220 GHz均匀永磁聚焦行波管电子光学系统的设计与实验研究

Uniform permanent magnetic focusing electron optical system for 220 GHz travelling wave tube

电子光学系统是行波管的核心部件之一,在太赫兹频段,电子束通道很小,导致高电流密度电子束的传输非常困难。基于220 GHz折叠波导行波管慢波结构设计所需束流参数,根据理论分析和电磁仿真软件,设计了一款采用均匀永磁聚焦对电子束进行约束的电子光学系统。仿真结果显示,当电子束通道直径0.3 mm、长度31 mm时,在阴阳极压差20 kV的条件下阴极发射电流141 mA,电子流通率100%。根据设计结果封接了流通管,实验结果显示,当阴阳极压差20 kV时,阴极发射电流138.5 mA,收集极电流125.5 mA,电子流通率91%。

Electron optical system is an very important part of folded waveguide traveling wave tube. An electron optical system of a 220 GHz travelling wave tube is designed. The theoretical analysis is based on Pierce electron gun theory and synthesis iteration proposed by Vaughan, and numerical simulation of optical gun is completed by 3D software. The beam is focused by uniform permanent magnetic focusing system, and the uniform permanent magnet design is obtained by theoretical analysis and simulation. Then the uniform permanent magnet is machined and tested. The test result is in agreement with the design result. The electron gun and permanent magnetic focusing system are completely simulated, Which indicates that the beam transmission rate is 100%. The beam tunnel of the device is 0.3 mm in diameter over a length of 31 mm. The electron optical system is machined and tested, and the test result shows the beam transmission rate is 91% at voltage of 20 kV.