神龙二号加速器绝缘环真空沿面闪络北大核心CSCD

在对神龙二号加速器绝缘环进行耐压考核时发现,感应腔中的绝缘支撑部件交联聚苯乙烯绝缘环在猝发多脉冲高压加载下出现的真空沿面闪络现象存在两种类型:阴极始发的闪络击穿和阳极始发的闪络击穿。通过计算绝缘环的沿面电场分布、对比击穿电压波形与绝缘环表面闪络放电烧蚀痕迹,结合小绝缘子样品实验结果对以上沿面击穿现象的机理进行了分析,认为可能是绝缘环端面与电极面的配合问题引起了加速段与注入器绝缘环击穿现象的差异。     

神龙二号加速器绝缘环真空沿面闪络

在对神龙二号加速器绝缘环进行耐压考核时发现,感应腔中的绝缘支撑部件交联聚苯乙烯绝缘环在猝发多脉冲高压加载下出现的真空沿面闪络现象存在两种类型:阴极始发的闪络击穿和阳极始发的闪络击穿。通过计算绝缘环的沿面电场分布、对比击穿电压波形与绝缘环表面闪络放电烧蚀痕迹,结合小绝缘子样品实验结果对以上沿面击穿现象的机理进行了分析,认为可能是绝缘环端面与电极面的配合问题引起了加速段与注入器绝缘环击穿现象的差异。     

纳秒脉冲下高气压SF6中同轴绝缘子沿面闪络影响因素实验研究

研究纳秒脉冲下的绝缘子沿面闪络影响因素对电磁脉冲模拟装置绝缘结构设计具有重要的借鉴意义。通过搭建绝缘子沿面闪络实验平台,实验研究了在0.5 MPa的SF6气体中,脉冲电压波形、绝缘材料和绝缘子沿面场强分布对绝缘子沿面闪络电压的影响。结果表明：绝缘子的闪络电压具有随着脉冲前沿时间减小而增加的趋势;相较于脉冲电压全波,绝缘子在脉冲电压前沿波形耐受下闪络电压较高;聚酰亚胺材料的绝缘性能最好;通过降低绝缘子沿面最大场强,改善电场分布可以有效地提高绝缘子的闪络电压。     

风沙流对高压绝缘子电位和电场分布的影响

研究风沙流对高压绝缘子电位和电场分布的影响,基于有限体积法建立绝缘子风沙气固两相流模型和风沙天气下绝缘子的风-沙-电耦合场模型,计算不同风沙天气下绝缘子表面沙尘的空间分布和沉积及其对绝缘子沿面电位和电场的影响,结果表明：风沙天气下绝缘子沿面电位和电场畸变受风速和粒径影响显著,电位的畸变幅度随风速和粒径的增加而升高,电场的畸变幅度随风速和粒径的增大而减少;风沙天气下绝缘子表面不同的沙尘空间分布和沉积导致绝缘子不同位置沿面电位和电场畸变不同.     

强流束二极管绝缘子结构设计与实验研究

 介绍了一种应用于强流束二极管的径向绝缘结构,并对其在纳秒脉冲条件下的沿面闪络放电现象进行了研究。使用计算机模拟静电场的方法,对锥形结构绝缘子表面的电场分布进行了研究,优化了几何结构参数。在脉宽为40 ns,重复频率100 Hz的脉冲功率源上对绝缘子进行了实验研究。在历时18个月及100 000次脉冲实验后,发现绝缘子表面具有明显的树枝状放电现象,树枝状放电的根部碳化严重,绝缘子深度方向被完全击穿碳化,出现孔洞。基于固-液交界面闪络特性,对树枝状放电的可能原因进行了探讨。     

“神龙二号”气体火花开关中绝缘结构的电场分析与优化

气体火花开关作为重要部件被大量地应用于直线感应加速器和Z箍缩等大型脉冲功率装置中。绝缘结构设计不合理会使得气体火花开关中出现局部电场畸变和电荷积聚等现象。在高电压脉冲下长时间或高频次运行时,火花开关中的绝缘子会发生沿面闪络现象,直接影响到脉冲功率装置的正常运行。鉴于此,对气体火花开关中的绝缘结构进行了有限元电场分析,用表面电荷的积聚定性解释了沿面闪络发生的原因。通过对绝缘子的几何结构和电极尺寸的优化设计,有效降低了绝缘子表面和电极表面的电场强度,其中阳极三结合点场强从9.4 kV/mm降至1.5 kV/mm,阴极三结合点场强从2.95 kV/mm降至0.98 kV/mm,绝缘子表面最高场强从10.8 kV/mm降至4.95 kV/mm。优化后的绝缘结构电场分布较为合理,降低了由于表面电荷的积聚而引发沿面闪络的概率。     

