向内发射同轴虚阴极振荡器理论分析与数值模拟

 针对向内发射同轴虚阴极振荡器进行了1维理论分析,给出了电流电压关系的数值解,估算了同轴漂移区空间电荷限制流及虚阴极位置;同时使用MAFIA程序进行了全3维PIC数值模拟研究,通过调节阴极电子发射区与阳极反射板之间距离进行了一系列计算,得到了圆波导中各传输模式频谱及功率。结果表明,尽管使用圆周对称的同轴结构,输出模式中TE₁₁和TM₀₁仍占主导地位,两种模式共同存在,相互竞争。在最佳情况下,当二极管电压为250 kV,电流为20 kA时,得到了微波输出总功率最高为740 MW,功率效率超过10%,主频为3.18 GHz,同时含有较强TE₁₁和TM₀₁模式成分的微波输出。     

电子初始能量对双向流二极管空间电荷限制流密度的影响

 从理论上研究了阴极发射电子初始能量对一维平面非相对论性双向流二极管内空间电荷限制电子、离子流密度的影响,并与阴极发射电子初始能量为0情况下的空间电荷限制电子、离子流密度进行了比较。     

Generation of High-Current Low-Energy Electron Beams in Systems with Plasma Emitters

Generation and transport of high-current electron beams are investigated in gas-filled diodes with plasma emitters based on arc and glow discharges. A space-charge neutralized beam with a current up to 1 kA was produced in a diode with a plasma emitter based on an arc discharge for an accelerating voltage of 15 kV. The beam is constricted from 8 cm down to 1 cm in diameter by a self-magnetic field and is transported through a distance of over 20 cm with an efficiency of 70%. A beam with a current of 80 A and a current density up to 100 A/cm² was produced in a glow-discharge diode. The beam was transported through a distance of 30 cm in a weak axial magnetic field with induction B = 0.015 T.     

Relation between space-charge-limiting current and electric field enhancement factor at curved surface cathode

A two-dimensional solution of space-charge-limiting current for a high current vacuum diode with a spherical cathode is presented. The relation between space-charge-limiting current and electric field enhancement factor at the cathode surface for the diode with a curved surface cathode is also discussed. It is shown that compared with the current given by the conventional Child—Langmuir law, which describes the one-dimensional space-charege-limiting current, the two-dimensional space-charge-limiting current in such a diode is enhanced due to the electric-field enhancement along the cathode surface. Among practical parameter ranges, enhancement factor η_b approximately satisfies η_b ≈ Aβⁿ, where β is the electric field enhancement factor at the cathode surface, and n is a constant between 1 and 2, which is confirmed to be universal for the diodes with curved surface cathodes.     

轴对称平板二极管空间电荷限制流的2维效应

 应用精度较高的体积加权电荷、电流分配模型,对轴对称平板二极管的空间电荷限制流2维效应进行了粒子模拟研究。选取电压分别为100 kV和1 MV两种情况,对空间电荷限制流受二极管尺寸影响的规律进行了模拟。模拟结果表明,2维效应使空间电荷限制流密度随二极管形状因子(阴极发射半径与阴阳极间隙的比值)的减小而增大,且受相对论效应的影响不明显。经数值拟合得到了空间电荷限制流2维效应与形状因子相关的二阶经验公式,其一阶系数与一阶理论结果基本一致,约为1/4。     

强流电子枪电子光学性能的研究

 利用SLAC-226程序对一种工业用大功率电子加速器(450kW)的电子枪光学系统性能进行了研究。计算程序以带电粒子的洛伦兹力运动方程的相对论形式为基础，在充分考虑了空间电荷效应和电子自身产生磁场的情况下编写而成。在该程序中，网格的划分采用正方形网格；解泊松方程采用半迭代切比雪夫法；解轨迹方程采用四阶龙格 库塔法。经过对轴上电位的优化计算，得到了轴上电场的分布，电子轨迹以及阳极孔处的径迹斜率等结果，并且对外加电场与空间电荷场对束流的聚焦作用作了比较分析。计算发现，电子初始角和初始能量（对束流的）聚焦性能影响很小，二极管间距 d=58.5mm时对束流聚焦最有利。     

Capacitance of a planar diode

The capacitance of a planar diode is analyzed in the quasisteady-state approximation. The differential capacitance is derived for three operating modes of the diode: with a negative voltage on the anode, with a space-charge limited anode current, and at current saturation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 104–112, April, 1971.     

