电子束泵浦注入锁定XeCl准分子激光理论模拟

模拟了强流电子束泵浦下,激光腔内的反应动力学过程,及不同注入时间、不同注入强度下注入锁定的激光生成、放大和输运过程。对实际非稳腔使用了一维伸展近似,并采用了预估—校正方法对光子输运方程进行求解。模拟结果表明,激光生成阶段,注入种子光源后,激光输出质量明显改善,使自发辐射部分受到了明显的抑制。得到了在不同注入强度、注入时间以及放大倍数下的激光输出的光谱特性,能量及各种效率的关系。发现锁定效果最佳时的注入时间出现在小信号增益峰值处。     

冷阴极微波电子枪初步研究北大核心CSCD

基于场发射的冷阴极微波电子枪兼具光阴极微波电子枪和热阴极微波电子枪的优点,可望提供低发射度、低能散以及较高流强的电子束,应用于自由电子激光等领域。介绍了这种电子枪的特点,以及在中国工程物理研究院应用电子学研究所的研究进展。场发射通常要求非常高的电场强度,通过对金刚石薄膜进行掺杂,可以降低其有效功函数,从而在相对低的场强下获得足够高的发射电流。结合场发射的特点,从腔型、反轰、加速效率以及束流孔径等方面对冷阴极微波电子枪进行了设计,并给出了初步的设计结果。利用粒子模拟程序对该电子枪的场发射情况进行了模拟,结果表明有望获得发射度很低的电子束团。     

强流脉冲电子束应力诱发的微观结构

利用强流脉冲电子束装置在各种工艺条件下对奥氏体不锈钢、单晶铝及多晶铝等面心立方金属进行辐照处理.利用扫描电子显微镜和透射电子显微镜等详细分析了辐照样品的变形组织与结构.通过分析，在一定程度上建立起强流脉冲电子束诱发的应力特征与变形结构之间的关系，并对目前现有的几种应力波数值模拟结果进行了分析.实验结果表明，强流脉冲电子束能够在材料内部诱发10²—10³MPa的应力，其传播方式与材料的 晶体结构关系密切.这一应力是导致材料深层性能与微观组织结构发生变化的根源所在. 关键词： 强流脉冲电子束 应力 微观结构 变形     

光学渡越辐射测量中能量分辨精度分析

 基于光学渡越辐射原理的用于高能强流电子束束流参数在线测量及诊断系统,具有时间响应快、分辨率高等特点,可以测量电子束的束剖面、发散角、能量等多个参数。分析了测量系统的结构参数（包括了透镜的焦距、成像面位置、CCD像元尺寸）对电子束能量测量精度的影响,并在理论上模拟了电子束的发散角的影响。还根据系统数据的特点,阐述了数据噪声对能量测量结果精度的影响,指出了光学渡越辐射测量中电子束能量分辨精度受到多种因素的影响,需要在数据处理时考虑修正。     

Spindt型与薄膜场致发射的数值模拟与特性比较

采用质点网格法（particle-in-cell）,利用MAGIC软件模拟了场致发射的物理过程.对两 种典型的场致发射模型（Spindt阴极发射体和金刚石薄膜发射体）分别进行了模拟.对Spind t阴极发射，研究了发射特性与尖端尺寸，尖端与栅极面的相对高度的关系.对金刚石薄膜发 射，比较了三极管和四极管的发射特性，以及薄膜面积对发射特性的影响，得出金刚石薄膜 发射体优于Spindt发射体的特性. 关键词： 场致发射 MAGIC程序 Spindt发射体 金刚石薄膜发射体     

基于时标系统的条纹相机动态畸变

针对神光Ⅲ原型实验中出现的动态畸变现象,开展了条纹相机动态成像特性研究。结合实验图像,利用CST Particle Studio软件模拟了强信号下变像管的成像过程,结果表明:在强信号下,变像管的空间电荷效应会造成电子束聚焦点与理想成像面距离减小,使得图像的放大倍数变小,产生信号弯曲现象,并且这一现象随着电流强度的增加更为明显。     

基于时标系统的条纹相机动态畸变

针对神光Ⅲ原型实验中出现的动态畸变现象,开展了条纹相机动态成像特性研究.结合实验图像,利用CST Particle Studio软件模拟了强信号下变像管的成像过程,结果表明:在强信号下,变像管的空间电荷效应会造成电子束聚焦点与理想成像面距离减小,使得图像的放大倍数变小,产生信号弯曲现象,并且这一现象随着电流强度的增加更为明显.     

