The oblique electron lens

An oblique electron lens is described that is especially applicable to image converters and camera tubes employing flat opaque photocathodes. The use of optical lenses, corrector plates, and/or mirrors (often employed in other electron lenses designed for use with opaque photocathodes) are eliminated. The oblique electron lens is well suited to ultraviolet and vacuum ultraviolet image converters, and to image converters employiug opaque negative electron affinity photocathodes. It is also possible to use this oblique electron lens for electronography. Measurements on an experimental tube show that a limiting resolution of 50 line pairs/mm is possible, but the intrinsic lens quality is believed to approach that of a conventional electromagnetic lens having uniform and colinear electric and magnetic fields.     

双静电四极透镜点聚焦特性分析与仿真

静电四级透镜具有优越的电子光学聚焦成像性能,单一静电四极透镜可实现电子束线聚焦,组合静电四极透镜系统拥有点聚焦的能力。文中对实现点聚焦的双静电四极透镜系统相关参数进行了计算,利用电子光学软件SIMION仿真发现,静电四极透镜之间的畸变场与两端的边缘场引起的像差会严重影响系统聚焦成像质量。仿真分析了系统像差与发射电子初动能的关系。结果表明:系统在保证点聚焦的情况下,增加电子发射初动能可以有效减小系统像差;当电子初动能增加至1105 eV时,最大发散角为2的电子束在聚焦平面上的弥散斑减小至3.2m28m。     

Theory of cathode trajectory characterization by canonical mapping transformation

The paraxial lens theory cannot directly be applied to the cathode trajectories inside the gun. This inconvenience makes the interpretation of cathode trajectories difficult since one cannot use the physical concepts familiar in the paraxial lens theory, such as focal length and magnification factor. We have proposed the canonical mapping transformation (CMT) to describe the electron trajectories inside the gun by relating the ray conditions on the cathode surface to those in the crossover plane. The method takes as variables the distance along the surface and the sine of the ray angle with respect to the surface normal to define ray conditions. It has been shown that the CMT can be characterized by a small number of optical parameters. One of the parameters is the 'electron gun focal length', an extension of the image side focal length in the paraxial lens theory. The crossover size of a triode gun can be calculated from the electron gun focal length and the initial transverse energy spread. The calculation predicts the dependence of the crossover size on the grid voltage due to the change in the electron gun focal length. The prediction is compared with the measurement and shows good agreement with it. Since the CMT optical parameters can be calculated from the representative trajectories only and as they predict practically all the necessary source properties of guns, the CMT can be used as a practical tool in the designing of various types of electron guns.     

Electron-beam microcolumn fabrication and testing

In this paper, we report the improvement of a process for full microfabrication of miniaturized electron lenses specially design for low-energy (100 eV) lithography tools. The main advantages of this technique are the following. It is batch processing oriented, meaning that lenses can be easily built in a full wafer fabrication. With this procedure it is possible to develop a completely integrated process for machining arrays of lenses. Lens bores are aligned using an electron lithography process, resulting in highly accurate positioning. Finally, the source lens chip has not only one but several sets of lenses with different aperture-sizes, each producing a different beam diameter. A scheme is proposed with which the appropriate lens can be selected by means of a deflection system.     

软磁样品对半浸没式物镜的影响及故障排除

由于半浸没式物镜极靴下方存在磁场,用扫描电镜表征磁性样品时存在因样品被吸入物镜而严重影响成像的风险.本文中,日立S4700型场发射扫描电镜突然出现图像信噪比急剧下降、像散不能消除的问题,经过分析和排查发现是由软磁性的泡沫镍被吸入物镜极靴导致的故障.本文从物镜结构、合轴、像散三个方面分析了磁性样品对电镜成像的影响,并结合...     

Single pole-piece objective lens with electrostatic bipotential lens for SEM

This report describes the characteristics for the development of a compound lens that consists of a single pole-piece objective lens and an electrostatic bipotential lens. By applying a relatively small voltage of around 1 kV to the specimen and the bipotential lens, the image quality for low acceleration voltage is improved to a condition better than with just a single pole-piece lens. Even if the wafer is tilted to a large angle, the electric field near the specimen does not become asymmetrical, and there is no occurrence of astigmatic aberration or a reduction of the secondary electron signal. Therefore, 300 mm diameter wafers can be tilted with large angles to observe patterns, particles and defects with high-resolution SEM. Lastly, when the specimen is not tilted, a topographic image of the specimen surface can be obtained by detecting the secondary electron with dual detectors.     

