HL-2A装置气体击穿延迟时间

气体击穿延迟时间实验数据表明,HL-2A装置的气体击穿过程可以用修改了的有电极放电汤森德电离公式,并考虑电子的几何损失来进行描述。     

快脉冲直线变压器气体开关技术

阐述了Z箍缩驱动惯性聚变装置对快脉冲直线变压器气体开关的需求背景,介绍了快脉冲直线变压器气体开关技术发展的基本要求及国际研究进展,归纳了近年来主要研究成果和对当前研究有重要借鉴意义的结论,给出了提高静态稳定性、降低触发阈值和延长开关寿命的措施。介绍了气体放电的汤逊和流注理论,指出:在不大于1.5106 Pacm范围内,汤逊理论完全适用于描述气体开关自击穿过程。根据巴申定律、Meek击穿判据,给出了开关气压和间距设计要点,分析了多间隙开关间隙数量和间隙的电压分布均匀性对开关自击穿电压的影响。根据触发击穿延时经验公式,归纳了降低触发电压阈值的技术途径。介绍了1维的电极熔蚀判据,并总结了减轻电极烧蚀的方法和措施最后指出开关技术研究总体策略和方法。     

纳秒脉冲下高能量快电子逃逸过程的计算

基于快电子的逃逸击穿机理将是一种能解释纳秒脉冲高过电压倍数下气体放电现象的理论，对高能量快电子的逃逸运动、碰撞电离引导电子崩的发展等进行了分析，并根据电子能量与阻力关系式，对电子的俘获或逃逸过程进行了计算.结果表明外加场强越高，更多的电子能逃逸，逃逸的能量阈值越低，气压对电子的逃逸过程影响也较大.同时也定性描述了纳秒脉冲下逃逸击穿放电过程. 关键词： 气体放电 快电子 逃逸击穿 纳秒脉冲     

纳秒脉冲气体放电机理探讨

 经典Townsend机理和流注理论是气体放电研究的基础,但在解释纳秒脉冲气体放电时均存在一定缺陷。基于经典气体放电理论,探讨纳秒脉冲气体放电机理,分析流注理论判据在纳秒脉冲气体放电中的有效性,解释纳秒脉冲下电子逃逸现象和基于电子逃逸的快速电离波击穿理论,仿真计算高能快电子的逃逸过程。结果认为基于高能量快电子的逃逸击穿将是可能解释纳秒脉冲下气体放电现象的依据。     

辅助放电针对气体间隙直流自击穿特性的影响

为降低气体放电间隙直流条件下自击穿电压分散性,尽可能不影响其自击穿电压,基于环形电极放电间隙,设计了一种在阴极中心植入辅助放电针的辅助放电电极结构。通过电场仿真,研究了辅助放电针直径、长度和顶部倒角对放电间隙场畸变的影响。实验研究了放电间隙无辅助放电针和植入辅助放电针后,其在干燥空气和SF₆气体中的直流自击穿特性。结果表明：辅助放电针直径越小、长度越长,电极环对其电场屏蔽作用越弱,放电间隙场畸变强度越大;辅助放电针对SF₆气体放电间隙直流自击穿电压影响较小,随着场畸变系数的增大,同一气压下干燥空气自击穿电压下降百分数为SF₆气体自击穿电压下降百分数的2～3倍;辅助放电针对直流条件下干燥空气和SF₆气体放电间隙自击穿电压稳定性具有有益作用,分散性减小百分数较无辅助放电针结构均提高约25%。     

高功率微波输出窗内侧击穿动力学的PIC/MCC模拟研究

高功率微波在受控热核聚变加热、微波高梯度加速器、高功率雷达、定向能武器、超级干扰机及冲击雷达等方面有着重要的应用.本文针对高功率微波输出窗内侧氩气放电击穿过程,建立了二次电子倍增和气体电离的一维空间分布、三维速度分布（1D3V）模型,并开发了相应的PIC/MC程序代码.研究了气压、微波频率、微波振幅对放电击穿的影响.结果表明：在真空情况下,介质窗放电击穿只存在二次电子倍增过程;在低气压和稍高气压时,二次电子倍增和气体电离共存;在极高气压时,气体电离占主导.给出了不同气压下电子、离子的密度和静电场的空间分布.此外还观察到,在500 mTorr时,随着微波振幅或微波频率的变化,气体电离出现的时刻和电离产生的等离子体峰值位置有较大差异,尤其是当微波频率（GHz）在数值上是微波振幅（MV/m）的2倍时,气体电离出现的较早.     

