Electron acceleration in the inverse free electron laser with a helical wiggler by axial magnetic field and ion-channel guiding

Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article. The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration. In free electron lasers, electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser. The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method. The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant.     

Electron density and electron redistribution in alloys—I: Electron density in elemental metals

The changes in electronic structure around each metal atom in an alloy are more accurately described in terms of electron redistribution than electron transfer. The important elements in a model for such electron redistribution are the electron configuration and radius of the positive ion cores and the conduction electron density and its variation in the interstitial regions. Positive ion core radii for metals are derived from an empirical relation between ion core radii and intermetallic distance with electronic configurations of the core from positron annihilation data. These derived ion core radii are in good agreement with those calculated for metal electron densities by Welch and Lynn from Hartree-Fock wave functions. Average conduction electron densities can be directly calculated from these radii and the experimental atomic volume; the variation of conduction electron density in the interstitial region is calculated by assigning electrons to octahedral and tetrahedral interstices according to the Interstitial Electron Model. The calculated electron densities and the interstitial variation agree very well with the experimental electron densities of Be as determined from X-ray diffraction data as well as with calculated electron densities for Na, Mg and Al. Ion core configurations are compared with those derived from band theory and also those of the Engle-Brewer Correlation and the Samsonov-Pryadkov-Pryadkov Configurational Model.     

Oblique Electron Thermal Waves in a Magnetized Plasma

Propagations of an oblique electron thermal mode under the electron plasma frequency without boundary effects are investigated experimentally and theoretically in a magnetized plasma. The phase, ray, and group velocity surfaces of the electron thermal mode are obtained in a polar coordinate. The experimental observation of the electron mode radiated from a point source is found to be in fair accord with the theoretical wave fronts which are obtained from the ray velocity surface. Wave fronts and ray trajectories of an oblique electron thermal mode radiated from a point source are numerically obtained in an inhomogeneous magnetized plasma with a use of an electrostatic kinetic theory. The spatial numerical results are indicated mainly below the electron plasma and cyclotron frequencies. Reflections of the mode in the plasma density lower than the electron plasma frequency are made clear numerically.     

Characteristics of secondary electron emission from few layer graphene on silicon (111) surface

As a typical two-dimensional (2D) coating material, graphene has been utilized to effectively reduce secondary electron emission from the surface. Nevertheless, the microscopic mechanism and the dominant factor of secondary electron emission suppression remain controversial. Since traditional models rely on the data of experimental bulk properties which are scarcely appropriate to the 2D coating situation, this paper presents the first-principles-based numerical calculations of the electron interaction and emission process for monolayer and multilayer graphene on silicon (111) substrate. By using the anisotropic energy loss for the coating graphene, the electron transport process can be described more realistically. The real physical electron interactions, including the elastic scattering of electron—nucleus, inelastic scattering of the electron—extranuclear electron, and electron—phonon effect, are considered and calculated by using the Monte Carlo method. The energy level transition theory-based first-principles method and the full Penn algorithm are used to calculate the energy loss function during the inelastic scattering. Variations of the energy loss function and interface electron density differences for 1 to 4 layer graphene coating GoSi are calculated, and their inner electron distributions and secondary electron emissions are analyzed. Simulation results demonstrate that the dominant factor of the inhibiting of secondary electron yield (SEY) of GoSi is to induce the deeper electrons in the internal scattering process. In contrast, a low surface potential barrier due to the positive deviation of electron density difference at monolayer GoSi interface in turn weakens the suppression of secondary electron emission of the graphene layer. Only when the graphene layer number is 3, does the contribution of surface work function to the secondary electron emission suppression appear to be slightly positive.     

The Magnetically Confined Electron Cloud Sustained by Thermionic Emission

The electron clouds in high vacuum which are confined by electromagnetic fields and sustained by thermionic emission are studied.The distributions of the electron density,the electron temperature,the drift angular velocity of electrons,the diffusion flow density of electrons and the electric potential in the electron cloud are discussed.     

ELECTRON TRANSPORT BEHAVIOR IN NORMAL AND ABNORMAL DIRECT CURRENT DISCHARGE CATHODE SHEATH

This paper studies the electron transport behavior in normal and abnormal helium direct current (dc) glow discharges using a Monte Carlo simulation, in which the influences of the electron initial energy and cathode surface reflection on the electron swarm behavior are considered. The electron-neutral atom collision processes and the electron swarm parameters (such as the number of collisions, collision rates, ionization coefficient, mean drift velocity, electron density, etc.) are analyzed. The results show that the variations of the initial energy of the electron emitted from the cathode and the cathode reflection cause a weak effect on the electron transport parameters in the two discharges. The results also indicate that the electron transport parameters are quite different in normal and abnormal discharges.     

