强流平板二极管阻抗特性分析

在“剑光一号”上搭建了二极管平台,理论估计了二极管阻值,进行了平板二极管阻抗和束流分布测量实验。结合法拉第筒阵列测得的束流密度分布、粒子模拟(PIC)仿真结果对二极管阻抗特性进行了全面的对比分析。结果表明,二极管工作于弱箍缩状态,阻抗阻值略低于估计值,阻抗曲线、法拉第筒波形以及束流箍缩程度三者间存在高度的相关性。当阻抗曲线处在前端(导通前)和末期(崩溃段)时,束流均处在未箍缩期间,法拉第筒信号无有效数据;阻抗曲线处在平区时,二极管工作平稳,束流箍缩情况和法拉第筒信号稳定,阳极边缘处的法拉第筒波形呈现双峰,与束流箍缩运动情况相符。     

恒流二极管及其用法

<正> 恒流二极管是庞大的二极管家族中的一员。在理想状态时,加在恒流二极管上的电压不管为何值,流过它的电流始终为一恒定值I_(H);恒流二极管的等效交流电阻力∞。图1示出了恒流二极管的符号,A为阳极,K为阴极。图2示出了恒流二极管的典型伏安特性曲线。当电压在0～V_S段内上升时,电流线性上升;电压在V_S～V_B段升高时,曲线上升趋缓并变得平坦,此     

用数字万用表巧测恒流二极管的I_H

<正> 测试方法及原理 恒流二极管CRD属于两端结型场效应恒流器件。主要参数有恒定电流I_H、起始电压Vs、正向击穿电压V_(BO)等。 笔者在实践中发现:可以利 用数字万用表的h_(FE)挡检测恒流 二极管的恒定电流I_H,方法是通 过DT1000型(或DT830型)数字 万用表h_(FE)的显示值换算出电流 值。这种测量方法简单实用、快捷     

2400系列数字源表在二极管测试中的应用

Keithley2400系列数字源表是一系列具有电流电压输出和测试功能的新型测试设备,可以用于电位器、电阻排及连接器等多方面的测试工作。本文介绍如何使用该系列产品建立二极管测试系统。 二极管在出厂前必须进行三项直流参数测试:正向电压(V_F)、击穿电压(V_R)和反向漏流(I_R)测试。通常上述测试需要几台仪器完成,如:数字表,电压源,电     

稳压二极管的测试

<正> 稳压二极管是电子产品中最常用的元件之一,它的主要参数有稳定电压(Vz)、稳定电流(Iz)、最大稳定电流(Izm)、电压温度系数(C_Tv)、动态电阻(Rz)、耗散功率(Pz)、正向压降(V_F)、反向电阻(R_R)、反向电流(I_R)等等。对于这些参数的精确测试,必须借助于专用设备和精密仪表,而在一般维修或业余条件下人们往往最为关注的是稳压二极管的性能和稳定电压值有多大。本文介绍用万用表、兆欧表和简单的自制电路判断稳压二极管性能和测试其参数稳定电压的方法。     

接线简便的恒流二极管

大家对稳压二极管很熟悉,有读者就会问,既然有稳压二极管,那么有没有稳流二极管呢？答案是肯定的,但通常不把这种器件叫稳流二极管,而是叫恒流二极管。恒流二极管（英文缩写为CRD）简称、匣流管”．是一种能在很宽的电压变化范围内提供恒定电流的半导体两端器件。     

真空二极管光电转换效率研究

在光子增强型热电子发射转换机制的理论基础上,研究了NaCsSb真空二极管在光照和加热条件同时作用下的表现.光电转换效率实验测试了在不同波长以及不同温度条件下,NaCsSb真空二极管的电流-电压曲线和功率-电压曲线,并计算了NaCsSb真空二极管的光电转换效率.实验结果表明,光照和加热条件共同具备时,NaCsSb真空二极管产生的功率约为仅提供光照条件时的两倍多.在同一波长下,加热时的真空二极管转换效率更高.     

