Effects of Harmonic Modulation of Current in Glow Discharge Dusty Plasma with Ordered Structures

New method of disturbance by imposing harmonic signals on discharge current in DC glow discharge with ordered structures is studied at low values of disturbing amplitudes in molecular nitrogen. Influence of disturbing signals with frequencies from 10 Hz to 100 kHz is observed. New effects of changing vertical size and position of dusty structures in discharge space observed. Forced oscillations of dust particles and self‐oscillating crystals stabilizing effect under different conditions registered. Studied dusty structure's vertical size change dependencies on frequency and amplitude of disturbing signal (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

直流大气压辉光放电高能电子密度的空间分布

利用针阴极和水阳极,在6 mm的空气隙产生了大气压空气辉光放电。该大气压辉光放电具有明显的负辉区、正柱区和阳极辉区等明亮的发光区。通过研究放电的电压电流特性,发现该放电处于亚辉光放电到正常辉光放电阶段。由于氮分子第二正带系337.1 nm的光谱强度反映高能电子密度,对337.1 nm谱线的强度进行了空间分辨测量。结果发现高能电子在针尖附近密度最大,而其他区域相差不多。随电压升高,高能电子密度减少。增大限流电阻,高能电子密度也减少。氧原子对杀菌消毒具有重要作用,利用发射光谱法对氧原子谱线强度的空间分布进行了测量,发现氧原子谱线强度与高能电子的空间分布及其随参数的变化关系一致。     

液相隔膜辉光放电等离子体自由基发射光谱研究

为了更好了解液相隔膜辉光放电等离子体引发的化学反应机理,运用发射光谱法研究了稀硫酸溶液隔膜辉光放电等离子体产生的自由基,估算了电子温度与电子密度。结果表明：当电压超过700 V时,观察到了羟基自由基和氢原子的发射光谱;当电压超过750 V时,除了羟基自由基和氢原子外,还观察到了氧原子的发射光谱;这些自由基的发射强度随电压升高而升高;稀硫酸溶液隔膜辉光放电等离子体的平均电子温度与平均电子密度分别为1.3×104 K与7.8×1017 cm-3。     

Quenching Effect of Microwave to DC Glow Discharge in Gas Lasers

Ｑｕｅｎｃｈｉｎｇ　Ｅｆｆｅｃｔ　ｏｆ　Ｍｉｃｒｏｗａｖｅ　ｔｏ　ＤＣ　Ｇｌｏｗ　Ｄｉｓｃｈａｒｇｅ　ｉｎ　Ｇａｓ　ＬａｓｅｒｓＱｕｅｎｃｈｉｎｇＥｆｆｅｃｔｏｆＭｉｃｒｏｗａｖｅｔｏＤＣＧｌｏｗＤｉｓｃｈａｒｇｅｉｎＧａｓＬａｓｅｒｓ￥ＷＡＮＧＹｕ...     

细长金属管内产生的直流辉光等离子体发射光谱诊断

利用发射光谱法对金属管内形成的稳定氩氮直流辉光等离子体进行了诊断。通过对等离子体发射光谱谱线的研究确定了等离子体中的活性粒子成分;根据氩原子的玻尔兹曼曲线斜率法计算了等离子体中的电子激发温度;采用氮分子第二正带系跃迁(C3Π_u→B3Π_g)的发射谱线计算了等离子体中的氮分子振动温度;研究了电子激发温度和氮分子振动温度随压强的变化特征。研究结果表明,在20 Pa下产生的Ar60%+N₂40%直流辉光等离子体中,活性成分主要是Ar原子、Ar离子、N₂的第二正带系跃迁(C3Π_u→B3Π_g)和N+₂的第一负带系跃迁(B2Π+_u→X2Σ+_g);电子激发温度约为(15 270±250)K;氮分子(C3Π_u)振动温度约为(3 290±100)K;随着压强的增加电子激发温度、分子振动温度逐渐降低。文章的研究结果对细长金属管内表面改性研究具有重要的意义。     

大气压氩气射流等离子体的光谱特性研究

等离子体喷枪是一种重要的等离子体源,已成为近几年低温等离子体研究的一个重要课题。本文利用钨针-钨丝网电极制作了直流喷枪装置,在大气压空气中产生了稳定的等离子体羽,并采用发射光谱的方法,对等离子体羽的等离子体参数进行了研究。在钨针电极与钨丝网电极之间放出耀眼的白光,钨丝网电极出口的气流下游有火苗形状的等离子体羽喷出。在电压保持不变的条件下(13.5 kV),等离子体羽长度随气体流量增加而增大;在气体流量保持不变的条件下(10 L·min-1),羽长度随外加电压的增大而增大。在气体流量一定的条件下,放电电压和放电电流呈反比例关系,即电压随着电流的增大而减小,说明放电属于辉光放电。采集了该喷枪在300～800 nm范围内的放电发射光谱,通过玻尔兹曼方法对放电等离子体电子激发温度进行了测量。结果表明,电子的激发温度随外加电压的增大而降低,随着工作气体流量的减小而升高。利用放电的基本理论对上述现象做了解释。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。     