非均匀磁场约束条件下的电子束空气等离子体特性

为了揭示大气环境电子束等离子体的性质,基于蒙特卡罗程序包Geant4建立了一个包含电离、激发以及轫致辐射等物理过程的计算模型,用于模拟非均匀磁场约束条件下高能强流稳态电子束的输运特性、以及大气环境等离子体的性质。结果表明:非均匀磁场可以有效控制电子束在空气中的输运轨迹,显著降低电子束的发散;随着电子束在空气中行程的增加,电子束能谱开始展宽并向低能区移动;输运装置出口能量损失比电子束射程末端高2个量级,且随着电子束输运距离的增加,等离子体密度降低;等离子体密度的高低与电子束能量直接相关。     

2MeV注入器脉冲电子束时间分辨能谱诊断研究

 介绍了利用磁分析器和电子束产生的契伦科夫辐射光诊断直线感应加速器脉冲电子束时间分辨能谱的原理、方法及诊断系统，对中物院2MeV感应叠加型注入器的2kA强流脉冲电子束时间分辨能谱进行实验诊断，并与二极管电压进行对比分析。测得能量约2.2MeV，60ns内最大能量变化为4%。     

大面积二极管束流诊断

本文叙述了新研制的用于测量大面积相对论性电子束流强的方形罗可夫斯基线圈、薄膜回流器及法拉第筒等三种装置的结构、特性及试验结果。     

电介质/半导体结构样品电子束感生电流瞬态特性

电子束照射下电介质/半导体样品的电子束感生电流(electron beam induced current,EBIC)是其电子显微检测的重要手段.结合数值模拟和实验测量,研究了高能电子束辐照下SiO2/Si薄膜的瞬态EBIC特性.基于Rutherford模型和快二次电子模型研究电子的散射过程,基于电流连续性方程计算电荷的输运、俘获和复合过程,获得了电荷分布、EBIC和透射电流瞬态特性以及束能和束流对它们的影响.结果表明,由于电子散射效应,自由电子密度沿入射方向逐渐减小.由于二次电子出射,净电荷密度呈现近表面为正、内部为负的特性,空间电场在表面附近为正而在样品内部为负,导致一些电子输运到基底以及一些出射二次电子返回表面.SiO2与Si界面处俘获电子导致界面附近负电荷密度高于周围区域.随电子束照射样品内部净电荷密度逐渐降低,带电强度减弱.同时,负电荷逐渐向基底输运,EBIC和样品电流逐渐增大,电场强度逐渐减小.由于样品带电强度较弱,表面出射电流和透射电流随照射基本保持恒定.EBIC、透射电流及表面出射电流均随束流呈现近似正比例关系.对于本文SiO2/Si薄膜,透射电流随束能的升高逐渐增大并接近于束流值,EBIC在束能约15 keV时呈现极大值.     

Self-consistent charging in dielectric films under defocused electron beam irradiation

We clarify the transient and equilibrium charging characteristics of grounded dielectrics due to low-energy defocused electron beam irradiation by a three-dimensional self-consistent simulation model. The model incorporates the electron scattering, transport and trapping. Results show that some electrons can arrive at the grounded substrate due to the internal field and density gradient, forming the leakage current. The transient charging process tends to equilibrium as the surface potential decreases and the leakage electron current increases. The positive and negative space charges are distributed alternately along the beam incident direction. In the equilibrium state, the surface potential and leakage electron current decrease to stable values with increasing film thickness and the trap density, but with decreasing electron mobility. Moreover, the surface potential of the dielectric thin film exhibits a maximum negative value with variation of the beam energy; for example, under the condition of the film thicknesses 0.5 μm and 2 μm, the maximum negative values of surface potentials are -13 V and -98 V in beam energies 2 keV and 3.5 keV, respectively. However, for the thick film, the surface potential decreases with the increase in beam energy.     

