空气中空心阴极不同放电模式下的发光特性

为了进一步揭示空心阴极放电中放电模式的转换机制,特别是空心阴极放电过程中自脉冲的形成机理,利用柱型空心阴极放电结构,在空气环境下研究了放电处于不同模式时的发光特性。测量得到了不同放电模式下的伏安特性曲线、放电发光图像、自脉冲阶段的脉冲波形等。实验结果表明随着放电电流的增加放电分为汤生放电模式、自脉冲放电模式、正常辉光放电模式和反常辉光放电模式。虽然所用电源为直流电源,但在自脉冲放电阶段电流和电压随时间呈周期性变化。实验结果表明在不同的放电模式下具有不同的发光特性。在由汤生放电转换为自脉冲放电模式和由自脉冲模式转换为正常辉光放电模式过程中,放电腔的径向中心处和轴向孔口附近均存在光强的突变。实验同时在200～700 nm范围内测量得到了不同电流时的发射光谱。结果表明发射光谱主要集中在330～450 nm,主要包括氮分子的第二正带系(C3Π_u→B3Π_g )和氮分子离子的第一负带系（B2Σ+_u→X2Σ+_g）。其中氮分子离子第一负带系具有较强的发射光谱。由于B2Σ+_u激发电位较高,因此该谱带较强发射光谱的存在表明空心阴极放电较其他放电形式更容易获得高激发态粒子和高能量电子。在650～700 nm附近存在一弱的发光谱带,主要为氮分子的第一正带发射谱（B3Π_g→A3Σ+_u）。在此基础上根据双原子光谱发射理论,结合氮分子第二正带系的三组顺序组带：Δν=-1,-2和-3,利用玻尔兹曼斜率法计算得到了不同放电模式下氮气的分子振动温度。结果表明在实验电流范围内分子振动温度在3 300 K左右,随着电流的增加而升高,并且在自脉冲消失时存在一突变迅速增强。由于电子能量、电子密度与分子振动温度密切相关,因此该结果也表明随着放电电流的增加电子平均能量和电子密度不断增加,当脉冲消失时,电子平均能量和电子密度出现跃变升高。最后,对空心阴极放电中自脉冲的形成机理进行了讨论,结果表明自脉冲放电源于放电模式的转换。     

空心针-板电极大气压氩气辉光放电的特性研究

大气压均匀放电等离子体在工业领域具有非常广泛的应用前景,它是利用直流电源激励的空心针-板放电装置,以氩气为工作气体在大气压空气中产生均匀稳定的放电。对氩气流量和气隙间距对辉光放电发光特性的关系进行了研究,结果表明放电所产生的等离子体柱连接两个电极,发光较为均匀(观察不到放电丝)。在板电极附近放电等离子体柱直径最大,最大直径随着电流和气流的增大而增大。放电伏安特性研究发现,与低气压辉光放电相类似,两电极间的电压随着电流的增大而减小,并且随气流和气隙间距的增大而增大。对该大气压直流均匀放电在扫描范围为330～450 nm的光学发射光谱进行分析,获得了放电等离子体的分子振动温度和谱线强度比I_391.4/I_337.1随氩气流量和气隙间距的变化关系。I_391.4/I_337.1均随流量和气隙间距的增大而降低。对等离子体柱的I_391.4/I_337.1沿气流方向(等离子体柱轴向)进行了空间分辨测量,并进行了定性分析,结果表明,振动温度及电子平均能量随着远离空心针口距离的增大而增大。这些结果对大气压辉光放电在工业中的应用具有重要意义。     

Current-voltage characteristics of a reflex discharge with a hollow cathode and self-heating electrode

Results are presented from experimental studies of the current-voltage characteristics of a reflex discharge with a self-heating electrode used in a source of atomic hydrogen. The processes occurring in a discharge cell and governing the main features of the characteristics obtained are investigated theoretically. An explanation of the general features of the discharge is proposed. It is shown that an abrupt decrease in the discharge voltage with increasing hydrogen flow rate is associated with penetration of the plasma into the hollow cathode and the ignition of a hollow cathode discharge. It is demonstrated that, as the discharge current increases, the glow discharge gradually transforms into an arc discharge with a heated cathode.     

Hollow Cathode Effect in a Long Perforated Cylindrical Cathode with External Coaxial Anode

The paper presents the main characteristics of transverse mode HCE glow discharges in spectral pure helium and neon and in a He/Ne mixture in a long perforated cylindrical cathode with an external coaxial anode. At optimum values of gas pressure, when HCE gets its climatic stage, the compact negative glow evenly “fills” the cathode cavity with maximum amplifications of current and radiation.     

Study of the rectangular hollow cathode discharge

The rectangular hollow cathode discharge is studied with respect to the applicability of similarity mechanisms analogously to other gas discharge types. Probe characteristics of the discharge are measured, the conditions of steady and continuous discharge glow in the cathode cavity are determined.     

