Gridded electron guns for high average power

The design and performance of electron guns producing high-average-power beams which are controlled by an intercepting-type grid are described. The design consists of a modification of the design of Pierce-type electron guns to allow for the effect of grid insertion, and calculation of the amplification factors based on the potential distribution. The performance is evaluated in terms of the beam shapes and average beam powers obtainable. Measured amplification factors are compared with calculated values. Factors influencing the measured beam shapes are discussed. Trajectories of electrons emitted as secondaries from the grid and those of electrons deflected by the lens effect of the grid wires were plotted using an analog computer and electrolytic tank. The shapes and focusing properties of electron beams from similar gridded and nongridded guns are compared. Expressions relating the average beam power capability to the gun and grid dimensions are developed. The calculated average beam power capabilities are compared with measured values. Average beam power as high as 8 kw has been obtained with electron guns of a size suitable for use in X-band twt's.     

Triode electron injection systems for hollow beams

Novel electron guns, in which a conical hollow electron beam is projected at a large angle to the axis into a coaxial deflection region, were tested. The guns have a triode structure so that the perveance can be varied easily. The strong deflection increases the effective perveance of the beam and makes the trajectories insensitive to current variations. In the form of a device with the gun at a large radius and projecting the beam inward, the electron paths are sensitive to scattering in the gun. The inverted gun, projecting the beam outward, is relatively free from this difficulty. The systems generally behave as expected, and should be quite useful for initiating variable-current hollow electron beams in various available focusing arrangements.     

关于无截获栅电子枪栅网形状的研究

本文叙述了采用三种不同形状栅网(方孔栅、六角孔栅、环形栅)的导流系数为1.4p的无截获栅栅控电子枪,在电子注分析器上进行实验的详细情况。文中扼要地介绍了无截获栅栅控枪使用三种不同栅网的设计方法,并给出了所用实验系统的结构。三种栅网的荧光屏显示和小孔扫描测试的结果表明,环形栅的电子光学性能最佳。从概念上定性地分析并讨论了环形栅优于其它栅的原因。这为今后设计无截获栅枪指出了方向。通过对多把无截获栅枪的实验研究和计算机计算,纠正了过去有关栅控枪和基础无栅枪性能上的一些概念上的错误结论。     

On grid-mesh shapes of non-intercepting gridded guns

A non-intercepting gridded gun with the perveance of 1.4μP is described. Three different gridmesh shapes (square, hexagonal and annular) are chosen, and the experimental results in an electron beam analyzer are given in detail. The design methods of the gun for each grid-mesh shape and the structures of the test system are briefly introduced. The results measured by using the fluorescent screen and pin-hole scanning technique are given. It turns out that the annular grid possessed the best electron optical performance. The reason that the performance of the annular grid is better than the others is qualitatively explained and discussed, so as to give the guide lines of how to design the non-intercepting gridded guns. Through the experiment and the computer calculation for several non-intercepting gridded guns, the previous wrong conceptional conclusions about the performances of the guns with and without grid may be corrected.     

A new type of cathode-ray tube with a crossed-field gun

This paper introduces a new type of cathode-ray tube with a crossed-field electron gun which produces an electron beam in a region where a nonuniform magnetic field and an electric field cross perpendicularly. The new configuration gives increased freedom in the design of crossed-field guns. As a result, a long, directly heated cathode can be readily applied to a gun structure which makes high perveance and instant operation possible with much improved cathode heating efficiency. The new gun provides ion trap action by virtue of a magnetic field which separates ions from electrons due to the difference in their masses. A new type of cathode-ray tube using this gun not only demonstrates these features but also requires relatively low operational voltages for beam acceleration and control electrodes. The paper includes an analysis of electron motion in a crossed field with a nonuniform magnetic field. It also shows practical configuration of electrodes and current characteristics of the gun.     

On the performance of high perveance electron guns

A design of high perveance electron gun has recently been proposed by Müller. An experimental investigation has been made of the electron beams produced from: 1) a gun designed directly from Müller's charts, and 2) a gun whose design is a modification of the Müller design to make it more suitable for high-voltage operation. The perveance in each case was about 2 × 10^-6. The distribution of the current density and the profile of the beam were examined, either by allowing the beam to fall on a plate coated with carbon, or by measuring the current passing through a pinhole in a screen which could be moved across the beam at a number of axial positions. Electrostatic experiments showed that the beams were initially annular, but further along the axis the current density became highest at the center. This is attributed to crossing trajectories resulting from lens aberrations in an anode aperture whose diameter is comparable with the cathode-anode spacing. With magnetic focusing, the current density distribution across the beam varied periodically along the axis to an extent which depended critically on the magnetic field conditions in the accelerating region of the gun.     

