介质阻挡均匀大气压辉光放电数值模拟研究

通过数值求解一维电子、离子连续性方程和动量方程,以及电流连续性方程,计算了氦气介 质阻挡大气压辉光放电电子、离子密度和电场在放电空间的时空分布,以及放电电流密度和 绝缘介质板充电电荷密度随时间的变化. 分析讨论所加电压频率、幅值及介质板性质等对均 匀大气压辉光放电性质的影响. 当外加电压频率足够高时,大量离子被俘获在放电空间,空 间电荷场又引起足够多的电子滞留在放电空间. 这些种子电子使得在大气压下发生汤森放电 ,放电空间结构类似于低气压辉光放电,即存在明显的阴极位降区、负辉区、法拉第暗区和 等离子体正柱关键词：大气压辉光放电介质阻挡数值模拟等离子体     

磁控溅射辉光放电特性的模拟研究

采用二维、自洽的PIC/MCC (particle-in-cell with Monte Carlo collision) 方法,模拟了磁控溅射辉光放电过程, 重点讨论了工作参数对放电模式和放电电流的影响. 模拟结果表明, 当工作气压由小到大或空间磁场从强到弱变化时, 放电模式会从阴极空间电荷主导的放电模式过渡到阳极空间电荷主导 的放电模式.在过渡状态,对应的工作气压与磁通密度分别为0.67 Pa和0.05 T; 随着工作气压的增大,放电电流先增大后趋向平衡,当工作气压超过2.5 Pa时,电流开始随工作气压的增大而减小; 而阴极电压增大时,放电电流近似线性增加.     

氩直流辉光放电等离子体中电子运动及能量的模拟

采用自动调节时间步长的蒙特卡罗模拟,对平行板放电系统中的氩气直流辉光放电系统中的等离子体区内电子的运动过程进行了跟踪和抽样。统计结果表明:在我们的实验条件下,等离子体中的电子在电场作用下出现明显的轴向漂移;在40000次抽样中,出现能量为E的电子数目随能量E增大呈下降趋势,场强增大将引起能量分布展宽和电子平均能量增加;即使场强达到15V·cm-1,等离子体激发和电离仍是很少的;场强和气压都能明显改变电子的平均自由程。     

接触热阻对水冷辉光放电电极温度分布影响的数值模拟

为了研究接触热阻对陶瓷绝缘水冷辉光放电电极温度及其分布的影响,利用计算流体动力学软件ANSYSCFX,模拟了电极表面温度、温差随氮化铝陶瓷与两侧铜导体之间接触热阻的变化。模拟结果表明：随着接触热阻的增大,氮化铝陶瓷与铜接触界面的温度跳变幅度增大,辉光放电电极整体温度上升,并且辉光放电电极表面的最高温度和最大温差均随之呈现指数上升的变化趋势。     

射频辉光放电CH4等离子体一维流体动力学模拟

完整建立一个关于射频辉光放电CH₄等离子体的流体动力学模型.模型包括基于迁移-扩散近似的粒子平衡方程、电子能量平衡方程,共包含了20种粒子(环境气体粒子,激发态粒子,离子和电子)和49类化学反应(电子-中性环境粒子、离子-中性环境粒子、激发态粒子-激发态粒子(中性环境粒子)).结果表明,在强电场区域有较高的电子反应率系数;等离子体中除源气体CH₄外,H₂,C₂H₆,C₃H₈,C₂H₄和C₂H₂也有较高的密度含量;激发态粒子中,CH₃含量最高,密度约为10¹⁹m^-3;在较低放电压力时(如18 Pa),CH₅⁺在离子成分中密度含量最高,当放电压力较高时(如67Pa),C₂H₅⁺在离子成分中占主导地位;除C₂H₅⁺外,其它各离子和激发态粒子在极板上的粒子流量随功率的增大逐渐升高.     

蒙特卡罗模拟在辉光放电鞘层离子输运研究中的应用

利用蒙特卡罗方法模拟氩气直流辉光放电鞘层内离子的运动过程.模拟基于离子与中性原子的电荷转移和弹性散射两种主要的散射过程,考虑了碰撞截面与能量相关和不相关两种情况,在弹性散射中采用了势场相互作用模型和刚性球碰撞两种模型.通过模拟得到不同气压和不同放电电压下离子入射阴极的能量分布和角度分布,并对几种模型的模拟结果进行了比较和讨论.关键词：辉光放电等离子体鞘层蒙特卡罗模拟     

实验研究射频辉光放电改善苎麻织物毛细效应的时效性

介绍射频辉光放电等离子体改善苎麻织物毛细效应的时效性的实验。分别在充入氩气、氮气、氧气的真空室中对苎麻织物进行射频辉光放电等离子体处理,在每一种处理过程中分别改变其处理时间、放电功率和真空室压强。测试了放置不同时间的经不同等离子体参数处理后的苎麻织物的毛细效应,得出各种参数的等离子体处理对苎麻织物毛细效应时效性的影响。实验结果表明,苎麻织物被等离子体离子体处理后毛细效应得到明显改善,其毛细效应随放置时间的变化为先快速下降,然后变缓,逐渐趋于稳定,这种毛细效应的改善具有良好的时效性,其中100W、40Pa的氧等离子体处理20分钟后的苎麻织物的毛细效应时效性最好。     