Electron energy loss and secondary emission mechanisms in BaO

Electron Loss Spectroscopy (ELS), X-ray Photoemission (XPS), Secondary Emission Energy Distribution, and Secondary Electron yield data have been obtained on both evaporated films and sprayed-on coatings of BaO. Using the ELS correlated with the XPS data, bulk and surface plasmon losses as well as excitonic and interband transition electron loss mechanisms have been identified. It was found that at low primary beam energies (<100 eV), structure in the secondary emission energy distribution could be correlated with a conduction band energy structure. This structure was consistent with the model used to explain the loss transitions. The structure in the energy distribution curves shows little, if any, correlation with plasmon decay mechanisms and other two-step electron emission processes. On the contrary, for the case of BaO (at least at low primary energies), the energy distribution data and structure in the secondary yield vs. primary beam energy data indicate that most secondaries are produced by direct excitation of secondaries by the primary electrons.     

Secondary electron yield measurements of carbon covered multilayer optics

Carbon contamination on extreme ultraviolet (EUV) optics has been observed in EUV lithography. In this paper, we performed in situ monitoring of the build-up and removal of carbon contamination on Mo/Si EUV multilayers by measuring the secondary electron yield as a function of primary electron energy. An electron beam with an energy of 2 keV was used to simulate the EUV radiation induced carbon contamination. For a clean EUV multilayer, the maximum secondary electron yield is about 1.5 electrons per primary electron at a primary electron energy of 467 eV. The maximum yield reduced to about 1.05 at a primary electron energy of 322 eV when the surface was covered by a non-uniform carbon layer with a maximum thickness of 7.7 nm. By analyzing the change in the maximum secondary electron yield with the final carbon layer thickness, the limit of detection was estimated to be less than 0.1 nm.     

Influence of charge deposition in a field-emission display panel

Field-emission displays (FEDs) have been studied intensively in recent years as a candidate for flat-display panels in the future. In a FED, electrons emit from field emitters. Some electrons may impinge on the insulator surface between cathode and gate electrodes and cause charging of that surface because the yield of secondary electron emission is usually not equal to one. The charging of the insulator walls between cathode and gate electrodes is one of the important factors influencing the performance of a FED. In this paper, a simulation program is used to calculate this charge deposition, electric field distribution and electron trajectories. From the change of the electric field upon charge deposition in the triode region, it is shown that the insulator surface is negatively charged at a low gate voltage, e.g. 20 V. However, positive charge is deposited when the gate voltage is high, e.g. 100 V. The simulations also show that the emission current will increase even further after coating the dielectric with a thin film of a material with a high-secondary emission coefficient such as MgO. If a cone-shaped dielectric aperture is used in a triode, the emission current will decrease after charge deposition. However, the focus performance of the electron beam is improving in this case.     

强电场中的脉冲束流强度测量方法

针对强电场中电场渗透的问题,采用特殊的法拉第筒法测量脉冲束流强度:在法拉第筒入口处用栅网屏蔽强电场,并用在收集板上加正压的方式抑制二次电子。采用解析计算和数值模拟方式对栅网的形状进行了选择,在同样的栅网丝宽和透过率的前提下,通过正六边形栅网的渗透电场最弱,因此选择正六边形栅网。将设计的法拉第筒用于一台真空弧离子源的束流强度测量,获得了该离子源的束流强度波形,其峰值流强约为550 mA;利用测量结果计算了混合离子束在Cu收集板上的二次电子发射系数,约为2.0。     

An application of the dust grain charging model to determination of secondary electron spectra