REB二极管的电场计算和实验研究

在百焦耳准分子激光实验中，采用了径向绝缘的大面积强流相对论电子束二极管（简称ＲＥＢ二极管）。对“天光一号”的ＰＦＬ线、有机玻璃隔板以及二极管腔内区域进行了二维轴对称电场计算，得到了直观的等位线图和电场分布图。结合二极管实验对计算结果进行了分析，用耐压因子概念解释沿面滑闪问题。另外，对一台焦耳级准分子激光加速器的二极管进行了优化电场设计。进行了有关改善三结合处电场分布的实验研究，给出三结合处电场强度在小于３ｋＶ／ｃｍ时，不会发生真空沿面击穿的结论。     

Blumlein主放电开关中绝缘结构对沿面闪络电压的影响北大核心CSCD

Blumlein主放电开关作为关键部件被大量地应用于强流电子直线感应加速器等大型脉冲功率装置中,其中绝缘子在主开关中起隔离水或油与气体的作用。设备在高电压脉冲下长时间或高频次作用时,绝缘子气体侧会出现沿面闪络现象,严重影响直线感应加速器的可靠运行。对Blumlein主放电开关中的绝缘结构进行了电场仿真计算,通过对绝缘子的几何结构和电极形状的优化设计,有效调控了绝缘子表面和电极表面的电场分布,试制了不同构型的绝缘子,开展了在标准雷电波脉冲条件下的沿面闪络研究。研究结果表明,优化后的绝缘子的最低和最高沿面闪络电压相比原始结构分别提升了约35.9%和37.2%。     

电极熔蚀导致的气体开关绝缘子性能劣化

气体开关导通时,电极材料熔融或汽化并从电极表面移出,导致开关绝缘子被染污,并可能诱发开关内绝缘闪络事故,直接影响气体开关寿命和脉冲功率系统稳定性。在开关内嵌入有机玻璃圆环,收集黄铜电极熔蚀产物,并研究其对开关绝缘子表面形貌和沿面绝缘强度的影响。实验结果表明,电极熔蚀会产生大量金属蒸汽和溅射液滴,且熔蚀产物具有明显的轴向分布特性,其中,金属蒸汽冷凝并附着在绝缘子表面,形成细微的金属粉末;溅射液滴轰击绝缘子表面,在局部区域形成密集的表面裂纹和金属颗粒嵌入物。在两种电极熔蚀产物的共同作用下,开关绝缘子表面绝缘电阻下降,闪络场强降低;同时,绝缘子表面轴向不同区域的绝缘电阻差别很大,引起绝缘子表面电压分布不均和局部电场增强,最终导致开关绝缘子闪络电压降低,闪络概率增大。     

多间隙气体开关绝缘子寿命

针对设计的一种堆栈式结构多间隙气体开关,分析了绝缘子污染对开关寿命的影响机理。对绝缘子表面电场分布进行了模拟计算,实验研究了绝缘子污染对开关自击穿电压的影响,得到了开关自击穿电压和绝缘子表面绝缘电阻的变化规律,开关在放电电流32 kA实验条件下工作13 000次后,自击穿电压平均值由171.5 kV降低至130.8 kV,绝缘子表面绝缘电阻由200 G下降至22.6 G,绝缘子已无法正常使用。同时提出了提高绝缘子抗污染能力、延长绝缘子寿命的措施和方法。     

Insulator-surface flashover conditioning: A streak photographicinvestigation

Conditioning behavior of surface flashover strength of a large-bandgap insulator (quartz) is investigated with the aid of streak photography in conjunction with electrical (voltage and current) and optical UV (phototube) diagnostics. The breakdown strength of the sample is found to be conditioned during the initial test as well as the subsequent test, performed after an overnight rest period. The results suggest that light emission during the initial test is dominated by visible light whereas during the subsequent test it is dominated by UV. The initial conditioning is attributed primarily to the desorption of absorbed molecules and rearrangement of the same by migration kinetics. Processes such as negative charge formation on the insulator surface and trapping of electrons in the deep traps are proposed to be responsible for the observed conditioning after the overnight rest period. The breakdown strength of the sample was found to degrade after experiencing breakdown at higher fields (i.e., after second day test). This deconditioning behavior is discussed in terms of evaporation of electrode material and deposition of the same on the insulator near the cathode end     

Characterization of charge distribution on the high voltage glass insulator string

Irregularity in charge distribution of an insulator may lead to accelerated aging and electrical breakdown. However, knowledge of charge distribution on the insulation surface is still insufficient albeit has gained worldwide attention. The insufficiency is particularly on the charge profile along the string insulator under AC excitation. Therefore, charges distributions on the surfaces of glass insulators without installed grading ring are investigated in this paper. Simulation and experimental results were found in good agreement when studying the charge distribution pattern along glass insulator string where the polarity of charge swinging occurs at the center of suspension string insulator of I-type.     