高入射能量下的金属二次电子发射模型

基于高入射能量电子产生二次电子发射的物理过程, 分别对高入射能量电子产生的真二次电子和背散射电子的概率进行理论分析与建模. 利用Bethe能量损失模型和内二次电子逸出概率分布, 推导出高入射能量电子产生有效真二次电子发射的系数与入射能量的关系式; 根据高入射能量电子在材料内部被吸收的规律, 推导出高入射能量电子产生背散射电子的系数与入射能量之间的关系式. 结合两者得到高入射能量下金属的二次电子发射模型. 利用该模型计算得到典型金属材料Au, Ag, Cu, Al的二次电子发射系数, 理论计算结果与采用Casino软件模拟金属内部散射过程得到的数值模拟结果相符. 关键词： 二次电子发射 高入射能量 金属表面 散射过程     

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研究了强激光等离子体中多光子非线性Compton效应下阻尼电子与光子的散射特性,推出了其微分散射截面表达式。研究表明,尾波场的涨落和随机误差是电子发生纵向群聚的根本原因,且能引起电子更剧烈的群聚。电子横向动量的变化是引起电子和光子散射的根本原因,其微分散射截面随与一个电子同时作用的光子数的增大而减小,随散射非弹性成分的增大而迅速减小,但比激光场中的情况来得慢一些。只有当与电子同时作用的光子数与散射非弹性成分相等时电子才能被光场俘获。     

Experimental studies of gyrotron electron beam systems

In order to provide electron beams of powerful gyrotrons, magnetron-injection guns operating in the regime of the temperature limited current are used. The electron beam quality and gyrotron performances are defined both by the cathode emission processes and the processes occurring in the electron beam during its formation and transportation. The results of measurements of the energy spectrum and velocity spread of the gyrotron electron beam in different regimes are given. Experimental data on the parameter of efficient emission inhomogeneity for different regimes are presented, as well as the dependencies of electron beam parameters on efficient inhomogeneity of the cathode     

Experimental Study of Planar Langmuir Probe Characteristics in Electron Current-Carrying Magnetized Plasma

Experimental study of planar Langmuir probe characteristics in a magnetized plasma with an electron current along the direction of the magnetic field shows that the usual procedure for determination of the electron temperature and plasma density, which is applicable in a current-free magnetized plasma, gives erroneous results for these plasma parameters. When this procedure is applied on the characteristics measured at two opposite orientations of the probe collecting surface with respect to the direction of the electron drift, different values of the electron temperature are obtained. These virtual electron temperatures and corresponding plasma densities calculated from the measured ion saturation currents are higher and/or smaller than the exact local electron temperature and plasma density. Calculation of particular averages of these quantities is proposed as a possible way to obtain correct results for the local electron temperature and plasma density. These averages are used in the approximate evaluation of the electron drift velocity from the electron saturation currents measured at the two orientations of the probe collecting surface.     

Cross sections of electron capture and electron capture ionization versus the impact parameter in collisions of a proton with multielectron atoms

The absolute differential cross sections of scattering of hydrogen atoms resulting from an electron capture and an electron capture ionization are measured for collisions of 4.5- and 11-keV protons with argon and xenon atoms. The range of scattering angles is 0°–2°. From the scattering differential cross section found experimentally, the probabilities of single-electron capture and electron capture ionization as a function of the impact parameter are calculated. The dependences of the incident particle scattering angle on the impact parameter (deviation function) for interactions with Ar and Xe atoms are calculated in terms of classical mechanics using the Moliére—Yukawa potential to describe the interaction of atomic particles. Analysis is given to the probabilities of electron capture and electron capture ionization versus the impact parameter and to the distribution of the electron density on different electron shells in a target atom versus a distance to the core. It is concluded that only electrons from the outer shell of the target atom are involved in the process of electron capture ionization. The cross section of electron capture ionization is calculated in the proton energy range 5–20 keV.     

Charge‐transfer complex formations of tetracyanoquinone (cyanil) and aromatic electron donors

Single‐electron oxidants are the primary reagents for investigations of the new oxidants and the development of electron‐accepting materials for application in optoelectronics. Quinones are the well‐known class of the neutral single‐electron oxidants. Here, we present the properties of the strongest neutral electron acceptor of this class tetracyanoquinone (cyanil) and investigate its electron‐accepting strength by analyzing the charge‐transfer complex formations with the aromatic donor molecules. Charge‐transfer complexes of tetracyanoquinone with aromatic electron donors are characterized spectroscopically in solution and isolated as the single crystals. Copyright © 2015 John Wiley & Sons, Ltd.     

Electron reconstruction in CMS

The reconstruction of the energy and momentum of isolated electrons in CMS combining tracking and electromagnetic calorimetry information is described. The emphasis is put on primary electrons with transverse momentum below 50 GeV/c. The energy deposited in the electromagnetic calorimeter is measured in clusters of clusters (superclusters) which collect bremsstrahlung photons emitted along the electron trajectory in the tracker volume. The electron tracks are built from seeds in the pixel detector found via a cluster-driven pixel hit matching algorithm, followed by a reconstruction of trajectories in the silicon strip tracker with a Gaussian sum filter. Electrons are classified using observables sensitive to the pattern of bremsstrahlung emission and electromagnetic showering in the tracker material. Energy scale corrections depending on the electron class are applied to the supercluster and estimates of associated errors are obtained. The electron energy is deduced from a weighted combination of the corrected supercluster energy and tracker momentum measurements. The electron direction is that of the reconstructed electron track at interaction vertex. The pre-selection of isolated electron candidates for physics analysis is described. Class-dependent observables combining tracking and calorimetry information are discussed for electron identification.     

