气体开关串级环形间隙放电相互影响机制研究

针对中空和非中空触发电极结构的两间隙开关,进行了触发击穿特性实验,对比两个间隙的击穿抖动和通道数,分析了串级两间隙的相互影响机制。实验结果表明：两只开关触发间隙击穿抖动和通道数变化规律基本一致;非中空开关自击穿间隙击穿抖动随工作系数的增大而减小,最小约3 ns,中空开关自击穿间隙击穿抖动始终约1 ns;非中空开关自击穿间隙难形成多通道放电,中空开关自击穿间隙通道数明显多于其他间隙。触发间隙首先放电产生紫外光,通过触发电极中空通孔预先照射自击穿间隙产生初始电子,是自击穿间隙击穿抖动减小、通道数增加的主要作用机制。     

A two-dimensional air streamer discharge modified model based on artificial stability term under non-uniform electric field at low temperature and sub-atmospheric pressure

In this paper, an improved air discharge fluid model under non-uniform electric field is constructed based on the plasma module COMSOL Multiphysics with artificial stability term, and the boundary conditions developed in the previous paper are applied to the calculation of photoionization rate. Based on the modified model, the characteristics of low temperature subatmospheric air discharge under 13 kV direct current voltage are discussed, including needle-plate and needle-needle electrode structures. Firstly, in order to verify the reliability of the model, a numerical example and an experimental verification were carried out for the modified model respectively. Both verification results show that the model can ensure the accuracy and repeatability of the calculation. Secondly, according to the calculation results of the modified model, under the same voltage and spacing, the reduced electric field under low temperature subatmosphere pressure is larger than that under normal temperature and atmospheric pressure. The high electric field leads to the air discharge at low temperature and sub atmospheric pressure entering the streamer initiation stage earlier, and has a faster propagation speed in the streamer development stage, which shortens the overall discharge time. Finally, the discharge characteristics of the two electrode structures are compared, and it is found that the biggest difference between them is that there is a pre-ionization region near the cathode in the needle-needle electrode structure. When the pre-ionization level reaches 10~(13) cm~(-3), the propagation speed of the positive streamer remains unchanged throughout the discharge process, and is no longer affected by the negative streamer. The peak value of electric field decreases with the increase of pre-ionization level, and tends to be constant during streamer propagation. Based on the previous paper, this paper constructs the air discharge model under non-uniform electric field, complements with the previous paper, and forms a relatively complete set of air discharge simulation system under low temperature and sub atmospheric pressure, which provides a certain reference for future research.     

预电离效应对ArF准分子激光特性的影响分析

利用流体模型对ArF准分子激光气体放电过程进行了数值模拟,通过对比不同初始预电离强度下的气体放电情况,分析了预电离效应对准分子激光系统放电特性的影响,并探究了不同气体参数下的预电离效果。结果表明,初始预电离强度对于极间击穿电压、ArF准分子的形成以及光输出特性均有显著影响。在保证均匀电场且有效放电的情况下,低的初始预电离强度难以“点燃”气体,但可以获得较高的激光输出能量,而提高初始预电离强度能有效降低击穿电压,却不利于气体对能量的吸收转化。此外,预电离效果受工作气压与F₂比例的影响,气压的升高或F₂浓度的增加,均会降低预电离的有效性。     

脉冲预电离纵向脉冲放电CO2激光器

提出了一种横向脉冲预电离小型扩散冷却纵向脉冲放电CO2激光器。在内径7.5mm、放电长度50cm的放电区实现了脉冲能量15mJ、脉冲峰值功率375W的激光输出。脉冲重复频率56Hz。预电离电极结构设计成螺旋状,改善了激光的光束质量。     

A low-jitter self-triggered spark-discharge pre-ionization switch:primary research on its breakdown characteristics and working mechanisms

MV pulsed switch plays a key role as the transfer switch in large electromagnetic pulse simulators.To broaden the range of self-triggering time,a novel spark-discharge pre-ionization switch,in which the main gap electric field is superposed at the trigger gap to let the electrons in its spark channel also become initial electrons,is proposed and tested.The design idea is:as electrons in the spark channel of the trigger gap always exist after its breakdown,the injection time of pre-ionization should have a more negligible effect on reducing the switch jitter.The experiment results under pulses with a rise time of～100 ns support the above assumptions.When the operating voltage is from～300 to～800 kV and the self-triggering time is～45％to～75％of the peak time,the breakdown time delay jitter is less than 2 ns,and the breakdown voltage jitter is smaller than 1.25％.Under specific self-triggering time,the breakdown time delay jitter is less than 1.5 ns,and the breakdown voltage jitter is smaller than 0.8％.     

Diffuse volume-discharges without pre-ionization formed in SF6 and C2H6 mixtures

It has been shown that a volume discharge is forming in non-uniform electric-field rough cathode and even anode without pre-ionization in SF6 and C2H6 mixtures. The discharge is presented with many diffuse channels attached to bright circular cathode spots that diverge towards the anode, with the channels overlapping, form a spatially uniform glow discharge. Self-Initiated Volume Discharge （SIVD） has been performed at a total mixture pressure up to 8 kPa and energy deposition up to 200 J/L. The experimental results indicate that Self-Sustained Volume Discharge （SSVD） in SF6 and C2H6 mixtures develops in the form of SIVD, which is promising for creation of high energy and pulse-pe- riodic HF laser.     

2kHz重复频率紧凑型TEA CO2激光器

报道了一种高脉冲重复频率,紧凑型横向激励大气压CO2激光器.激光器使用紫外电晕预电离方式,放电均匀、稳定.自由振荡情况下,激光脉冲输出能量达到15 mJ,输出脉冲宽度为60 ns.气体高速循环系统采用涡轮增压技术,最高循环风速可达100 m/s以上,激光脉冲重复频率为2 kHz.     

Microwave-assisted pre-ionization experiments on GLAST-Ⅲ

GLAss Spherical Tokamak(GLAST-Ⅲ) is a spherical tokamak with an insulating vacuum vessel that has a unique single-passage capability for incident microwaves.In this work,electron cyclotron resonance heating(ECRH)-assisted plasma pre-ionization in GLAST-Ⅲ is explored for three radio-frequency(RF) polarizations(the O-,X-,and M-modes) at different toroidal-field(TF) strengths and filled gas pressures.The optimum hydrogen pressure is identified for efficient plasma pre-ionization.A comparison of the plasma pre-ionizations initiated by the O-,X-,and M-modes shows prominent differences in the breakdown time,location,and wave absorption.In the case of O-mode polarization,microwave absorption occurs for a relatively shorter duration,resulting in a bell-shaped electron-temperature(T_e) temporal profile.Microwave absorption is dominant in the case of the X-mode,leading to a broader T_e temporal profile.The M-mode discharge contains features of both the X-and O-modes.Efficient plasma pre-ionization is achieved in the X-mode polarization for the intermediate TF strengths(with a central toroidal magnetic field B_0=0.075 T).Traces of the electron-number density show a similar tendency,as revealed by T_e.These results suggest that the X-mode is the best candidate for efficient plasma pre-ionization at low filled gas pressures(~10~(-2) Pa) in small tokamaks.     

连续预电离脉冲氙灯电源研究

设备采用外触发预电离模式,分别设计了高压触发和预燃电流维持两个功能,同时支持手动和自动两种触发模式。在连续预电离状态下氙灯放电电流达到200mA,该状态下能保证灯内一直有电流流过,同时在主放电压1 400V下氙灯可顺利完成主放电。该配套设备已成功应用在主动补偿脉冲发电机驱动带脉冲预燃电源系统中。