多路高电压纳秒矩形波脉冲发生器的研制

为满足脉冲功率实验中对多路高电压纳秒矩形波激励的需求,研制了一台21路高电压纳秒矩形波发生器。此发生器由一个单路高电压纳秒矩形波脉冲发生器和一个21路分路器组成。其中单路高电压纳秒矩形波脉冲发生器可输出幅值约1.07kV、半高宽约10ns、上升沿约1.45ns的矩形波脉冲。利用21路分路器可将该矩形波脉冲分为21路矩形波脉冲,测得每路脉冲幅值可达51V,半高宽约为10ns,上升沿约为2.25ns。     

快上升沿电磁脉冲作用下PIN二极管中的电流过冲现象

 为了研究瞬态电磁脉冲对PIN二极管的干扰，利用基于扩散漂移模型的基本半导体方程，采用半导体器件一维瞬态数值仿真的方法,对快上升沿阶跃电磁脉冲作用下PIN二极管中的电流密度和电荷密度分布的变化进行了研究，分别观察了正反偏电压脉冲作用下过冲电流的产生过程并进行了分析。分析表明，过冲电流是和PIN二极管在高频下的容性表现相关的，无论是在正电压还是负电压情况下，脉冲上升沿时间越短、初始正偏压越高，则过冲电流密度的峰值越高。     

电磁脉冲作用下PIN二极管的响应

采用自主开发的二维半导体器件效应模拟软件,对电磁脉冲作用下PIN二极管的响应进行了数值模拟研究,分析了PIN管在脉冲电压上升沿时间内出现的电流过冲现象。结果表明:过冲电流与高频下PIN二极管的电容性有关,过冲电流的峰值与上升沿时间有关,上升沿时间越短,峰值越大;PIN管的掺杂也会对过冲电流产生影响,P层、N层的掺杂浓度越高,过冲电流的峰值越大,过冲电流的波形下降越快;I层掺杂浓度对过冲电流也有一定影响,但并不显著。     

不同条件下大气压脉冲弥散放电特性

利用上升沿约0.5 s、半高宽约6 s、幅值可达40 kV的微秒脉冲电源和上升沿约150 ns、半高宽约300 ns、幅值可达50 kV的纳秒脉冲电源激励大气压弥散放电,并分别采用刀型和锯齿电极放电。通过电压电流测量和发光图像拍摄,改变施加电压种类、脉冲重复频率、高压电极结构和气隙距离等参数,研究了不同条件下弥散放电特性。实验结果表明:纳秒脉冲电源和微秒脉冲电源均能在大气压空气中激励大面积的弥散放电,弥散放电面积最大达90 cm2;放电的均匀性受脉冲参数与电极形状影响显著,其中刀型电极条件下纳秒脉冲激励的弥散放电均匀性最佳;相同条件下纳秒脉冲弥散放电的瞬时功率大于微秒脉冲弥散放电,最高可达275 kW,而纳秒脉冲弥散放电的能量小于微秒脉冲弥散放电;保持其他条件不变,弥散放电传导电流幅值随着气隙距离的增加而降低,放电强度随着脉冲重复频率的增加而增强,弥散放电的工作电压范围随着脉冲重复频率的增加显著降低。因此在低频、刀型电极结构中易于获得均匀与较大工作电压范围的大气压弥散放电。     

宽带高抑制性能电磁脉冲防护电路设计与实验

强电磁脉冲易通过天线、孔缝、线缆等多种耦合途径进入电子系统内部,造成敏感电子设备出现短暂故障或永久损毁。安装电磁脉冲防护电路可有效提高电子设备抗强电磁脉冲能力。基于LC选频网络和瞬态电压抑制(TVS)二极管,设计了一种宽带高抑制性能电磁脉冲防护电路,防护电路工作带宽超过2 GHz、插入损耗低于0.6 dB。系统性研究了防护电路对频谱分布在工作带宽内多种电磁脉冲(方波脉冲、宽带高功率微波、窄带高功率微波)的防护能力。结果表明:防护电路对不同类型电磁脉冲电压抑制比大于40 dB、耐受功率超过387 kW、而响应时间仅0.7 ns。该防护电路具有工作频带宽、电磁抑制性能好、响应速度快、耐受功率高等特点,对电子信息系统电磁防护加固具有重要意义。     

