空间电荷限制流与传导电流的定量关系

 从空间电荷限制流假设、Poisson方程及电子正则动量守恒关系出发，推导了平板形、同轴圆柱和共顶点同轴圆锥三种导体构形的空间电荷流随传导电流变化的广义Poisson方程，给出了求解方法及解的基本特征，分析比较了三种导体构形空间电荷限制流的基本性质。通过推导，计算和分析可得：各种电压条件下传导电流对空间电荷限制（SCL） 流的作用效果不一样，电压越高传导电流提高磁绝缘程度的作用越显著；当几何因子(即高阻抗)较小时其它两种导体的SCL流与平板形相差较大，几何因子较大时与平板形十分接近；同样电压条件下负极性的SCL流比平板形小、正极形正好相反，而相同几何因子条件下同轴圆筒的SCL流比共顶点同轴圆锥的小；在分析研究低阻抗MITL时，采用SCL流的平板近似不会带来大的误差。在描述时变脉冲作用于MITL时，可以通过对SCL流随电压、传导电流变化的曲面函数插值的方法确定各个时刻的磁绝缘状态。     

同轴慢波结构相对论高功率微波产生器理论分析

 推导了同轴波导的空间电荷限制流，其值大于圆波导的空间电荷限制流。因此在阴极电势和束流相等的情况下，同轴波导中的束流具有更高的动能，同轴器件有可能获得更高的微波转换效率。理论推导出同轴慢波结构中考虑束流空间电荷影响的色散方程，利用Matlab进行了编程求解。不考虑束流空间电荷影响时，编程计算结果与Superfish模拟结果一致。由考虑束流空间电荷影响的色散方程数值计算结果，可知文献中提出的同轴慢波结构相对论高功率微波产生器工作在准TEM模的π模，频率为7.67 GHz，峰值时间增长率较高，电子束损失的能量与其初始能量之比为34%。这些结果均与文献中的数值模拟结果一致。同时理论分析说明该种器件无论在能量转换效率，还是在产生微波脉冲的上升时间上均具有优势。     

求解三种导体构形中相对论电子形成的空间电荷限制流

在无横向磁场作用下，真空中损失到金属导体阳极表面的空间电荷限制（SCL）流将达到最大。在无限大平板构形导体中，这个最大的SCL流只与阴阳极电压和间距相关；而对于在磁绝缘传输线（MITL）中广泛应用的同轴圆筒和共顶点同轴圆锥构形，其最大SCL流还与导体的几何因子及极性参量有关。研究这3种典型构形的最大SCL流，是研究横向磁场对SCL流影响规律的起点，是设计同类MITL构形的基础。     

箔聚焦强流相对论环形束在同轴波导中的传输

 结合箔聚焦和静电线聚焦的特点,对箔聚焦强流相对论环形电子束在同轴波导中的传输进行了研究。通过数值求解电势满足的泊松方程,得到电势、电场分布及系统的空间电荷限制流,并根据电子的运动方程得到包络电子的平衡条件及其运动轨迹。     

同轴结构中压力波法测量空间电荷分布的物理模型研究

从压力波法测量平板样本中空间电荷分布的理论分析出发,提出了对于同轴结构的固体电介质中空间电荷分布的压力波法测量的物理模型,并得出了测量电流的解析的数学表达式.依据泊松方程,考虑样品内的电场强度、介电常数和空间电荷密度随外界声波扰动而发生变化,将圆柱试样受到的压力波的影响分解成样品形变和质点位移两部分,进而得到了以同轴结构中空间电荷分布的压力波法测量的电压与电流表达式.测量电流的数学表达式表明,对于同轴结构,压力波法的测量电流信号不像平板结构中那样基本正比于空间电荷分布,而是应该做进一步的修正处理.     

库仑定理导出的2维空间电荷限制流一级近似公式

 为了准确计算空间电荷效应,从库仑定律和电流连续性方程出发,通过求解带电粒子群在空间某点产生的电场,再考虑到一系列合理的近似,最后得到了轴对称圆柱导体构形的空间电荷限制流的2维一级近似公式,结果显示,对于有限平面的电荷限制流大于经典1维限制流。     

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。     

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。     

离子对Rod—pinch二极管工作特性的影响

用于X射线闪光照相的Rod—pinch二极管aRPD）具有电学性能稳定、产额高、焦斑直径小（可达到亚毫米量级）以及结构简单等优点。由于受电场和磁场的影响，二极管中带电粒子的流动方式可以分为空间电荷限制流（SCL）、弱箍缩（WP）和磁绝缘限制流阻）3种基本模式。大量实验和理论研究表明，离子对RPD的工作模式有显著影响，这里结合同轴结构二极管工作模式的半解析描述方法，利用PIC粒子模拟程序，深入研究离子对于RPD工作特性的影响。     

相对论速调管三轴提取腔的分析与设计

分析了同轴漂移管中电子束的空间电荷限制流和能量分布，为了降低S波段相对论速调管放大器(RKA)中电子束空间电荷效应及势能，提高RKA的束波转换效率，提出了三轴结构的输出腔，理论分析RKA的束波转换效率达到36%，比同轴提取腔的束波转换效率提高了9个百分点. 采用数值计算程序设计了三轴提取腔，粒子模拟了S波段RKA的微波提取，取得了与理论分析一致的结果. 采用590kV/5kA的空心电子束，经过预调制腔和群聚腔等两个腔的调制后，采用三轴提取腔提取微波，得到了约1.0GW的微波功率，效率35%. 理论研究结果与实验结果吻合得较好. 关键词： 相对论速调管放大器 三轴提取腔 空间电荷限制流     

Ein Nachweis der Raumladung bei raumladungsbeschränkten Defektelektronenströmen in Anthrazen

A method is described with which the space charge of the excess hole current in anthracene, flowing under space-charge limitation, can be detected in spite of the short persistance of this charge in the crystal. One injecting (ohmic) and one non-injecting (blocking) electrode is used. After space-charge-limited current flow is established, a reverse voltage is suddenly applied which causes the excess space charge in the crystal to flow out through the ohmic electrode without additional carriers entering through the blocking electrode. The magnitude of the space charge so measured agrees with that expected from the capacitance of the crystal.     

