非链式HF激光器SF6气体介质放电特性

采用放电图像拍摄和放电波形测量两种方法研究了放电激励HF激光工作介质SF6气体的放电特性。实验结果表明:SF6气体放电可以分为主放电、剩余电压维持和电弧放电3个阶段。主放电阶段为均匀体放电,电容储能大部分在此阶段沉积于放电等离子体中;剩余电压维持阶段无明显放电;在电弧放电阶段激光器以电弧形式消耗剩余储能。通过对放电波形的分析,获得剩余电压及主放电阶段能量沉积效率随充电电压的变化规律。随着充电电压提高,剩余电压下降,沉积效率逐渐提高。沉积效率最大值对应于主放电与电弧放电相接的时刻。     

放电激励重复频率非链式HF激光器

 利用紫外预电离横向放电和气体循环结构建立了一套放电激励重复频率HF激光装置。研究了激光器工作介质SF6/C2H6混合气体放电特性和激光输出特性,获得激光器单次运行的最佳输出参数;通过对激光器重复频率运行时不同气体流速、充电电压与气体总压条件下的放电状态和输出能量的比较,分析了激光器重复频率稳定运行的必要条件。结果表明：所研制的激光器最大单脉冲能量0.6 J,峰值功率3 MW,电光转换效率2.4%;当混合气体工作介质以3.5 m/s的流速循环时,激光器稳定运行的最高工作频率可达50 Hz,脉冲输出能量稳定在0.26 J,平均功率达到13 W。     

H_2辉光放电清洗时轰击器壁的离子能量测量与分析

一、引言 辉光放电是清洗锻炼环流器真空室器壁的有效手段。H_2辉光放电时,氢离子轰击器壁与器壁中的C和O发生化学反应,生成CH_4,H_2O等气体;同时,这些离子提供能量使得吸附在器壁表面的杂质气体脱附,从而被泵出真空室外,达到清洗锻炼的目的。由于辉光放电时,离子轰击的能量较高,会引起一定的溅射沉积。我们在模拟真空室(六通装置)进行了辉光放电,对各种参数下的离子能量进行了测量,从中找出了离子能量与极间电压(阳极与器壁之间的电压)、放电电流、以及气压、离子流密度之间的某些关系。     

间隙绝缘电极辉光放电实验观察

实验研究了ITER H2/He辉光放电壁处理(GDC)系统的电极合理的间隙绝缘参数及标定辉光过程中沉积在电极头部的热负载.进行了H2/He击穿电压特性试验,在ITER GDC预期的壁离子电流密度条件下研究了H2/He辉光放电电压和试验电极上热负荷与压强的关系、试验电极启辉耐受特性、试验电极温度与热负荷的关系以及在不同区...     

纳秒脉冲电压下同轴场畸变开关多通道放电特性

使气体开关形成多通道放电是减小开关电感、通道电阻、电极熔蚀,提高开关寿命和稳定性的有效措施。设计了一种同轴场畸变气体火花开关,研究了开关在纳秒脉冲电压下的多通道放电现象。研究了脉冲电压上升速率与多通道放电特性的关系,比较了两种体积比的SF6/Ar混合气体多通道放电特性。实验结果表明:一定气压下,平均通道数随着脉冲电压上升率增加而增多,电流分布趋向均匀;相同脉冲峰值与气压比值,不同气压下,高气压下的通道数较多;SF6/Ar混合气体中,氩气含量较高情况下多通道放电特性较好。最后,结合J.C.Martin的多通道放电理论对实验结果作出了初步解释。     

平台式和斜坡式表面放电辐射源放电特性的比较

 介绍了平台式和斜坡式两种结构的表面放电辐射源,研究了在1.0 μF和1.5 μF储能电容、15~30 kV充电电压等实验条件下两种辐射源的放电特性,并对实验结果进行了比较分析。得到如下结论：对于斜坡式辐射源,增加电极间距可导致放电回路面积增大,因此等效电阻和等效电感也将增加;在相同电压及电容值条件下,斜坡式辐射源的放电电流、平均沉积功率均小于平台式辐射源的相应值,但放电沉积效率略大;电压升高使放电周期、电流达到峰值时间及放电沉积效率呈减小趋势,对于同一种辐射源,使用1.5 μF电容时放电回路参数更加匹配,放电沉积效率得到提高。     