大气压空气中重复频率纳秒脉冲气体放电模式研究

利用上升沿100ns、脉宽150ns的单级磁压缩纳秒脉冲电源,通过电压电流测量和放电图像拍摄实验,研究了大气压空气中极不均匀电场结构重复频率纳秒脉冲气体放电的放电模式。结果表明纳秒脉冲气体放电存在三种典型的放电模式:电晕放电、弥散放电和火花放电。施加的脉冲电压幅值对放电模式影响显著,随着电压幅值的增加,放电依次经历电晕、弥散和火花放电。固定电压幅值时,放电可能同时存在两种模式。重复频率加强了放电强度,弥散放电的激发电压随重复频率的增加变化不大,但火花放电的激发电压随着重复频率的增加而降低。因此降低重复频率有利于在较大电压范围获得大气压空气弥散放电。     

紧凑型重复频率高压纳秒脉冲电源及其仿真模型

纳秒脉冲等离子体在诸多实际的工程应用中依赖于小型化且可靠的纳秒脉冲电源实现。设计了一种紧凑型全固态高压纳秒脉冲电源,该电源主要由直流电源部分、绝缘栅双极晶体管及其驱动控制电路、可饱和脉冲变压器、磁脉冲压缩网络等组成。通过理论计算分析、PSpice电路仿真以及实验研究表明,其最终可以在800 的输出负载阻抗上获得幅值40 kV、脉冲宽度100 ns左右、脉冲上升沿约50 ns的高电压脉冲,重复频率最高可达5 kHz。     

变压器寄生参数和负载特性对高压脉冲波形的影响

构建了输出电压幅值为0～20 kV、脉冲重复频率为0.25～20 kHz的双极性高压脉冲电源实验平台,研究了变压器寄生参数与负载特性对输出脉冲波形的影响。采用等效电路复频域解析方法,分析了变压器寄生参数对输出脉冲波形的上升沿、平顶及下降沿的影响规律,并通过改变变压器绕线方案间接验证。发现变压器分布电容和漏感越大,输出脉冲波形上升沿与下降沿越平缓,过冲电压幅值越大,并采用脉冲变压器二次侧均匀密绕、一次侧均匀疏绕、高匝数的方案进行优化。进一步分析了纯阻性、阻容性或阻感性负载特性对输出高压脉冲波形的影响规律,发现电阻值增大（5～50 kΩ）,过冲电压幅值增大,脉冲上升沿和下降沿变陡;当负载电阻回路串联小电容时,过冲电压幅值显著增大,而电容值高于一定值时输出脉冲波形恢复至与纯电阻波形一样;当负载电阻回路串联电感时,输出脉冲波形下降沿变平缓。     

车辆线缆瞬态电磁脉冲耦合仿真与抑制技术

瞬态电磁脉冲可通过车辆互联线缆耦合至电子系统内部，造成电子设备受扰甚至损毁，研究瞬态防护器件对电磁脉冲的抑制特性可为车辆电磁防护设计与实施提供有力支撑。本文以发动机电控系统为研究对象，考虑关键金属结构、线缆与电子设备，建立发动机电磁仿真模型，计算获取了瞬态电磁脉冲作用下线缆端口耦合干扰特性；基于电磁脉冲注入方法设计并搭建了瞬态防护器件测试平台，获取了瞬态电压抑制器与压敏电阻两类典型瞬态防护器件的响应时间、钳位电压、尖峰泄露等响应特性；在仿真与测试结果的基础上，选取一型瞬态电压抑制器应用于凸轮轴位置传感器信号线的电磁防护。研究结果表明，该型瞬态电压抑制器对线缆瞬态电磁脉冲耦合干扰抑制能力接近20 dB，置于滤波器前端可有效抑制线缆耦合干扰，保护终端设备。     

基于半导体开关和LTD技术的高重频快沿高压脉冲源

采用快开通功率MOSFET,通过优化驱动电路、磁芯参数以及耦合结构,设计了基于半导体开关和直线变压器驱动源（LTD）技术的高重频快沿高压脉冲源。该脉冲源由四级LTD串联而成,可实现单次脉冲和最高频率2 MHz脉冲串输出。脉冲最高幅值约2.3 kV,上升沿约7 ns,脉宽约90 ns,下降沿约20 ns,输出电压效率约95%。该脉冲源结构紧凑,输出脉冲稳定,实现了模块化设计,可作为重频电磁脉冲模拟源使用。     

