新型PDP放电单元着火特性的研究

采用数值方法 ,研究了新型荫罩式PDP(SM PDP)放电单元的着火特性 ,并与传统表面放电式PDP(ACC PDP)作了比较。计算了沿不同放电路径下的气体着火电压 ,讨论并分析了两种结构中 ,某些结构参数的变化对于着火特性的影响。模拟发现 ,SM PDP单元的着火电压要低于ACC PDP ,且在两种结构中 ,电极间距、放电空间大小、介质层对着火电压的影响程度也有一些不同。     

新型PDP放电单元着火特性的研究

采用数值方法，研究了新型荫罩式PDP(SM-PDP)放电单元的着火特性，并与传统表面放电式PDP(ACC-PDP)作了比较。计算了沿不同放电路径下的气体着火电压，讨论并分析了两种结构中，某些结构参数的变化对于着火特性的影响。模拟发现，SM-PDP单元的着火电压要低于ACC-PDP，且在两种结构中，电极间距、放电空间大小、介质层对着火电压的影响程度也有一些不同。     

针尖曲率对敞开式针-柱电极结构气体放电的影响

针对目前气体放电装置需外接体积庞大的供气系统,且电极间距较大、应用范围受限这一问题,设计了一种新型的可在大气压环境下工作的小型针-柱放电电极结构.在镇流电阻阻值为12 MΩ,测试电阻为1 kΩ,放电电阻12 MΩ,紫铜圆柱直径4 mm,针-柱间距1.5 mm,室温,无外界通入气流的条件下,分别选取了针尖曲率半径为27μm、47μm和79μm的3种不锈钢针作为放电阴极进行气体放电实验.实验结果表明,针尖曲率半径越小,起始电晕放电所需电压越小,放电电流越大.针尖曲率半径27μm的不锈钢针能实现稳定的电晕放电和辉光放电,针尖曲率半径为47μm和79μm的不锈钢针则直接由电晕放电过渡到火花放电.采用小曲率的针尖实现大的放电电流和辉光放电,将在材料表面处理、化学分析仪器离子源等的应用中发挥更大的作用.     

EAST辉光放电清洗电极的升级及实验研究

本文介绍了EAST装置辉光放电清洗电极的升级及实验研究.在常规的杆式辉光电极基础上,升级为具备主动水冷散热的板式电极,通过数值模拟和实验研究,证实新电极能满足辉光电流从3 A提升至6 A的散热需求,可长时间稳定运行.新电极在1000 V电压下的击穿气压略低于常规电极,提高He辉光运行电流,从而显著提升对氘(D)的清除率...     

精密电极结构实现小间隙大气压辉光放电离子源

分析了电极结构精密度对大气压辉光放电稳定性的影响,设计并加工了一套高装配精度的线-筒型离子源.内外电极直径分别为0.16mm和4mm.当电压达到-3.5kV时电晕放电开始发生,放电电流波形为典型的特里切尔脉冲;当电压升高至-4.5kV时放电电流变为直流,表明进入辉光状态.通过放电电流波形可以清晰地观察到从电晕放电到辉光放电的过渡过程,并分析了其物理过程.放电实验表明,该装置可以稳定地实现大气压辉光放电,放电电流与施加电压成正电阻特性,而电极之间的电压在放电电流增大的情况下保持不变.这些放电特性与典型的低气压辉光放电一致.放电电流可达毫安量级,电离度较高,可有效提高检测灵敏度.质谱实验表明该离子源可以很好地离子化甲酸、乙酸、苯酚、苯甲酸等化学物质.     

射频辅助的直流辉光放电清洗在HL-2A装置上的应用

本文介绍了一套射频电极系统在HL-2A装置上的相关辉光放电清洗实验研究。本系统主要由具有水冷功能的螺旋结构射频电极和碟形波纹管伸缩传送装置组成。在高频交变电场作用下电子与气体分子发生碰撞的几率增加,射频电极对清除真空室器壁表面的低质量数杂质效率更高。电极通过循环水冷却,使其长时间使用不会产生明显变形,提高了该系统运行的安全性。系统工作时,通过步进电机无极调速来驱动丝杠带动与射频电极相连接传送杆压缩碟形波纹管前后运动快速调整电极位置。实验结果表明,射频天线形式的电极可作为直流辉光的阳极工作,射频辅助启辉降低了直流辉光的启辉气压和电压,提高了装置与抽气机组运行的安全性。射频辅助比纯直流辉光具有更高的清洗效率,为进一步开展与射频相关的壁处理研究提供了条件。     

