Investigation of field-emitted electron beam behaviors using a line collector in a triode electron gun system

The performance of a field-emission scanning electron microscope (SEM) is primarily dependent on the characteristics of the electron source. Field-emission electron sources provide a high current density, which can be used to produce a beam that can be focused through an electrostatic lens. Using a single 〈1 1 1〉 crystalline tungsten tip, we fabricated and tested a field emitter having a 91 nm radius and a stability under 14%. In this electron source, two electrostatic lenses consisting of 1st and 2nd anodes were designed and implemented and their performance dependence on variations in electrode shape, position, and applied voltage was investigated using a first-order finite-element method simulation. We also developed a line collector capable of measuring beam distribution and quantifying shifts in the electrical optical axis to characterize the behavior of a field-emitted electron beam as focused by an electrostatic optical system.     

毫米波带状注电子枪的设计方法

利用理论分析和仿真模拟相结合的方法对带状电子注的产生进行了系统的研究,并提出了一种带状注电子枪的设计方法.首先通过理论分析,提出了一种计算带状注电子枪结构参数的迭代算法,即根据注电压、注电流、电子注注腰处半厚度、阴极半厚度和阴极宽度,计算出带状注电子枪的阴极柱面半径、阴阳极间距、阳极柱面半径和射程等主要参数;在此基础上,通过仿真模拟,为毫米波真空电子器件设计了一种带状注电子枪.     

一种新型三极管取样门电路设计

超宽探地雷达在无损检测系统中应用越来越广泛,采样电路是整个无损系统设计的关键。基于等效采样原理设计出一款新的三极管取样门电路。该电路克服了现有二极管取样门电路的缺点,很好地实现采样保持。利用先进设计系统(ADS)软件对该取样门电路进行仿真,输入脉冲重复频率为10 MHz的2 ns三角波信号,采样时钟重复频率为10 MHz且与被采样信号有100 ps延时差。对其进行采样,经过该取样门电路后,输出信号为2 μs。在聚四氟乙烯板上实现该电路,利用信号发生器输入一个90 ns的正弦波作为被采样信号,采样时钟为100 ns,经过该取样门电路后,输出信号周期为1 μs。实测与理论结果都表明该电路可以降低输入信号的频率,实现利用低速A/D对高速信号的数据采集,大大降低了整个系统的成本。     

The accuracy of numerical solutions for electron gun design

The solution of Poisson's equation and the equation of motion by numerical methods is discussed. By considering the truncation error due to the use of difference equations in the one-dimensional case, it is shown, on the basis of a perturbation theory, that the error in the solution is proportional to the mesh sizeh. This theory is shown to be in good agreement with numerical solutions obtained on a computer. A correction formula is then derived which makes it possible, by obtaining sointions for two different mesh sizes haand hb, to form a space-charge-flow solution accurate to second order inh. It is also shown that more accurate forms of the difference equation may be obtained to represent the steady space-charge flow. By these various means, it is possible to increase the accuracy of numerical solutions by an order of magnitude or more. Thus, by using a coarse mesh, but better accuracy, the speed of computation may be considerably increased.     

The multipactor electron gun

An electron source based on the multipactoring principle and preliminary experimental results are described. Several uses of such a gun are suggested.     

Non-adiabatic electron gun for gyrotrons

A non-adiabatic electron gun for gyrotron application is presented. Numerical investigations show some important advantages over presently used electrons guns of the magnetron type. In particular, the influence of space charge and the roughness of the emitter surface on the beam properties is significantly reduced. This allows the generation of a hollow electron beam with a low velocity spread and the operation of the gun over the full current range, almost up to the space charge limit.     

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.     

电子枪理论研究的新进展

本文简要回顾了电子枪发展的历史,评述了电子枪理论研究方面的新进展,重点介绍了日本学者Fujita和Shimoyama的新近研究成果。最新的研究表明,对冷场发射和扩展的肖特基发射电子枪,存在阈值电流。当束流,Ib增大,超过阈值电流时,枪的表观亮度逐渐下降。当对整个电子光学柱体进行评价时,必须把亮度和束流的函数关系考虑在内。这时会出现关于电子枪的若干新概念。整个电子光学柱体的电子探针性质曲线由三个区域组成,即：（1）恒定束斑（d）区;（2）d∝I3/8b,妒区;（3）d∝I3/2b区。以往的理论只指出了3／8次方区的存在。3／2次方区的存在是一个新的发现。它解释了历史上曾注意到的一个事实,即当应用的束流进入μA量级时,扩展的肖特基发射和冷场发射枪的性能反而不如传统的钨丝热发射枪。     