Simulation of the Field Emission Arrays with Parallel Wedge Emitter, Gates and Co-Planar Lens

Using the particle-in-cell (PIC) simulation code MAGIC, the wedge emitter, parallel gate and anode with and without co-planar lens have been simulated. The electron beam streamlines and the X-V_x phase space have been evaluated, which show that the co-planar lens focuses the electron. Simulation results are presented for a single FEA's cell with the anode biased at 500V and spaced 100μm from the cathode, which indicated that the electron beam width at anode is about 60.2μm for without lens FEAs, after add the lens with ?70V, the electron beam width will be decrease to 8.1μm, meanwhile the maximum transverse velocity will decrease from ±1×10⁶m/s to ±1.46×10⁵m/s.     

Development of a magnetizing stage for in situ observations with electron holography and Lorentz microscopy

A magnetizing stage, by which approximately horizontal magnetic fields can be applied to thin-foiled specimens, has been developed so that magnetization process can be observed in situ with electron holography and Lorentz microscopy. It is possible to apply magnetic field up to 200 Oe without serious image distortion by utilizing the magnetizing stage, beam-deflection-back coils and a magnetically shielded objective lens. The devised system can be used to studies of magnetization processes in many soft magnets.     

Influence of space charge on the Langmuir limit for focused electron beams

A theoretical investigation of the validity of Langmuir's expression for the limiting current density in a focused electron beam when space-charge forces are significant was carried out by computing the performance of a series of simple electron tubes, each consisting of a Pierce gun coupled by a thin lens to an equipotential drift space. The analyses show that, while the cathode current density and the peak current density in the spot are related, they are not directly proportional as stated in Langmuir's expression which, therefore, does not give an accurate prediction of the current density that can be obtained in the spot. The dimensions of the tubes were chosen such that this conclusion is also valid in the case of television picture tubes. It is also shown that thermal velocities have only a minor influence on the lens strengths required to focus beams, and that the focused spots havea Gaussian distribution of current density even though the emission density in a Pierce gun is uniform.     

静电圆锥透镜曲轴电子束聚焦理论的研究

在曲轴宽电子束聚焦理论的基础上，本文研究了静电圆锥透镜聚焦性质，提出了静电场中考虑主轨迹为平面曲线情况下电子束的焦点、焦距等电子光学基本参量的定义。作为例子，给出了两种类型的静电圆锥透镜的电子光学在不同电参量下的关系曲线。     

Hybrid computer aided design of thick electrostatic electron lenses

The synthesis of space charge free electron lenses can be approached by first assuming solutions for Laplace's partial differential equation in terms of cylindrical harmonics. The hybrid computer can quickly generate these assumed solutions and their gradient by working with the differential equations obtained from product separation of variables. The gradient is used in the integration for the trajectory to determine if the lens is useful. If so, either equipotential surfaces or the potentials along a desired surface are generated with the computer to guide the physical realization of the lens. Certain cases where space charge cannot be neglected are solved by truncation of rectilinear electron flow. Poisson's equation is solved in the computer to serve as a Cauchy boundary condition to Laplace's equation outside the electron beam. The hybrid computing technique and the experimental verification of some of the results in cathode-ray tube electron lenses are presented.     

A high-resolution electron gun for thermoplastic recording using prefocus deflection

A demagnification gun of high resolution was developed for thermoplastic recording by deflecting the electron beam at the entry of a large focusing lens. The unconventional approach of prefocus deflection allows close spacing between the "short" focusing lens and the target (phosphor screen or thermoplastic tape) required for demagnification and results in a gun with a relatively short length. The diameter of the focusing lens is about three times larger than the 25-mm diameter area to be scanned in order to keep spot distortions of the deflected beam at a minimum. Electrostatic focusing combined with magnetic deflection was selected. The special focusing lens that is used is shaped for low aberrations, increased demagnification and increased deflection sensitivity. Small deflection fields are required since the electron beam is being deflected in the accelerating field while the electron velocities are still low. The gun operates at 10 kv and delivers a 5-micron spot at 1µa. This corresponds to a resolution of 5000 spot diameters at average current densities in excess of 5 amp/cm². In spite of the high resolution, the over-all length of the gun measured from the target is only 9 inches.     