纳米碳管阵列场增强因子的计算

采用悬浮球模型，结合对称的镜像电荷层方法，对静电场中纳米碳管阵列的场增强因子进行了计算，并在考虑极板间距的情况下，对其计算结果做了修正.结果表明：纳米碳管阵列的间距对纳米碳管阵列的场发射性能影响很大.当纳米碳管阵列中碳管间距小于碳管高度时，场增强因子随间距的减小而急剧减小；而当碳管间距显著大于碳管高度时，场增强因子几乎不变.但当考虑阴阳极之间单位面积通过的场发射电流时，可论证当管间距与管高度相若时，能使场发射电流密度最佳(最大).另外，极板间距对场增强因子的影响很小，但是可以通过减小极板间距，来降低纳米碳管作为场发射体的场发射的开启电压，优化纳米碳管的场发射性能. 关键词： 纳米碳管阵列 场增强因子 开启电压     

爆炸电子发射初期阴极表面电场的研究

为了研究二极管爆炸电子发射初始阶段阴极表面复杂的物理现象及规律, 建立了由场致电子发射阴极构成的一维平板真空二极管物理模型,通过自行编程数值求解泊松方程, 考虑了发射出的电子对阴极表面电场的非线性影响,自洽模拟得到了阴极表面电场随时间的变化情况. 模拟结果表明,爆炸电子发射初期,阴极表面电场随时间的增加而呈现出不断振荡的规律, 且振荡幅度越来越小,最终到达一个稳态的值,二极管两极板之间的外加电场越大, 阴极表面稳态电场的绝对值越大;电场增强系数越大,阴极表面稳态电场的绝对值越大. 在整个时间演变过程中,阴极表面的实际电场强度决定着阴极发射的电流密度大小, 反过来阴极发射的电流密度又会影响到阴极表面的电场.     

同心球之间空间电荷限制电流的简单理论

在高功率微波二极管的设计中,空间电荷限制电流因其与二极管的特性及虚阴极形成关系密切而显得十分重要,虽然Langmuir和Blodgett给出的数值解十分有用,但是在实际的应用中一个简单的函数表达式还是更为方便,同时也可以避免当R_c/R_a很大时带来的级数发散问题.第一性原理已经应用在平行板和共轴圆柱之间二维空间电荷限制电流的推导,它的可靠性也已经得到了大量的验证.本文利用第一性原理推导出了同心球二极管空间电荷限制电流的解析表达式,其中的 关键词： 第一性原理 同心球二极管 空间电荷限制电流     

静电加速管中强流空间电荷效应的研究

 对一种工业用大功率电子加速器(450kW)的加速管中的空间电荷效应作了5点假设，建立了物理模型。对模型的束内外径向电位分布、空间电荷对轴上电位的影响，以及空间电荷力对束流传输的影响等进行了理论分析，得到了束内径向电位分布。结果表明：束流内部径向电位沿径向均呈抛物线变化，并在轴上达到最小值；而空间电荷产生的束内电场与半径呈线性变化；空间电荷不仅会引起轴上电位的跌落，而且对束流有发散作用，特别是在电子速度较低时更为明显。在考虑了空间电荷效应后，强流静电加速管的电场设计关键在加速管的前端，与弱流加速管相比，强流加速管的电场变化要大得多。     

Field emission of carbon nanotube array with normal-gate cold cathode

A hexagon pitch carbon nanotube (CNT) array vertical to the normal gate of cold cathode field emission displayer (FED) is simulated by solving the Laplace equation. The calculated results show that the normal gate causes the electric field around the CNT tops to be concentrated and emission electron beam become a column. The field enhancement factor and the emission current intensity step up greatly compared with those of diode structure. Emission current density increases rapidly with the decrease of normal-gate aperture. The gate voltage exerts a critical influence on the emission current.     

平面二极管爆炸发射阴极特性实验研究

 在电压0.6~1.0 MV,脉冲重复频率为100 Hz条件下,实验研究了爆炸发射阴极的有效发射面积、平均发射电流密度、二极管阻抗、电子束能量损耗机制等特性。结果表明：阴极有效发射面积随时间呈方波变化,在脉冲开始后5 ns内有效发射面积基本达到稳定。在碳纤维、天鹅绒、石墨、不锈钢4种阴极材料中,碳纤维阴极有效发射面积最大且变化相对稳定,并且碳纤维阴极具有最大的平均发射电流密度。二极管阻抗随着阴阳极间隙的增加并非呈平方关系增加,而是呈线性增长,阻抗失配是降低电子束能量传输效率的主要机制。     

A new algorithm for solving space-charge problems with thermally-emitted electrons

The paper deals with the extension of the known older results regarding the space-charge limitation of current in a plane diode to a more complex case with more electrodes. The method involving the usage of a computer can be used under certain assumptions the most important of which is that the electron paths are only slightly curved and that the electrical field is only two-dimensional.     