短波接收天线系统核电磁脉冲注入试验

为评估高空核电磁脉冲(HEMP)对某型短波接收天线系统的威胁,对包含浪涌保护器在内的天线前端设备进行HEMP传导注入试验。采用纳秒级快前沿方波源和双指数波电流源,分别测试不同浪涌保护措施的快脉冲响应。结果表明,主要由于天线末端的气体放电管在高过压比下很快动作(1 ns量级)、信号浪涌保护器内瞬态电压抑制器(TVS)限幅、信号传输设备内放大器饱和限幅等多重作用,注入幅度约3.5 kV的快前沿方波、电流峰值1.8 kA的双指数波(20/500 ns)脉冲都能及时泄放,只在传输设备输出端产生一个幅度饱和(< 3 V)、持续μs量级的干扰信号。对这一类低工作电压天线系统,利用基于市售浪涌保护器的多重防雷措施能够同时实现对核电磁脉冲传导环境的防护。     

Nanosecond discharge in sulfur hexafluoride and the generation of an ultrashort avalanche electron beam

A discharge in the presence of a nonuniform electric field and the generation of an ultrashort avalanche electron beam (UAEB) are studied in the insulating gas SF₆ at the pressures 0.01–2.50 atm. High-voltage nanosecond pulses (about 150 and 250 kV) and the voltage pulses with an amplitude of 25 kV and a duration of tens of nanoseconds are applied across the gap. An electron beam is obtained behind the AlBe foil with a thickness of 45 μm at a sulfur hexafluoride pressure in a gas-filled diode of up to 2 atm. It is demonstrated that, at relatively high pressures (greater than 1 atm) and in the presence of high-voltage nanosecond pulses across the gap, the UAEB pulse FWHM increases. The spectra of the diffuse and contracted discharges in sulfur hexafluoride are measured.     

高压多脉冲硅堆汇流结构

利用形成线并联的方法产生高压三脉冲,需要在形成线和加速腔负载间串联硅堆隔离网络,以隔离不同形成线间的相互影响,并将不同形成线先后产生的高压脉冲汇流成三脉冲串传输到加速腔。硅堆放置于封闭的油箱中,箱体结构的设计将直接影响汇流后三脉冲的波形品质和硅堆的使用寿命。通过对高压硅堆内部电势分布的模拟分析和实验验证,明确了影响硅堆使用寿命的主要原因;设计实验测量了汇流结构各部分对汇流脉冲前沿的影响程度,综合分析汇流结构对硅堆使用寿命的影响,明确了汇流结构的优化方向,并在此基础上确定了神龙二号三脉冲直线感应加速器硅堆汇流结构的最终设计。     

250 kV，1 MHz重复率方波三脉冲源

 阐述了一种新的实现高功率高重复率方波脉冲源的技术途径，利用高压快恢复整流硅堆把三个独立的方波脉冲合成为一个MHz重复率的方波三脉冲。通过合理的串并联设计，可以提高硅堆在高频脉冲下的反向耐压，并使硅堆通过的正向脉冲电流达到kA量级。方波三脉冲源输出指标达到了电压250 kV，脉冲电流10 kA，峰值功率2.5 GW，重复率1 MHz，脉冲上升时间约40 ns，脉冲平顶宽度50 ns。     

Electron flux spatial distribution in an ultrashort avalanche electron beam generated at atmospheric air pressure

The results of experimental study on generation of ultrashort avalanche electron beams (UAEB) in gas-filled diodes are considered. The spatial distribution of the flux of runaway electrons and X-rays generated in the gas diode fed by nanosecond high-voltage pulses was studied. It was shown that the UAEB in the gas-filled diode (at an air pressure of 1 atm) with sharply nonuniform electric field is generated from the interelectrode region into a solid angle exceeding 2π sr. Narrowing of the cathode-anode gap results in a decrease in the current amplitude of the beam generated to side walls of the gas diode and an increase in the beam current pulse duration in both axial and radial directions. Current pulses of the beam initiated from the side surface of the tubular cathode were detected.     

Magnetic-spiker excitation of gas-discharge lasers

A review is presented on the use of magnetic-spiker circuits to electrically excite rare-gas-halide and CO₂ gas-discharge lasers. The design and operation of the diode, switch, overshoot, and charge modes of magnetic-spiker excitation will be described. Special emphasis has been placed upon understanding the dynamical behaviour and saturation properties of the magnetic core material at high frequencies. The effect of voltage risetime, preionization, pulse-forming network design, and prefire on laser performance is also described. Experimental data are presented on a new and very simple magnetic-spiker circuit called the modified overshoot mode. A relatively long optical pulse magnetic-spiker KrF laser is also desribed which uses self-timed corona preionization initiated by the spiker circuit. The use of magnetic-spiker excitation to produce high output laser energies, high repetition rates, and long optical pulses is discussed. Applications of magnetic-spiker lasers in the field of medicine, microelectronics and materials processing will be reviewed.     

