TE（A）激光器中放电电极的设计与选择

介绍了TE（A）激光器中Rogowski电极和近似Rogowski电极、Chang电极和紧凑式Chang电极、两类Ernst电极和紧凑式Ernst电极的设计方法。给出了上述放电电极的面型和表面电场分布，简述了制造上述电极的注意事项。在同等电场均匀度和均匀电场分布范围的情况下，对比了保角映射型电极的尺寸大小和电场分布特点。综合放电电极的面型、制造难度、辉光放电实验可知，在要求高能量和高功率的场合下，选择Ernst电极较好；在脉冲激光指标要求一般的场合下，选择近似Rogowski电极较好。     

Modelling of the influence of interelectronic interaction on the stationary characteristics of a resonant tunnel diode with spacer layers

The influence of the interelectronic interaction on the stationary characteristics of a resonant tunnel diode (RTD) with spacer layers (spacers) is investigated by means of a self-consistent solution to Schr?dinger and Poisson equations. It is demonstrated that the interelectronic interaction influences significantly the RTD voltampere characteristics, in particular, it decreases the peak current density and displaces the position of maxima of the peak current dependence on the emitter spacer size. It is also demonstrated that the hysteresis of the RTD volt-ampere characteristics vanishes for definite spacer sizes.     

Oscillatory ferromagnetic interlayer coupling in [Pt(5 Å)/Co(4 Å)]3/Cr(x Å)/[Co(4 Å)/Pt(12 Å)]3 multilayers with perpendicular anisotropy

Investigation has been performed on the interlayer coupling between two Co/Pt multilayers with perpendicular anisotropy separated by Cr spacers. As a function of the Cr spacer thickness, only ferromagnetic interlayer coupling has been observed between the two Co/Pt multilayers in contrast to the oscillatory interlayer coupling between ferromagnetic and antiferromagnetic observed in ferromagnetic layers with in-plane anisotropy separated by Cr spacers. It is the strength of the ferromagnetic interlayer coupling that has been observed to be oscillatory as a function of the Cr spacer thickness with a period of about 7 Å.     

First-principles studies of interlayer exchange coupling in (Ga,Co)N-based diluted magnetic semiconductor multilayers

Interlayer exchange coupling (IEC) in a series model diluted magnetic semiconductor (DMS) multilayer consisting of two magnetic (Ga, Co)N layers separated by non-doped or Mg-doped GaN non-magnetic spacers has been studied by first-principles calculations. The effects of the spacer thickness and hole doping to the IEC were studied systematically. It is observed that (1) for the GaN spacers without Mg doping, the IEC between two magnetic (Ga, Co)N layers is always ferromagnetic, which is clarified as an intrinsic character of the Ruderman–Kittle–Kasuya–Yoshida (RKKY) interaction based on a two-band model for a gapped system; and (2) for the Mg-doped GaN spacers, the IEC is tunable from ferromagnetic to antiferromagnetic by varying the spacer’s thickness and the dopant’s site.     

Metallic-type oscillatory interlayer exchange coupling across an epitaxial FeSi spacer

We study interlayer exchange coupling in epitaxial Fe/Fe(0.56)Si(0.44)/Fe trilayers. Iron-silicide spacers with high structural and compositional homogeneity for thicknesses up to 34 A are grown by coevaporation from two electron-beam sources. The coupling strength oscillates with spacer thickness for temperatures from 20 to 300 K with two antiferromagnetic maxima at 12 and 26 A, and it clearly increases with decreasing temperature down to 80 K. We conclude that the coupling across ordered Fe(1-x)Si(x) ( x approximately 0.5) is described by the conventional theory of interlayer coupling across metallic spacers.     

Resonant tunneling of electrons through virtual interference states formed as a result of reflection from the boundary of strongly doped region of GaAs

The paper is devoted to analysis of the electron transport through one-barrier GaAs/AlAs/GaAs heterostructures. The oscillating component of transport characteristics of symmetric one-barrier GaAs/AlAs/GaAs heterostructures with spacers, which is associated with resonance tunneling of electrons via virtual states formed in the spacer region of the structures due to reflection of electrons from the n^?-GaAs/n⁺-GaAs interface and their subsequent interference. It is shown that electrons are predominantly reflected coherently from the boundary of the strongly doped region as in the case of one-dimensional averaged potential of randomly arranged (beginning from this boundary) impurities. It is shown that low-energy virtual resonances are suppressed due to electron scattering as a result of their interaction with longitudinal optical (LO) phonons in the spacer region.     