陶瓷表面放电光泵浦源放电特性研究

为了提高表面放电光泵浦源的寿命,以Al_2O_3陶瓷作为放电基板,研制了分段表面放电光泵浦源。基于放电电压和电流波形,详细研究了泵浦源的放电周期,放电通道电阻,能量沉积效率和等离子体功率密度。发现泵浦源的放电周期、放电通道电阻和能量沉积效率均随放电间隙长度和混合气体气压的增大而变大,随充电电压的增加而减小;而等离子体功率密度主要取决于充电电压和放电间隙长度,基本不随混合气体气压的改变而变化。在充电电压为26. 8 kV,气压为100 kPa,放电间隙长8 cm的条件下,泵浦源的能量沉积效率约为82%,等离子体功率密度达到了9. 36 MW/cm。实验研究表明:Al_2O_3陶瓷表面放电光泵浦源具有良好的放电特性,较同等条件下聚四氟乙烯表面放电光泵浦源的等离子体功率密度更高,可产生更强的真空紫外辐射,辐射亮度温度大于23 kK。Al_2O_3陶瓷表面放电光泵浦源适用于光泵浦XeF_2气体形成大功率XeF(C-A)蓝绿激光。     

放电引发的非链式高功率重复频率HF/DF激光器

高功率重频HF/DF激光因其具有的波长和功率优势成为当前中红外激光技术发展的热点之一。介绍了利用紫外预电离横向放电结构和工作气体循环系统建立的放电引发高功率重频HF/DF激光装置。在对激光工作介质SF6/C2H6混合气体放电特性和激光输出特性研究的基础上,开展了强电负性气体的重频均匀体放电技术和气体快速循环置换技术研究,解决了泵浦源重频放电能量在气体介质中的有效沉积和提取问题,实现了激光器50Hz的重频稳定运行和能量稳定输出,HF激光的平均功率达到28W,脉宽100ns,峰值功率5.6 MW。     

辉光放电预处理对聚酰亚胺绝缘子真空沿面闪络电压的影响

为提高绝缘子的真空沿面闪络电压,采用氩气下辉光放电对绝缘子进行处理,研究了辉光放电频率、放电电流大小和处理时间对绝缘子真空闪络电压的影响。结果表明,辉光放电能极大提高绝缘子的真空闪络电压。未处理的绝缘子真空闪络电压为55 kV左右;经高频辉光放电预处理40 min后,绝缘子真空闪络电压达到100 kV;经工频辉光放电预处理40 min后,绝缘子真空闪络电压可达125 kV,高出高频下25 kV;同时,辉光放电电流（数十mA）越大,处理后的绝缘子真空闪络电压越高,但随着辉光放电电流的增大,闪络电压的增加幅度趋于饱和。     

分段表面放电沉积效率研究

 利用一种结构紧凑的分段表面放电辐射源模块，详细研究了在不同电压、电容、气压实验条件下回路等效电阻、等效电感及放电能量沉积效率的变化规律，利用四分幅相机拍摄获得了不同实验条件下的放电等离子体通道图像，分析讨论了放电等离子体运动对放电能量沉积效率的影响，提出了提高能量放电沉积效率的有效途径。     

Dynamics and correlated performance of a photo-triggered discharge-pumped HF laser using SF6 with hydrogen or ethane

3 , has been performed in Ne/SF₆/H₂ and Ne/SF₆/C₂H₆ mixtures. Parameters involved have been the storage line capacitance and the circuit inductance, the capacitors charging voltage, the RH-molecule type and partial pressure, and the X-ray dose for the preionization. High laser performance has been achieved with C₂H₆: an output energy up to 3 J corresponding to a specific energy of 9.6 J/l at an efficiency of 4.7%, which strengthens the advantage of the photo-triggering technique to energize high-power HF lasers. However the optimum performance achieved with H₂, 5.75 J/l and 3.5%, are lower. It is shown, through a time-resolved study of the electrical discharge and spatial dynamics correlated to laser power and energy measurements, that discharge instabilities are responsible for the poor laser performance of the mixture with H₂. These instabilities, which lead to arc development, are characteristics of the discharge in Ne/SF₆. It is demonstrated for the first time that addition of a heavy hydrocarbon, such as C₂H₆, to that mixture induces the discharge stabilization so that the laser emission arises in a homogeneous active medium. This effect allows us to achieve better laser performance than with H₂. Received: 17 March 1998/Revised version: 13 July 1998     