高频H型放电离子源的场特性

 从Maxwell方程组出发，推导了高频H型放电离子源放电空间的场分布, 并采用Mafia软件进行了三维实体建模，计算了高频离子源放电击穿前和稳定工作后的电磁场分布，得到了高频离子源放电空间电磁场分布的直观图像。通过比较击穿前高频电场的轴向和环向分量，得出了轴向电场在高频离子源击穿中起主要作用的结论，并进而推导出了高频离子源的击穿判据，得出了气体击穿时离子源击穿电压和放电管内气压的关系，与实验结果符合较好。     

宽气压范围空气中微波击穿电场的计算公式

为了简便快捷地计算微波击穿电场,依据电子扩散模型的基本理论,结合气体放电的基本参量,应用特征扩散长度的概念,给出了适合于规则结构微波部件的击穿电场的计算方法。为避免各种气体参数的不确定性对计算准确度的影响,对等效直流电场与特征扩散长度之间的实验关系进行了拟合,并根据等效直流电场的定义,得出了一个适用于较高气压范围的击穿电场计算表达式。为了将该计算表达式扩展到更低的气压范围,综合考虑了电子扩散模型和基于二次电子发射现象的真空微放电机理,引入了一个合理形式的等效扩散长度,进一步给出了适合于更广气压范围的微波击穿电场的计算表达式,计算结果更符合A.D.Macdonald的实验结果。     

旋转滑动弧放电等离子体滑动放电模式的实验研究

交流旋转滑动弧放电能够在大气压下产生大面积、高活性的非平衡等离子体.为了研究交流旋转滑动弧的滑动放电模式、放电特性及光谱特性,本文采用高速相机与示波器同步采集旋转滑动弧的放电图像和电信号,采用光谱仪采集光谱信号,分析旋转滑动弧运动过程中电弧的动态行为、电信号及光谱信号特征.实验结果表明,旋转滑动弧放电过程中存在两种不同的滑动放电模式,即伴随击穿滑动放电模式(B-G模式)与稳定滑动放电模式(A-G模式).其中B-G模式以电弧旋转滑动过程中伴随击穿-熄灭-击穿的高频击穿现象为主要特征,而A-G模式以持续稳定的连续电弧滑动为主要特征.本文讨论了工作参数影响滑动弧放电模式、放电特性及光谱特性的工作机制.研究发现,电弧的放电模式和放电特性是激励电压与气体流量共同作用的结果.当气体流量较大、激励电压较小时,滑动弧为B-G模式主导的高频击穿不稳定放电;而当激励电压较大、气体流量较小时,滑动弧则为A-G模式为主导的稳定滑动放电.     

气体介质对多间隙气体开关电晕均压与自击穿特性的影响

快脉冲直线变压器型驱动源(FLTD)是近年来快速发展的新型脉冲功率源技术,多采用多间隙气体开关作为开关器件。电晕均压措施有利于提升开关击穿性能,但不同气体中电晕放电有显著区别。本文首先研究了空气中针电极对单间隙电晕放电特性的影响,确定了电晕针电极的尺寸,之后研究了N2,CO2,SF6/N2混合气体、C4F7N/N2混合气体中的电晕放电特性,研究了电晕均压6间隙气体开关击穿电压及其稳定性随气体种类和气压的变化规律。实验结果表明,N2中电晕电流较大且不稳定,空气中电晕电流比N2中低,且电晕放电较为稳定,微量强电负性气体加入会极大降低电晕放电电流。当采用空气和N2作绝缘介质时,气体开关击穿电压随气压升高线性增加,但存在低值击穿,微量强电负性气体混合N2可显著提升击穿电压的稳定性。1%SF6/99%N2混合气体在0.18 MPa时,击穿电压约为197.33 kV,标准偏差占击穿电压比例为1.50%,1%C4F7N/99%N2混合气体在0.15 MPa时,击穿电压约为190.42 kV,标准偏差为0.55%。这表明,微量环保替代气体C4F7N与N2的混合气体对于提升多间隙气体开关击穿电压稳定性有显著作用。     

Mechanisms controlling the transition from glow silent discharge tostreamer discharge in nitrogen

Low-energy dielectric-barrier controlled discharges in nitrogen are studied by undertaking electrical measurements to determine mechanisms controlling the transition from glow to streamer-like discharge. The highest and the lowest values of the frequency and the amplitude of power supply voltage leading to a glow discharge have been found dependent on the gas flow and the nature of the surface in contact with the discharge. These boundary values have been related to the criteria necessary for initiating a Townsend breakdown rather than a streamer breakdown commonly observed under such conditions. This implies: (1) that the seed electron density just before the breakdown is high enough to allow the development of numerous small avalanches under a low field avoiding the formation of only one large avalanche mechanism at the origin of the streamer formation; and (2) to let the time for ions issued from the first avalanches to reach the cathode before the electrical field becomes large enough to induce the formation of large avalanches. Practically, the transition from a Townsend breakdown to a streamer breakdown is analyzed from electrical measurements data coupled to the visual aspect of the discharge. Without any gas flow, the obtaining of an atmospheric pressure glow discharge (APGD) is mainly limited by the species etched from the surface in contact with the gas. Indeed, these species can be quenchers of the nitrogen metastable molecules, which are the species at the origin of the formation of seed electrons via the Penning effect. This limitation can be overcome by the use of a laminar gas flow. However, this type of gas flow through the discharge induces a depletion of N₂ metastables and, consequently, influences the electron density at the entrance of the discharge, leading to a tendency on this part of the discharge to transit to a streamer-like one     