The tunica vasculosa lentis; an expedient system for studying vascular formation and regression

We examined, with scanning electron microscopy, the tunica vasculosa lentis of the postnatal rat. It consisted of an extensive two-dimensional capillary network, spreading over the posterior and lateral surfaces of the lens. During the postnatal days, capillaries were associated with incipient pericytes and frequently had sprouts with a lamellipodial extension. Stellate angioblastic cells occurred in the meshes of the vasculature, which attached to the pre-existing capillaries with their processes. Both capillary sprouts and angioblastic cells may be involved in vasculogenesis. At the eighteenth postnatal day, the tunica underwent remarkable regressive changes: many capillaries degenerated or were totally eliminated, leaving faint traces on the lens surface. What appeared to be macrophages adhered to degenerating capillaries. With its rapid developmental sequence reported previously and the findings obtained herein, the vasculature provides an expedient system to study the cytological mechanism involved in vascular formation and regression.     

In-the-lens secondary electron analyser for IC internal voltage measurements with electron beams

A new analyser scheme for voltage measurements on integrated circuits is described. The analyser is built into the objective lens of a scanning electron microscope. It features small working distances, high voltage resolution capability, high transmission, and reduced sensitivity to measurement errors.     

可视电话、可视门铃用显像管电子枪的研制

可视电话、可视门铃具有广阔的发展前景,其显像管电子枪属于关键部件。本文介绍了用于可视系统三电位短电子枪的特点,电子枪透镜结构和工作原理,以及电子透镜的结构设计。实验结果表明,电子枪的性能参数符合设计要求。     

An electrostatic image tube with planar photocathode

It has been possible to flatten the electron image of a planar photocathode sufficiently well to obtain images with good center-to-edge focus on a planar screen. The essential element in the new tube is a spherical mesh with strong curvature. This mesh serves the dual function of a prefocusing lens in the approach space, and a field-flattening lens in the image space following. Additional advantages include an incidental correction of pin-cushion geometry and improved high voltage stability. Image resolution of over 16 line pairs/millimeter has been realized with meshes as are available at present. Further progress is entirely possible pending future developments in the technology of high-resolution meshes.     

New possibilities for an all-electrostatic camera tube with a single-and-positive lens system

In order to develop extremely compact camera tubes which feature low power consumption comparable to solid-state imagers, we have developed an all-electrostatic camera tube based on electron optics characterized by a single-and-positive lens system composed of disk and cylinder electrodes. The new system was found to be very useful in producing compact high-performance camera tubes, due to its simple configuration and lack of negative lens component.     

A combined objective lens for electrons and ions

Nanofabrication is possible using focused ion beam technology, but the observation of these structures with the same ion beam is not possible because of its erosion effect. Therefore a general purpose instrument for nanotechnology based on particle optics has to combine an ion and an electron beam. The objective lens, the final lens above the specimen, has to focus both beams on the specimen. An objective lens that combines magnetic and electrostatic fields has been designed for this purpose. Its aberration coefficients allow a 1 nm ion beam and a 0.3 nm electron beam.     

彩色显像管中主聚焦透镜的研究

在COTY系统中,采用XL透镜来改善会聚性能,减小会聚/聚焦之间的矛盾。XL透镜可以在不损失聚焦性能的前提下缩小束间距提高会聚特性。但是在XL透镜中边束像差比中束大得多,为了进一步降低像差,本文提出在XL电子枪中采用OLF透镜来扩大透镜的孔径,改善分辨率。本文给出了三维计算机程序,对主聚焦透镜进行三维计算,得到了球差系数和其它光学参量。这些数据证实了在新的方案中球差确实被降低,而且会聚特性也得以改善。     

About scan magnification of TV picture tubes

In a television receiver the horizontal deflection is of critical importance because of the high deflection power. Recently various proposals have been published, according to which the electron beam is to be deflected over a small angle only, in order to diminish the deflection power. Subsequently this small deflection angle is to be increased by an electrostatic or magnetic lens. In the present paper, it is shown with the aid of general laws of electron optics that such a scan magnification by an electrostatic or magnetic lens necessarily causes a decrease of the resolution, and thereby, of the quality of the television picture, unless known possibilities of increasing the resolution are employed simultaneously. The calculation also affirms that with magnetic deflection, unlike electrostatic deflection, post-acceleration does not lead to a significant reduction in deflection power with unchanged resolution.