdown of long discharge gaps in a wide range of initial gas pressure and produce a plasma pinch at moderate voltages of the generator. A new nonpinch mechanism of radiation generation is discovered in the soft X-ray range of the spectra. This mechanism offers a higher efficiency of conversion of electrical energy to the energy of an inverted medium.     

A hard-tube pulser of 60 kV, 10 A for experiment and modeling inplasma immersion ion implantation

This paper describes an experiment and modeling in plasma immersion ion implantation using a high-voltage pulsed power system. This consists of a high-voltage pulse generator that uses a hard tube switch. The reason for using this type of circuit category in the Plasma Immersion Ion Implantation (PIII) facility rather than a previously used pulse-forming network (PFN) circuit configuration is stated. The experimental results of the application of this device to a glow discharge PIII are also discussed. In order to assess these results, a simple electrical model describes the plasma as a resistive load in parallel with a capacitance taking into account the pulse rise-time distortion caused by a long connecting coaxial cable. Plasma parameters for PIII processing, such as ion average implantation current and plasma sheath thickness, are calculated from the experimental settings     

Decoloration of azo dye by a multi-needle-to-plate high-voltage pulsed corona discharge system in water

The decoloration efficiency of azo dye (Acid Orange 7, AO7) using a multi-needle-to-plate high-voltage pulsed corona discharge system was investigated in this paper. The effect of several parameters, including peak pulse voltage and pulse frequency of the discharge system, initial pH and electrical conductivity of the dye solution, mode of needle electrode distribution and gas flow rate on the decoloration rate of the dye wastewater was reviewed. The results obtained show that the pulsed discharge system with a multi-needle-to-plate electrode could dispose azo dye wastewater efficiently. The decoloration rate increased with an increase in applied peak pulse voltage and pulse frequency. Decoloration was more efficient in the acidic solution, and the decoloration rate displayed no marked change under solutions of differing electrical conductivity. For the case in which we example the effect of gas flow rate on the decoloration efficiency of Acid Orange solution, we found that better decoloration efficiency occurred using the seven-needle-to-plate discharge system, which had more discharge anodes.     

脉冲放电脱硫反应器中高能电子密度分布的光谱研究

脉冲流光放电产生的大于等于11.2 eV的高能电子能将处于基态的氮分子激发到N₂(C3Π_u)态,测试脉冲流光放电时的N₂(C3Π_u→B3Πg)发射光谱相对强度可以得出脉冲流光放电产生的高能电子的密度。实验在室温常压下研究了空气中线-板式脉冲流光放电脱硫反应器内高能电子密度分布情况,并研究了脉冲电压、反应器的线线间距对反应器内高能电子密度分布的影响。实验结果表明,反应器内的高能电子主要集中在放电线附近高电场区内,随着离放电线的距离增大,高能电子密度减小;脉冲电压对高能电子密度有很大影响,随着电压的升高,高能电子密度基本呈线性增大;线板间距固定,线线间距为线板间距的0.6～1倍时,反应器内高能电子密度分布较为均匀。     

Fast high-voltage pulse generation using nonlinear capacitors

Many pulsed power applications require short high-voltage pulses with a high-repetition rate. Conventional high-voltage discharge pulse-switches such as thyratrons, spark gap switches, and vacuum tube switches have a short lifetime, whereas the semiconductor switches have a long lifetime and high reliability. The semiconductor switches, however cannot be directly applied to fast high-voltage pulsed power generation due to their limited operating voltage ratings despite their relatively long switching times. Therefore, they are used with voltage amplification and a pulse compression stage. This paper describes two pulse generators that use the semi-conductor switches and nonlinear capacitors: one is based on an opening switch (IGBT) and inductive energy storage, the other is a combination of a closing switch (RSD) and capacitive energy storage     

脱硫用重复频率脉冲电源设计

 简单介绍了高压脉冲电晕法脱硫的基本原理，以及对重复频率脉冲电源性能的要求；分析脱硫反应器独特的电气特性对电源系统的影响；对重复频率脉冲电源的设计方法及技术路线进行相关探讨。     

基于谐振电路与脉冲变压器的高压脉冲源设计

提出一种基于谐振电路与脉冲变压器结合的高压脉冲实现方案,该方案利用电容与电感的谐振效应,结合脉冲变压器的升压作用,在仅使用一个半导体开关的条件下,实现高压脉冲的输出,其结构简单,成本低,并且可实现零电压关断。并对于电路的运行模式进行了理论分析,搭建了原理样机进行实验。容性负载条件下,实现频率1～ 15 kHz、幅值0～ 10 kV可调的高压脉冲输出,对比分析了续流支路以及续流电阻对于输出高压脉冲波形的影响。利用该脉冲电源进行DBD放电实验,成功驱动介质阻挡放电反应器,验证了该方案的可行性。     