Radiation hardness of gas discharge tubes and avalanche diodes used for transient voltage suppression

The widespread use of gas discharge tubes (GDTs) and avalanche diodes for transient voltage suppression (TVS) in many cases results in their exposure to ionizing radiation. The aim of this paper is to investigate the influence of irradiation on these TVS devices’ characteristics, by exposing them to a combined neutron/gamma radiation field. Experimental results show that irradiation of TVS diodes causes a lasting degradation of their protective characteristics. On the other hand, GDTs exhibit a temporary change of performance. The observed effects are presented with the accompanying theoretical interpretations, based on the interaction of radiation with materials constituting the investigated devices.     

低抖动纳秒级前沿的氢闸流管高压脉冲源

 试验用功率MOSFET驱动氢闸流管，做成幅度可达15kV、前沿小于10ns、抖动低于1ns的高压纳秒级前沿脉冲源。简要介绍了脉冲源的电路结构，着重从氢闸流管储氢器加热电压、阴极加热电压、触发脉冲幅度、前沿和延迟几方面测量分析了其对脉冲源输出特性的影响。     

Modeling of transient electroluminescence overshoot in bilayer organic light-emitting diodes using rate equations

When a voltage pulse is applied under forward biased condition to a spin-coated bilayer organic light-emitting diode (OLED), then initially the electroluminescence (EL) intensity appearing after a delay time, increases with time and later on it attains a saturation value. At the end of the voltage pulse, the EL intensity decreases with time, attains a minimum intensity and then it again increases with time, attains a peak value and later on it decreases with time. For the OLEDs, in which the lifetime of trapped carriers is less than the decay time of the EL occurring prior to the onset of overshoot, the EL overshoot begins just after the end of voltage pulse. The overshoot in spin-coated bilayer OLEDs is caused by the presence of an interfacial layer of finite thickness between hole and electron transporting layers in which both transport molecules coexist, whereby the interfacial energy barrier impedes both hole and electron passage. When a voltage pulse is applied to a bilayer OLED, positive and negative space charges are established at the opposite faces of the interfacial layer. Subsequently, the charge recombination occurs with the incoming flux of injected carriers of opposite polarity. When the voltage is turned off, the interfacial charges recombine under the action of their mutual electric field. Thus, after switching off the external voltage the electrons stored in the interface next to the anode cell compartment experience an electric field directed from cathode to anode, and therefore, the electrons move towards the cathode, that is, towards the positive space charge, whereby electron–hole recombination gives rise to luminescence. The EL prior to onset of overshoot is caused by the movement of electrons in the electron transporting states, however, the EL in the overshoot region is caused by the movement of detrapped electrons. On the basis of the rate equations for the detrapping and recombination of charge carriers accumulated at the interface expressions are derived for the transient EL intensity I, time t_m and intensity I_m corresponding to the peak of EL overshoot, total EL intensity I_t and decay of the intensity of EL overshoot. In fact, the decay prior to the onset of EL overshoot is the decay of number of electrons moving in the electron transporting states. The ratio I_m/I_s decreases with increasing value of the applied pulse voltage because I_m increases linearly with the amplitude of applied voltage pulse and I_s increases nonlinearly and rapidly with the increasing amplitude of applied voltage pulse. The lifetime τ_t of electrons at the interface decreases with increasing temperature whereby the dependence of τ_t on temperature follows Arrhenius plot. This fact indicates that the detrapping involves thermally-assisted tunneling of electrons. Using the EL overshoot in bilayer OLEDs, the lifetime of the charge carriers at the interface, recombination time of charge carriers, decay time of the EL prior to onset of overshoot, and the time delay between the voltage pulse and onset time of the EL overshoot can be determined. The intense EL overshoot of nanosecond or shorter time duration may be useful in digital communication, and moreover, the EL overshoot gives important information about the processes involving injection, transport and recombination of charge carriers. The criteria for appearance of EL overshoot in bilayer OLEDs are explored. A good agreement is found between the theoretical and experimental results.