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%。     

消色散270°偏转磁铁系统设计及束流动力学研究

对三种常用结构的270°偏转磁铁进行系统的分析研究,采用数值计算和模拟方法对双磁铁不对称偏转结构、三块90°磁铁偏转结构和70°+130°+70°偏转结构这三种不同的270°偏转磁铁系统进行模拟,给出偏转系统的消色散传输条件,并且分析了束流包络在偏转系统和出口管道中的变化情况。经过分析对比,详细列出了三种结构的优势与劣势。双磁铁不对称结构适用于医用加速器,三块90°磁铁偏转结构适用于需要在出口长距离漂移的辐照加速器,而70°+130°+70°偏转结构可以满足出口一定距离的无损漂移,同时实现相对较低的成本,是工业辐照加速器较为经济适宜的选择。     

皮秒微脉冲电子束团诊断

介绍一种基于皮秒扫描相机的微脉冲电子束团诊断系统和实验方法。该系统具有很高的灵敏度、皮秒的时间分辨能力和机动灵活的特点,满足射频直线加速器和储存环上电子束团诊断的要求。在我国,我们首次利用该类系统测量了北京正负电子对撞机(BEPC)储存环中脉冲电子束团的波形和初步测量了北京自由电子激光装置射频直线加速器的微脉冲电子束团的时间分布。     

纳秒级时间分辨光谱诊断系统及其辐射防护

强流电子束二极管是强脉冲辐射环境模拟装置和高功率微波技术中的重要研究方向,通过时间分辨光谱诊断研究阴极等离子体的特性是分析强流脉冲电子束二极管工作性能的可靠方法之一。介绍了具有纳秒级时间分辨能力的光谱诊断系统及其工作原理、系统组成和性能参数,并阐述了低抖动同步触发系统的实现方法和时序关系。同时,针对强脉冲辐射模拟装置产生的强脉冲电磁辐射和强X、γ射线辐射对光谱诊断系统造成严重干扰的情况,设计了电磁屏蔽室和铅屏蔽室对诊断系统进行保护。对黄铜阴极的等离子体进行时间分辨光谱测量,实验结果表明,随着二极管脉冲电压和电流的上升,参与形成阴极等离子体的元素和物质成分明显增多。该光谱诊断系统的时间分辨能力为10 ns,最小可达2 ns,同步触发系统的抖动小于4.0 ns,为深入研究二极管的阴极发射机理开辟了新的技术途径。     

基于移位双光栅色散元件的X射线谱仪研制

本文针对激光等离子体X射线诊断的需求,设计开发了移位双光栅X射线谱仪.该谱仪采用高线对密度和低线对密度的两种光栅组成移位双光栅作为核心衍射组件,高密度光栅能够提高中、高能区(1000—5000 eV)的能谱分辨率,低密度光栅足够满足低能区(100—1000 eV)测量的能谱分辨率要求,控制了低能区谱线的分布空间,保证足够的测量范围.两种光栅相互配合实现了谱仪整体性能提升.本文提出了移位双光栅X射线谱仪结构设计方法和参数指标,完成了移位双光栅X射线谱仪的集成调试和实验应用,获得了时间分辨的X光谱实验数据,测谱范围0.1—5.0 keV,谱分辨0.04 nm,时间分辨好于30 ps.移位双光栅X射线谱仪可以最大程度地利用记录面的长度,实现高时间分辨和宽谱X射线测量.     

