Design of a mirror aberration corrector and a beam separator for LEEM

A SPLEEM (spin polarized low energy electron microscope) has been designed with a numerical simulation of electrostatic and magnetic field distributions and electron ray trajectories. Highly (more than 90%) spin polarized electron source has been used. A Wien type spin manipulator and a magnetic lens type spin rotator are used to align spin direction. A magnetic field free objective lens is designed to observe magnetic domain structure of magnetic materials. High or low magnification mode can be selected by using a combined electrostatic and magnetic objective lens for a high spatial resolution and a wide imaging area observation. An electrostatic mirror aberration corrector is installed after the image forming objective lens. A double deflection 45° beam separator is used to bend the direction of electrons from the source to the objective lens and from the objective lens to the mirror aberration corrector.     

Electron scattering cross section measurements in a variable pressure scanning electron microscope

Scattering of the incident electron beam in the variable pressure scanning electron microscope (VPSEM) affects the ability to perform quantitative chemical measurements. However, the manner in which the sum of the elastic and inelastic scattering cross sections varies as a function of gas type and accelerating voltage in the VPSEM is not well understood. A dual Faraday cup was constructed to measure the scattered fraction of the primary beam as a function of gas pressure, working distance, and accelerating voltage in air, water vapor, and argon environments. Experimentally measured values of the scattering cross section agree with previous experimental work, and agree within a factor of two with those values calculated carefully from theory.     

Beam analysis of scanning electron microscope according to the mirror effect phenomenon

In a scanning electron microscope the influence of electronic beam parameters on the electron-mirror images has been investigated. A simple theoretical model for scanning electron beam behavior in terms of beam and surface potentials is presented. The derived expression relates the scanning beam parameters and parameters of an irradiation region. Influence of a beam (the size and current), scanning potential, working distance, trapped charge and the irradiated area on electron mirror images are defined. Results show that the electron beam current has a considerable effect on the deduced mirror images in comparison with the other beam parameters. So it could be adapted for adjusting the phenomena of mirror effect. Moreover, the trapped charges have been calculated and the results examined in comparison with experimental data.     

Electron radiation damage in copper in the high voltage electron microscope

The various factors influencing the nucleation of radiation damage in the HVEM are reviewed. A method for obtaining quantitative information from observations is given. The effect of reirradiation at room temperature on the damage formed at elevated temperatures is shown. This effect may give experimental information concerning the strain fields surrounding large dislocation loops.     

一种紧凑型光纤显微物镜的设计

针对光纤通信网络建设及运维任务对光纤接续机器提出的便携小巧、精准可靠的需求,开发了一种结构紧凑、成像清晰的光纤物镜。基于光学理论和实际使用要求对物镜的基本光学参数进行了分析,利用Zemax软件设计出一种紧凑型高分辨率的光纤显微物镜,该物镜包含5片常用牌号玻璃球面透镜,放大倍率为6×,数值孔径0.24,共轭距离47.3 mm。系统具有良好的成像质量,0.7视场内在奈奎斯特频率60 lp/mm处MTF大于0.36,在频率90 lp/mm处MTF大于0.15。对设计结果进行了蒙特卡罗公差分析,良品率超90%,装调较宽松,成本低廉,可进行批量生产。另外,针对设计好的物镜进行成像过程仿真,结果显示待接纤芯特征清晰锐利,有利于机器对准接续。     

Study on the design and Zernike aberrations of a segmented mirror telescope

The segmented mirror telescope is widely used. The aberrations of segmented mirror systems are different from single mirror systems. This paper uses the Fourier optics theory to analyse the Zernike aberrations of segmented mirror systems. It concludes that the Zernike aberrations of segmented mirror systems obey the linearity theorem. The design of a segmented space telescope and segmented schemes are discussed, and its optical model is constructed. The computer simulation experiment is performed with this optical model to verify the suppositions. The experimental results confirm the correctness of the model.     

Spherical mirror analyzer as an instrument for electron coincidence spectroscopy

The time-of-flight characteristics of a spherical-mirror electrostatic energy analyzer of charged particle fluxes are investigated under conditions of ideal solid-angle focusing for a point source located on the symmetry axis of the spectrometer. It is shown that the time it takes a particle to move from the source to the ideal focus, also located on the symmetry axis, is, to first order, independent of particle direction for directions near the normal to the axis. This time-of-flight focusing realized in this way enables efficient use of the spherical-mirror analyzer in electron spectroscopy methods in which each emission event is registered separately. Zh. Tekh. Fiz. 69, 109–113 (January 1999)     

Investigation of the reflection-type double-pass confocal microscope with a phase-conjugate mirror

New experimental results about a reflection-type double-pass confocal microscope with a phase-conjugate mirror are presented. Exploiting the change of polarization of the light, when it is reflected at the object, gives the possibility to enhance the axial resolution of the microscope compared to that of the conventional confocal microscope by a factor of 65%. Furthermore, investigations on the time behavior of the PCM are presented. Received: 11 January 1999 / Revised version: 25 January 1999 / Published online: 7 April 1999     

医用电切镜的照相物镜设计

本文简要介绍一种专用照相物镜的设计方法,并给出计算结果。一、概述在医用硬管内窥镜中,根据不同使用要求又分为腹腔镜、电切镜及膀胧镜等等。我们根据上海某工厂的使用要求,     