S波段大功率行波管电子枪设计

采用皮尔斯电子枪综合法设计，并在综合法设计中引入圆筒电极聚焦和双阳极设置概念，再通过Egu。数值模拟、优化，方便、快速设计出了S波段大功率螺旋线行波管高导流系数、大电流、高电流密度电子注电子枪，该电子枪成功加工装配在行波管整管中。     

A method of reducing the effects of anode aperture in high-perveance convergent electron guns

A new theoretical method of designing convergent electron guns of high perveance for use in microwave tubes is presented here. A differential equation which represents electron trajectories in a convergent electron stream has been deduced under certain approximations. Electron trajectories in an electron stream and boundary values along its boundary were numerically calculated by solving the differential equation by means of an electronic computer. Boundary values on the virtual anode surface under space-charge-limited conditions were used as the initial values for the calculations. Focusing electrodes were determined to satisfy the boundary conditions on the stream boundary. The design procedure is also shown. The electron guns designed by this method are somewhat different in structure from the conventional ones which are usually designed experimentally rather than theoretically. In these new electron guns, nearly uniform current densities will be obtained over the whole cathode area, while in conventional convergent guns of high perveance, electron emission density near the center of the cathodes is usually reduced due to the influence of the anode aperture. Laminar flow will be obtained at points near the minimum stream diameter also in guns designed by this method. Digital computer experiments were performed and the results proved this hypothesis to be reasonable. An electron gun of 1.72 × 10^-6perveance and area convergence ratio of 70:1 is shown as an example.     

基于Spindt冷阴极的行波管电子枪设计

针对X波段小型化Spindt冷阴极螺旋线行波管进行了电子枪设计.基于皮尔斯型电子枪结构,联合PPM高频聚焦系统,以电子注聚焦特性为优化目标,采用CST粒子工作室对电子枪结构和工作参数进行了优化设计,获得了 30 mA工作电流下电子注填充比为0.68的良好电子注聚焦.在此电子枪结构和高频结构下,分析了特定电流下电子注聚焦...     

The design and performance of a magnetron-injection gun

The space-charge flow solutions described by Kino and others in connection with the crossed-field carcinotron gun can be generalized to form the basis of a magnetron-injection gun design suitable for the production of hollow electron beams. In the first part of the paper this generalization is described. From the resulting flow it is possible to determine by an approximate method the electrodes to produce a gun of desired perveance with nearly uniform current density at the cathode. This technique has been used to design guns having ratios of cathode length to a diameter considerably greater than unity. The close agreement between the results obtained on several experimental guns and the theoretical predictions is described, along with the effect of departures from the prescribed fields given by the design method.     

FDTD方法及其在多注电子光学系统研究中的应用

采用时域有限差分(FDTD)方法对L波段100 kW多注速调管的单个电子枪进行三维模拟计算,通过设置最小网格尺寸和发射时间间隔,得出的电流和导流系数与采用EGUN等软件计算的结果相一致,通过从MAFIA中导入三维磁场数据,模拟了位于径向不同位置处电子注通道的电子轨迹,研究发现在磁场均匀性较好的情况下,位于径向不同位置处的电子轨迹相差很小,同时讨论了如何减少模拟时间的问题.本文最后计算了多个注的电子枪,求得了电流值和导流系数,从中导入数据可以分段模拟多注速调管高频互作用段的注波互作用,以及收集极区域的电子发散.     

Synthesis of the Pierce gun

The design of a Pierce gun is uniquely defined by four parameters: beam voltage, current, waist radius, and cathode current density. The gun convergence angle, cathode spherical radius, anode-cathode spacing, and throw (distance to the waist) are calculated by an iterative procedure which typically converges in four cycles to 0.1°. The anode lens formula of Danielson, Rosenfeld, and Saloom is combined with inverted forms of the Langmuir-Blodgett solution for the spherical diode and the Universal Beam Spread equation for the tunnel region; the iterations match the trajectories at the anode plane. Correction for spherical aberration is made by the method of Frost and Purl as quantified by True. The inverted equations are simple enough to be solved in a few minutes with a programmable calculator. The experimental data of Frost and Purl is used to demonstrate the validity of the procedure for guns of medium perveance.     

The grid lens effect in convergent Pierce guns

In a conventional Pierce-type gun, the anode aperture causes a potential reduction in the cathode-anode region from the ideal Langmuir potential distribution. For low-voltage gating of the electron beam, a mesh grid of spherical shape (conforming to an equipotential surface) is used in front of the cathode. When this grid is operated at the Langmuir potential depicted by its relative position, there is a difference in the potential gradients on its two sides. This difference causes a lens action at each mesh element which results in a displacement of the actual electron trajectory from the ideal laminar trajectory in the region beyond the anode. A means for calculating these displacements as a function of distance along the axis is developed. As the grid lenses are divergent, the images of the mesh elements in any plane beyond the anode are larger than those for ideal laminar flow, resulting in a current density distribution which differs from that of the ideal beam. A means of calculating the current density profile by summing the effects of the grid lenses is devised, and the method is applied to a sample gun design to illustrate the effect on the current density distribution.     