“神龙一号”电子束时间分辨能谱测量新方案

介绍了"神龙一号"直线感应加速器电子束时间分辨能谱测量新方案——用螺线管磁场旋转束流法测量其出口电子束能谱,阐述了旋转束流法基本原理及测量方案设计,并且讨论了测量误差。此方案所测能谱为时间分辨离散型束流能谱,其误差与所测离散束流能谱相关。通过测量"神龙一号"加速器末端的电子束流在螺线管磁场中的旋转角度及角度展宽,从而得到脉冲电子束流能谱。     

神龙二号多脉冲电子束束参数的时间分辨测量技术

神龙二号是一台三脉冲强流脉冲电子束直线感应加速器,就其多脉冲的电子束束参数的测量而言,基本要求是单个脉冲可分辨,进一步的要求是脉冲内时间可分辨。基于光学渡越辐射原理及瞬态发射度测量系统原理,发展了一种束斑与发散角可以分开测量的光学布局结构,结合多台高速分幅相机,成功研制了一套完整的多脉冲电子束束参数的测量系统,其特点是灵活的组合测量方式,全面满足了神龙二号复杂艰难的调试及参数测量工作要求。测量系统最高时间分辨测量能力达到约2 ns的水平,单个脉冲可以获得至少8个时间分辨的束参数测量结果。     

用于Z箍缩X辐射谱诊断的柱面凸晶摄谱仪的性能分析

 考虑X光源的空间尺寸和晶体的摇摆曲线,用光线追迹方法计算了诊断丝阵Z箍缩等离子体X辐射谱的柱面凸晶摄谱仪的色散、能谱分辨和空间分辨以及系统参数对它们的影响。结果表明：决定柱面凸晶摄谱仪能谱分辨的主要因素是光源尺寸以及光源-晶体之间距离;增大光源-晶体之间距离能够改善能谱分辨,但导致径向空间分辨能力下降。并依此建立了云母晶体摄谱仪,在“强光一号”装置上对系统进行了测试,获得时间积分铝丝阵负载Z箍缩等离子体X辐射谱。     

基于太赫兹脉冲加速及扫描电子束的高时间分辨探测器

与传统条纹相机加速和偏转电子束的方法相比,太赫兹强场的加速梯度和扫描偏转梯度有明显优势,具备实现飞秒级超高时间分辨的能力.本文基于这一新技术设计了一款基于太赫兹场操控电子束的超小型高时间分辨探测器.从理论上分析了加速区的时间弥散与电子脉冲发射时刻以及初始时间弥散的关系,并讨论了空间电荷效应对时间弥散的影响;设计并优化了加速区和偏转区的太赫兹脉冲耦合增强装置,太赫兹脉冲电场在该装置中的增强系数最高可达9.39.最终通过计算和分析本探测器的时间弥散,得到了时间分辨率优于50 fs的结果.     

用变换方程测量窄带阿秒超紫外线XUV脉冲的强度时间结构

阿秒超紫外线(extreme ultra-violet, XUV)与飞秒超短激光脉冲共同激发惰性气体原子产生光电子，其终态能量与光电子产生时刻即激光相位有关. 介绍光电子的激光相位确定法，并利用光电子能谱本身(其比例谱)，计算出待测窄带XUV脉冲的强度时间结构. 研究表明，在与激光线性极化方向成0°或180°方向测量得到的光电子能谱动态范围大，容易解谱. XUV脉冲的时间宽度的测量范围为半个激光振荡周期，时间分辨率主要取决于测量系统的时间晃动和控制精度. 关键词： 光电子能谱 相位确定法 变换方程 脉冲强度时间结构     

低能电子显微术及其应用

低能电子显微术是新发展起来的一种显微探测技术。它的特点是利用低能（１－３０ｅＶ）电子的弹性背散射使表面实空间实时成像，具有高的横向（１５ｎｍ）和纵向（原子级）分辩率，且易与低能电子衍射及其他电子显微术相结合。近年来它已有效地应用于金属和半导体表面的形貌观测、表面相变、吸附、反应及生长过程的研究。     

On the interpretation of the electron anomalous magnetic moment

Guided by a Compton-sized model, we demonstrate that: (a) the magnetic self-energy of the electron, as estimated initially by Rasetti and Fermi, can be directly related to both the sign and the magnitude of the electron anomalous magnetic moment; and (b) the classical expression for the magnetic self-energy of the electron exhibits the same characteristic logarithmic divergence that occurs in QED. This electron model quantitatively reproduces the spin, magnetic moment, and gyromagnetic ratio of the electron, correct to first order in = e² /c. It also relates the quantum-mechanical spin projection angle to the vanishing of the electric quadrupole moment, and it is capable of reproducing point-like scattering behavior.     

