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。     

Electron beam in the presence of a periodic magnetic field with allowance for the thermal velocities of electrons

Equations are derived to study the effect of the initial transverse thermal velocities of electrons on the configuration of an intense electron beam in an electron-optical system with a significant divergence for the case of the beam focusing by a periodic magnetic field. It is demonstrated that the minimization of the effect of thermal velocities of electrons in the electron-optical system with the given level of the periodic focusing field and the cathode radius and temperature and the limiting compression of the beam in the presence of such a field is reached with the shaping systems in which an optimal magnetic flux passes through the cathode and the flux depends on the parameters of the thermal beam and the focusing field.     

Transport of electron beams in periodic permanent-magnet focusing systems with nonharmonic distribution of the magnetic field

The results of the study of the transport of electron beams in periodic magnetic fields are presented for the case when the distribution of the magnetic field is essentially different from a sinusoidal distribution in different parts of the drift channel. An easy-to-implement nonharmonic distribution of the magnetic field is found. This distribution ensures a small ripple of the envelope of a high-intensity electron beam. The results of application of combined periodic permanent-magnet (PPM) focusing systems in high-powered pulse travelingwave tubes (TWT) are presented for the TWTs having a slow-wave structure that is superposed with the pole pieces of the PPM focusing systems.     

A low potential collector employing an asymmetrical electrode in an axially-symmetric magnetic field

A collector for a beam-type tube with an axial magnetic focusing field can be made to operate at a potential near cathode potential without returning secondary electrons, if the beam is deflected and caused to pass an asymmetrical electrode properly positioned in the axially symmetric magnetic focusing field. Collection takes place in a region of radial electric field. Experimental results on such a device indicate successful operation, provided the velocity spread in the beam is not too large.     

一维阵列电子注平面聚焦系统磁场分布特性

针对平面集成行波管对一维阵列电子注聚焦的应用需求,设计了4通道电子注平面磁聚焦系统。将各通道磁场轴向和横向分量沿轴分布特征计算结果与测试结果进行对比,确认了Opera软件计算磁场分布特征的准确性。为与轴对称周期永磁(PPM)聚焦系统电子注通道内磁场分布特性进行对比,建立了轴对称PPM聚焦系统模型,测试结果与计算结果一致性较好。通过平面聚焦系统与轴对称PPM聚焦系统电子注通道内的磁场纵向和横向分布特性对比表明,两种聚焦系统电子注通道内纵向和横向磁场具有相同的分布特征,在离轴相同位置的圆周上横向磁场分量与轴向分量的比值均为B_x/B_z≈0.11,该平面聚焦系统可实现一维阵列圆形电子注的良好聚焦。     

The design of periodic magnetic focusing structures

Charts are presented which facilitate the design of permanent-magnet periodic structures for focusing electron beams. These charts include curves showing the peak magnetic field required for periodic focusing in terms of the electron-beam parameters, the magnet and pole-piece dimensions required to obtain this peak field, and the resultant weight of the focusing system. Thus, sufficient information is given to design completely a periodic permanent-magnet focusing structure for a given electron beam. The design of a focusing structure for a 1-watt X-band tube is carried through in detail to exemplify use of the charts.     

Chaotic oscillations in electron beam with virtual cathode in external magnetic field

This article presents the results of a numerical study of external magnetic field influence on the conditions and mechanisms of virtual cathode (VC) formation in a relativistic electron beam. It also considers other related issues, e.g. peculiarities of nonlinear dynamics of electron beam with VC under changed external magnetic field, different mechanisms of VC oscillation chaotisation leading to complication of vircator system dynamics and appearance of multi-frequency VC oscillations. General systemic mechanism of VC oscillation chaotisation has been identified which is connected with formation of electronic patterns in electron beam whose interaction in the common field of spatial charge determines appearance of additional inner feedback. Transition from chaotic to periodical oscillation regime is found to be connected with destroying the mechanism of secondary electronic structures (electron bunches) formation. Besides, the influence of extent of screening of electron gun from magnetic field is discussed.     

Electron-beam flow in superimposed periodic and uniform magnetic fields

Theoretical and experimental results are presented on the focusing of an electron beam by means of a magnet structure which produces, along the axis of the beam, a periodic magnetic field superimposed on a uniform field. The relation between space-charge and magnetic-field parameters for minimum ripple is derived. The flow in superimposed uniform and periodic magnetic fields is shown to be degraded from the flow of electrons in a magnetic field which has a sinusoidal variation along the axis. The results indicate the flow conditions to be expected, where such combined fields are unavoidable. The focusing of electron beams in this type of superimposed magnetic field and in Brillouin flow are compared.     

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...     

Hollow-beam focusing with electrostatic and periodic magnetic fields

A new method of focusing a hollow cylindrical electron beam is presented. The focusing system consists of a cylindrical center conductor inside the beam, a cylindrical outer conductor enclosing the beam, and a series of periodic magnets outside the tube. A radial electrostatic field between the conductors provides an outward force on the electrons. The periodic magnetic field produces an inward force on the electrons. The inward and outward forces can be adjusted to provide a balance of all the forces acting on the electrons at both boundaries of the beam by choosing the electric and magnetic fields properly. An approximate analysis has been made and is presented which gives necessary design information. A number of curves are presented which are useful in designing focusing systems of this type. Experimental results on a beam tester show that current transmission of over 90 per cent for perveance up to 11 micropervs can be obtained readily. The adjustments are not critical and the performance is very stable.     