Investigation an Effective Interaction Potential of Dust Particles in Nonideal Dusty Plasma

Interaction between dusty particles remains to be an interesting issue that still requires deeper theoretical and experimental investigations. In the present paper we formulate a theoretical approach to the calculation of effective interaction potential of dust particles on the basis of Poisson equation and experimentally measured pair correlation functions. By application of our model to the data from the liquid phase of dust formations in stratified dc glow discharge, it is shown that there is an attractive component in the interaction of dust particle (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Time Evolution from Weak to Strong Coupling in a Spherically Confined Dusty Plasma

Langevin dynamics simulations are performed to study the emergence of correlations in a spherically confined dusty plasma. We follow the time evolution of a laser‐heated initial plasma during its approach to the neutral gas temperature. The effect of the cooling rate is investigated in detail and the time scales for the emergence of the shell structure are compared. In strongly damped systems the correlation buildup is found to be slower than in weakly dissipative systems. The role of the confinement potential for the shell structure is explored by means of Monte Carlo simulations. In a linear and a quartic confinement the shells emerge at the cluster boundary, but density modulations are also found near the trap center in the former case (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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。     

UV Radiation Source Based on the Plasma of a Glow Discharge in a Mixture of Helium with Water Vapors

The results on the optical characteristics of the glow–discharge plasma in an He/H₂O mixture are presented. It has been established that it is a source of UV radiation in the region 306–315 nm (_max = 309.6 nm). Radiation lines of the atoms of hydrogen (H 486.1 nm and H 656.3 nm) and helium (491.1, 501.1, 587.6, and 667.8 nm) were recorded in the visible region of the spectrum; they can be used as diagnostic lines in measuring the parameters of this plasma (n _e, T _e) by the method of emission spectroscopy. The intensity of the UV bands and of the spectral lines HI and HeI have been optimized depending on the partial pressure of helium and the discharge current. The results obtained are of interest for the development of an ecologically pure source of UV radiation on the basis of chemiluminescence of water vapors in a longitudinal glow discharge.     

Ion Heating in Dusty Plasma of Noble Gas Mixtures

Ion heating in dusty plasma of noble gas mixtures is studied by the observation of dust particles in stratified glow discharge. The particles and their formations can be used as a “contact‐free” probe of the ion flows. It is shown that under condition of experiments transition of dust particles into crystalline state in pure gases occur at much lower pressures in comparison to the case of gas mixtures. This observation is also supported by the evaluation of “effective” kinetic temperature of dust particles as defined from the velocity distribution function at the same set of discharge parameters. Absolute value of temperature of dust component in the mixture of helium and argon indicates important role of argon ionization process (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

大气压介质阻挡辉光放电中放电电流的测量与分析

介质阻挡放电产生的低温等离子体具有广泛的应用前景而成为研究热点。文章利用平行平板介质阻挡放电装置,在流动的氦气中实现了大气压均匀辉光放电,得到了大气压下的均匀等离子体。利用电学方法将放电电流从总电流中分离出来,从而得到了辉光放电的放电电流。通过分析放电电流、外加电压、气隙上电压以及壁电荷电量之间的相互关系,可以研究气体放电过程中壁电荷积累的微观动力学行为。实验结果表明壁电荷主要是在放电电流脉冲持续期间积累的,但电流脉冲结束后,由于气隙电压没有改变极性,壁电荷还会逐渐积累,气隙电压改变极性后,壁电荷量随时间减小。这些结果对壁电荷在介质阻挡辉光放电中作用的深入研究和大气压介质阻挡辉光放电的工业应用具有重要意义。     

Characteristics of a Glow Discharge in a Krypton/Elegas/Air Mixture

The longitudinal glow discharge in the Kr/SF₆/air mixture at a pressure of P = 0.7–6.0 kPa has been investigated. The electric characteristics and plasma radiation in the spectral region 150–340 nm are studied. The optimization of the radiation brightness (power) at = 249 nm in the KrF(B–X) mixture and in the nitrogen bands is carried out depending on the workingmedium composition and current magnitude. It is shown that a d.c. discharge in the Kr/SF₆/(N₂:O₂) mixture can be used in the multiwave UV–VUV radiation source on a system of the KrF and N₂ molecular bands.     