Pulsed power corona discharges for air pollution control

Successful introduction of pulsed corona for industrial purposes very much depends on the reliability of high-voltage and pulsed power technology and on the efficiency of energy transfer. In addition, it is of the utmost importance that adequate electromagnetic compatibility (EMC) is achieved between the high-voltage pulse source and the surrounding equipment. Pulsed corona is generated in a pilot unit that produces narrow 50 MW pulses at 1000 pps (net average corona power 1.5 kW). The pilot unit can run continuously for use in industrial applications such as cleaning of gases (100 m³/h) containing NO or volatile organic compounds (VOCs) or fluids (e.g., waste water). Simultaneous removal of NO and ethylene to obtain clean CO₂ from the exhaust of a combustion engine was tested at an industrial site. Various chemical processes, such as removal of toluene or styrene from an airflow are tested in the laboratory. We developed a model to analyze the conversion of these pollutants. To examine the discharges in the reactor we use current, voltage, and E-field sensors as well as a fast charge-coupled device (CCD) camera. Detailed energy input measurements are compared with CCD movies to investigate the efficiency of different streamer phases. EMC techniques incorporated in the pilot unit are based on the successful concept of constructing a low transfer impedance between common mode currents induced by pulsed power and differential mode voltages in signal lines and external main lines     

Observation of pulsed fast electron precipitations and the cyclotron generation mechanism of burst activity in a decaying ECR discharge plasma

We have detected and investigated quasi-periodic series of pulsed energetic electron precipitations in the decaying plasma of a pulsed ECR discharge in a mirror axisymmetric magnetic trap. The observed particle ejections from the trap are interpreted as the result of resonant interaction between energetic electrons and a slow extraordinary wave propagating in the rarefied plasma across the external magnetic field. We have been able to explain the generation mechanism of the sequences of pulsed precipitations at the nonlinear instability growth phase in terms of a cyclotron maser model in which the instability threshold is exceeded through a reduction in electromagnetic energy losses characteristic of the plasma decay.     

Corona discharge processes

Applications of corona discharge induced plasmas and unipolar ions are reviewed. Corona process applications emphasize one of two aspects of the discharge: the ions produced or the energetic electrons producing the plasma. The ion identities depend on the polarity of the discharge and the characteristics of the gas mixture, specifically on the electron attaching species. The electron energies depend on the gas characteristics and on the method of generating the corona. In general, in an application using ions, the corona induced plasma zone will occupy a small fraction of the total process volume, while a process using the electrons will fill most of the volume with the plasma. Current state-of-the knowledge of ionized environments and the function of corona discharge processes are discussed in detail     

Multipoint barrier discharge process for removal of NOxfrom diesel engine exhaust

We investigated the application of the dielectric barrier discharge process to the removal of NO_x from exhaust gas of a 20-kVA diesel engine generator. A multipoint-to-plane geometry was used as an electrode for low-voltage operation. A pyrex glass plate with a 2-mm thickness was put on the plane electrode as the dielectric barrier. The reactor consists of six discharge cells, with each cell consisting of five stacked multipoint-to-plane electrodes where the exhaust gas flows with a high flow rate. The exhaust gas was successfully treated at a flow rate of 1.2 m³/min, In order to produce repetitive high-voltage pulse, we made two switching electronic devices, an insulated gate bipolar transistor (IGBT), and a pulse transformer. This pulse modulator supplied the voltage with peak value of 10 kV and repetition rate of 2.5 kp/s (pulses per second) to the reactor. The energy transfer efficiency of the pulse modulator is 65% at 300 W of the power consumed in the reactor, The NO_x (NO+NO₂) in the exhaust gas was reduced by 35 ppm with an electrical efficiency of 32 g/kWh     

全固态高重频高压脉冲电源

设计了一款全固态高重频高压脉冲电源,主电路采用以IGBT为主开关的半桥式固态Marx电路,驱动电路采用磁芯隔离带负压偏置的同步驱动方案,并由FPGA提供充放电控制信号和故障诊断、保护。该方案既可实现对多级电容的低阻抗的快速并联充电控制,又可实现截尾功能以加快脉冲后沿获得方波脉冲,且可实现百μs以上的宽脉冲输出,可用来产生高压脉冲电场。此外,该电源还可在突发模式下输出脉冲个数和频率均可调的多个高频脉冲系列。实验表明,该输出电压幅值可高达40 kV,输出峰值电流可达100 A,重频可达30 kHz,上升沿和下降沿均低于100 ns,突发模式下重频可高达200 kHz。所设计的脉冲电源输出参数连续可调,且体积小巧。     

A wire-to-wire type nonthermal plasma reactor with ferroelectric pellet barrier

A new wire-to-wire type of discharge plasma reactor with ferroelectric pellet barrier has been proposed and investigated experimentally. It was found that there were intense microdischarge currents taking place on the AC corona-charged surfaces of the ferroelectric pellet barrier. These surfaces were placed on the bottom wire electrode in the reactor. This type of nonthermal plasma reactor was found to generate a corona discharge twice per half cycle of the applied AC high voltage, once from the upper corona wire and again from the surface of the pellet barrier.As a result, the proposed plasma reactor has the potential to greatly increase ozone production and may find use as an effective means for removing pollutant gases.     