Computer experiments on electron guns

Computer techniques for analyzing an axially symmetric or two-dimensional electrode system with an emitting surface can be used to obtain cathode current density distribution, beam minimum radius and its location, as well as possible electrode current interception. Here, comparison is made of available experimental data from two axially symmetric Pierce-type guns. The choice of the two axially symmetric Pierce-type guns was made for their different value of PV/T ratio, an invariant for transverse scaling. One of them has a low ratio of PV/T(approx 0.1 times 10^{-6}), which signifies considerable beam spread due to the effects of the Maxwellian velocity distribution of the thermal electrons leaving the cathode. The other gun has a high perveance of2 times 10^{-6}, and thus relatively high PV/T ratio where beam spreading is mainly due to space-charge forces alone. Good agreement with experimental data is shown. Computer techniques of this type can be a valuable tool for diagnostic purposes of any type of space-charge-flow devices (e.g., electron guns, ion guns for space propulsion, linear accelerators, etc.) and enable the engineer-designer to arrive quickly and cheaply at an optimum configuration.     

A new evaluation method of electron optical performance of high beam current probe forming systems

A new numerical simulation method is presented for the electron optical property analysis of probe forming systems with point cathode guns such as cold field emitters and the Schottky emitters. It has long been recognized that the gun aberrations are important parameters to be considered since the intrinsically high brightness of the point cathode gun is reduced due to its spherical aberration. The simulation method can evaluate the 'threshold beam current I(th)' above which the apparent brightness starts to decrease from the intrinsic value. It is found that the threshold depends on the 'electron gun focal length' as well as on the spherical aberration of the gun. Formulas are presented to estimate the brightness reduction as a function of the beam current. The gun brightness reduction must be included when the probe property (the relation between the beam current l(b) and the probe size on the sample, d) of the entire electron optical column is evaluated. Formulas that explicitly consider the gun aberrations into account are presented. It is shown that the probe property curve consists of three segments in the order of increasing beam current: (i) the constant probe size region, (ii) the brightness limited region where the probe size increases as d approximately I(b)(3/8), and (iii) the angular current intensity limited region in which the beam size increases rapidly as d approximately I(b)(3/2). Some strategies are suggested to increase the threshold beam current and to extend the effective beam current range of the point cathode gun into micro ampere regime.     

Design of hollow and strip beam guns

This paper covers a study of strip and hollow beam guns. An automatic electron trajectory tracer has been used to study the properties of the slit-anode lens common to these types of guns. A thin beam approximation was made so that a flat-bottom electrolytic tank could be used. The results of this study have been incorporated into gun design charts. Eight hollow beam guns have been built and tested experimentally. The experimental data of these guns compare favorably with the data obtained from the anode-lens study. The limitation of thermal velocities on the maximum area compression of strip and hollow beam guns is discussed. The experimental results of a focusing scheme which uses a uniform magnetic field to focus a hollow beam down concentric drift tubes are discussed.     

均匀磁聚焦和周期磁聚焦部分屏蔽流过渡区的设计

本文叙述均匀磁聚焦和周期磁聚焦部分屏蔽流过渡区设计的一种方法,指出对于阳极电位与慢波线电位不同的电子光学系统,以及这两个电位虽然相同,但导流系数大,阳极孔效应严重的电子光学系统,它们的过渡区的设计,必须采用非等位空间中的傍轴电子轨迹方程。并对用部分屏蔽流周期磁聚焦的电子光学系统,电子枪区中的电子轨迹与磁力线重合的问题提出一些看法。     

A gun and focusing system for crossed-field traveling-wave tubes

A problem encountered in the design of crossed-field traveling-wave tubes (particularly M-type amplifiers or backward-wave oscillators) is a limitation on current due to the restricted cathode size in the usual gun systems. The scheme considered here incorporates into a crossed-field device the techniques commonly used in O-type devices for designing converging Pierce-type strip-beam guns, which can increase the effective cathode area by perhaps ten times. A design procedure is presented for getting a well-formed beam from such a gun, which is magnetically shielded, through a fringing crossed-field region into the uniform-field region of interaction. An analysis of electron flow through the fringing-field region, including the effect of space charge, is presented. A trajectory equation, solved on a digital computer, yields trajectories for the beam and design curves for various values of the important parameters. The results show the scheme to be feasible. Results are also presented from tests on an experimental, demountable tube used to test the focusing scheme. About 90 to 95 per cent of the current entering the crossed-field region could be focused to the collector, and the system behaved generally as the design predicted. An evaluation of the experimental data showed the scheme to be useful.     

S波段多注宽带速调管的研制

本文介绍了S波段200kW多注宽带速调管的研究工作。给出了多注速调管及其电子光学和聚焦系统、宽带输出电路的设计和计算结果。并给出了我国第一批实验型多注宽带速调管的性能:工作电压19kV时,控制极负偏压为7kV,脉冲电流32.25A,导流系数12.3P,电子注直流通过率91.8％。最大输出功率252kW,平均功率3.5kW,效率41％,增益49dB,带宽9.1％,带内功率波动1.7dB。     

The range of magnetron injection gun parameters

Here, for the first time, the computer designs of axially symmetric magnetron injection guns are given in detail, and the practical problems of computing the electrodes are discussed. These designs have been experimentally used, showing that the design procedure is sufficiently accurate for predicting the characteristics. The important design parameters such as perveance, area convergence and magnetic field required are given for the interesting range of the normalized "computer" parameters. A method is suggested for computation of the resulting hollow beam from a truncated cone cathode, and the design of a transition region is discussed.