一种有机/金属肖特基二极管的实验研究

提出了一种简单有效的有机/金属肖特基二极管的制备方法:通过简单的真空气相沉积工艺,依次将有机材料PTCDA(C24H8O6)薄膜和金属电极Au蒸镀在透明导电玻璃ITO上.通过在室温条件下对该二极管的电流-电压(I-V)特性的测试发现,其整流系数可达104.根据标准肖特基理论以及实验所得电容-频率(C-f)和电容-电压(C-V)的测试结果,得到该有机肖特基势垒高度在0.2～0.3eV范围内.     

一种有机/金属肖特基二极管的实验研究

提出了一种简单有效的有机/金属肖特基二极管的制备方法:通过简单的真空气相沉积工艺,依次将有机材料PTCDA(C24H8O6)薄膜和金属电极Au蒸镀在透明导电玻璃ITO上.通过在室温条件下对该二极管的电流-电压(I-V)特性的测试发现,其整流系数可达104.根据标准肖特基理论以及实验所得电容-频率(C-f)和电容-电压(C-V)的测试结果,得到该有机肖特基势垒高度在0.2～0.3eV范围内.     

沟道掺杂浓度对恒流二极管电学特性的影响

设计了一种基于N－JFET结构的恒流二极管,分析了其沟道掺杂浓度与恒流值、开启电压、击穿电压以及温度特性之间的关系。利用SILVACO仿真软件对恒流二极管沟道掺杂分布进行优化设计,最终得到一个开启电压为2 V,击穿电压大于90 V,恒流值为40 mA,温度系数为－0．33%/K的恒流二极管。     

有源光电式电流互感器的研究

光电式电流互感器已经成为国内外研究的热点,其中Rogowski线圈、高压侧电路的供电电源是目前研究工作的重点。在此介绍了有源光电式电流互感器基本原理,叙述了Rogowski线圈采样原理。Rogowski线圈的性能易受外界磁场和环境温度等因素的影响,对Rogowski线圈的制作提出了改进。有源光电式电流互感器高压侧供能问题仍未得到很好的解决,对母线电流取能、电容电流取能、激光供能、太阳能供电几种供能方式进行了研究分析。     

法拉第磁光效应法测量强脉冲磁场

介绍法拉第磁光效应法测量强脉冲磁场的装置和测量原理,给出了由测量波形推算磁场的详细方法,并将测量结果与微分环法测的结果进行了比较。     

透射电子显微镜原位磁场双倾样品杆的研制

本文简述了透射电镜磁场双倾样品杆的设计方案,展示了Philips/FEI透射电镜磁场双倾样品杆的研制成果.利用该样品杆可以产生100 Oe的连续磁场,也可以产生140 Oe以上的瞬间磁场.通过“U”型磁组件和样品杯的巧妙设计,尽可能的减小了电子束在横向磁场中的偏移量.     

频率和幅度双可调铁氧体LTCC衰减器

电路小型化需要多频段可调元器件,基于CPW(共面波导)结构采用最新的铁氧体LTCC(低温共烧陶瓷)技术,内埋若干偏置线圈以产生内部偏置磁场,调节线圈内电流大小以控制偏置磁场大小,从而控制衰减器的工作频率,同时,控制通电线圈的个数以改变衰减器的衰减幅度,进而实现频率和衰减幅度双可调的衰减器。首先介绍了基于铁氧体材料的衰减器基本原理,然后展示了基于铁氧体LTCC 技术的无内置线圈衰减器的设计、制作和测量,在外加偏置磁场的条件下,验证了铁氧体LTCC 衰减器的理论可行性,经实测,该衰减器可以在4～9 GHz之间实现频率可调以及相应的衰减幅度可调。随后提出了有内置线圈的铁氧体LTCC 衰减器模型,并展示了线圈静态磁场、衰减器频率可调和幅度可调的仿真结果。最后制作了该衰减器并完成了实测,在铁氧体LTCC特有内部衰减场上实现了频率和幅度双可调衰减器,从而给出了可调衰减器的新思路。     

Computer calculations of avalanche-induced relaxation oscillations in silicon diodes

A digital computer program has been employed to study relaxation oscillations of a silicon p-i-n junction diode reverse-biased into avalanche. The computed plots of diode current and voltage versus time and of diode current versus diode voltage are in good agreement with those obtained experimentally by Hoefflinger. The electric field and charge density distributions across the junction are given for selected times during the breakdown and current decay phases of the oscillations. The electric field is characterized by the formation of a saddle during the avalanche buildup. The variations of power output, efficiency, frequency, and average diode voltage are presented as a function of average current for one particular set of diode and circuit parameters.     