A Method of Separation of Polydisperse Particles in the Plasma of Radio‐Frequency Discharge

A method of separation of polydisperse dust particles in the plasma of radio‐frequency (RF) capacitive discharge is considered. Investigations of plasma equipotential field enabled us to determine conditions for separation of polydisperse dust particles. The simplicity of the technology made it possible to obtain small dispersed particles of different materials. Samples of small dispersed microparticles of silica and alumina were obtained. The size and chemical composition of samples were examined using a Quanta 3D 200i scanning electron microscope (SEM, FEI, USA). The average size of separated silica nanoparticles was 600 nm, that of silica and alumina microparticles was 5 μm. Two separation methods were developed: the first one used a special trap and shape of the bottom electrode of RF discharge (for separation of microparticles) and the second used an electrical trap (for separation of nanoparticles). The graphs of particle size distribution were constructed using graphical and mathematical calculations. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectroscopic Determination of Oxygen DC Glow-Discharge Temperature: Radial Profile of Gas Temperature

Rotational temperature in the oxygen DC glow discharge is determined from atmospheric A-band of molecular oxygen. Two methods of estimation of this parameter taking into account the quality of the detected spectra are analysed and compared. Radial profile of the rotational temperature is measured. No radial variations of rotational temperature have been observed in the positive column under our experimental conditions.     

N2交流辉光放电等离子体喷束的光谱测量及特性研究

建立了一套交流放电产生N2等离子体喷束的装置,该装置可对氮气进行高达15 kV连续放电.采用浓度调制光谱技术对放电辉光光谱进行探测,并对实验中放电电流和光谱信号的关系进行了讨论.沿着束流的轴向探测了不同位置N2等离子体的发射光谱,发现其激发态振动温度随着束流的下降先降低继而升高,并根据实验条件分析了其变化规律和产生机理.研究了束流中N2 /N2比例变化过程,发现随着束流向下两者比例逐渐升高,并结合实验装置进行讨论.     

Kinetics of the Excited States of Helium in an Atmospheric-Pressure Glow Discharge in a Helium-Nitrogen Mixture

Using an atomic-absorption spectral analysis technique, we determined the concentrations of helium atoms in states 2¹S, 2¹P, 2³S, and 2³P in an atmospheric-pressure glow discharge in helium (99.98%) and in a mixture of helium with nitrogen (99.5%He+0.5%N₂). It is shown that the population of the lower excited levels of helium atoms (n = 2) in its mixture with nitrogen is almost an order of magnitude smaller than in the case of a discharge in helium. The maximum of the concentration of excited atoms in a discharge both in helium and in its mixture with nitrogen is in the cathode region at a distance of about 0.1 mm from the cathode. The reaction of quenching of excited helium atoms by nitrogen molecules is responsible for the sharp decrease in the concentration of He(n = 2) on addition of nitrogen into helium. Presented at the 5th Symposium on Physics and Diagnostics of Laboratory and Astrophysical Plasmas, Belarus, Serbia and Montenegro, Minsk, Belarus, September 20–23, 2004; 12th International Congress on Plasma Physics, October 25–29, 2004, Nice, France. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 530–537, July–August, 2005.     

Discharge Operation Mode Manipulation of Radio Frequency Atmospheric Pressure Glow Discharges in Argon

Stable operation of radio frequency atmospheric glow discharges is widely desired by most processing applications for their conveniency and feasibility, many of which have been addressed with the noble gas of helium and low discharge current density in stable operation regime of α mode. Here, the operation mode manipulation of rf atmospheric pressure glow discharge in argon is investigated using a one‐dimensional self‐consistent modeling approach. Stable operation regime of α mode is found to expand with rinsing excitation frequency and reducing discharge gap distance. The sheath characteristics in terms of sheath voltage and sheath thickness are given to explain the of α ‐γ mode transition. Furthermore, stable operation of discharge in γ mode is proposed tobe achieved by introducing dielectric barriers, which is indicated by monotonously growing of applied voltage with discharge current density (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of Selective Excitation of Gold Atoms in a Nonequilibrium Oxygen Plasma of a Combined Glow Discharge

The effect of selective excitation of gold atoms in a nonequilibrium oxygen plasma of a combined glow discharge (CGD) has been revealed. When working with alumina oxide as a matrix where the content of aluminum is about 30 wt.%, the atomic lines of Al are not seen at all in the CGD spectrum. But the atomic lines of gold have a very high intensity. Even when the aluminum and gold atomic lines overlap, gold can be detected at a content of 10^–7%. This effect has been registered both in synthetic and natural ore samples.     

Dust in Plasma II. Effects of Secondary Electrons: Ionization and Surface Emission

In this second paper, the effect of secondary electrons on the charge and potential of a dust particle immersed in plasma has been studied. The processes of electron‐induced ionization and those of photo‐electron and secondary electron emission from the particle surface as a function of primary electron temperature have been taken into account. Starting from temperatures as low as 6 eV in an Ar plasma, ionization produces an extra ion flux to the dust surface comparable to that of the ion charge exchange effect. For what concerns the surface emission, results show that a transition from negative to positive dust charge/potential takes place, and that the transition regime is characterized by a non‐monotonic behavior of the electric potential around the particle. In the case of photoelectric emission, the dust charge and potential are monotonic decreasing functions of the electron temperature, while in the case of emission induced by primary electrons a minimum charge/potential is reached before they grow towards positive values. In no case multiple dust charge states have been observed due to the presence of the potential well attached to the particle surface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)