四阳极直流辉光放电正柱区数值分析

分析了具有中间开窗电极四阳极直流辉光放电装置的氦气放电中阴极与较近阳极间放电正柱区的电子密度、电子温度和等离子体碰撞频率, 及其空间分布随放电气压变化规律。结果表明电子密度在径向上呈类似于抛物线的分布, 而碰撞频率和电子温度在整个放电管内近似均匀分布。探讨了不锈钢阳极座和矩形窗口对这些参数的影响, 为进一步进行装置仿真和实验研究提供参考。     

PICPMCC 数值模拟四阳极直流辉光放电

利用OOPIC 代码并结合MCC 方法考察四阳极低气压直流辉光放电中粒子间的碰撞, 并对其进行了数值模拟。首先分析OOPIC 代码的计算流程, 给出模拟的边界条件和时间、空间步进; 然后对所得到的等离子体密度、温度的分布情况进行了分析。结果表明, 放电气压、电流以及环电极的有效宽度均影响等离子体密度和温度的径向分布。当气压为300Pa 时, 电子密度在径向较大范围内是均匀分布的, 而当气压升高到800Pa 时, 其径向不均匀增大, 且总的密度和电子的平均温度下降。放电电流的增大使得等离子体密度和温度均相应升高。但环电极有效宽度的减小使得等离子体密度的分布更不均匀, 并使总的密度和平均温度均下降。     

微腔等离子体放电过程的数值研究

采用2维自洽完全流体模型,数值研究了阳极为通孔的高气压微腔放电结构中等离子体参数的变化过程。模拟结果获得了当氩气压强为13.3 kPa时,放电中的电势分布、等离子体密度分布、径向电场分布和电子温度分布等重要参数的演化过程。模拟结果表明在放电过程中,阴极附近的电场由轴向电场逐步转变为径向电场,等离子体密度最大值位于放电腔中间处,并随时间推移由阳极附近向阴极附近移动,电子温度的最大值出现在阴极环形鞘层区域。     

Numerical studies of atmospheric pressure glow discharge controlled by a dielectric barrier between two coaxial electrodes

The glow discharge in pure helium at atmospheric pressure, controlled by a dielectric barrier between coaxial electrodes, is investigated based on a one-dimensional self-consistent fluid model. By solving the continuity equations for electrons, ions, and excited atoms, with the current conservation equation and the electric field profile, the time evolution of the discharge current, gas voltage and the surface density of charged particles on the dielectric barrier are calculated. The simulation results show that the peak values of the discharge current, gas voltage and electric field in the first half period are asymmetric to the second half. When the current reaches its positive or negative maximum, the electric field profile, and the electron and ion densities represent similar properties to the typical glow discharge at low pressures. Obviously there exist a cathode fall, a negative glow region, and a positive column. Effects of the barrier position in between the two coaxial electrodes and the discharge gap width on discharge current characteristics are also analysed. The result indicates that, in the case when the dielectric covering the outer electrode only, the gas is punctured earlier during the former half period and later during the latter half period than other cases, also the current peak value is higher, and the difference of pulse width between the two half periods is more obvious. On reducing the gap width, the multiple current pulse discharge happens.     

Quenching Effect of Microwave to DC Glow Discharge in Gas Lasers

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Simulation of radio-frequency atmospheric pressure glow discharge in γ mode

The existence of two diffe1：ent discharge modes has been verified in an rf （radio-frequency） atmospheric pressure glow discharge （APGD） by Shi [J. Appl. Phys. 97, 023306 （2005）]. In the first mode, referred to as a mode, the discharge current density is relatively low and the bulk plasma electrons acquire the energy due to the sheath expansion. In the second mode, termed γ mode, the discharge current density is relatively high, the secondary electrons emitted by cathodc under ion bombardment in the cathode sheath region play an important role in sustaining the discharge. In this paper, a one-dimensional self-consistent fluid model for rf APGDs is used to simulate the discharge mechanisms in the mode in helium discharge between two parallel metallic planar electrodes. The results show that as the applied voltage increases, the discharge current becomes greater and the plasma density correspondingly increases, consequentially the discharge transits from the a mode into the γ mode. The high collisionality of the APGD plasma results in significant drop of discharge potential across the sheath region, and the electron Joule heating and the electron collisional energy loss reach their maxima in the region. The validity of the simulation is checked with the available experimental and numerical data.     

Glow discharge in helium at atmospheric pressure as a source of spectrum excitation

Self-maintained glow discharge at atmospheric pressure in a helium flow is used as an excitation source of spectra for analysis of the metals Na, Ca, Pb, Cd, and Zn in aqueous solutions of their salts. The intensities of the analytical lines of these metals are obtained as a function of the concentration, and the detection limits for each element are determined. Deceased. Institute of Molecular and Atomic Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Misnk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 711–715, November–December, 1997.     

Discharge characteristics in plasma display cell at high frequency

We present the experimental and simulation studies of the glow discharge plasma in a macroscopic AC plasma display panel cell operating at a high frequency. We find that at high frequencies the plasma from the previous pulse has a significant influence on the discharge properties. The xenon excitation efficiency is larger than that at low frequencies.The discharge mode and efficiency at high frequencies have been discussed in this paper.     

Transmission problems in contrasting chiral media

Time harmonic electromagnetic waves are scattered by a homogeneous chiral obstacle embedded in a homogeneous chiral environment. The corresponding transmission problem is reduced, with the use of Beltrami fields, to an integral equation over the interface between the obstacle and the surrounding medium. This integral equation is known to be weakly uniquely solvable except for a discrete set of electromagnetic parameters of the obstacle. We establish classical solvability, and in some interesting cases (mirror conjugated and isoimpedant chiral media) it is shown that unique solvability is established without the exception of any set of electromagnetic parameters.