耦合腔行波管多级降压收集极的模拟设计

本文中较全面地讨论了多级降压收集极的物理模型.通过分析3个工作频率点高频输出端的电子注特性来设计多级降压收集极:借助电子注层流性参量,对带有再聚焦磁场的散群聚区进行优化,得到磁场参量的初始值;运用电子轨迹等效电位图,确定各电极的初步电位,通过收集极区结构和电极电位的优化得到较高的收集极效率;通过收集极的全面优化使收集极效率得到了进一步的提高;在考虑二次电子发射情况下,对收集极结构和电极电位进行优化,在保证收集极效率的情况下使二次电子回流率为零.模拟结果表明:借助电子注层流参量设计出带有再聚焦磁场的散群聚区使电子轨迹层流性得到较大改善;合理的结构和电极电位能得到较高的收集极效率;二次电子发射对收集极效率影响较大,合理的调节外凸锥形电极的倾角能避免二次电子回流.此设计运用于一耦合腔行波管收集极的模拟计算,达到了良好的效果.

Design Simulation of Multistage Depressed Collector for Coupled Cavity Traveling Wave Tubes

The physical model of multistage depressed collector (MDC) for coupled cavity traveling wave tube (TWT) was developed,with which the design of MDC was simulated by analyzing the electron beam characteristics of the RF output at three operating points.The impacts of secondary electrons,and collector strusture and its potential on MDC efficiency were studied.In the simulation,first,the initial values of the magntic field was evaluated by optimizing the debunching section of the periodic permanent magnetic (PPM) field,with the help of the given laminar electron beam.Next,the initial potentials of different electrodes were determined by means of the equivalent potentials of the electron orbits.Finally.the MDC efficiency was improved by optimizing the structures of the collector and the potentials of the MDC electrodes.Similarly,when it comes to secondary electron emission,high MDC efficiency and zero back-streaming rate of secondary electron were also achieved.The simulated results show that the secondary electrons emission strongly affects the MDC efficiency.We suggest that a judicious choice of the electrode's cone angle may eliminate back-streaming of secondary electrons.