Space-charge-limited 2D electron flow between two flat electrodes in a strong magnetic field

An approximate analytic solution is constructed for the 2D space-charge-limited emission by a cathode surrounded by nonemitting conducting ledges of width Lambda. An essentially exact solution (via conformal mapping) of the electrostatic problem in vacuum is matched to the solution of a linearized problem in the space charge region whose boundaries are sharp due to the presence of a strong magnetic field. The current density growth in a narrow interval near the edges of the cathode depends strongly on Lambda. We obtain an empirical formula for the total current as a function of Lambda which extends to more general cathode geometries.     

An action for a classical string,the equation of motion and group invariant classical solutions

A string action which is essentially a Willmore functional is presented and studied. This action determines the physics of a surface in Euclidean three space which can be used to model classical string configurations. By varying this action an equation of motion for the mean curvature of the surface is obtained which is shown to govern certain classical string configurations. Several classes of classical solutions for this equation are discussed from the symmetry group point of view and an application is presented.      

4层圆盘锥形磁绝缘传输线的等效电路模型

 根据磁绝缘特征将PBFA Z加速器的4层圆盘锥形磁绝缘传输线结构分成几段串联的集中电感，结合磁绝缘临界电流、空间电荷限制流、Mendel磁压力平衡及丝阵内爆动力学等计算模型，并引入主要的结构参数，建立4层圆盘锥形磁绝缘传输线的等效电路模型，模型计算结果与实验结果、其它模型计算结果符合较好，模型可以用于定性或半定量设计及分析类似结构的磁绝缘传输线。     

Space charge solution of Rittner photoconductor equation for a HgCdTe detector

The steady-state charge continuity equations are linearized to derive a space charge field that accompanies the ambipolar diffusion and drift described by the Rittner equation. The space charge field is evaluated for a typical 14.2 μm cutoff wavelength HgCdTe detector operating at 85 K. It is found that the space charge density is ∼10⁻⁵ times the hole and electron population density generated by photon flux. This corroborates that Rittner's equation gives an accurate solution for the hole and electron densities. But, at relatively high photon flux levels that are found in some Geostationary Operational Environment Satellite instrument channels, the small average space charge field can have a noticable effect on the linearity of detector response. Divergence of electric field terms in the continuity equations, which are absent from the Rittner equation, can also contribute a non-linearity to detector response.     

Space-charge-limited current of vacuum arc thruster

To optimize thrust performance, the expression of space-charge-limited current for vacuum arc thruster is derived from Poisson's equation. The commonly used ring-type and coaxial-type vacuum arc thrusters are simplified to the equivalent current sheet in planar geometry and cylindrical capacitor, respectively, for this calculation. Both the spatial distribution and peak magnitude of space-charge-limited current are given explicitly, together with their dependences on gap distance, applied voltage, charge number, and ion mass. For typical experimental parameters of the vacuum arc thruster, it is shown that the maximum current density drops significantly when the gap distance becomes large and grows when the applied voltage increases; moreover, a cathode material of lower atomic weight yields a higher current density. The expressions of total current for these two types of vacuum arc thruster are also presented. This work, to our best knowledge, is the first application of space-charge-limited current to the vacuum arc thruster and practically very interesting for engineering design.     

Open circuit thermally stimulated discharge current measurement on PMMA:PEMA:PVDF ternary blends

Ternary blends of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. The open circuit thermally stimulated discharge current (OC-TSDC) technique was used to study the hetero charges, homo-charges and interfacial charge formation in ternary system. The present investigation was carried out on bilaterally metallized electret. The thermograms were characterized with multiple peaks in the temperature ranges from 40, 60, 80 and 100oC and the current direction was, in general, found to correspond to homo- charge, i.e., the same as that during charging with a few exceptions. The resultant current polarity corresponds to the dominant charging process. To distinguish between homo-charge decay by ohmic conduction and space charge limited drift in an open circuit, homocharge magnitude is changed by varying the polarizing voltage. Decay of ohmic conduction is independent of the initial charge; however, space-charge-limited (SCL) drift dependence on the injection level. A high initial charge will enhance the drift because it increases the field that drives the charges to adhering back electrode. This proves unequivocally that the, ρ peak is caused by the motion of excess charges and not by dipole relaxations, hence, the useful for microelectronics and many special purpose insulation.     

离子对rod-pinch二极管工作特性的影响

 利用PIC粒子模拟方法，结合对同轴结构二极管工作模式的半解析描述，研究了离子存在与否对rod-pinch二极管（RPD）工作特性的影响。模拟给出了二极管的伏安特性、不同时刻电子和离子的相空间分布以及空间电流分布等。结果表明随着电流逐渐增大，其工作模式从空间电荷限制流依次向弱箍缩流和磁绝缘流转变。只有存在离子的情况下，电子才能沿着阳极杆表面运动并在其末端发生箍缩，表明RPD中离子电流的存在对于RPD工作是必需的。