The effect of magnetic field on plasma particles in dusty plasma

In this work, we present the investigation of the formation features and internal structure of dust clouds created in plasma of glow discharge in the external magnetic field corresponding to a range of moderate and strong fields, at which the ion component is magnetized. The analysis of the plasma magnetization in the presence of dust components is carried out. We defined the values of magnetic induction at which the changes in dynamics of plasma particles in magnetic field in light inert gases are expected. The experimental setup was built in two versions. For the purpose of generating of magnetic field, the first setup was equipped with ordinary magnetic coils, and the second one included a superconducting solenoid. The discharge tubes, the main chambers where plasma was ignited and maintained in a glow discharge in lowered pressure, also have certain peculiarities, which we describe below. While using helium as a bulk gas, our study focused only on the dust trap in the region of narrowing discharge current. For neon, we used two traps: the striation trap and one just mentioned above placed in the narrowing of the discharge tube. As a result, the steady dust structures in a glow discharge under the magnetization of ions and electrons were obtained for the first time. Dust structures were rotated and tended to form a dust cluster and shell structure. A number of parameters of magnetization achieved in experiments were calculated.     

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为探究射频离子源驱动器线圈电气参数对射频放电的影响,主要进行了射频离子源等离子体激发的物理分析,并计算了射频电源的频率选择与线圈放电电流、线圈匝间电压以及放电气压之间的关系,设计了射频离子源驱动器的主要参数。研制的射频离子源驱动器装置,成功获得氢等离子体射频放电。实验结果和理论计算结果符合很好。     

大面积NBI 射频离子源电气参数设计分析

为探究射频离子源驱动器线圈电气参数对射频放电的影响,主要进行了射频离子源等离子体激发的物理分析,并计算了射频电源的频率选择与线圈放电电流、线圈匝间电压以及放电气压之间的关系,设计了射频离子源驱动器的主要参数。研制的射频离子源驱动器装置,成功获得氢等离子体射频放电。实验结果和理论计算结果符合很好。     

Nonlinear dynamics of radio frequency plasma processing reactorspowered by multifrequency sources

The source frequency has a strong influence on plasma characteristics in RF discharges. Multiple sources at widely different frequencies are often simultaneously used to separately optimize the magnitude and energy of ion fluxes to the substrate. In doing so, the sources are relatively independent of each other. These sources can, however, nonlinearly interact if the frequencies are sufficiently close. The resulting plasma and electrical characteristics can then be significantly different from those due to the sum of the individual sources. In this paper, a plasma equipment model is used to investigate the interaction of multiple frequency sources in capacitively and inductively coupled RF excited plasmas. In capacitively coupled systems, we confirmed that the plasma density increases with increasing frequency but also found that the magnitude of the DC bias and DC sheath voltage decreases. To produce a capacitively coupled discharge having a high plasma density with a large DC bias, we combined low and high frequency sources. The plasma density did increase using the dual frequency system as compared to the single low frequency source. The sources, however, nonlinearly interacted at the grounded wall sheath, thereby shifting both the plasma potential and DC bias. In inductively coupled plasmas (ICP), the frequency of the capacitive substrate bias does not have a significant effect on electron temperature and density. The DC bias and DC sheath voltage at the substrate were, however, found to strongly depend on source frequency. By using additional RF sources at alternate locations in ICP reactors, it was found that the DC bias at the substrate was varied without significantly changing other plasma parameters, such as the substrate sheath potential     

高频离子源等离子体的光谱诊断

 采用发射光谱法研究了高频离子源的等离子体性质。该离子源应用于ZF-200keV中子发生器中，是一种电感耦合型无极环形放电高频离子源。实验采用绝对定标后的光学多道分析系统测定了离子源等离子体在不同阶段氢原子巴耳末谱线系中前三条谱线的强度，并采用部分局部热力学平衡状态的理论，计算出了相应阶段高频离子源等离子体的电子温度、氢原子浓度、氢离子浓度等参数，并进行了简要分析。     

