DC column plasma kinetics in a longitudinal magnetic field

The cylindrical column plasma of a neon dc glow discharge under the influence of a weak longitudinal magnetic field is studied. An extended, fully self-consistent model of the column plasma has been used to determine the kinetic quantities of electrons, ions and excited atoms, the radial space charge field, and the axial electric field for given discharge conditions. The model includes a nonlocal kinetic treatment of the electrons by solving their spatially inhomogeneous kinetic equation, taking into account the radial space charge field and the axial magnetic field. The treatment is based on the two-term expansion of the velocity distribution and comprises the determination of its isotropic and anisotropic components in the axial, radial, and azimuthal direction. A transition from a distinctly nonlocal kinetic behavior of the electrons in the magnetic-field-free case to an almost local kinetic behavior has been found by increasing the magnetic field. The establishment of the electron cyclotron motion around the column axis increasingly restricts the radial electron energy transport and reduces the radial ambipolar current. The complex interaction of these transport phenomena with the alterations in the charge carrier production leads finally to a specific variation of the electric field components. The axial field increases by applying weak magnetic fields, however, decreases with increasingly higher magnetic fields. At higher magnetic fields, the radial space-charge field is considerably reduced     

Experimental determination of space charge density associated with flow electrification phenomenon: Application to power transformers

At the solid/liquid interface, a charge zone called the Electrical Double Layer (EDL) appears. It is constituted of two zones of opposite sign, one in the solid and another one in the liquid. When a liquid flows through a pipe, an axial streaming current is generated. This current is due to the convection of the charges coming from the electrical layer in the liquid. The experimental methods for the determination of space charge density have been clearly identified in the case of fully-developed EDL. On the contrary, there is a need for further exploration in the case of a non-fully developed EDL. The purpose of this paper is to calculate the fully developed space charge density at the wall by streaming electrification experiments which are conducted in the case of non-fully developed EDL. Moreover, it introduces a simplified procedure for the experimental determination of space charge density as a function of liquid flow velocity. This procedure can be conducted for the investigation of flow electrification phenomena in transformers with oil/metal configuration.     

毫米波圆柱波导自由电子激光放大器的数值模拟

本文以单粒子理论为基础，在不计空间电荷效应的近似条件下推导了带轴向引导磁场的三维圆柱波导非线性模拟方程组。用CAGFEL程序计算、分析了在带入口区、常数摇摆器条件下两组不同物理参数的自由电子激光放大器的物理模型。计算结果可靠，物理图象合理。对于其中的第二组参数还着重考查了光波频率、输入功率和摇摆器场振幅改变对输出功率和效率的影响。上述这些计算结果对0．7MeV 自由电子激光放大器的设计和实验具有一定的参考价值。     

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。     

径向线内电子束的空间极限电流

为了对径向线内电子束的空间极限电流及相关物理参量进行分析, 在径向方向无穷长与束流密度轴向均匀的假设条件下, 对电势满足的线性泊松方程进行了解析求解, 得到了空间极限电流的解析表达式, 接下来对束流密度轴向非均匀分析条件下电势满足的非线性方程进行了数值求解, 并与解析结果进行了对比。研究表明径向电子束具有较高的空间极限电流且当束流接近于极限电流传输时, 束密度的非均匀性明显增加, 相关结论可以为径向高功率微波器件的设计提供指导。     

Breakdown of the homogeneity of weakly conducting liquids in high electric fields

A study of the structure of electrohydrodynamic flows shows that the electric charge carriers are ions that are practically frozen into the surrounding liquid. In other words, ions in weakly conducting liquids are capable of forming more or less stable structures whose viscoelastic properties are different from those of an uncharged liquid. One method of studying this effect is to investigate the velocity dispersion of ultrasound on charged supermolecular formations. The results of theoretical and experimental investigations of acoustic dispersion in liquid dielectrics subjected to prebreakdown electric fields are presented. A model problem of sound propagation in a liquid in which supermolecular structures have formed around elementary charge carriers is studied theoretically. Approximate formulas describing the dispersion of the acoustic phase velocity as a function of the electric field parameters and the electrophysical parameters of the liquid are obtained. The frequency dependence of the sound velocity is of a resonance character, the resonance frequency being determined by the electric charge density and the mass of the charged supermolecular structures. The experiments showed that the space charge affects the velocity of acoustic waves in liquid dielectrics. Zh. Tekh. Fiz. 67, 105–111 (October 1997)     

轴对称电荷分布非静态轴外场的一种计算方法

利用麦克斯韦方程组和轴对称性,给出了轴对称电荷分布非静态轴外场的一种计算方法.     