碳纳米管冷阴极Pierce电子枪

为发展场致发射冷阴极毫米波电真空辐射源器件, 对利用大面积碳纳米管冷阴极产生大电流、高电流密度电子注的电子光学系统进行了研究.通过在Pierce电子枪阴极表面引入栅网结构, 解决了碳纳米管冷阴极场致发射所需的强电场和电子聚束问题.在碳纳米管冷阴极实验测试数据的基础上, 采用粒子模拟软件对上述电子光学系统进行了仿真.研究了栅网对注电流、注腰半径和电子注散射的影响, 分析了阳极电压和外加轴向磁场对电子注的聚束作用.优化后的仿真结果表明在阴极发射面为3.03 cm2时, 该电子光学系统能够产生210 mA、60 kV, 电流密度为6.7 A/cm2, 最大注半径为1mm的电子注.     

Ring-and-line-focus electron beams from a glow-discharge gun

Electron guns have been developed in which a high-voltage cold-cathode discharge, at low pressure, generates an electron beam. By shaping the cathode, the beam may be focused in a particular contour. For example guns operating at 3kW at 15kV have been designed to focus in an annular ring or in a line.     

A new electron gun for picture display with low drive signals

The paper discribes an approach to the problem of picture tube guns for small signal service. A Pierce-type cathode delivers a collimated parallel beam of 1600 microamperes at 250 volts (microperveance: 0.4). This beam is injected into a cylindrical cavity of appreciable length (3/4-inch long, 1/4-inch diameter). It is focused upon a small aperture at the far end using a parabolic axis potential. This axial focusing field is approximated by three cylinder segments at two intermediate voltages. To modulate the beam by lateral deflection, the cavity is again bisected through an axial plane and signal voltage is set up between half cylinders. This modulation by two crossed-electrostatic fields ("CFM" modulation) has been successfully applied in transistorized television, using a seven-volt video signal on a beam of 900 microamperes.     

Multipactoring electron gun for high duty linacs

A high duty factor electron gun suitable for linac applications is described. This gun operates on the secondary emission principle to generate a pulsed, monochromatic electron output beam in excess of 20 mA average current. It has been operated at 14 percent duty factor and shows a high degree of stability and ease of control.     

A theory for coupling gridded gun design with PPM focussing

This paper presents theoretical and experimental methods for the design and optimization of gridded Pierce electron guns. The design of periodic permanent magnet (PPM) focussing systems to control the nonlaminar beams originating from such grided guns is discussed. Simplified relationships are developed which directly couple the, heretofore separate, gun and PPM focusing design problems.     

The influence of the spacings of the electron gun's triode on its characteristics

The behavior of a group of triodes of an electron gun having all the same cutoff voltage is discussed with respect to its physical dimensions. Especially the relation between gun characteristics and a design number (A, B) is investigated whereAis the distance between cathode surface and modulator and B between modulator and anode. For a fixed-grid drive pulse the total emitted cathode current and the portion of it passing through a beam-limiting aperture increases with increasingB(decreasingA) whereas the resolution decreases. If the electrical parameters like anode voltage and cut off voltage are already determined it can be concluded that there is a certain design number (A, B) for optimized beam density on a phosphor screen.     

A long pulse, high-current electron gun for e-beam sustained excimer lasers

A new kind of electron gun is described which has produced 5-μse-beams at 130 keV and 2 A/cm². Scaling estimates are presented which predict that this gun could operate at 400 keV and 10 A/cm², beam parameters suitable for pumping excimer laser systems. For this application the gun has the advantages that thee-beam is nearly monoenergetic and the pulse widths longer than that possible with other presently usede-guns.     

Improved electron gun for the beam-indexing color-television display

Improved gun design has considerably increased the brightness of the 110°-25 in beam-indexing color display (triplet pitch ≈ 1.2 mm). Without dynamic correction for deflection errors the color reproduction in normal picture material is now satisfactory up to peak currents of about 2.5 mA (against 1.5 mA for the old gun).