Investigation of the effect of electron cyclotron heating on runaway generation in the KSTAR tokamak

Wave enhanced runaway generation is expected to play an important role in the conversion of plasma current into runaway current during major disruptions. The fast electrons created by electron cyclotron heating (ECH) were used to study this issue in KSTAR. It is found that the fast electrons driven by ECH can enhance runaway production in the flat top phase with high loop voltage. The runaway current in disruptions was not enhanced by the ECH produced fast electron population due to the strong magnetic fluctuations which inhibited the generation of runaway electrons. It is found that a complete loss of existing REs during thermal quench has occurred in KSTAR limiter configuration discharges.     

Near threshold photodetachment cross section of negative atomic oxygen ions

A 40-target state close-coupling calculation for the photodetachment cross section of negative atomic oxygen near threshold is carried out with core－valence electron correlation by using the R-matrix method. It was shown that after considering the excitations of two electrons from the 2s shell, the electron affinity of O^- (2s^22p^5{}^2P°) agrees with the experimental result much better than that just considering the excitations of electrons only from the 2p shell as well as only one electron from the 2s shell. Total cross section as well as the main contribution of the ionization channels to the partial cross section are illustrated to show the structure near threshold clearly.     

The effects of self-fields on the electron trajectory in a two-stream free electron laser with a helical wiggler and an axial guiding magnetic field

A theory for the two-stream free-electron laser(TSFEL) with a helical wiggler and an axial guide magnetic field is developed.In the analysis,the effects of self-fields are taken into account.An analysis of the two-stream steady-state electron trajectories is given by solving the equation of motion.Numerical calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of self-fields.The stability of the trajectories is studied numerically.     

Relaxation between electrons and surface phonons of a homogeneously photoexcited metal film

The energy relaxation between the hot degenerate electrons of a homogeneously photoexcited metal film and the surface phonons (phonon wave vectors in two dimensions) is considered under Debye approximation. The state of electrons and phonons is described by equilibrium Fermi and Bose functions with different temperatures. Two cases for electron scattering by the metal surface, namely specular and diffuse scattering, are considered.     

北京自由电子激光器电子束截面监测系统

报告了北京自由电子激光器(BFEL)从30MeV直线加速器出口到摇摆磁铁出口束流输运段的束流截面监测系统。该系统由四台遥控气动可伸缩荧光屏探头、光学放大系统、闭路电视摄象系统及视频图象处理系统组成。利用该系统进行模拟实验,其系统空间分辨率约100μm,达到BFEL总体要求。利用该系统可以测量摇摆磁铁入口处及内部电子束和准直激光的截面、位置和畸变,进行束流准直、聚焦和发射度测量。     

Holes drilling in gold and silver decahedral nanoparticles by the convergent beam electron diffraction electron beam

The 200?kV focused electron beam in the convergent beam electron diffraction patterns mode in a transmission electron microscope (TEM) with field emission gun is able to drill holes in gold and silver decahedral nanoparticles. However, although they are done under the same circumstances, the holes are shapeless in the silver and faceted in gold nanoparticles. In addition to this, the holes are closed during their high-resolution TEM observation in both materials. To comment their differences, displacement energy considerations are taken into account as function of the sputtering energy in order to modify the displacement cross-section of the processes.     

Simulation of relaxation processes in electron beams at high magnetic fields

Molecular-dynamics simulations of relaxation processes in electron beams at high magnetic fields are presented. The result of the longitudinal–longitudinal relaxation and the rate of the transverse–longitudinal relaxation are calculated for magnetic fields between 0.006 and 0.1 T for electron beam parameters typical of those in low-energy electron coolers. Comparisons with theoretical and experimental values are made. This revised version was published online in July 2006 with corrections to the Cover Date.