强流二极管阳极靶温度和热形变模拟

以电子束在靶中的能量沉积剖面为桥梁,建立了二极管阳极靶温度和热形变模拟方法。该方法可获知二极管不同工作状态下靶的温度分布和热形变情况,为靶热-力学损伤研究提供基础数据,为二极管构型设计和寿命提升提供技术支撑。将该方法应用于“强光一号”短γ二极管,计算结果显示:当阳极离子密度大于1014 cm?3时（强箍缩）,靶表面温度最高可达5500～6000 ℃,热形变量达约4.5 mm;无离子流时（弱箍缩）,温度处在4500 ℃左右,形变为2.8～3.5 mm。     

有限尺寸宏粒子空间电荷场研究

 用格林函数理论导出了圆柱对称系统中有限尺寸宏粒子一维和二维空间电荷场权函数的表达式，比较了有限尺寸宏粒子空间电荷场权函数与圆盘或圆环模型空间电荷场权函数的差别，得到了与圆盘或圆环模型空间电荷场权函数[1]不同的、更合理的计算结果。并用这两种空间电荷场权函数模拟了螺旋线行波管中的注波互作用过程，得到了其输出功率曲线，表明了用有限尺寸宏粒子计算的互作用输出功率比圆盘或圆环模型计算的输出功率饱和位置提前，饱和值增加。     

Gain-bandwidth trade-off in a transistor laser: quantum well dislocation effect

The Authors report an analytical model to investigate optoelectronic characteristics reliance of a Transistor Laser on Quantum Well Location. Using simulated base recombination lifetime, optical frequency response for different quantum-well locations extracted. Slipping the well towards the collector, improves the optical bandwidth where a maximum of ≈54 GHz is observed. No resonance peak, limiting factor in diode lasers, is occurred in this enhancement method. Analyzing current gain (β) as a function of the quantum well location, exhibits a decrease in β when the well moved in the direction of the collector so that a trade-off between optical and electrical properties of transistor laser is evident. The trade-off is utilized in conjunction with previously reported experimental researches to find an optimum place of quantum well for desired performance.     

磁场对球头阴极二极管特性的影响

 采用全电磁PIC粒子模拟方法研究了磁场对球头阴极二极管物理特性的影响。结果表明外加磁场主要是通过对二极管束流轨迹的改变来影响二极管的物理特性。由于外加磁场将约束其产生电子束的发散，结果使其空间电荷限制电流减小，其值在无外加磁场并且自磁场可以忽略时的空间电荷限制电流值的0.5~1倍范围内。当外加磁场足够强时，束流轨迹主要受外加磁场控制，二极管产生的电子束既不箍缩也不发散。强外加磁场条件下的空间电荷限制电流近似为无外加磁场时的一半；在无外加磁场条件下，在阳极处的束流半径随二极管电压电流的增大而减小，空间电荷限制电流增强因子随束流半径的减小而减小，随二极管电压电流增大而减小。这一系列结果是在二极管电流小于其自箍缩临界电流条件下得到的。     

The Electrostatic Trapping of an Intense Relativistic Electron Beam in a Magnetic Mirror

Observations of rapid axial oscillations of an intense relativistic electron beam in a magnetic mirror are reported. The mirror field primarily provides radial confinement of the relativistic electrons. The axial confinement was achieved by placing thin aluminized mylar foils at the conjugate mirror field maxima. The region between these foils was filled with a few Torr air to provide a beam induced plasma for charge and current neutralization. The regions outside these foils were maintained at ~10-4 Torr. One foil formed the anode of a space-charge limited relativistic electron diode which launched the beam into the mirror. When the beam passed through the second foil it was no longer charge neutralized. In a manner quite similar to the anode foil oscillations observed by others, a space-charge limited electrostatic well was established which stopped the electrons and re-accelerated them through the foil-thereby reflecting the beam. When the reflected electrons re-entered the diode, they were once again "electrostatically" reflected. This process continued until the oscillating beam was either lost through the "virtual cathodes" outside the foils, dissipated in the drift region or quenched in the diode plasma after gap closure.