小间隙针-柱结构电晕放电和辉光放电实现离子风的特性

设计了一种小间隙针-柱放电结构,通过大气压环境下稳定的气体放电,实现离子风.放电阴极采用针尖直径为56.4μm的不锈钢针,放电阳极采用直径4 mm、长60 mm的紫铜圆柱.放电电源采用0~-20 000 V的负直流高压电源,在镇流电阻12 MΩ、放电电阻12 MΩ、测试电阻1 kΩ、针-柱间距2.2 mm、大气压、无外界通入气流、室温条件下进行放电实验.TDS1002B-SC泰克示波器记录的特里切尔放电波形、伏安特性曲线以及数码相机拍摄的放电发光图像验证了针-柱结构产生了稳定的电晕放电和辉光放电.实验中采用testo 405-V1风速仪进行风速测量.不同针-柱间距和不同镇流电阻阻值的实验结果都表明:在电晕放电阶段,离子风风速随放电电压的增大而增大;进入辉光放电后,离子风流速反而减小.     

碳纳米管工具电极的制备

纳米工具电极是进行纳米电解加工的必备条件,其特征尺寸直接影响纳米结构的最终尺寸.提出了利用电弧放电将碳纳米管束焊接在钨针尖上的纳米工具电极制备方法,并通过试验研究了钨针的针尖圆弧半径和放电电压对制备碳纳米管工具电极的影响.试验结果表明,不同尖端圆弧半径的钨针,所需有效放电电压不同,圆弧半径越小,有效放电电压越小,强电场分布越集中,越容易将碳纳米管束焊接在针尖的顶端;圆弧半径越大,强电场分布区域越大,越不容易控制碳纳米管束焊接的方向性.在针尖圆弧半径约为100 nm和300 nm的钨针上,放电电压分别为25 V和35 V时,成功制备出碳纳米管工具电极.     

平面磁控溅射的放电特性

本文分析了平面磁控溅射放电的物理过程，从而解释实测的放电特性──伏安特性，着火电压与气压的关系，并提出平面磁控溅射放电可以认为是一种特殊形式的异常辉光放电。     

辉光等离子放电体在表面合金化技术中的研究EI北大核心

辉光等离子放电体直接影响着材料表面合金化时的电压、气压及温度分布从而影响到材料表面的均匀性、组织结构与性能特征。本工作利用发射光谱分析法对表面合金化技术中辉光等离子放电体进行了研究,通过玻尔兹曼方程式和谱线展宽法求得在不同工艺条件下辉光等离子体的电子温度、电子密度。分析了电压、气压对电子温度、电子密度的影响。结果表明:电子温度随工作电压的升高,工作气压的增大先减少后增大,然后又减少;电子密度在放电电压500~1000V,放电气压30~100Pa时是1021m-3在1012~1025m-3范围内,表明该辉光放电体属于典型的异常辉光等离子放电。     

Breakdown voltage of glow discharge of pin electrodes

One of the shortcomings of glow discharge tube is its high breakdown voltage. In this paper, 2-pin electrode, 3-pin electrodes and 4-pin electrode are fabricated. The breakdown voltages of glow discharge of these electrodes have been measured within the pressure range of 0.4-2.5 kPa. The breakdown voltages vary obviously for the different kinds of electrodes, and the maximum difference of the breakdown voltages is about 208 V. Electric fields of the electrodes are calculated and the results consist with the experimental results. It is concluded that the breakdown voltage can be significantly reduced by adjusting electrode structure without changing the distance between electrode pins. The proposed electrode structure has potential applications in devices of glow discharge.     

Breakdown voltage of glow discharge of pin electrodes

One of the shortcomings of glow discharge tube is its high breakdown voltage. In this paper, 2-pin electrode, 3-pin electrodes and 4-pin electrode are fabricated. The breakdown voltages of glow discharge of these electrodes have been measured within the pressure range of 0.4–2.5 kPa. The breakdown voltages vary obviously for the different kinds of electrodes, and the maximum difference of the breakdown voltages is about 208 V. Electric fields of the electrodes are calculated and the results consist with the experimental results. It is concluded that the breakdown voltage can be significantly reduced by adjusting electrode structure without changing the distance between electrode pins. The proposed electrode structure has potential applications in devices of glow discharge.     