Pathways in the molecular fragmentation for the C2H5OH/He electrical discharge

ABSTRACT

This study focuses on the glow discharge generated with a gases mixture of Ethanol (C₂H₅OH) and Helium (He), at different concentrations maintained at a total pressure of 2.0 Torr. We used optical emission spectroscopy (OES) to analyze the discharge mixture at different concentrations of Helium. Single Langmuir probe data was used to determine the Electron Energy Distribution Function (EEDF). For the total C₂H₅OH/He mixture plasma concentrations, the EEDF has a Maxwellian distribution function. A decrease in He concentration results in significant changes in the EEDF, this behavior is related to the increase in the C₂H₅OH percentage must increase the energy loses of the electrons in the inelastic collision with C₂H₅OH producing a significant change in the EEDF, therefore, the EEDF pattern results in an increase of electron–molecule reaction rates. The rise in electron temperature for increasing Helium percentage is explained by the decreasing electron energy loss in the inelastic collisions with C₂H₅OH molecule. It observes a decrease of electron density ne as a function of the Helium percentage, which can be related to the ratio between ionization cross sections of Helium and C₂H₆O molecule. The active species are generated in the electron-molecule processes, which are associated with electron impact dissociation of C₂H₅OH and Helium electronic impact excitation in the gas phase. The emission optical spectra (OES) show changes in the intensity of the most important peaks of the plasma mixture, which indicates the dependence in the formation of the plasma as a function of the percentage of the gases. The changes in the intensities of the same observed species are due to different processes of excitation and ionization energies of the system, in addition to the increase of He metastable states He I. Hydrogen is the main product obtained from the decomposition of C₂H₅OH.     

Properties of the dielectric barrier discharge in mixtures of methane with helium

The influence of the chemical composition of the feeding gas mixtures CH₄-He on the physical properties of dielectric barrier discharge was investigated experimentally as well as theoretically. Certain changes in the shape of charge-voltage characteristics (Lissajous figures) were observed when the content of He was varied within the range 0–90%. An increase of the He concentration was found to cause monotonous but not linear decrease of the ignition voltage as well as of the burning voltage of the discharge. Measurements of the burning voltage were used to estimate the characteristic energy of electrons in the mixtures under consideration. These estimates were compared with experimentally determined values of the energy consumption for the synthesis of C₂H₂, C₂H₄ and C₂H₆, respectively. It was demonstrated that the observed dependencies of the energy consumption upon He content can be explained taking into consideration the influence of the chemical composition of feeding gas mixture upon the characteristic energy of electrons in the dielectric barrier discharge. Dedicated to Prof. Jan Janča on the occasion of his 60th birthday. The work was supported by the Sonderforschungsbereich 198 “Kinetik partiell ionisierter Plasmen”.     

羟基碳纳米管吸附SF6放电分解组分的DFT计算

本文根据密度泛函理论(density functional theory , DFT), 采用MS分子动力学仿真软件对羟基修饰的单壁碳纳米管(SWNT-OH) 吸附SF₆局部放电分解的四种主要组分SOF₂, SO₂F₂, SO₂和CF₄进行了详细的理论计算, 通过分析气体分子和SWNT-OH的前线轨道, 吸附过程中吸附能、电荷转移量和电子态密度的情况, 以及吸附前后SWNT-OH能隙的变化, 评判了SWNT-OH对气体分子的敏感性和选择性, 给出了SWNT-OH是否可以制备气体传感器检测SF₆局部放电分解组分的理论依据.     