Photo-excitation of space charge fields and reorientation of a nematic liquid crystal of discotic molecules

A new reorientation effect in nematic liquid crystals of discotic molecules, which occurs under the combined influence of DC-electrical and optical fields, has been observed and investigated for the first time. It is shown that an illumination with intensity as low as 10⁻³ W/cm² is sufficient for producing a strong photo-induced reorientation process which indicates a rather large nonlinear optical coefficient. The dependence of the photo-excitation on the applied voltage as well as on the intensity and the wavelength of the light wave was investigated. Furthermore, a first model, which explains the experimental observations resulting from photo-induced space charge fields and related field-induced reorientation of the discotic molecules, will be discussed.     

声脉冲法空间电荷测量系统的研究

气体中空间电荷的分布与电晕放电的机理紧密相关, 获取电晕放电过程中空间电荷分布对深入研究电晕放电起始、自持过程有着重要作用, 但是如何准确获得电晕放电过程中的空间电荷分布一直是国际上尚未解决的难题. 本文基于声脉冲法提出一种电场信号解耦算法, 推导了空间电荷在声场中被调制产生的电场信号与声脉冲信号和空间电荷密度之间的数值关系, 讨论了不同测量情况下声发射系统的设计要求; 搭建了一套可用于实时测量针板电极电晕放电空间电荷分布的非接触式测量系统, 该系统主要包括声脉冲发生模块、空间电荷模块及电场信号解耦算法模块. 运用该系统实现了声脉冲激发作用下电场信号的测量, 通过提出的电场信号解耦算法得到了空间电荷密度, 对其测量结果与电晕电流法测量结果进行比较, 验证了电场信号解耦算法的有效性. 该算法可以应用于空间电荷一维、二维和三维测量系统中.     

基于类耿氏效应的低密度聚乙烯中空间电荷包行为的模拟仿真

低密度聚乙烯材料中的空间电荷包现象通常会引起严重电场畸变而影响其击穿特性. 本文借鉴半导体中的耿氏效应的负微分迁移率机理来描述电荷包的形成机理,并结合载流子的注入条件及体内陷阱对电荷迁移的影响等因素,对文献中报道的两类外加场强不同且迁移趋势各异的空间电荷包行为进行了模拟仿真,模拟的电荷包大小随电场变化规律,电荷包迁移速率随时间变化规律等与相应实验结果符合.模拟结果表明,产生耿氏效应的负微分迁移率是造成电荷包非弥散传输的主要原因,其与材料电极注入情况及体内陷阱态的共同作用导致了空间电荷包行为迁移的多样性. 关键词： 空间电荷包 耿氏效应 模拟仿真 负微分迁移率     

Transient velocity induced by electric injection in blade-plane geometry

Electric charge injection in blade-plane geometry has been widely studied. Previous works on this geometry were carried out with a DC electrical signal. In this paper, a Heaviside step voltage is applied on the device in order to observe the liquid transient behavior. Particle Image Velocimetry (PIV) measurements are performed on negative and positive voltage steps. The transient behavior of the velocity induced by charge injection is discussed for both polarities. The influence of the frequency of an AC square signal is also investigated, and a comparison between AC and DC behaviors is presented.     

Mass Transfer in Free Convection Developing in a Magnetic Field

The interaction of a charged hydrated particle with an external magnetic field is analyzed under conditions of diffusion and convective mass transfer. A model of forming local space charge regions in the bulk of a solution is suggested. The model is used to study the feasibility of changing the velocity and redistribution of charged particles in an aqueous medium. The results of theoretical calculations are tested experimentally by quantitative estimation of the rate of the convective liquid flow developed in crossed electric and magnetic fields.     

对于自共振激光加速器中轴向场问题的讨论

从洛仑兹力方程的旋量形式出发，讨论了电磁场中电荷运动的轴向电场和轴向磁场问题以及平面波的脉冲和Larmor功率。这些问题是研究自共振激光加速器的基础。From the spinorial form of the Lorentz force equation, the problems about axial electric field and axial magnetic field of charge motion in electromagnetic fields, as well as plane wave pulse and Larmor power have been discussed in this paper. These problems are the foundation of studying the autoresonance laser accelerator (ALA).     

Crystallographic fringe orientation diffraction efficiency in bismuth silicon oxide

We report the first experimental measurement of fringe-angle applied electric field scaling of space charge growth and of crystallographic orientation effects in the initial development of the diffraction efficiency of thick holograms produced by the photorefractive effect in a bismuth silicon oxide (BSO) crystal. Diffraction efficiencies of holograms made by interfering two plane waves on the [¯110] face are measured as a function of the angle between the fringe pattern and the applied electric field. As the crystal is rotated relative to the interference fringes, the applied field may be scaled to yield identical space charge growth. Polarization-dependent diffraction measurements agree with the theory of a birefringent grating when optical activity is included as a separate, serial effect. Both the rotation-scaled applied electric fields and the crystallographic variations in the birefringent diffraction grating are consistent with charge transport processes in which the initial space charge fields are perpendicular to the interference fringes over growth times extending nearly into the steady state regime.     