会切磁场多极离子源中磁场对等离子体特性的影响

本文提出了会切磁场多极离子源中,磁场对等离子体参数以及可引出离子束流和放电室阳极收集的离子电流影响的实验研究结果,并对该结果进行了分析讨论。     

高气压空气环状感性耦合等离子体实验研究和参数诊断

等离子体的电子密度分布, 电子碰撞频率分布, 覆盖面积, 厚度是影响其覆盖目标电磁散射特征的关键属性. 对此, 本文开展了在20 cm×20 cm×7 cm石英腔内感性耦合等离子体(ICP)的放电实验, 观察了在高气压条件下, 空气ICP的环形放电形态, E-H模式跳变现象和分层结构, 测量了其电负性核心区和电正性边缘区宽度和厚度随功率、气压的变化趋势, 并通过COMSOL Multiphysics对平板线圈磁场强度分布的分析和电负性气体扩散理论给予上述现象合理的解释, 同时, 利用微波透射干涉法测量了核心区域的电子密度随功率和气压的变化曲线, 利用理论模型计算了边缘区域的电子密度分布, 最后通过辅助气体Ar发射谱线的玻尔兹曼图形法得到了核心区和边缘区的电子激发温度.     

Scaling characteristics of plasma parameters for low-pressureoxygen RF discharge plasmas

For a low-pressure (1-100 mtorr) oxygen RF discharge plasma, the scaling laws for the densities of charged species such as positive ion, negative ion, and electron are estimated in terms of external and internal plasma parameters for the ion-flux-loss-dominated region based on the global balance equations. The scaling formulas are compared with Langmuir probe measurement results performed on a planar inductively coupled oxygen plasma. The transition point from the ion-flux-loss-dominated region to the recombination-loss-dominated region moves to a lower pressure region as the absorbed power increases     

Experimental and theoretical study of density,potential, and current structures of a helium plasma in front of an radio frequency antenna tilted with respect to the magnetic field lines

Potential and density structures in the vicinity of an radio frequency (RF) electrode/antenna in a magnetized plasma are investigated using an RF-compensated cylindrical Langmuir probe. These measurements were performed in the ALINE plasma device in which only electrons can be considered well magnetized. Very precise 2-D maps of the plasma parameters are drawn thanks to a 3-D automatic manipulator on which the probe is mounted. The effect of the tilted magnetic angle between the RF-biased surface and the magnetic lines is also studied thanks to a tilting electrode. Comparison of several simplistic models with the experiments proved the reliability of simple Langmuir probe measurements in such an RF and magnetized environment (space potential vs. tilting angle of the antenna with respect to magnetic field lines and recovery of the floating potential structure using measured currents). A fluid model based on total current density and ion diffusion equations over the biased flux tube provides the same density structures in front of the electrode as the measurements. Those density structures display a “bunny ears” shape and can be explained using transverse RF and collisional current behaviour: In front of the antenna, the transverse ion currents deplete the magnetized flux tube, while at the edge of the biased flux tube, the same currents increase the density.     

磁场引起的潘宁离子源阻抗变化研究

以11 MV回旋加速器潘宁离子源作为研究对象,通过调节磁场强度研究了磁场对工作在弧放电模式下的潘宁离子源的影响规律,深入分析了该放电模式下的放电自持机制、磁场引起的阻抗变化规律、异常发光现象。实验在6 mL/min氢气流量下,保持离子源弧流不变,调节磁场强度,记录磁场强度对弧压的影响。实验结果表明:二次电子发射机制与热电子发射机制在潘宁源自持放电过程中发挥了同样重要的作用;在强磁场情况下离子源阻抗受到磁场变化影响不大,在磁场小于0.15 T时磁场的作用才变得明显;当磁场减弱至等离子体进入阻抗增长区后,存在一段等离子体剧烈放电、光强突然增加的区域。在实验的基础上,得到了设计潘宁源的启发,并分析了磁场对等离子体电导率影响的微观物理机制,这些有助于研制或使用工作在弧放电模式下的潘宁离子源。     

Contribution to the application of the langmuir probe technique for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process