Intense Sheet Electron Beam Transport in a Uniform Solenoidal Magnetic Field

In this paper, the transport of intense sheet electron beams in a uniform solenoidal magnetic field in high-power vacuum electronic devices is theoretically examined with the 3-D beam optics code MICHELLE. It is shown that a solenoidal magnetic field can be an effective transport mechanism for sheet electron beams, provided the beam tunnel is matched to the beam shape, and vice versa. The advantage of solenoidal magnetic field transport relative to periodic magnetic transport resides in the feasibility of transporting higher current density beams due to the higher average field strength achievable in practice and the lower susceptibility to field errors from mechanical misalignments. In addition, a solenoidally transported electron beam is not susceptible to voltage cutoff as in a periodic magnetic focusing system; hence, device efficiency is potentially higher.     

Effect of a magnetic field on the structure of a high-current electron beam with a compensated charge

A mathematical model of a high-current electron beam with a compensated charge is developed. The effect of the 3D axially symmetric magnetic field induced by the beam current is taken into account. The model is based on the method of current tubes, which makes it possible to calculate electron trajectories in the presence of an external axially symmetric magnetic field. It is demonstrated that, in the presence of an external axially symmetric magnetic field, the beam rotates around its axis and the azimuthal current is induced. The shapes of electron trajectories are strongly affected by the magnetic field of the azimuthal current. The electron trajectories are calculated for various beam currents and external magnetic fields. It is shown that a significant nonlinearity leads to crossing of the trajectories of the initially laminar beam, sheath formation after passing the crossover, and collisionless thermalization of the beam. The boundary of the region inside which the beam can stably overcome the first crossover is determined.     

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.     

Electron Beam Optics System PIC Simulation for MMW TWTs

The basic feature and design method of MMW TWTs electron optics are analyzed in this paper. With the increasing area convergence ratio of the electron gun in TWTs, the initial thermal velocity of electrons at cathode and the non-magnetic shielded effect can no longer be neglected. It brings new challenge for the design and simulation of MMW TWTs electron optics. A method of investigation the beam DC characteristics is described using particle-in-cell (PIC) simulation and incorporate electron beam optics model integrated electron gun with periodic permanent magnetic focusing system. It is valuable for achieving the goal of “first-pass design success” and the electron optics engineering design and optimization.     

Equilibrium solutions for partially immersed relativistic electron beams

The equations relating the beam radius and axial electron velocity to easily measurable external beam parameters are developed for solid, relativistic beams. The beam parameters are tunnel voltage, beam current, axial magnetic field, cathode magnetic field, tunnel radius, and cathode radius. The equations are sufficiently complex to warrant the use of a digital computer if many cases are to be evaluated. Error indicators are formulated to prevent use of the relations beyond their range of validity. The equilibrium solutions for relativistic electron beams from unshielded cathodes show that the required magnetic focusing field is lower than that computed from nonrelativistic formulas. The angular magnetic field produced by the beam itself aids in focusing the electrons. The potential depression due to space charge is analyzed. Correction curves are given which allow the use of nonrelativistic equations in predicting equilibrium behavior. The maximum possible microperveance of relativistic beams is shown to be lower than the classical value of 25.4.     

Electron beam characteristics in radially varying periodic magnetic fields

Periodic magnetic fields are being widely used for the light-weight focusing of beams in high-power traveling-wave tubes. In many tube designs, there exists a considerable amount of radial variation in the magnetic focusing field. The effect of this radial field variation is investigated analytically as an extension of the previous work in this field. The usual design curves of α vs β are plotted with three variable parameters: ripple, cathode shielding parameterK, and radial field variation parameter x0. It is noted that it is important to keep the magnetic-field strength constant at the beam edge over a considerable variation of the magnetic-field parameter x0.     

浸没流多透镜多注电子光学系统的模拟研究

该文采用先2维后3维的计算方法,对L波段高峰值功率多注速调管电子光学系统进行了模拟设计。采用均匀场浸没流多透镜聚焦系统对电子注进行聚焦,获得了通过率100%,填充因子55%,特性良好的旁轴电子注。模拟计算表明,多透镜系统可有效调整电子注平衡半径,电子枪区均匀场可有效调整电子注波动性及层流性,聚集系统可在阴极磁感应强度为0.001~0.01 T,主磁场为0.06~0.13 T的范围内实现对旁轴电子注的良好聚焦。     

强流静电会聚电子枪系统计算机模拟研究

轻、小型层流电子枪在电子束焊接,微波器件等方面具有广泛的应用,希望得到稳定的、环形分布且会聚良好的电子束.但传统电子枪的聚焦系统如磁聚焦或电磁混合聚焦存在结构复杂、重量大的缺点.我们采用具有优异电子发射和抗中毒能力的LaB6作为阴极材料,纯静电聚焦的方式进行仿真、设计.经过理论探讨和计算机模拟仿真,在5 000 V总电压下,输出300 mA强流电子束,导流系数达到了3.35 μA/V3/2.为下一步具体的结构设计提供了可靠依据.     

Instability regions of an electron beam in superimposed periodic and uniform magnetic fields

The stability of an electron beam in a superimposed sinusoidal and uniform magnetic field is theoretically and experimentally investigated. The first instability region degenerates to a point within the first well-known passband for a zero uniform field component, whereas the second instability region coincides with the first stopband of the sinusoidal field. These considerations are of practical significance for periodic magnetically-focused electron beams.     

均匀磁场聚焦部分屏蔽流电子注的一种设计方法

本文叙述了适用于轴对称强流电子光学系统各种磁结构的部分屏蔽流过渡区的设计方法。通过综合选取磁系统和电子枪参数,实现了磁系统与电子枪的最佳匹配,获得了屏蔽系数大于0.8,波动小于1％的电子注。