Electroforming and electric breakdown of a thin-film MIM system

The influence of the voltage polarity and also the thickness and material of the upper electrode on the electroforming and breakdown of a thin-film MIM system has been investigated. It is shown that the processes in the insulator in the breakdown and forming have the same nature. On the basis of the experimental results it is concluded that the main factors which distinguish the forming from the breakdown are the magnitude of the energy deposition on the formation of a discharge channel in the insulator and the nature of the gas release from the discharge channel. These determine the geometrical sizes and morphology of the defects formed in the MIM system under the influence of the voltage and are in the one case formed channels and in the other breakdown channels.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 58–63, January, 1992.     

Electrical breakdown of dysprosium oxide films

The principal laws governing the electrical breakdown of dysprosium oxide films in silicon metal — insulator — semiconductor structures are investigated. The dependence of the breakdown field E_br on the rise rate of the voltage on the structure K_v, the temperature, the material and area of the electrode, and the humidity of the environment is studied. The dependence of the time delay of breakdown on the amplitude of a rectangular voltage pulse is investigated. It is established that the breakdown field increases linearly with log K_v for all insulator thicknesses, and the saturation of E_br is observed at K_v>10⁵ V/sec. It is found that E_br does not depend on the electrode material and decreases as the area of the electrode or the temperature is increased. The maximum breakdown field is determined: E _br ^max =14 MV/cm. The mechanism of the precursory stage of breakdown, i.e., the period of transient buildup of critical charge in the insulator, is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 95–101, August, 1995.     

A simple knife-edge design for initial phase optimization in plasmafocus

A simple knife-edge design was described that enabled easy optimization and investigation of the initial phase for the plasma focus devices. It enhanced the initial breakdown process along the insulator surface by allowing free adjustment or fine-tuning of the insulator length and by forming a sharp knife-edge with effective field emission. The plasma pinching was much improved with neutron yield equal or above that predicted by the scaling law. This knife-edge design is especially suitable for the optimization of medium and large-scale plasma focus devices where it would be otherwise rather difficult to modify the insulator configuration directly     

Exploring the warped bulk

In this study, a gallium nitride (GaN) high electron mobility transistor (HEMT) with recessed insulator and barrier is reported. In the proposed structure, insulator is recessed into the barrier at the drain side and barrier is recessed into the buffer layer at the source side. We study important device characteristics such as electric field, breakdown voltage, drain current, maximum output power density, gate-drain capacitance, short channel effects and DC transconductance using two-dimensional and two-carrier device simulator. Recessed insulator in the drain side of the proposed structure reduces maximum electric field in the channel and therefore increases the breakdown voltage and maximum output power density compared to the conventional counterpart. Also, gate-drain capacitance value in the proposed structure is less than that of the conventional structure. Overall, the proposed structure reduces short channel effects. Because of the recessed regions at both the source and the drain sides, the average barrier thickness of the proposed structure is not changed. Thus, the drain current of the proposed structure is almost equivalent to that of the conventional transistor. In this work, length (L _r) and thickness (T _r) of the recessed region of the barrier at the source side are the same as those of the insulator at the drain side.     

One-dimensional breakdown voltage model of SOI RESURF lateral power device based on lateral linearly graded approximation

A novel one-dimensional(1D) analytical model is proposed for quantifying the breakdown voltage of a reduced surface field(RESURF) lateral power device fabricated on silicon on an insulator(SOI) substrate.We assume that the charges in the depletion region contribute to the lateral PN junctions along the diagonal of the area shared by the lateral and vertical depletion regions.Based on the assumption,the lateral PN junction behaves as a linearly graded junction,thus resulting in a reduced surface electric field and high breakdown voltage.Using the proposed model,the breakdown voltage as a function of device parameters is investigated and compared with the numerical simulation by the TCAD tools.The analytical results are shown to be in fair agreement with the numerical results.Finally,a new RESURF criterion is derived which offers a useful scheme to optimize the structure parameters.This simple 1D model provides a clear physical insight into the RESURF effect and a new explanation on the improvement in breakdown voltage in an SOI RESURF device.     

A new analytical model for the surface electric field distribution and breakdown voltage of the SOI trench LDMOS

A new analytical model for the surface electric field distribution and breakdown voltage of the silicon on insulator (SOI) trench lateral double-diffused metal-oxide-semiconductor (LDMOS) is presented. Based on the two-dimensional Laplace solution and Poisson solution, the model considers the influence of structure parameters such as the doping concentration of the drift region, and the depth and width of the trench on the surface electric field. Further, a simple analytical expression of the breakdown voltage is obtained, which offers an effective way to gain an optimal high voltage. All the analytical results are in good agreement with the simulation results.