高速时空分辨光谱仪的构建及其在水中纳秒脉冲火花放电光谱诊断中的应用

近年来对水中高压脉冲放电等离子体特性的诊断研究越来越受到重视。测量单个放电脉冲放电等离子体的时间-空间分辨发射光谱,有助于研究水中脉冲放电等离子体的时空演化动力学特性和规律。在本研究中将四分幅超高速相机和单色仪结合,构建了一种跟踪单个放电脉冲的高速时空分辨光谱仪,开发了相应的光谱分析软件。用波长632.8 nm的He-Ne激光器,在1 200 g·mm-1刻线光栅条件下对光谱仪的性能进行了测试。结果表明：对应He-Ne氦氖激光632.8 nm谱线的像素分辨率为0.013 nm。在曝光时间20 ns时,单色仪狭缝宽度0.2 mm时632.8 nm谱线的仪器展宽为(0.150±0.009)nm,仪器展宽随着狭缝宽度的增加呈现增大趋势。曝光时间的变化不会引起仪器展宽的变化,能够确保在调节相机曝光时间的过程中不影响光谱仪性能。利用该高速分辨光谱仪对水中纳秒火花放电发射光谱进行了测量,单次曝光获得了单一脉冲放电等离子体时空演化光谱。今后进一步完善实验室的电路条件消除放电干扰,可以对单个放电脉冲进行更细致的测量,为研究单个放电脉冲等离子体参数的时空演化特性提供良好的技术手段。     

重复频率脉冲功率系统触发器设计

根据重复频率脉冲功率系统中大功率开关器件氢闸流管的触发原理,针对选用的氢闸流管VE4147的触发要求,设计了直流偏压-150 V、空载电压2 000 V、脉冲电流10 A、脉冲宽度800 ns、重复频率10 kHz的触发器。设计中着重从增强抗干扰能力、降低功耗、改善散热等方面进行考虑,保证触发器以10 kHz的重复频率持续工作,已经应用于100 kV/2 kHz高压脉冲电源、70 kV/10 kHz氢闸流管老练平台、150 kV/1 kHz可调脉宽电晕等离子体驱动源等多个重复频率脉冲功率系统中。     

大气压空气中重复频率纳秒脉冲气体放电模式研究

利用上升沿100ns、脉宽150ns的单级磁压缩纳秒脉冲电源,通过电压电流测量和放电图像拍摄实验,研究了大气压空气中极不均匀电场结构重复频率纳秒脉冲气体放电的放电模式。结果表明纳秒脉冲气体放电存在三种典型的放电模式:电晕放电、弥散放电和火花放电。施加的脉冲电压幅值对放电模式影响显著,随着电压幅值的增加,放电依次经历电晕、弥散和火花放电。固定电压幅值时,放电可能同时存在两种模式。重复频率加强了放电强度,弥散放电的激发电压随重复频率的增加变化不大,但火花放电的激发电压随着重复频率的增加而降低。因此降低重复频率有利于在较大电压范围获得大气压空气弥散放电。     

Removal of four kinds of volatile organic compounds mixture in air using silent discharge reactor driven by bipolar pulsed power

A silent discharge reactor initiated by bipolar pulsed power substituting the traditional ac power was used to remove the volatile organic compounds (VOC_s) mixture of acetone, benzene, tetrachloroethylene and m-xylene. The results indicated that the silent discharge driven by bipolar pulsed power could effectively input pulsed energy, produce strong instant discharge and energetic particles, and thus enhance the removal efficiency of the mixed VOC_s. The order of the removal efficiency of mixed VOC_s followed as acetone < benzene < tetrachloroethylene < m-xylene no matter what power supply was used. Comparing with single-compound, the removal efficiency of m-xylene only fell a little but those of the other three components fell a lot in the process of the mixed VOC_s treatment. In addition, controlling the status of electrical discharge plasma by changing the discharge parameters (such as capacitance of the pulse capacitor and pulse repetitive rate) was found to be an efficient way to enhance the removal efficiency of the mixed VOC_s. In this system, the Cp = 2 nF was the optimal capacitance for the bipolar power supply combined with the silent discharge reactor that had the best energy conversion efficiency for removal of mixed VOC_s. A higher pulse repetitive rate and longer residence time could also increase the removal efficiency of mixed VOC_s.