电子全息法及其在观测微电场分布中的应用

介绍了电子全息术的工作原理以及制备静电场样品的新方法:一个置于薄导电碳膜上的非导电粒子,例如直径为0.31μm聚乙烯乳剂小球,在电子显微镜中观察时,由于静电积累效应,它将成为一个荷电体,这个荷电体带有正电量Q,并能用一个点电荷场来模拟这个合成电场。采用这个模型,能用电子全息法观测由该点电荷形成的静电场分布及荷电体大小。 关键词：     

点电荷在接地金属球形空腔内的电场分布

利用镜像法求解出点电荷在接地导体球壳内的电场分布,进而考虑相对论效应,讨论了点电荷在球壳内的受力情况.结合Mathematica11.3进行绘图,直观地展示了球壳内电场空间分布的特点.     

用全息干涉法测量酒精灯火焰温度分布的实验

近年来,全息干涉测量技术在无损检测,流动显示以及工程热物理量的非接触测量方面的应用越来越广泛,已经成为量度学中理想的高精度和非接触的测量技术。本文介绍一种全息干涉测量方法,通过拍摄一张酒精灯火焰全息图,对轴对称火焰的内部瞬间特性(主要是折射率及温度空间分布)进行     

用双图全息相移干涉法计算与时间有关的位相分布

提出一种双图全息相移干涉法．该方法可以用来计算与时间有关的位相分布，两幅全息干涉条纹图可以同时得到，并且有固定的９０°位相差．虽然两幅条纹图的位相可以随着时间变化，如环境影响，或载荷变化，但他们之间的位相差恒定．该方法利用二维傅氏变换，结合偏振相移法以及分光技术．     

利用数字重现电子全息图观测微电磁场分布

采用数字方法重构电子全息图，分别研究了荷电乳剂小球(0.31μm)的微电场分布及强磁材料中磁畴的磁力线分布精细结构.利用噪声消除及位相差放大技术提高了重现分辨率，并获得了一些新结果. 关键词：     

电子顺磁共振成像法

电子顺磁共振成像（EPRI）可以成为确定在肿瘤和其他生物组织内氧分子分布的一种重要手段．对于许多疾病来说，氧的存在与否是非常重要的，例如由于缺乏氧分子会使癌细胞在对待辐射和化学治疗时有一定的抵抗性．美国芝加哥大学的Pelizzari C博士和他的同事们一直在研究如何测试氧分子在生物体内的分布状况，他们认为电子在生物体内可具有反映这种性质的能力，     

高频放电CO2激光器电子能量分布及输运系数

利用文献中给出的截面数据，引入高频放电激励ＣＯ２激光器的Ｂｏｌｔｚｍａｎｎ方程，对其进行数值求解，研究了频率对电子能量分布及输运系数的影响。     

磁控管法测电子荷质比e／m理论公式推导的改进

一、引言 1987年《大学物理》发表了测定电子荷质比e/m的各种方法的四篇文章。其中文献是在考虑空间电荷分布效应情况下导出r_k→0时电子运动轨迹的近似解,从而导出临界条件下测算电子荷质比的公式:e/m=(8u_a)/(r_a~2B_c~2)。并在注中说明A.W.Hull曾作过类似工作,得到结果与文献[1]完全一致,但推导方法有所不同。本文提出一种完整的推导方法,对历史上已有过的推导方法作了改进使之更符合实际。其主要改进之点为: (1)本文简化设想阴极具有电荷线密     

等电子谱线法测量Mg/Al等离子体电子温度空间分布

 在“星光Ⅱ”激光装置上对Mg/Al混合材料埋点靶进行三倍频激光打靶实验,用空间分辨晶体谱仪测量靶材料发射的X光光谱,获取了示踪离子谱线实验数据。采用多组态Dirac-Fock方法计算所需原子参数,并在局域热动平衡条件下建立了双示踪离子谱线强度比随电子温度的变化关系。在此基础上由双示踪元素等电子谱线法确定了Mg/Al混合材料埋点靶激光等离子体电子温度空间分布。     

等电子谱线法测量Mg/Al等离子体电子温度空间分布

在“星光Ⅱ”激光装置上对Mg/Al混合材料埋点靶进行三倍频激光打靶实验,用空间分辨晶体谱仪测量靶材料发射的X光光谱,获取了示踪离子谱线实验数据。采用多组态Dirac-Fock方法计算所需原子参数,并在局域热动平衡条件下建立了双示踪离子谱线强度比随电子温度的变化关系。在此基础上由双示踪元素等电子谱线法确定了Mg/Al混合材料埋点靶激光等离子体电子温度空间分布。     

Numerical study of an electrostatic plasma sheath with non-thermal electrons and charged nanoparticles

Numerical solutions of the multi-fluid equations are used to investigate the effects of non-thermal electrons on the structure of an electrostatic plasma sheath in the presence of nano-sized dust grains. It is assumed that electrons obey the Cairns distribution [Cairns et al. Geophys. Res. Lett. 22, 2709 (1995)], with a parameter α that determines the effect of non-thermal electrons and shows the deviation from the Maxwellian distribution. The results revealed that sheath parameters are strongly modified in the presence of non-thermal electrons and with increasing α the sheath width increases. With the increase in α, the absolute dust charge increases while the dust density is reduced.     