Theory of gas breakdown in an inhomogeneous field

Consideration is given to an independent electrical gas discharge in an inhomogeneous field, with photoionization of the gas as secondary mechanism. The condition for an independent discharge to exist is derived; this condition enables the breakdown voltage to be calculated, and also explains the short times required to form the discharge and the fact that the breakdown voltage is independent of the cathode material. The same condition may be considered as a criterion for the ignition of a self-sustaining corona in a long spark gap with nonuniform geometry.     

Similarity law for a homogeneous discharge in the presence of a strong field and analogues of the Stoletov constant for the pulsed regime

It is demonstrated that the similarity relationships (breakdown curves), which establish a dependence of the field strength divided by the pressure on the product of the pressure and the delay time of the breakdown, are realized upon the uniform breakdown of the gas gap in the presence of both rectangular and triangular voltage pulses, which is interesting for the physics of gas and plasma discharges, and remain valid for strong fields. The breakdown criterion is described with a two-valued curve such that the effective multiplication of electrons in gas becomes possible in the presence of both weak and strong fields and at small products of the pressure and the pulse time. An analogue of the Stoletov effect, which corresponds to a maximum in the current with respect to pressure at a given voltage pulse, is demonstrated for the pulsed discharge. The analogues of the Stoletov constant are calculated for non-self-sustained pulsed discharges in various gases. The minimum delay time of the breakdown is also determined by these constants.     

横向表面放电光泵浦源特性研究

 介绍了一种用以泵浦XeF(C-A)激光的横向表面放电辐射源,比较详细地研究了这种泵浦源的放电击穿特性、放电电流与充电电压及不同气体介质的关系、表面放电均匀性以及不同气体成分对表面放电辐射特性的影响。得到了放电击穿时间、放电峰值电流随充电电压、不同气体介质变化的曲线;分析了提高放电均匀性的途径,在电极长50cm、间距6cm、充电电压25kV条件下获得了均匀放电。获得了各种实验条件下放电辐射的光谱曲线;通过对辐射光谱的分析,研究了有利于光解离XeF₂的最佳实验条件,当p_Ar:p_N2=1:1时,放电在远紫外波段产生的辐射最强。     

Electrostatic analysis for designing of efficient discharge cell structures in AC plasma displays

The high luminous efficacy of plasma display demands high luminance at reduced discharge power. The discharge power can be reduced by several steps, one of them being reduction of gas breakdown voltage. In this paper, improved discharge cell structures are introduced that favor reduction of the gas breakdown voltage. The simulated electric field profiles for these structures indicate the low voltage requirement with increased electric field concentration in the discharge gap. The experimental measurements of breakdown voltage and discharge delay time in the test panels also support the simulation results. The important features of these discharge cell structures are discussed.     

预试环实验

本文叙述加热场与垂直场分开供电后预试环所作的氢气击穿、平衡、杂散场测量、垂直场波形调整和放电清洗等实验。得到了重复性较好的托卡马克等离子体,其电流峰值为10kA,持续时间2.5ms。     

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.     

Optimum conditions of the runaway electron beam generation during a uniform gas breakdown

It was shown that a uniform breakdown of a gas gap must be accompanied by the Stoletov effect, i.e., a current maximum in pressure at a given voltage pulse. Analogues of the Stoletov constant were calculated for the pulsed non-self-sustained discharge in various gases. These constants also determine the minimum breakdown delay time. It was shown that the maximum current of the electron beam generated in the gas-filled diode is reached at a pressure corresponding to the maximum current and for an electrode spacing corresponding to the electron drift length during the pulse.     

Decrease in the static electric gas breakdown voltage in the presence of free electrons in a discharge gap

The dependence of the gas breakdown voltage U _B on the anode-cathode spacing d, pressure p, and other gas characteristics in the presence of a steady external ionizer in the discharge gap was determined within the avalanche discharge theory. The case was considered where the spatial charge created by the external ionizer did not distort the electric field in the discharge gap. In the absence of external ionizer the obtained dependence comes down to the well-known expression for the gas breakdown voltage (the Paschen law).