In the present paper the Langmuir probe technique was applied for plasma monitoring in the Ar and n-hexane mixture plasma during the polymerisation process. The experiments were performed in a stainless steel DC magnetron reactor with a planar magnetron cathode. Within the investigated range of the gas pressure, no time-stable condition of the discharge was found. The regular oscillations, of a frequency of approximately 32 kHz, were observed in the Ar and 20% n-hexane mixture at the total pressure of 10 Pa and the discharge current of 8 mA. The experimentally obtained probe characteristics were used to determine the density and the average energy of electrons. In the DC magnetron stainless steel reactor the electron average energy in the Ar and n-hexane mixture plasma was about one order of magnitude smaller than in the case in which the working gas inside the reactor was the pure Ar. The probe measurements in the magnetron reactor were supplemented by the experiment in the customary glass discharge tube with a hollow cathode. In the glass discharge tube and in the Ar and 10% n-hexane mixture plasma a region of plasma parameters was found, in which the plasma was stable and no instabilities were observed. At such conditions the experiments in the glass discharge tube were used for the study of the efficiency of the probe surface cleaning methods used. This report was financially supported by grant 202/97/1011, 202/98/0116 and 202/98/0666 of the Grant Agency of Czech Republic, by the grant 75/98 of the Grant Agency of Charles University and by project COST 516. This work has been done within the framework of Association for Education, Research and Application in Plasma Chemistry.     

利用离子声波朗道阻尼测量氧化物阴极放电中的离子温度

作为等离子体重要参数之一, 特别是在低温等离子体中离子温度的测量一直较为困难. 在磁化线性等离子体装置氧化物阴极脉冲放电条件下, 利用栅网激发离子声波, 通过测量波幅在朗道阻尼作用下随空间的演化, 利用阻尼长度是离子温度和电子温度的函数, 计算得到离子温度为0.3 eV. 测量值与国外类似装置利用光谱诊断所得结果基本相同.     

Influence of plasma extraction on a cylindrical low-pressure RFdischarge: a PIC-MC study

A model is presented for plasma extraction from a cylindrical RF discharge. Even though the extraction geometry is two-dimensional, the model proposed here allows to discuss extraction in a one-dimensional geometry. Specific results are obtained for a low-pressure RF discharge between cylindrical electrodes with a high asymmetry. These are calculated with the help of a PIC-MC computer simulation. The influence of extraction on the plasma characteristics, the ionization efficiency, and the influence of an axial magnetic field are calculated and discussed     

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基于感应耦合等离子体(ICP)技术设计了一套用于在硅基片上制作形成超浅结的等离子体浸没注入(PIII)系统。该ICP PIII系统工作腔室为圆柱形,采用射频功率源,注入偏压源为一脉冲直流电压源,系统与Langmiur探针相连。探针诊断结果表明,该系统的等离子体离子密度达到1017m-3,离子密度径向均匀性达到3.53%。硼和磷的超低能注入试验的二次离子质谱测试结果表明：掺杂离子注入深度在10nm左右,最浅的注入深度为8.6nm(在注入离子密度为1018cm-3时);注入离子剂量达到了1015cm-2以上;掺杂离子浓度峰值在表面以下;注入陡峭度达到了2.5nm/decade。     

高通鸟笼线圈激发螺旋波等离子体特性研究

研制了高通鸟笼线圈,使用氩气作为工质气体对射频天线的工作性能进行了初步评估。利用COMSOL5.4模拟出了鸟笼天线在13.56MHz的工作频率下,电场和磁场呈线性极化分布。对鸟笼线圈进行了电路结构解剖,推导出了其谐振频率计算公式。利用热耦合红外测温仪测试了正常工作状态下的鸟笼线圈外表温度明显低于传统射频天线,电容器最高温度仅65.8°。使用光谱仪对螺旋波等离子体放电光谱特性进行诊断。通过朗缪尔探针诊断了不同压强和磁场强度下螺旋波等离子体密度,在1.0Pa、600Gs、射频功率700W条件下等离子体密度达到1.62×10¹⁸m^-3。诊断了正向功率和反向功率对应的等离子体密度,其与磁滞现象变化趋势雷同。测试了螺旋波等离子体的径向密度分布,其在轴心处密度达到最高。探究了无磁场条件下等离子体特性,其密度值不会发生大幅度跃迁,纵向磁场是引发螺旋波等离子体放电的关键因素,低压条件下有利于得到更低的电子温度,最低达到2.67eV。表明鸟笼线圈低热耗、高馈入的特性使其在激发大体积的高密度螺旋波等离子体方面具有明显优势,可以投入到下一阶段氢气螺旋波等离子体的激...     