电子全息术再现中的若干问题

讨论了“冻结”在电子全息图中的位相信息的再现方法.实验结果表明两次曝光技术不但能直接获取位相信息,不需要激光再现,而且能给出定量结果.这也意味着,在一次实验中用电子显微镜可以同时获得振幅和位相两种信息.     

2D strain measurement in sub-10 nm SiGe layer with dark-field electron holography

In this paper, we carried out the two-dimensional (2D) strain measurement in sub-10 nm SiGe layer; images were obtained by dark-field electron holography (DFEH). This technique is based on transmission electron microscopy (TEM), in which dark-field holograms were obtained from a (400) diffraction spot. The measured results were compared to the X-ray diffraction (XRD) results in terms of the strain value and the depth of strain distribution in a very thin SiGe layer. Subsequently, we were able to successfully analyze the 2D strain maps along the [100] growth direction of the nanoscale SiGe region. The strain was measured and found to be in the range of 1.8–2.4%. The strain precision was estimated at 2.5 × 10⁻³. As a result, the DFEH technique is truly useful for measuring 2D strain maps in very thin SiGe layers with nanometer resolution and high precision.     

Off-axis electron holography of hetero-interfaces

Off-axis electron holography is one of the new emerging methods for high spatial resolution characterization of interfaces in materials. It enables recording and retrieval of both amplitude and phase of an electron wavefunction scattered by a specimen. Phase changes introduced by magnetic and electrostatic fields have been studied in the first applications of electron holography to domain walls in ferromagnetic and ferroelectric materials and to p-n junctions. Planar defects in single crystals, such as stacking faults, have been observed with strong phase contrast due to dynamical diffraction.Applications to heterogeneous interfaces have only started. High phase contrast due to mean inner potential differences is found for interfaces between high and low atomic number materials. Dynamical contributions to the phase of the transmitted beam are important for epitaxial interfaces in strongly diffracting orientations. Numerical hologram reconstructions yield quantitative amplitude and phase images of an interface which are energy filtered and are in perfect registry. Both are function of specimen thickness. The thickness dependence can be eliminated by division of the phase image with a logarithm of the amplitude image. This ratio maps the product of the mean inner potential and the mean free path for inelastic scattering across a hetero-interface in weekly diffracting orientations.Resolution enhancement through aberration correction has not been demonstrated for interfaces as yet. Holography of interfaces in plan view is unexplored.     

自聚焦棒透镜准直系统的装配误差引起的附加耦合损耗分析

Latex particles are general samples used for electron holography. Electrostatic field outside charged latex particles has been investigated. The observation of electrostatic microfield inside charged latex particles (0.31 μm) is reported. Digital reconstruction is employed to decode the electron image holograms. Experimental results are presented. Correspondent analysis is also given.     

Observation of Electrostatic Microfield Inside Charged Latex Particles by Digital Reconstruction from Electron Holograms

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纳米结构中磁斯格明子的原位电子全息研究

斯格明子(skyrmion)磁序结构与晶体微观结构的关联是新型功能磁材料和器件研发的重要问题.本文利用微纳加工技术制备了形状、尺寸均可控的磁纳米结构,通过电子全息术观察定量地分析了斯格明子磁序结构,确定了材料晶格缺陷和空间受限效应对斯格明子磁结构形成和稳定机制的影响,系统地分析了斯格明子基元的磁功能与材料微结构的关联.文中主要探讨了两个问题:1)斯格明子在磁纳米结构中的空间受限效应.重点研究斯格明子磁序随外磁场和温度变化的演变规律,探索其演变过程的拓扑属性和稳定性;2)晶格缺陷对斯格明子磁结构的影响,重点考察晶界原子结构手性反转对斯格明子磁序的影响.这些研究结果可为研发以磁斯格明子为基元的磁信息存储器及自旋电子学器件提供重要实验基础.     

基于可调谐静电啁啾镜的电子脉冲压缩技术

分析了基于双级反射静电系统的电子脉冲压缩技术方法。类比于光子脉冲压缩用多层介质啁啾镜, 将该静电系统称为可调谐静电啁啾镜：根据静电啁啾镜电气结构参数的设置, 入射电子脉冲在系统中U形反射运动飞行时间与其初始轴向能量具有相应不同的色散关系, 也即正负啁啾特性。讨论了该啁啾镜正负啁啾属性的可调谐性及脉冲压缩技术细节, 并给出了计算实例。     

动态微粒场分析的同轴全息技术

本文描述了采用同轴远场全息术测量柴油机动态油雾场的实验方法和原理,并讨论了横向放大率、全息图的衍射效率及离焦象几个方面的问题。     

Potential of digital holography in particle measurement

This paper describes the potential power of digital holography in particle measurement and its expected development in the near future. In digital holography, image reconstruction is carried out numerically on a computer using observed hologram patterns and some quantitative information can be derived from the reconstructed images. In this paper, the basic concept and procedure of digital in-line holography are shown mainly for particle depth measurement and the performance test results obtained in numerical simulations and experiments are demonstrated to examine the potential of the present method.