The design and performance of grid-controlled, high-perveance electron guns

The focusing electrode and a probe projecting through the cathode serve as control electrodes for the current from a convergent-beam electron gun. The principal advantage of this type of "grid" is that there is no interception of the high-current-density beam by the probe-grid. This paper presents the design procedure and experimental results for typical probe-gridded guns. The design procedure is used to obtain the desired perveance, beam diameter, and approximate laminar electron flow. The probe geometry that results in a minimum beam distortion is discussed. The range of values of amplification factor obtainable and the influence of probe geometry on this factor are discussed. The magnetic field required for focusing the beam from a probe-gridded gun is compared with that required for perfect laminar flow and for focusing the beam from a nongridded gun of similar design. An electrolytic tank in conjunction with an analog computer was used to plot electron trajectories, with the effect of space charge included, for the probe-gridded gun and a similar nongridded gun. A comparison of the electron optics of the gridded and nongridded gun is made. Electrical breakdown and beam current during the interpulse time are problems considered. Methods used to minimize electrical breakdown and interpulse beam current are presented. Several models of probe-gridded guns were constructed. The measured characteristics of these guns demonstrate that the advantages of grid control can be obtained with only a minor effect on gun perveance and beam focusing.     

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.     

Interaction of Two Beams with a Cavity†

Theoretical results for the small-signal interaction of two co-directed electron beams with the fields of a cavity show that, for a field that is a rectangular pulse in space and for beam transit angles less than 15 radians and beam perveances that are physically realizable with ordinary electron guns, the two-stream beam loading resistance is almost a superposition of the loading effects of the two streams considered separately, even when growing waves are present. Effects of high perveance are included in the theory which predicts a maximum in the curve of negative beam conductance versus perveance with one or two streams, when a negative conductance occurs at all. Experimental results on a tube with two hollow concentric beams confirm those theoretical predictions.     

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.     

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。     

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 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.     

大回旋电子枪中的CUSP磁场研究

会切(CUSP)磁场是产生大回旋空心CUSP电子注的关键,该文分别对CUSP磁场中双曲正切模式和Moster-Molnar模型进行探讨,通过理论分析和数值模拟,建立适合于大回旋器件用CUSP磁场的物理模型;并对CUSP磁场设计中的影响因数进行探讨;同时探讨了CUSP磁场与大回旋空心CUSP电子枪的关系,结果表明:改变CUSP磁场的阴极区磁场的变化对设计低速度零散、低纹波、高速度比值α的轴向环绕大轨迹CUSP电子枪有较大的影响。     

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.     

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.     

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.     

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.     

Computer Simulation of Axis-Encircling Beams Generated by an Electron Gun with a Permanent Magnet System

Results from computer aided design of a novel electron gun generating axis-encircling beams are presented and discussed. Numerical experiments were performed by the new version of the software package GUN-MIG named GUN-MIG/CUSP. It is based on a self-consistent relativistic model and is developed as a problem oriented tool for analysis of electron-optical systems with magnetron injection guns (MIG) and electron guns with field reversal (cusp guns), forming axis-encircling beams. As a result of the simulations an electron-optical design of a novel electron gun with permanent magnet system was accomplished. The gun is expected to form high quality beams with small velocity spread and beam ripple. Parameters of the generated beams are appropriate for a prospective weakly relativistic high harmonic large orbit gyrotron (LOG). The development of such device is in progress now at the Research Center for Development of Far-Infrared Region (FIR Center) at Fukui University.     

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.     

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。     

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.     

关于磁控注入式电子枪的噪声问题

磁控注入式电子枪能提供高导流系数的电子注,可应用于大功率微波管中。但是,通常认为这种电子枪属于交叉场型的,具有交叉场器件固有高噪声的特性。这使它的应用受到了限制。 有两个实验打破了上述这种看法。1962年C波段低噪声行波管应用磁控注入式电子枪获得了3.1dB的噪声系数。1965年S波段中功率前向波放大器获得了3.5dB的噪声系数。但这些器件均限于中小功率范围,阴极长度很短,即阴极长径比很小的情况;而对于大功率管中使用的磁控注入式电子枪,能否获得足够小的噪声系数的问题,尚有待于进一步深入研究。 本文简要讨论了影响大功率微波管中磁控注入式电子枪噪声的主要因素以及通过改变阴极区磁场分布的方法来减小噪声的实验结果。     

X波段行波管阳极控制电子枪设计

大功率电子枪设计中的主要问题是如何构成强流电子束和使电子枪中电子束聚焦。利用差值计算的方法初步确定了电子枪几何尺寸参数,进而应用数值模拟的方法计算了电子枪的结构及束流特性,设计了应用于X波段连续波大功率行波管的阳极控制电子枪。该电子枪设计参数为：阳极调制,导流系数为0．44μP,射程大于37mm,注腰半径为1mm。结果表明,该电子枪可完全满足x波段连续波大功率行波管对互作用电子束的要求。     

大屏幕彩色显像管电子枪聚焦性能分析

电子枪聚焦性能是由电极结构决定的，本文通过计算机模拟的方式对3种典型的用于大屏幕彩色显像管电子枪的为形貌进行了系统的模拟，对各电子枪聚焦特性进行了分析和比较表明电子束形成区，主透镜结构对屏幕中心，角部的着屏光点及不同电流下了聚焦的稳定性都有较大的影响。     

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.