Rotationally resolved electronic spectroscopy of a nonlinear carbon chain radical C6H4

Rotationally resolved electronic spectrum of the origin band in the 2A″-X2A″ transition of a nonlinear carbon chain radical C₆H₄⁺ has been recorded in the 604 nm region using cw cavity ring down spectroscopy. The radical was produced by a discharge through an acetylene-helium mixture in a supersonic planar expansion. The rotational structure has been analysed and precisely determined. A band having a-type prolate rotational structure has also been observed near 581 nm. By considering the results of ab initio calculations this band is assigned to a transition involving the excitation of the ν₁₂ fundamental in the upper 2A″ electronic state of the same C₆H₄⁺ isomer.     

工作压强对射频辉光放电H2/C4H8等离子状态的影响

利用辉光放电技术采用等离子体质谱诊断的方法研究了不同工作 压强下H₂/C₄H₈混合气体等离子体中 主要正离子成分及其能量的变化规律, 并分析了压强对H₂/C₄H₈混合气体的离解机理以及主要正离子形成过程的影响. 结果表明: 随着工作压强的增加, 碳氢碎片离子的浓度和能量均逐渐减小. 当工作压强为5 Pa时, H₂/C₄H₈混合气体等离子体中C₃H₅⁺相对浓度最大; 压强为10 Pa时, C₃H₃⁺相对浓度最大; 压强为15, 20 Pa时, C₂H₅⁺相对浓度最大; 压强为25 Pa时, C₄H₉⁺相对浓度最大. 对H₂/C₄H₈等离子体中的主要组分及其能量分布所进行的定性分析, 将为H₂/C₄H₈混合气体辉光放电聚合物涂层的工艺参数优化提供参考技术基础. 关键词： 辉光放电技术 等离子体质谱诊断 工作压强     

Gas Chromatography Analysis of Discharge Products in N2‐CH4 Gas Mixture at Atmospheric Pressure: Study of Mimic Titan's Atmosphere

In this paper, we report presence of various organic products formed in a flowing atmospheric glow discharge fed by gas mixture containing 1‐5 % of methane in nitrogen, which mimics the Titan's atmosphere. Gaseous products from the discharge exhaust were analysed by Gas Chromatography with Mass Spectrometry (GC‐MS). The experimental results revealed C₂H₂, HCN, and CH₃CN as the major products. Various hydrocarbons and nitriles were the other determined gaseous products. Whilst many of these compounds have been predicted and/or observed in the Titan atmosphere, the present plasma experiments provide evidence of both the chemical complexity of Titan atmospheric processes and the mechanisms by which larger species grow prior to form the dust that should cover much of the Titan's surface. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of SF6 on HF laser plasma parameters

Summary This paper presents the results of calculations of electron drift velocity, mean energy and ionization, and attachment coefficients in SF₆: C₃H₈: He mixtures performed according to the multiterm Boltzmann-equation analysis. The parameters for wide variation of gas mixture composition andE/N values are obtained. The results presented may be useful in studying the HF laser action, analysis of the gas discharge, and research, development and modelling of this type of lasers. The authors of this paper have agreed to not receive the proofs for correction.     

Intensification of shock-induced combustion by electric-discharge-excited oxygen molecules: numerical study

Mechanisms of combustion enhancement in a supersonic H₂–O₂ reactive flow behind an oblique shock wave front are investigated when vibrational and electronic states of O₂ molecule are excited by an electric discharge. The analysis is carried out on the base of updated thermally nonequilibrium kinetic model for the H₂–O₂ mixture combustion. The presence of vibrationally and electronically excited O₂ molecules in the discharge-activated oxygen flow allows to intensify the chain mechanism and to shorten significantly the induction zone length at shock-induced combustion. It makes possible, for example, to ignite the atmospheric pressure H₂–O₂ mixture at the distance shorter than 1 m behind the weak oblique shock wave at a small energy E_s = 1.2 × 10^–2 J · cm^–3 input to O₂ molecules. At higher pressure it is needed to put greater specific energy into the gas in order to ignite the mixture at appropriate distances. It is shown that excitation of O₂ molecules by electric discharge is much more effective for accelerating the hydrogen–oxygen mixture combustion than mere heating the gas.