沿面闪络流体模型电离参数粒子模拟确定方法

介绍了粒子模拟确定高功率微波介质沿面闪络击穿流体模型相关电离参数的方法.对粒子模拟方法 (包括带电粒子动力学方程、次级电子发射以及蒙特卡罗碰撞模型)和流体整体模型方法 (包括连续性方程和能量守恒方程)做了简介.基于自编的1D3V粒子模拟-蒙特卡罗碰撞程序给出了在高(低)气压、不同气体种类以及不同微波场强和微波频率下流体模型电离参数的粒子模拟结果,包括电离频率、击穿时间、平均电子能量、电子能量分布函数类型.研究结果表明:平均电子能量与电子能量分布函数类型关系不大;中低气压下,电子能量接近Maxwell分布,电子能量分布函数类型对电离参数几乎没有影响;中高气压下,电子能量分布函数类型对电离参数有重要影响,其依赖系数X趋于高阶形式.不同气体的电子能量分布函数类型不同,需要利用粒子模拟对电子能量分布函数类型进行标定.同时,电子能量分布函数依赖系数与微波场强和频率也有关系,其随微波场强增加而增大,随微波频率增加而减小.在给定考察范围(微波场强在7 MV/m以下,微波频率在40 GHz以内),中低气压下,平均电子能量随微波场强增加而迅速增大,电离频率随微波场强增加先增大后降低,平均电子能量随微波频率增加而降低,电离频率随微波频率增加先增加后降低;高气压下,平均电子能量随微波场强增加而缓慢增大,电离频率随微波场强增加而增大,微波频率对平均电子能量和电离频率影响不大.     

Study of Diffusion Bonding of 45 Steel through the Compacted Nickel Powder Layer

The microstructure of the transition zone and powder spacer, the concentration distribution of chemical elements over the width of the diffusion-bonded joint, and microhardness of 45 steel–compacted Ni powder spacer–45 steel layered composites formed by diffusion bonding have been investigated. It has been shown that the relative spacer thickness χ < 0.06 is optimal for obtaining a high-quality joint has been formed under a compacting pressure of 500 MPa. The solid-state diffusion bonding is accompanied by sintering the nickel powder spacer and the formation of the transition zone between the spacer and steel. The transition zone consists of solid solution of nickel in the α-Fe phase and ordered solid solution of iron in nickel (FeNi₃).     

亚纳秒前沿有界波模拟器传输线设计的理论分析与实验

 介绍了亚纳秒前沿有界波模拟器的组成、主要技术指标和传输线结构。用时域有限差分法对模拟器的场传播和场分布进行了数值模拟,并实测了工作区域的电场分布。测量结果表明:不同位置处场的上升时间基本不变,约为800 ps,1 m×1 m×1 m工作区域内的电场两侧不均匀性约为10%,前后位置约为±50%,满足技术指标要求,场的分布与数值模拟结果相一致。     

Microscopic theory of dipole-exchange spin waves in magnetic multilayers

A microscopic model is employed to calculate the spectrum of dipole-exchange spin waves in multilayers in which thin ferromagnetic films are separated by non-magnetic spacers. Two configurations are considered: in one the films have magnetizations parallel to each other, in the other the magnetizations are antiparallel. The calculations extend a previous microscopic formalism that allows the calculation of the dipole-exchange spin wave spectrum in thin films. The results show the splitting of the frequency bands and the mode mixing caused by the dipolar interaction between the films as a function of spacer thickness.Received: 26 May 2004, Published online: 12 August 2004PACS: 75.30.Ds Spin waves - 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.) - 75.70.-i Magnetic properties of thin films, surfaces, and interfaces     

集成电光器件电极的数值分析法

本文描述了一种数值分析方法,计算了集成光学中电光器件电极的电场分布。在电极无限薄的假设条件下,把数值分析法计算的结果同保角变换法的结果进行了比较,并讨论了电极厚度和缓冲层对电场以及特征参量的影响。计算结果表明电极厚度对电场分布影响较小,但特征阻抗和有效介电常数随电极厚度增加明显减小。而且使用缓冲层使波导的有效深度增加,电场强度减小,特征阻抗和有效介电常数都发生很大变化。利用这些特性可对集成光学电光器件的电极进行优化设计。     

棒束通道CHF预测方法研究

本文采用实验和数值计算分析相结合的方法,研究了带定位格架棒束通道内过冷流动沸腾工况下临界热流密度(CHF)发生情况.提出了通过采用CFX4.4程序对带定位格架棒束通道内过冷流动沸腾计算来预测CHF发生位置的方法.结果表明,随着程序的发展和物理模型的完善,计算流体动力学方法(CFD)将成为核燃料棒束组件临界热流密度实验、设计和安全评估强有力的计算分析工具.     

Influence of a hydrophilic spacer on the structure of a phospholipid monolayer

Summary We present the results of thermodynamical and X-ray grazing incidence diffraction experiments performed on Langmuir monolayers of ether lipids with hydrophilic spacers between the glycerol backbone and the phosphatidylcholine head group: DHPC, DH-E01-PC, and DH-E02-PC. As a spacer the oxy-ethylene group is used, which is a typical hydrophilic unit of non-ionic tensides. It turns out that the introduction of the hydrophilic spacers leads to a fluidization of the monolayer and reduces the tilt angle of the chains. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Calculation of the eigenvalues of pure quadrupole interaction in Mössbauer effect studies

Summary Two approximate formulae to calculate the eigenvalues of pure quadrupole interaction in M?ssbauer effect studies have been proposed and the eigenvalue coefficients in the formulae have been given for various excited states and ground states of the nucleus with different spin. All the eigenvalues of pure quadrupole interaction between both excited state and ground state of nucleus with spinI=3/2÷9/2 and the electric-field gradient with different asymmetry parameter (η=0÷1.0) have been calculated by these formulae. The results show that the accuracies in all the calculations are more satisfactory or same in comparison with those obtained by the formula of Shenoy and Dunlap, especially when the asymmetry parameter of electric-field gradient is larger than 0.8 for the nucleus with spinI=5/2.     

