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.assessment of relative electron gun performance The assessment of relative electron gun performance Comments on the paper entitled “ Digital computer studies of electron guns for electron microscopes “†

A method of comparing the basic performance of electron guns is described. The method is applied to some recently computed results on two versions of an electron gun which has a hairpin-filament cathode.     

Transport of noise fluctuations in convergent flow crossed-field electron guns

The transport of noise fluctuations in convergent flow or so-called Kino-type crossed-field electron guns is investigated in terms of a two-dimensional computer simulation of the gun by the well-known Monte Carlo method for studying stochastic processes. The exact electrode configurations are simulated in the computer memory. After sufficient time has elapsed for the electron flow to achieve a steady-state condition 2000 additional time intervals are computed and then a statistical analysis is made of the fluctuation quantities. Six emission spots are considered on a finite-width cathode. The analysis is facilitated by the development of a rapid method for the solution of Poisson's equation (two-dimensional). Of particular interest in the results is the improved laminarity of the flow in the KG-M gun and the fact that there is significant space-charge smoothing throughout the gun region in both Kino-type guns. Of greater significance and as yet not explainable is the fact that Ψ versus ωct has local peaks when the space-charge density, which is spatially varying, passes through the Brillouin value (ω_{p}-ω_{c}for this condition). This knowledge could be profitably used in deciding on the location of the gun exit plane. The fact that the laminarity of the flow is sensitive to slight changes in the electric field near the cathode indicates that an absolute evaluation of the noise performance of KG-A and KG-M guns is difficult and may only be obtained through appropriate experiments.     

微电真空折叠波导行波管放大器的电子枪设计

研制工作于太赫兹波段的微电真空折叠波导行波管(FWG-TWT)放大器,需要设计束流集中且发射度小、结构紧凑的热阴极电子枪.本文首先依据典型皮尔斯电子枪的设计理论,通过编程计算初步选定了热阴极电子枪的基本结构参数,然后利用模拟工具对电子枪的结构参数模型进行了初步的仿真优化.针对工作频率为0.22 THz的微型折叠波导行波...     

A design method for crossed-field electron guns

A design method for crossed-field guns based on a space-charge-flow solution in crossed fields is given. By using the method of analytic continuation in the complex plane, it is shown that it is possible to find the exact form of the electrodes required The design results in a gun similar to the French "short gun" with the great advantage that the current emitted from the gun and the current density at the cathode can be predicted. It is also shown that by making certain approximations to the exact space-charge-flow solution, a new type of gun can be designed, a "long gun" which can have extremely high convergence. The theory for this latter gun is extremely simple and the electrode shapes can be given entirely in analytic form.     

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.     

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.     

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。     

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.     

The effect of tolerances in conical flow Pierce guns II—The perturbed flow in the magnetic field

The first-order perturbations to a beam initially in nonrippling Brillouin flow, which results from several common manufacturing errors in conical flow Pierce guns, are calculated. The manufacturing errors are changes in cathode-anode spacing, changes in cathode curvature, tilt, and transverse displacement of the cathode-focus electrode assembly, and tilt and transverse misalignment of the whole gun to the magnetic field. Errors in cathode-to-focus electrode spacing are not discussed. The tolerances which destroy the rotational symmetry of the gun are shown to cause the smooth beam to perform a helical motion; the tolerances which preserve the symmetry are shown to produce an undulating beam. Using the results of Part I of this paper [1], the magnitudes of individual gun tolerances are related to the effects they produce in the magnetic field. A method of setting limits to the individual gun tolerances is presented and illustrated by calculating tolerances for a gun used in an X-band traveling-wave tube. The calculated tolerances are found to have values which may readily be achieved by careful engineering.     

Low-voltage color tube gun assembly with periodic focusing

One type of color tube, often referred to as the post acceleration color tube, requires a gun of unique design. The gun operates at relatively low voltages of 5000 to 7000 volts as compared with 20,000 to 30,000 volts in other types of color tubes. The tricolor gun assembly described consists of three individual guns arranged in a plane. This limits the inside diameter of the electrodes to 0.358 inch as compared with half an inch or more in conventional guns. The individual guns are either triodes or tetrodes with periodic focusing. In spite of the above mentioned restrictions the spot size is about 0.038 inch at 300 microamperes screen current per gun and 7000 volts anode voltage. The depth of focus is very satisfactory because of small beam diameter.     

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.     

Some experiments with a new type of crossed-field gun

The construction and testing of a crossed-field gun based on an exact space-charge flow solution will be described. All the characteristic parameters of a gun of this type may be obtained analytically. Experimentally the gun was found to perform essentially as predicted. This gun has a moderately high convergence and produces a beam whose gross features give a very good approximation to planar Brillouin flow. Work by Anderson has indicated that crossed-field beams produced by a gun of this type may be somewhat less noisy than similar beams produced by other types of guns.     

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。     

The effect of tolerances in conical flow Pierce guns I—The perturbed flow within the gun

A first-order perturbation analysis of the dc effects of several important tolerances in conical flow Pierce guns is presented for the case in which the gun is part of a solenoid focused system used to produce a smooth Brillouin beam. In this, the first of two parts, the flow up to the anode of the gun is analyzed. The data presented permit calculation of the magnitude of the perturbations at the anode due to various manufacturing errors. These errors are: changes in cathode-anode spacing, changes in cathode curvature, tilt, and transverse displacement of the cathode-focus electrode assembly. The theory does not permit the analysis of cathode to focus electrode tolerances. The perturbations at the anode serve as boundary conditions for the flow beyond the gun which is calculated in the companion paper. A comparison of the magnitude of effects at the anode calculated by the theory and obtained from an experimental study shows that reasonably good agreement exists between theory and experiment.     

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.     

彩色CRT高分辨率电子枪技术

本文综合简介了日本三大类高分辨率电子枪技术,第一类是三角形电子枪;第二类是一字形电子枪,也是目前在彩色高分辨率 CRT 中广泛使用的电子枪,文中着重介绍其改进;第三类是单枪三束电子枪。最后,还简单介绍了高分率电子枪用阴极。     

空间行波管阴极寿命试验

本文介绍了对用于空间行波管的M型阴极进行的寿命试验。阴极寿命试验的载体选用普通玻璃二极管与电子枪,用于试验的M型阴极在40支普通玻璃二极管中的累计试验时间已经超过681000 h,在16支电子枪和2支行波管中的累计试验时间已经超过275000 h。对阴极的钡蒸发测量表明在空间行波管的工作年限内,M阴极主要受到膜层退化的影响,而一般不会出现钡耗尽的问题。因此基于电子枪寿命试验的数据,由膜层退化导致的阴极实际功函数增加,得出了M型阴极寿命模型,并对一定工作条件下的阴极寿命时间进行推算。同时作者发现：对于长期的阴极寿命试验,普通玻璃二极管不能有效保持其内部真空度,阴极发射下降较快;在电子枪中,阴极发射稳定。电子枪更适合作为阴极寿命试验的载体。     

Tangential magnetic field immersion of a hollow beam electron gun

Harris flow is one of a number of equilibrium electron beams requiring a launching method which imparts angular momentum to the stream. Immersion of the electron gun region in a magnetic field tangent to the cathode and orthogonal to the electron trajectories provides a means of rotation free of the defocusing and discontinuity effects of previous methods. Centrifugal-force spreading is eliminated by electric-field compensation in the gun. This compensation results in field lines at an angle to the stream edges and necessitates gun electrode design by a curvilinear flow method. An immersed gun of this kind has produced a stable Harris flow beam containing 86 per cent of the total energy in rotational motion. Anode transmission is in excess of 95 per cent.