Stationary structure of a high-frequency discharge maintained by a distributed electromagnetic source in the presence of an external magnetic field

The stationary structure of an axisymmetric high-frequency discharge maintained by a given source in an external dc magnetic field is investigated. The source is assumed to be a current wave that travels over the discharge tube surface in the direction of the external magnetic field. The source current has a single azimuthal component and its frequency belongs to the lower hybrid range. The main emphasis is placed on the special case where the electron heat conduction length across the external magnetic field exceeds considerably the tube radius. The dependences of discharge plasma parameters on the current amplitude and propagation constant along the tube have been found for this case. The results of numerical calculations of the distributions of the field and the power of the Joule loss in a discharge are presented.     

Self-Focusing and Channeling of Wave Beams in a Nonuniform Magnetic Field under Conditions of Ionization Nonlinearity

We study experimentally the effect of ionization self-channeling of waves at the whistler frequencies in a nonuniform magnetic field. It is shown that the formed plasma nonuniformity localizes the radiation from a short high-frequency source inside a discharge channel stretched along an external magnetic field. We found a possibility to control the parameters of the formed plasma-wave channel as well as the dispersion characteristics and structure of wave fields in wide limits by varying the magnetic field in a specified spatial region. We propose a method for the formation of a plasma resonator and test this method in the laboratory experiment. The spatial plasma and field distributions in this resonator are similar to those along a geomagnetic field tube of the magnetospheric resonator. We reveal the plasma instability in such a resonator in the vicinity of the frequency of electron bounce oscillations between magnetic mirrors.     

级联弧放电氦等离子体特性研究

采用另加偏压的单阴极弧氦放电直线等离子体装置对氦等离子体的基本特性进行了研究。对氦轴向输运规律做了描述并与光谱测量数据做了定性地比较。实验结果表明,氦等离子体的电子温度与电子密度均随放电电流、约束磁场的增加而增加。氦原子与氦离子的辐射光谱随放电电流、偏压、磁场的变化规律进行了测量分析,同时氦离子对钨靶积分辐照效应进行了观察。这些结果不但提供了氦等离子体的基本特性,对于研究氦离子与面向等离子材料相互作用导致产生气泡、肿胀、脆化损伤等的评估,特别是对将来伴有(n, α)反应时具有一定的参考价值。     

An experimental study of the plasma parameters of a hybrid low-pressure RF discharge

This paper presents an experimental study of the plasma parameters of a hybrid radio-frequency (RF) discharge, which is a new modification of an RF discharge. The discharge is maintained by both vortex and potential RF electrical fields. To generate a hybrid RF discharge, an RF power input unit is used in the form of a parallel-connected inductor and capacitor coatings. A blocking capacitor is included in the capacitive channel of the discharge. The paper presents data from the study of the influence of power coupled to the plasma, argon pressure, and blocking capacitance on the plasma parameters, i.e., the electron energy distribution, temperature, and density and plasma potential. The role of the capacitive channel in the variations in properties and the characteristics of the discharge are considered.     

Wave diagnostics of plasmas using a dielectric waveguide

We study the dispersion characteristics of a planar dielectric waveguide in a magnetized plasma. A method is proposed to determine the parameters of an RF discharge plasma by comparing experimental and theoretical dependences of the transmission coefficient of the sounding microwave signal through a dielectric waveguide on the external magnetic field. Experimental tests showed good agreement between the results of measurements of the plasma density in the discharge by the method proposed and using Langmuir probes. The possibilities of using metal-oxide (dielectric)-semiconductor (MOS) structures as tunable rejector filters, phase rotators, and modulators are discussed. N. I. Lobachevsky State University of Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 3, pp. 215–224, March, 1999.