The diffraction-dependence of electron damage in a high voltage electron microscope

Abstract

In a high voltage electron microscope the intense electron beam used for imaging can cause visible aggregates of point defects to form in metals in just a few minutes. The diffraction-dependence of the defect cluster production was studied experimentally in Cu and Fe using a 1000 kV electron microscope. Also, a simple method for calculating the diffraction-dependence of the atomic displacement rate was devised from multiple-beam wave-mechanical diffraction theory. The calculations indicate that the rate of point defect production should vary at most by a factor of ～1.7 with Bragg deviation in systematic diffraction cases, and that this variation should decrease rapidly with increasing depth in the crystal. The experimental observations are consistent with these predictions. In addition, the theory allows the diffraction-dependence of the displacement rate to be explained in terms of Bloch wave properties. Some new observations of the defect structures in electron-irradiated Cu and Fe are also described.     

Electron and plasma stream reflection at a nonadiabatic mirror

Experimental investigations of the phenomena occurring when low density electron and plasma beams are injected into a nonadiabatic magnetic mirror are presented. Effects of nonadiabaticity and mirror ratio on the reflectivity of the magnetic mirror are measured. Transition of the mirror from adiabatic to strongly nonadiabatic results in setting up of a potential barrier which enhances the reflectivity.     

时间分辨电子显微镜的数值模拟

对时间分辨电子显微镜进行了数值模拟。通过求解从样品透射出来的电子在静态磁场和动态电场的混合场中的运动,评价时间分辨电子显微镜的动态时空特性。根据该数值模拟,时间分辨电子显微镜能够在荧光屏上获得样品在不同时刻的6幅显微分幅图像。     

Closed-form representations for third-order aberrations of two-aspherical mirror aplanats with the mirror tilt and decenter

Approximate equations are derived for imaging aberrations of two-aspherical-mirror aplanats for soft X-ray imaging. These expressions include the Seidel terms for unperturbed states and the axial coma resulting from the tilt and decenter of the mirror surface. A simple analytical method for reducing both the Seidel terms and the axial coma enables us to design novel soft X-ray imaging systems utilizing a wide field of view with reduced sensitivity to mirror misalignments. The method is illustrated by applying it to a two-mirror system for soft X-ray microscopy with a magnification m =−1/50. The design example showed an appreciable reduction in sensitivity, as compared with the existing anastigmatic designs that include a standard Schwarzschild configuration. Imaging aberrations of the novel system are also confirmed by a numerical ray tracing method.     

高变倍比连续变焦体视显微镜物镜设计

为了实现体视显微镜物镜的大变倍比连续变焦,同时尽量避免使用非球面以及衍射元件,采用双组联动型变倍补偿形式,设计了大变倍比连续变焦距体视显微镜物镜系统。该系统实现0.8~16倍的20倍连续变焦,系统工作距离达到91 mm,后工作距离达到200 mm,双组联动型结构不仅实现了大变倍比,同时保证系统结构尽量简单。设计结果表明:双组联动型变倍补偿形式对实现大变倍比以及简化结构是有利的。通过对系统成像质量以及凸轮拟合曲线进行分析,系统组元移动曲线光滑,成像质量达到要求。     

Electron microscope investigation of small particles

In this review paper some possibilities to investigate small particles (1–1000 nm) with the electron microscope are treated. The transmission electron microscope is a unique tool to obtain information from small particles. This information covers the important area where atomic and bulk properties meet. The emphasis is focused on observations in connection with gas evaporation, adhesion between particles, possible vibration at contact, particle twinning, dynamical effects, martensitic transformation and superlattice crystals.     

Imaging surface reactions with a photoemission electron microscope

The photoemission electron microscope (PEEM), invented more than 60 years ago, began being utilized for imaging surface reactions less than 10 years ago to make observations of pattern formation during heterogeneous catalytic CO-oxidation on platinum. First investigations of adsorption and reaction of oxygen on a previously CO-covered Pt surface are discussed, showing the growth of isolated oxygen islands (O-islands) up to millimeter sizes. Features like plane wave-front propagation and a “memory effect” of islands have been observed. Next pattern formation during CO-oxidation on a Pt(110) surface is studied, where both of the reactants are supplied from the gas phase. By creating boundaries on the surface utilizing microlithography single spiral waves can be isolated. Here experiments with reactive boundaries of Pd are shown, where in addition to observations of common pattern formation with CO and oxygen on top of the surface, subsurface oxygen areas become an important feature. The latter also plays a dominant role for the oscillation cycles within a circular Pt(110) domain.     

Measurements of scan nonlinearity in a scanning electron microscope

A method for measuring the scan nonlinearity of a scanning electron microscope is discussed. This method is tested using a mass-produced microscope and demonstrates good results.     

Lateral resolving power of a time-of-flight photoemission electron microscope

The lateral resolution of a time-of-flight photoemission electron microscope has been theoretically analyzed. It has been shown that the resolution limit can reach a few nanometers. The lateral resolution will be higher if the photoelectrons forming the image are characterized by a smaller acceptance angle obtained with the help of diaphragms in the crossover plane, a higher initial energy and a narrower interval of electron energies. The experimental results are in good agreement with the theoretical predictions. PACS 68.37.Xy