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1.
A numerical analysis of the microdischarge in a surface-type AC plasma display cell has been made using the time-dependent, three-dimensional (3-D) fluid equations to understand the discharge characteristics. We investigate the breakdown dynamics with the width of address electrode and barrier ribs, because the typical 3-D parameters in an AC plasma display panel (AC PDP) model are the width of address electrode and the barrier ribs. It has been clarified that the width of address electrode has important role of the formation of discharge volume with the wall annihilation by barrier ribs and the accumulation of wall charges on the part of address electrode. The obtained time dependent spatial characteristics of an AC PDP discharge with the width of address electrode and the effect of wall annihilation by barrier ribs will help us to design the optimized AC PDP cells to get stable write and sustain discharges  相似文献   

2.
As plasma processing reactors approach higher density, the sheath models which neglect the radio frequency (RF) response of the ions become invalid. This work show that the nature of the collisionless RE ion sheath can be described in a number of different regimes of parameter space. These regimes can all be visualized on a single two-dimensional (2-D) plot where the horizontal axis is the ion plasma frequency divided by the frequency, and the vertical axis is the electron oscillating velocity divided by the ion sound speed  相似文献   

3.
In the atomic vapor laser isotope separation (AVLIS) process, a vapor is ionized by pulsed laser beams, and the ions are extracted by negatively biased collectors. We compute the unsteady dynamics of the photoplasma using a two-dimensional (2-D) particle-in-cell (PIC) code. Collisions between ions and neutral species are simulated by a Monte Carlo technique. The plasma dynamics is visualized by snapshots of particle positions showing the directions of their velocities. The three kinds of particles (electrons, photo-ions, and ions created by charge exchange) are marked by different colors. The graphic outputs illustrate the motion of the electrons toward the anodes, the vertical drift of the plasma, its erosion by the transient ion sheath, and nonselective ionization by charge exchange  相似文献   

4.
5.
Physical qualities of dusty plasma in the pulsed radio-frequency C_2H_2/Ar microdischarges are carefully investigated by a one-dimensional hydrodynamic model and aerosol dynamics model.Since the thermophoretic force has a great effect on the nanoparticle density spatial distribution,the neutral gas energy equation is taken into accounted.The effects of pulse parameters(dust ratio,modulation frequency) on the nanoparticle formation and growth process are mainly discussed.The calculation results show that,as the duty ratio increases,the mode transition from the sheath oscillation(a regime) to the secondary electron heating(7 regime) occurred,which is quite different from the conventional pulsed discharge.Moreover,the effect of modulation frequency on the width of sheath and plasma density is analyzed.Compared with the H_2CC~-ions,the modulation frequency effect on the nanoparticles density becomes more prominent.  相似文献   

6.
高密度等离子体工艺总体模型初探   总被引:1,自引:0,他引:1  
介绍了与高密度等离子体工艺相关的模型和数值模拟方法,即连续流和动力学方法。在漂流-扩散方程的连续流模型和单元粒子/蒙特卡罗碰撞动力学模型的基础上,提出了一个等离子体工艺模型。讨论了对等离子体鞘层、等离子体刻蚀和淀积过程的模拟方法,提出了一个高密度等离子体工艺总体模型的初步方案。  相似文献   

7.
Modeling of plasma behavior in a plasma electrode Pockels cell   总被引:1,自引:0,他引:1  
We present three interrelated models of plasma behavior in a plasma electrode Pockels cell (PEPC). In a PEPC, plasma discharges are formed on both sides of a thin, large-aperture electro-optic crystal (typically KDP). The plasmas act as optically transparent, highly conductive electrodes, allowing uniform application of a longitudinal field to induce birefringence in the crystal. First, we model the plasma in the thin direction, perpendicular to the crystal, via a one-dimensional fluid model. This yields the electron temperature and the density and velocity profiles in this direction as functions of the neutral pressure, the plasma channel width, and the discharge current density. Next, me model the temporal response of the crystal to the charging process, combining a circuit model with a model of the sheath which forms near the crystal boundary. This model gives the time-dependent voltage drop across the sheath as a function of electron density at the sheath entrance. Finally, we develop a two dimensional MHD model of the planar plasma, in order to calculate the response of the plasma to magnetic fields. We show how the plasma uniformity is affected by the design of the current return, by the longitudinal field from the cathode magnetron, and by fields from other sources. This model also gives the plasma sensitivity to the boundary potential at which the top and bottom of the discharge are held. We validate these models by showing how they explain observations in three large Pockels cells built at Lawrence Livermore National Laboratory  相似文献   