用发射光谱法测量氮气直流辉光放电的转动温度

本文报道了氮气气压分别为10和20Pa时，对直流辉光放电的发射光谱进行测量和分析的结果。选择的研究对象为N2放电中形成的N2^ B^2∑u^ →X^2∑g^ 跃迁的Δv=v′-v″=0谱带系中v′=0→v″=0谱带的R支。在阴极背面辉光区、阴极鞘层区、正柱区以及阳极辉光区中分别选择一点进行了转动分辨的发射光谱的测量。利用自己编写的光谱拟合程序，获得了相应的实验条件下N2^ 的转动温度，给出了转动温度随放电电压的变化趋势，其结果可以用直流放电的帕邢定律得到很好的解释。在10和20Pa气压下，放电的阴极鞘层区、正柱区、阳极辉光区中的转动温度都随放电电压呈现出了不同的变化趋势，甚至是完全相反的变化趋势。我们认为这是由于气压不同时，放电状态不同所致：气压为10Pa时的放电是正常辉光放电，而气压为时20Pa的放电为反常辉光放电。     

The Hollow Cathode Discharge as a Spectrochemical Emission Source

Abstract

The hollow cathode discharge (HCD), a specialized type of glow discharge, has been the subject of investigations by physicists (in particular) and chemists for over a half century. Several hundred literature reports may be found concerning various aspects of the HCD. Despite this, many analytical chemists today would consider the HCD as merely a sharp line source for atomic absorption spectrometry (AAS). While this is certainly its most important present application, the HCD has a long history as a spectrochemical emission source allowing direct excitation and analysis of samples. Excellent sensitivities have been reported, but experimental difficulties, including construction of a demountable hollow cathode tube, have limited overall past acceptance of the HCD as an analytical emission technique. However, the current interest by analytical spectroscopists in new methods of atomization and excitation has revived interest in glow discharges. Also, the commercial availability of two demountable hollow cathode tubes and associated vacuum systems now allows easy accessibility to the technique.     

微放电等离子体多负辉区结构融合过程数值模拟研究

高气压下的微型电热推进器(MPT)中的放电等离子体存在多负辉区结构,其负辉区有融合趋势。对矩形微放电等离子体推进器(RMPT)的负辉区融合过程进行了二维模拟分析,在方法上采用了非平衡态的自洽流体模型,并考虑了离子电流加热和三体碰撞过程。结果显示:矩形微放电等离子体推进器(RMPT)在低电流条件下存在两个稳定的负辉区,当超过某一电流阈值条件后,两个负辉区会在腔体中心重合。分析了这一过程的成因,认为其融合过程本质上是空心阴极的导通过程,其融合与否与鞘层电压有关。     

Gas-Discharge Sources with Charged-Particle Emission from the Plasma of a Hollow-Cathode Glow Discharge

The peculiarities of a magnetron discharge with a cold hollow cathode and an uncooled rod cathode are considered. It is shown that the thermionic emission of the rod cathode heated in the discharge makes a major contribution to the discharge characteristics and to the emissivity of the gas-discharge plasma and that a glow discharge can gradually change to the diffusion mode of operation of an arc discharge. Ion and electron sources with improved physical characteristics and general technical data are described. It has been demonstrated that the electrode structure of a hollow-cathode magnetron discharge holds promise not only as an emitting-plasma generator, but also as a source of atomic hydrogen and atomic flux of a consumable (sputtered and evaporated) rod cathode.     

Density of fast electrons on the Axis of a Zylindrical Hollow-Cathode Discharge

Fast electrons leaving a hollow cathode discharge axially through the orifice of a hole probe undergo ionizing collisions with the discharge gas in and behind the orifice. Ar⁺⁺ ions produced in this way are used as a monitor for the density of fast electrons, N_ef, on the axis of the negative glow of a cylindrical hollow cathode discharge. Data on N_ef as dependent on the pressure of the Ar discharge gas and on the discharge current are obtained and an analytical expression for these dependences is found and discussed.     

Glow Discharge with an Extended Hollow Cathode

Russian Physics Journal - A low-voltage low-pressure glow discharge with a hollow cathode is discussed. The discharge is ignited in a reflective discharge system with two symmetric peripheral...     

Glow Discharge Characteristics of Hollow Needle-Plate Electrode in Atmospheric Pressure ArgonSCIEI北大核心CSCD

Atmosphere pressure uniform plasma has the broad application prospect in the industrial field. Using hollow needle cathode - plate anode device excited by direct-current voltage, a uniform and stable glow discharge is generated at atmospheric pressure in ambient air with argon used as working gas. The influence of the experimental parameters (including gas flow rate and the gas gap width) on discharge has been investigated by optical method. It can be found that a glow-discharge plasma column can bridge the two electrodes. The plasma column is uniform, and no filaments can be discerned. Near the plate electrode, the diameter of the plasma column is largest of all positions. The maximal diameter of the plasma column increases with increasing the discharge current or the gas flow rate. Through electrical method, the voltage-current characteristic has been investigated. It has been found that the discharge voltage decreases with increasing the current which is similar with the characteristic of glow discharge in low pressure. It increases with increasing the gas gap width or the gas flow rate. By analyzing the optical emission spectrum scanning from 330 to 450 nm emitted from the direct-current glow discharge, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated as functions of the gas flow rate and gas gap width. Results indicate that both the vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 decrease with increasing the gas flow rate or the gas gap width. In addition, the molecular vibrational temperature and the intensity ratio of spectral lines I-391.4/I-337.1 have been investigated in spatial resolution along the direction of gas flow(plasma column axial), and give a qualitative analysis as well. It is found that the vibrational temperature and the average electron energy increase with increasing the distance from the hollow needle cathode. These results are important to the industrial applications of glow discharge.     