Effects of the electric field shape on nano-scale oxidation

An axisymmetric continuum model for oxide growth by the scanned probe oxidation technique is presented. The model includes equations describing the electric fields, hydroxyl and hydrogen ion concentrations, and oxide free boundaries defining the system. The governing system of partial differential equations tracks ion transport in the liquid and oxide layers and includes reactions at the substrate/oxide interface. Further, space charge effects are considered near the substrate/oxide interface. Two liquid configurations, semi-infinite layer and hemispherical drop of liquid, are examined to determine the potential in the liquid region. The AFM tip is modeled as either a point or a ring source of charges. The asymptotic limit of a small aspect ratio (height to width) oxide feature is used to reduce the governing equations to a quasi-one-dimensional system to determine the ion transport. The solution of the reduced system leads to an evolution equation for the oxide thickness and radius. Numerical simulations of the evolution equation predict oxide features that qualitatively agree with experimental observations. A parametric study is conducted to determine the influence of key operating and material parameters on the thickness and radius of the oxide, and the electric and ion concentration fields in the system.     

CYCIAE-100轴向注入线设计及中心区束流匹配

采用包含空间电荷效应的束流光学计算软件TRANSOPTR对CYCIAE-100回旋加速器轴向注入线进行设计,在综合考虑空间布局、元件选择、真空度、空间电荷效应、轴向磁场和造价等问题后,最终确定了轴向注入线的聚焦结构。将数值跟踪获得的真实磁场下螺旋偏转板传的输矩阵编写到TRANSOPTR程序中,从而实现了从离子源出口至偏转板出口的束流光学匹配。介绍了CYCIAE-100回旋加速器轴向注入线的设计思想、布局结构和束流光学计算结果,并给出了主要元件的设计结果。在确定中心区结构和对中轨道后,采用多粒子轨道跟踪的方法进行中心区束流匹配的研究,通过对数值模拟的结果进行椭圆拟合并结合解析公式计算得到注入点处匹配矩阵,为注入线的设计提供拟合条件。     

PCT Theorem for the Operator Product Expansion in Curved Spacetime

We consider the operator product expansion for quantum field theories on general analytic 4-dimensional curved spacetimes within an axiomatic framework. We prove under certain general, model-independent assumptions that such an expansion necessarily has to be invariant under a simultaneous reversal of parity, time, and charge (PCT) in the following sense: The coefficients in the expansion of a product of fields on a curved spacetime with a given choice of time and space orientation are equal (modulo complex conjugation) to the coefficients for the product of the corresponding charge conjugate fields on the spacetime with the opposite time and space orientation. We propose that this result should be viewed as a replacement of the usual PCT theorem in Minkowski spacetime, at least in as far as the algebraic structure of the quantum fields at short distances is concerned.     

New type of magnetorotational instability in cylindrical taylor-couette flow

We study the stability of cylindrical Taylor-Couette flow in the presence of combined axial and azimuthal magnetic fields, and show that adding an azimuthal field profoundly alters the previous results for purely axial fields. For small magnetic Prandtl numbers Pm, the critical Reynolds number Re(c) for the onset of the magnetorotational instability becomes independent of Pm, whereas for purely axial fields it scales as Pm-1. For typical liquid metals, Re(c) is then reduced by several orders of magnitude, enough that this new design should succeed in realizing this instability in the laboratory.     

Singularities at real points of ℋ space

In the presence of gravitational radiation, there are ordinarily no shear-free slices of null infinity. A four-complex-dimensional set of shear-free slices of complexified null infinity do exist. They comprise the manifold space. In general, there are no preferred real subspaces of space associated with slices of real null infinity. However, for radiation fields possessing a twist-free axial symmetry, a two-parameter family of shear-free slices of real null infinity exist and therefore pick out a preferred two-dimensional real subspace of space. In this paper, we study the geometry of these 2-spaces for the particular case of quadrupole radiation fields for which determination of the shear-free slices reduces to the standard problem of determining orbits of a particle moving in a potential. Our principal interest is the investigation of possible singularities caused by sufficiently intense radiation fields. We find that such singularities do occur for radiation fields having the characteristic powerc ⁵/G.     

Classical Yang-Mills fields in a Robertson-Walker universe

A class of exact solutions of the coupled Einstein-Yang-Mills system is constructed for a Robertson-Walker geometry. In flat space the gauge fields which we consider interpolate continuously between the two-meron and the one-instanton fields. In curved space, our solutions are periodic with period and amplitude determined by the interpolating parameter.