Ultralow-voltage boron-doped diamond field emitter vacuum diode

A boron-doped diamond field emitter diode with ultralow turn-on voltage and high emission current is reported. The diamond field emitter diode structure with a built-in cap was fabricated using molds and electrostatic bonding techniques. The emission current versus anode voltage of the capped diamond emitter diode with boron doping, sp² content, and vacuum thermal electric (VTE) treatment shows a very low turn-on voltage of 2 V. A high emission current of 1 μA at an anode voltage of less than 10 V can be obtained from a single diamond tip. The turn-on voltage is significantly lower than comparable silicon field emitters     

类 ? 型同频率高功率微波功率合成器的设计

利用基于波导结构的功率合成器来合成高功率微波,是提高窄带高功率微波源输出能力的一个有效方式。本文 设计了一种特殊的类? 型高功率微波合成器,该合成器可以用来合成X 波段同一个频率下的两束高功率微波。文中给出 了该合成器的设计方法及仿真结果,并且将该合成器结构与新型同轴双电子束高功率微波源[1]结合进行了粒子模拟,结果 表明,当加载的二极管电压为674kV,导引磁场为0.8T,内电子束电流为6.6kA,外电子束电流为14.3kA 时,该同轴双 电子束高功率微波源输出的两路微波经功率合成器合成以后输出了频率为9.74GHz,功率高达3.5GW 的微波。     

An E-J Collocated 3-D FDTD Model of Electromagnetic Wave Propagation in Magnetized Cold Plasma

A new three-dimensional finite-difference time-domain (FDTD) numerical model is proposed herein to simulate electromagnetic wave propagation in an anisotropic magnetized cold plasma medium. Plasma effects contributed by electrons, positive, and negative ions are considered in this model. The current density vectors are collocated at the positions of the electric field vectors, and the complete FDTD algorithm consists of three regular updating equations for the magnetic field intensity components, as well as 12 tightly coupled differential equations for updating the electric field components and current densities. This model has the capability to simulate wave behavior in magnetized cold plasma for an applied magnetic field with arbitrary direction and magnitude. We validate the FDTD algorithm by calculating Faraday rotation of a linearly polarized plane wave. Additional numerical examples of electromagnetic wave propagation in plasma are also provided, all of which demonstrate very good agreement with plasma theory.      

Effects of electron-beam confinement on klystron efficiency

This paper describes experiments which were devised to examine large-signal performance in klystrons focused by magnetic fields of finite magnitude. The experimental results are related to the theoretical analyses of Brewer, who treated small-signal bunching for magnetic fields of various magnitudes, and of Webber, who treated large-signal bunching for an infinite magnetic field intensity. The experiments agree with these theories where they apply, and additionally, the Webber theory continues to describe the transition from small to large signal for finite magnitude magnetic fields, when one uses the appropriate reduced plasma frequency in the bunching parameter. The relation of output cavity RF driving current, output cavity voltage, and magnetic field to conversion efficiency is also examined. It is found that maximum output power is obtained by maximizing driving current, but that with driving currents being equal, higher efficiency may be obtained in the beams which are magnetically more tightly confined; it appears that the higher magnetic field allows the output voltage to rise higher without defocusing the beam in the output cavity.     

Modeling of magnetic field stimulation of bent neurons

The authors consider a simple model of magnetic stimulation of a long bent neuron located in a semi-infinite volume conductor with a planar interface. It is shown that the stimulating coil characteristics (size, shape and location) and the neuron shape affect the location of the stimulation. The activating function, defined as the electric field derivative along the neuron, has two components. One component depends on the derivative of the electric field along the straight section of the neuron, and the other on the field magnitude. The maximal stimulation point is at the bent part of the nerve and its position depends on the nerve shape and coil parameters. The analysis also has shown a better performance (a stronger stimulus) for a double-circular (figure eight) coil than for a double-square coil