Non-Self-Sustained Hollow-Cathode Glow Discharge at Low Burning Voltages

Russian Physics Journal - The results of investigations of low-voltage burning modes of a non-self-sustained glow discharge with a ~0.2 m3 hollow cathode at low (≈1 Pa) pressure, which is...     

Atmospheric Pressure DC Glow Discharge in Semiconductor Gas Discharge Electronic Devices

The stabilization of dc glow discharges in a dc plasma is studied experimentally in air and neon media functions of pressure $p$, interelectrode distances $d$, and diameter $D$ of the cathode areas in the semiconductor gas discharge electronic devices (SGDED) with GaAs cathode. Comparision of current and discharge light emission (DLE) from SGDED are used for the determination of the stabilization under low- and atmospheric-pressure glow microdischarge conditions. It is found that uniform DLE can be generated in Ne up to atmosphere pressure different from the case in air under specific conditions. Apart from the homegeneous results, nonhomogeneous current–voltage characteristic forms are also observed for some parameter sets. The experimental results reveal different discharge behaviors in both gas media at atmospheric pressure.      

Non-local model of hollow cathode and glow discharge

A general form of the non-local equation for an ionization source in glow discharge and hollow cathode 3D-simulation is formulated. It is a fundamental equation in hollow cathode theory, which allows formulation of a complete set of field equations for a self-consistent problem in a stationary glow discharge and hollow cathode. It enables us to describe the region of negative glow and the hollow cathode effect and compare calculation results of electrical dependencies (pressure-voltage) with experimental data, – under conditions of gradual appearance of the hollow cathode effect.     

Influence of the Discharge Burning Conditions on Distributions of the Parameters of Plasma Generated in a Non-Self-Sustaining Glow Discharge Inside a Hollow Cathode

Russian Physics Journal - The parameters of the plasma of a non-self-sustaining glow discharge generated inside a metal hollow cathode 300 mm long and 25 mm in inner diameter are investigated. A...     

Electron Energy Distribution and Optical Characteristics of a Hollow Cathode Discharge

A model is proposed for the formation of the electron energy distribution in a hollow cathode discharge. On the basis of this model, an integral equation has been derived to calculate the electron distribution function over the entire cathode cavity volume. The equation holds true for both the isotropic distribution, and the case when the local distribution function is anisotropic. Solutions of the kinetic equation obtained are presented, for electron energies over 2–3 eV and up to the cathode fall potential. It is shown that the electron energy distribution function in this interval determines the optical characteristics of the hollow cathode discharge. A comparison is given of the calculated and measured radiation powers for the cases of the hollow cathode discharge in xenon and carbon dioxide. The discrepancy between the theoretical and experimental data does not exceed 20%.     

介质阻挡放电点燃大气压直流均匀放电的光谱研究

由于大气压均匀放电等离子体在工业领域具有广泛的应用前景,为了获得大尺寸的大气压均匀等离子体,采用氩气作为工作气体,在大气压空气环境中利用同轴介质阻挡放电点燃了针-板电极间的大气隙(气隙宽度达到5 cm)直流均匀放电。研究发现,同轴介质阻挡放电能够有效降低针-板电极间的击穿电压。该均匀放电由等离子体柱、等离子体羽、阴极暗区和阴极辉区组成。其中等离子体柱和阴极辉区都是连续放电。而等离子体羽不同位置的放电是不同时的。事实上,等离子体羽放电是由从阴极向着等离子体柱移动的发光光层(即等离子体子弹)叠加而成。利用电学方法测量了放电的伏安特性曲线,发现其与低气压正常辉光放电类似,均具有负斜率。采集了放电的发射光谱,发现存在N₂第二正带系、氩原子和氧原子谱线。通过Boltzmann plot方法对放电等离子体电子激发温度进行了空间分辨测量,发现等离子体柱的电子激发温度比等离子体羽的电子激发温度低。通过分析放电机制,对以上现象进行了定性解释。这些研究结果对大气压均匀放电等离子体源的研制和工业应用具有重要意义。     

Experimental Measurements on the Current Balance at the Cathode of a Cylindrical Hollow Cathode Glow Discharge

The contribution of positive ions, photons and metastable particles to the secondary emission of electrons from the cathode of an argon glow discharge with cylindrical cathode is measured by sampling the plasma species through a small orifice in the cathode wall and analyzing them in a high vacuum region. Additional experiments are made with a second apparatus which enables the sampling fo plasma species from the negative glow and the dark space. The paper describes the experimental techniques used in both cases and presents estimates on the validity of the results obtained. The positive ions are found to be the dominant contribution to the discharge current at the cathode. The secondary emission of electrons is — in decreasing order of importance — due to impact fo singly charged ions, doubly charged ions and metastable atoms.