An atmospheric pressure glow discharge optical emission source for the direct sampling of liquid media

A glow discharge optical emission spectroscopy (GD-OES) source that operates at atmospheric pressure is described. This device utilizes an electrolytic solution containing the analyte specimen as one of the discharge electrodes. The passage of electrical current (either electrons or positive ions) across the solution/gas phase interface causes local heating and the volatilization of the analyte species. Collisions in the discharge region immediately above the solution surface result in optical emission that is characteristic of the analyte elements. Operation of this device with the analyte solution acting as either the cathode or anode is demonstrated. Current-voltage (i-V) plots reveal abnormal glow discharge characteristics, with operating parameters being dependent on the electrolyte concentration (i.e., solution conductivity) and the gap between the solution surface and the counterelectrode. Typical conditions include discharge currents of 30-60 mA, and potentials of 500-900 V. Electrolyte solutions having pH, pNa, or pLi values of 0.5-2 and interelectrode gaps of 0.5-3 mm produce stable plasmas in which the analyte solutions flow at rates of up to 3.0 mL/min. Preliminary limits of detection are determined for the elements Na, Fe, and Pb to be in the range of 11-14 ppm (approximately 60 ng) for 5-microL sample volumes.     

Numerical Simulation of Two-Dimensional Structure of Glow Discharge in View of the Heating of Neutral Gas

A two-dimensional computer model of glow discharge is given, which takes into account the heating of ambient gas and the external electric circuit. The structure of a glow discharge in molecular nitrogen is investigated numerically in the pressure range from 1 to 20 torr at an electric field intensity of up to 4 kV/cm. The regularities of heating a gas are investigated at different pressures and electric field intensities. It is demonstrated that, at a pressure p = 1 torr, a glow discharge burning in the mode of normal density of current assumes a toroidal shape.     

Two-dimensional axisymmetric simulations and the heating effects associated with DC atmospheric pressure discharges during the post-streamer stage

Numerical results are presented for the development of the post-streamer discharge stage in atmospheric pressure air. The model used comprises Poisson, charged-particle continuity and Navier-Stokes equations developed in two-dimensional cylindrical axisymmetric co-ordinates. Applied direct current voltage of 20% above the breakdown threshold is applied in a 1 mm gap between two parallel plate electrodes. Starting from a single electron as the initial condition, the transitory regime from the streamer to the glow discharge is analysed, and the glow discharge is shown to consist of the cathode fall, negative glow, positive column and anode regions. The positive column is shown to propagate in the form of a return wave towards the anode. The very fast redistribution of the electric field just after the streamer hits the cathode is presented. Furthermore, the current density at the cathode fall and anode regions is shown to increase and extend radially outwards, justifying the inclusion of a two-dimensional axisymmetric model to study the radial effects in the discharge. Neutral gas heating starts to occur with the initiation of the post-streamer discharge stage, and the neutral gas temperature increases at the cathode by approximately 180 K     

A two-dimensional model of glow discharge in view of vibrational excitation of molecular nitrogen

A two-dimensional model is suggested of dc glow discharge with parallel electrodes. The model includes equations for electron and ion concentrations, which are related to the Poisson equation for electric potential. The collision ionization and electron-ion recombination are described using empirical relations. Processes of vibrational excitation of N₂ molecules are considered. The vibrational kinetics of nitrogen are described in view of excitation by electron impact, vibrational exchange, and vibrational-translational relaxation. The finite-difference model used for solving kinetic equations is described. Results are obtained for a two-dimensional model of glow discharge in nitrogen at a pressure of 5 torr and an emf of 2000 V. The obtained fields of distribution of electron temperature and populations of vibrational levels of nitrogen are analyzed. The results enable one to estimate the fraction of electric field energy utilized for the excitation of vibrational states.     

A high-power low-pressure iodine lamp pumped by glow discharge

We present the working characteristics of a high-power UV-VUV electric-discharge lamp filled with a working mixture of helium and iodine vapor (He-I₂) at a low pressure (0.1–1.5 kPa) and pumped by a dc glow discharge at a power of 15–200 W. The power of the total output UV radiation and the main emission peak at λ = 206.2 nm were studied as dependent on the electric power supplied to the glow discharge and on the partial pressure of helium in the He-I₂ mixture. The emission characteristics of the glow discharge plasma were studied in the spectral range from 200 to 350 nm. In this range, the lamp is operating predominantly on a resonance emission line of excited iodine atoms (λ = 206.2 nm, FWHM = 0.10–0.12 nm) and on a system of electronic-vibrational bands of excited iodine molecules with the main peak at λ = 342 nm. The contribution of the resonance emission due to excited iodine atoms to the total UV emission from the glow discharge plasma does not exceed 50%. The optimum partial pressure of helium is within 400–800 Pa. The total UV radiation power of the lamp operating in the optimum regime reaches 25 W at an efficiency of η ≤15%.     

Numerical simulation of surface glow discharge in molecular nitrogen

The DC surface glow discharge in molecular nitrogen at a pressure p = 10 Torr and voltages V ₀ = 600, 700, and 1000 V is considered based on the diffusion-drift model. The local maxima of the electric field strength and the current density on electrodes are determined. The temperature fields induced by Joule heating in the near-electrode regions are analyzed.