Dust grains – objects of different shapes with a size distribution from micro to nanometers – are generally considered as a part of many space as well as laboratory plasmas. Among various dust charging processes, electron-induced secondary emission plays an important role in plasmas containing a noteworthy portion of high-energy electrons. Since a part of secondary electrons has not the energy high enough to overcome the surface potential barrier, the resulting grain charge is determined not only by the secondary emission yield (related to the grain material and size) but also by the secondary electron spectrum. We have developed a model of secondary electron emission from small dust grains. In the present contribution, we discuss the profile of a secondary emission yield that can be received from the model and the measured equilibrium grain charge, both as functions of an incident electron beam energy. A comparison of these quantities leads to an estimation of secondary electron spectra. We have found that: (1) the energy spectrum of secondary electrons does not change with the energy of primary electrons and (2) the energy spectrum depends on the target material being harder for gold and silver than for glass grains.     

Anomalous asymmetry of carbon nanopillar growth on both sides of a thin substrate irradiated with a focused electron beam

The dynamics of carbon nanopillar growth on both surfaces of amorphous carbon films 40–180 nm thick irradiated with a focused electron beam with an energy of 20 keV is studied. Prolonged irradiation causes the retardation and even complete termination of nanopillar growth on the upper side of the substrate while growth on the lower side continues. This unexpected result is explained by the dissociation of precursor molecules diffusing along the substrate by secondary electrons emitted from the conical nanopillar tip. The substrate acts as a filter allowing primary electrons to easily pass, but intercepting low energy secondary electrons. The lower efficiency of secondary electrons emitted in the lower half-space may be due to a decrease in the current density within the expanding beam of scattered electrons.     

新型二次电子倍增阴极构型设计与动力学过程

提出了一种可由脉冲功率驱动的新型二次电子倍增阴极构型,并对其进行了动力学过程的初步理论研究。首先,针对该二次电子倍增阴极,建立了动力学模型,获得了二次电子的位移和速度方程,讨论了电子初始出射速度对其轨迹、渡越时间和碰撞能量的影响,理论给出了渡越时间和碰撞能量的近似解析表达式。其次,通过动力学方程与Vaughan二次电子产额经验公式的耦合求解,获得了该二次电子倍增阴极的工作区间,并对其进行了细致讨论。结果表明:该新型二次电子倍增阴极二极管概念上是可行的,在涂敷高二次电子产额系数材料的圆柱形介质上施加合适的轴向和径向静电场(MV/m量级)以及轴向静磁场(T量级),可以达到电子沿阴极表面螺旋行进过程中实现二次电子倍增并最终获得电流沿轴向放大的设计目标。另外,讨论了正电荷沉积引发的二次电子倍增饱和现象,并对阴极发射电流密度进行了理论粗估,结果表明:阴极发射电流密度可达kA/cm2水平,具备强流发射特性;增加外加径向场强幅值可有效提升阴极发射电流密度。     

电子辐照聚合物带电特性多参数共同作用的数值模拟

电子辐照聚合物样品的带电特性是扫描电子显微镜成像、电子束探针微分析以及空间器件辐照效应等领域的一个重要研究课题. 通过建立基于蒙特卡罗方法的电子散射和时域有限差分法的电子输运的数值模型, 并采用高效的多线程并行计算, 模拟了电子非透射辐照聚合物样品的带电特性, 得到了带电稳态下的样品底部泄漏电流密度、表面负电位以及样品总电荷密度等带电特征量受入射电子能量、入射电流密度、样品材料的电子迁移率、样品厚度等相关参数共同作用的影响. 结果表明, 一个参数的变化使表面负电位增强时, 其他参数对负电位的影响将增强. 样品的带电稳态特征量在同一个电流平衡的模式下受参数影响的变化是单调的. 当电流平衡模式发生变化时, 如在入射电子能量较低的条件下, 样品内部的总电荷量会随着样品厚度的增大而先增加后减小, 出现局部极大值. 样品底部的泄漏电流密度随着入射电流密度的增大而近线性成比例地增大. 研究结果对于揭示电子辐照聚合物的带电规律及微观机理、预测不同条件下的样品带电状态具有重要科学意义.