Mechanisms for the Formation of Electric-Field Pulsation Spectra in the Near-Surface Atmosphere

We present the results of detailed measurements of the spectrum of short-term (f 0.001-1 Hz) pulsations of the electric field of the near-surface atmosphere under the fair-weather and fog conditions. It is shown that the electric-field pulsations at frequencies 10^-2-10^-1 Hz have a power-law spectrum under both fair-weather and fog conditions. The spectral index varies in a range of from -1.23 to -3.36 depending on the experimental conditions, but the most probable values of the index fall in a range of from -2.25 to -3.0. The spectra corresponding to long time intervals of about a few hours are more steep. The relation of the spectral characteristics to the formation of aeroelectric structures (AESs) is studied. The distribution obtained for the structured spectra is bimodal, i.e., it exhibits two maxima in the ranges of spectral indices from -2.75 to -3.0 and from -2.25 to -2.5. The nonstructured-spectrum distribution is asymmetric and has a pronounced maximum corresponding to hard spectra with indices from -2.5 to -3.3. The intensity of the electric-field pulsations under fog conditions increases by about an order of magnitude compared to the case of fair-weather conditions. The mechanisms of spectrum formation of electric-field pulsations and their relations to the pulsation spectra of the electric-charge density with allowance for the neutral-gas turbulence and the presence of AESs are analyzed. We point out the key role of the nonlocal relation between the electric-field intensity and the space-charge density under conditions of spatially inhomogeneous turbulence. Model problems of the spectrum of electric-field fluctuations generated by a homogeneous and structured turbulence in the presence of charge-density fluctuations, considered as a passive tracer, are solved.     

硅中钛杂质对激光电场分布影响的数值模拟

采用T-matrix数值方法模拟光学系统常用的光学材料硅中金属钛杂质对激光电场分布的影响。分析了不同球形杂质数目、不同杂质球半径、不同球形杂质间距、不同球形杂质排列以及不同相对介电常数杂质对激光电场分布的影响,通过数值模拟了解到:电场幅值的最大值总是出现在沿入射波极化方向上,电场幅值的增大与相邻两球的耦合有关,且两球间距越小电场幅值的最大值越大;相对介电常数实部越小、虚部越大的杂质会导致较大的电场幅值最大值。     

Tesla变压器次级线圈电位分布

 为研究Tesla变压器锥形次级线圈的电位和电场分布问题,建立了非均匀参数双传输线模型,采用差分方法获得波动方程的数值解。计算结果表明：脉冲形成线充电过程中,最高场强点从次级线圈小半径端逐渐向大半径端移动;脉冲形成线快速放电后,次级线圈场强最大点位于大半径端部;脉冲形成线不能正常放电时,次级线圈最大场强点也位于大半径端部,此时场强达到最大值,约为平均场强的1.5倍。     

The effect of spatial quantization of the electronic spectrum on the exchange interaction in multilayers

A strong influence of the quantization of the electronic spectrum of nonmagnetic spacers in multilayers is discovered on the dependence of the exchange interaction on the thickness of the spacer. It is shown that the antiferromagnetic dip is observed experimentally in Fe/Cr multilayers, as small thicknesses can be interpreted in terms of the simple RKKY approximation.     

Ab Initio Study of Electric Transport and Interlayer Exchange Coupling in Fe-Si-Fe Systems

We present a first principles study of the magnetoresistance (MR) perpendicular to the planes of atoms and the interlayer exchange coupling (IEC) in Fe-Si-Fe trilayers. In both cases the dependence on the number of spacer layers is investigated, whereby the spacer thickness ranges between 3 and 21 Å for the IEC and extends to 33 Å for the MR in order to obtain the asymptotic behavior. Additionally, the influence of alloy formation at the interfaces on the MR and the IEC is examined. The calculations of the electronic structure are performed within the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method and the transport properties are derived from the Kubo-Greenwood equation. Our results give evidence that inter-diffusion is one of the origins of the small MR, which is observed experimentally in Fe/Si/Fe trilayers. AFM coupling occurs for spacers thicker than 4 Å which is in accordance with the experimental findings. It seems that interdiffusion stabilizes AFM coupling in Fe-Si-Fe trilayers.     

4f–3d exchange coupling in Gd/X/Co (X=Pt, Cr) multilayers

We have studied the interlayer exchange coupling between Gd and Co through Pt and Cr spacers in a series of multilayers. Magnetization curves have been analyzed with a model, taking into account bilinear and biquadratic interlayer exchange couplings between Gd and Co. The interlayer exchange coupling constants have been determined as a function of the Pt or Cr spacer layer thickness.