8.
Fast-decaying phosphors are essential for a 3D plasma display panel (PDP) with high image quality. However, conventional green and red PDP phosphors have slow-decaying characteristics. We present the luminescence properties of new phosphors for 3D PDP application. Decay times of Y3Al5O12:Ce3+, (Y,Gd)Al3(BO3)4:Tb3+, and (Y,Gd)2O3:Eu3+ were significantly shorter than those of conventional PDP phosphors. CIE chromaticity coordinates and luminescence efficiencies of the phosphors were also suitable for PDP application. The development of fast-decaying PDP phosphors has enabled commercialization of 3D/2D switchable PDP television for the first time in PDP industry.  相似文献   

9.
A collisional model that describes the response of a microwave multipolar bucket plasma to a high-voltage pulse with finite risetime has been developed for plasma immersion ion implantation (PIII). The agreement between this model and the measurements of the sheath position and target current in a 100 mtorr helium plasma is found to be much improved when the risetime of the pulse and the ion energy distribution during the PIII process is considered  相似文献   

10.
The sheath motion in a capacitively coupled RF discharge is highly nonlinear. The voltage waveform on a cylindrical probe placed in the sheath region is measured as a function of position and time. A circuit model of the probe-discharge system relates the observed probe voltage to the sheath motion. The equations derived from this circuit model are solved numerically with varying nonlinear sheath motions; the resulting waveforms are compared with the experimental observations to determine the actual sheath motion. The time-varying plasma potential is also determined, indirectly, from the comparison. The authors also report observation of oscillations related to the plasma frequency, whose peak harmonic component can be calculated from a single plasma model. These oscillations can be a useful plasma diagnostic for determining plasma density. The presence of these high-frequency oscillations may significantly enhance the rate of stochastic heating of electrons  相似文献   

11.
We have used a commercially available monochrome plasma display panel (PDP) to study the electrical and optical properties of PDPs. The monochrome PDP was filled with helium at a pressure of 0.5 atm with the visible light emission observed directly from the gas discharge. The PDP is driven by an AC voltage source, operating at ~130 V at 50 kHz. With nanosecond resolution we have measured the current in the panel and the spectrally resolved light emission from the panel as a function of applied voltage. This study of a helium-filled conventional PDP is designed to provide data needed for improved modeling calculations of the plasma discharge. The ultimate goal is to achieve improved designs and efficacies for large-screen color PDP's  相似文献   

12.
采用一维无碰撞的动力学鞘层模型计算了脉冲等离子体在恒压引出时的等离子体鞘层厚度变化,分别对短脉冲和长脉冲放电时的离子源发射面演变进行了分析。结果表明:对于短脉冲放电,发射面位置的变化相对等离子体密度的变化存在一定时间的延迟;对于长脉冲的上升沿和直流放电的开启阶段,鞘层厚度变化的速度与离子初始速度相关,稳定后发射面的位置与离子初始速度和等离子体密度的乘积相关。  相似文献   

13.
Dust particles often appear in industrial plasmas as undesirable product of the plasma-wall interactions. Large particles of several micrometers in diameter are concentrated in a thin layer (the sheath) above the lower electrode of the rf driven parallel plate device, where the electric force is strong enough to compensate particle’s gravity. Experimental and theoretical uncertainties are significantly increased in the plasma sheath. Common models of dust charging in the plasma sheath suppose the Maxwellian electron energy distribution function (EEDF) in conjunction with a flux of cold ions satisfying classical Bohm criterion at the sheath edge. In this paper we generalize this model to arbitrary EEDF with adapted Bohm criterion. We limit our considerations to collisionless or slightly collisional plasma, where the EEDF inside the sheath is expressed through the EEDF in the plasma bulk. Derived theoretical formulas are incorporated into numerical model, describing collisionless radio frequency (rf) plasma sheath together with the electrical charge, various kinds of forces, balancing radius and oscillation frequency of particles.  相似文献   

14.
张黎  张永强  贺佳  谭福利  赵剑衡 《强激光与粒子束》2018,30(5):051001-1-051001-5
采用二维雷诺平均N-S方程,数值模拟研究了大气条件下短脉冲激光与固体靶相互作用所产生等离子体的动力学过程。采用k-ε两方程模型用于湍流的数值模拟,分别利用ROE格式和二阶中心格式对对流通量和粘性通量进行离散处理;用高斯-赛德尔隐式格式对方程进行时间推进求解。数值模拟给出了激光引发靶蒸气等离子体侧向膨胀、稀疏等二维流体动力学过程的物理图像,讨论了靶与光斑尺寸对脉冲激光冲量的影响。结果表明,不同宽度固体靶受到的激光冲量有很大差异,固体靶宽度越大,受到的激光冲量也越大。  相似文献   