Donor impurity-related photoionization cross section in GaAs cone-like quantum dots under applied electric field

The donor impurity-related electron states in GaAs cone-like quantum dots under the influence of an externally applied static electric field are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron–impurity correlation effects. The uncorrelated Schrödinger-like electron states are obtained in quasi-analytical form and the entire electron–impurity correlated states are used to calculate the photoionisation cross section. Results for the electron state energies and the photoionisation cross section are reported as functions of the main geometrical parameters of the cone-like structures as well as of the electric field strength.     

直流空心阴极放电中鞘层区电子的输运过程

采用蒙特－卡洛方法对空心阴极放电中鞘层区电子的输运过程进行了研究，电子在鞘层区被非均匀电场加速，两次碰撞之间的步长是由电子与中性粒子的碰撞频率确定。模型中三种碰撞截面积是由实验和理论数据拟合而来。研究了电子平均能量、电子密度和电离系数在径向的分布。电子能量的空间分布结果与实验很好地符合。 关键词：     

电子清刷对微通道板增益及输出信噪比的影响

电子清刷是微通道板生产流程中常用的除气方法,会引起微通道板其他性能参量的变化.为研究电子清刷对微通道板输出信噪比及增益的影响,根据信噪比及增益的定义讨论了微通道板性能参量的测试方法,研制了微通道板参量测试系统.应用微通道板参量测试系统对微通道板进行了电子清刷处理,测试清刷过程中不同阶段微通道板的信噪比及增益变化.实验表明:微通道板增益随清刷时间增加而降低,同时增益稳定性提高;电子清刷过程中微通道板的输出信号及噪音的变化率与微通道板增益的变化率基本相同,输出信噪比基本不变.增益变化是影响清刷过程中信号及噪音变化的主要因素,并且电子清刷对微通道板输出信噪比影响较小.     

毫米波速调管电子光学系统的研究

电子光学系统是毫米波速调管长寿命和整管性能实现的关键,毫米波速调管零件尺寸较小,为了在Ka波段和W波段实现千瓦量级的输出功率,要求具有高的电子注通过率及低的阴极负荷。对Ka波段和W波段电子光学系统特性进行了分析,确定了Ka波段10 kW分布作用速调管和W波段1 kW分布作用速调管电子光学系统的设计方案,利用软件对电子枪和聚焦系统的结构进行计算,并采用CST仿真软件对设计的电子枪发射的电子注在聚焦磁场中的状态进行优化。设计出的Ka波段速调管电子光学系统,电子枪工作电压26 kV,发射电流2 A,互作用区长度30 mm,磁场强度大于0.6 T,流通达到100%。设计的W波段速调管电子光学系统,电子枪工作电压17 kV,电流0.65 A,互作用区长度20 mm,磁场大于0.9 T,流通达到100%。已制成Ka波段速调管和W波段速调管,设计的电子光学系统能够满足速调管工程化需求。     

含负折射率介质的一维光子晶体构成的相干热辐射源的辐射特性及控制

电子清刷是微通道板生产流程中常用的除气方法,会引起微通道板其他性能参量的变化.为研究电子清刷对微通道板输出信噪比及增益的影响,根据信噪比及增益的定义讨论了微通道板性能参量的测试方法,研制了微通道板参量测试系统.应用微通道板参量测试系统对微通道板进行了电子清刷处理,测试清刷过程中不同阶段微通道板的信噪比及增益变化.实验表明:微通道板增益随清刷时间增加而降低,同时增益稳定性提高;电子清刷过程中微通道板的输出信号及噪音的变化率与微通道板增益的变化率基本相同,输出信噪比基本不变.增益变化是影响清刷过程中信号及噪音变化的主要因素,并且电子清刷对微通道板输出信噪比影响较小.     

Exchange and correlation effects in a semiconductor quantum-well wire

The exchange and correlation effects of a quasi-one-dimensional electron gas are investigated by using the self-consistent-field approximation theory proposed by Singwi, Tosi, Land and Sjölander for the response function of the electron system. The present results are applied to GaAs-GaAlAs rectangular quantum-well-wires with the appropriate form factors that take into account the influence of the finite width of the electron layer. The plasmon dispersion relation and structure factor are calculated as a function of electron density and thickness of the wire. Results for the total energy per electron including kinetic, exchange and correlation energies and electron effective mass are presented. The Hartree-Fock and the random-phase approximation (RPA) results are also presented for comparison. We have found that exchange and correlation effects are more evident in wires of reduced dimensions.     

Chaotic characteristics of electron motion in the static magnetic fields and self-fields of the electron beam

In this paper We study the properties of electron motion when a nonneutral electron beam goes through a static magnetic field. The self-electronic and magnetic fields also affects on the test electron. The Hamiltonian equations of electron motion are deduced and the Poincare surface of section and the Lyapunov exponent are used to prove that the electron motion becomes chaotic when the fields are strong enough.