15.
The widely used Child-Langmuir law for sheath thickness evaluation in semi-infinite collisionless plasmas makes the assumptions of quasi-neutrality (ne=ni) and zero electric field intensity E=0 at the sheath edge, as well as applying the Bohm criterion for ions entering the sheath. However, through a whole region fluid model, Poisson's equation has been solved numerically for the steady-state solution through the sheath and presheath without these assumptions. With the sheath edge defined, as in the Child-Langmuir law, at the place where the ion velocity is equal to the Bohm velocity, the sheath thickness of a bounded collisionless or weakly collisional plasma has been found with this model in some cases to be much larger than that obtained with the Child-Langmuir Law. The sheath thickness discrepancy is significant under conditions found in low pressure high density plasma (HDP) tools for plasma processing. Results presented indicate that the sheath thickness is very sensitive to the electric field and space charge density at the sheath edge. The electric field and space charge density can be successfully estimated by an intermediate scale matching method, and are used to derive a modified expression for the potential in the sheath that can be solved numerically for sheath thickness. With these results, the matching problem, arising when sheath and plasma are modeled separately, can be overcome  相似文献   

16.
等离子体浸没离子注入(PIII)是用于材料表面改性的一种廉价高效、非视线的技术.采用等离子体粒子模型,通过假设电子密度服从Boltzmann分布,求解Poisson方程和Newton方程,跟踪离子在等离子体鞘层中的运动形态及特性并进行统计分析,研究了不同上升速率和形状的6种波形上升沿对鞘层时空演化、离子注入能量和剂量的影响.结果表明,在PIII过程中,脉冲上升沿影响了等离子体鞘层的扩展,且不同波形诱导的鞘层厚度间存在最大差值.电场强度在鞘层的外边缘区域存在陡降区,离子的运动为非匀加速过程.可以通过调整脉冲 关键词: 等离子体浸没离子注入 鞘层 粒子模型 上升沿  相似文献   

17.
A three-dimensional model has been developed for simulating the behaviour of inductively coupled plasma torches (ICPTs), using customized CFD commercial code FLUENT ?. The helicoidal coil is taken into account in its actual 3-D shape, showing the effects of its non-axisymmetry on the plasma discharge. Steady state, continuity, momentum and energy equations are solved for argon optically thin plasmas under the assumptions of LTE and laminar flow. The electromagnetic field is obtained by solving the 3-D vector potential equation on a grid extending outside the torch region. In order to evaluate the importance of various 3-D effects on calculated plasma temperature and flow fields, comparisons of our new results with the ones obtainable from conventional 2-D models and from an improved 2-D model that includes 3-D coil effects are presented. The presence of wall temperature hot spots due to plasma discharge displacement from the torch axis is evidenced, while the use of the new 3-D code for optimization of induction coil geometry and plasma gas inlet features is foreseen. Received 5 September 2002 Published online 13 December 2002 RID="a" ID="a"e-mail: colombo@ciram.ing.unibo.it  相似文献   

18.
Magnetic and collisional effects on capacitive radio frequency (RF) discharges for magnetically enhanced reactive ion etching (MERIE) are investigated. Using simplified plasma and sheath models, a collisional magnetic-sheath equation that governs the sheath dynamics under a de magnetic field crossed with a sinusoidal RF electric field is obtained. The sheath equation includes global effects of the bulk plasma. Together with the power-balance equation and the particle-conservation equation, the sheath equation is used to extract a circuit model and predict the electrical behavior of MERIE reactors. Numerical results on the plasma density and the power in MERIE reactors agree well with reported experimental results and the circuit model describes the repeated discharge properties well  相似文献   

19.
In the present paper, argon (Ar) plasmas in a bell jar inductively coupled plasma (ICP) source are systematically studied over pressures from 5 to 20 mtorr and power inputs from 0.2 to 0.5 kW. In this study, both a two-dimensional (2-D) fluid model simulation and global model calculation are compared. The 2-D fluid model simulation with a self-consistent power deposition is developed to describe the Ar plasma behaviour as well as predict the plasma parameter distributions. Finally, a quantitative comparison between the global model and the fluid model is made to test their validity  相似文献   

20.
段萍  李肸  鄂鹏  卿绍伟 《物理学报》2011,60(12):125203-125203
为进一步研究霍尔推进器壁面二次电子发射对推进器性能的影响,采用流体模型数值模拟了二次电子磁化效应的等离子体鞘层特性.得到二次电子磁化鞘层的玻姆判据.讨论了不同的磁场强度和方向、二次电子发射系数以及不同种类等离子体推进器的鞘层结构.结果表明:随器壁二次电子发射系数的增大,鞘层中粒子密度增加,器壁电势升高,鞘层厚度减小;鞘层电势及粒子密度随着磁场强度和方位角的增加而增加;而对于不同种类的等离子体,壁面电势和鞘层厚度也不同.这为霍尔推进器的磁安特性实验提供了理论解释. 关键词: 霍尔推进器 磁鞘 二次电子  相似文献   

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