220 GHz折叠波导返波管束流光学系统设计和实验研究

本文介绍了220 GHz折叠波导行波管电子束流光学系统的设计过程。总体来讲，该系统可分为收敛性皮尔斯电子枪、磁聚束段和单极降压收集极。对于一个工作在太赫兹频段的电真空器件而言，极其细长的束流孔道让电子注以较高的流通率穿过慢波结构变得十分困难。空间电荷效应，加工装配精度和热初速等原因都是限制流通率的重要原因。研发一个具有足够流通率的实用束流光学系统对于220 GHz折叠波导返波管的研制是迫切的且十分棘手的任务。通过理论方法和数值工具，系统的三个部分将先后被设计，以满足束波互作用分析提出的电子注要求。基于这样的设计和开展的误差分析，流通管样管成功封管并进行了初步测试。实验数据表明这样的束流光学系统可以产生15.4 kV，22 mA的电子注，并能以80%以上的流通率通过直径0.19 mm，长30 mm的束流管道。

Design and experimental study of beam optical system for 220 GHz folded waveguide BWO

In this paper, the design process and experimental results of a beam optical system (BOS) for a 220 GHz folded waveguide (FW) backward wave oscillator (BWO) are demonstrated. The BOS is comprised of three parts: the Pierce convergent electron gun, the magnetic focusing transmission section and the single-stage depressed collector. For a vacuum electronics device operating in terahertz frequency (THz) regime, the ultra-small and long beam tunnel makes it tough for electron beam to pass through at a high rate. The space charge effect, the machining and assembly precision, the thermal velocity spread and thermal expansion will all make things worse. Therefore, to develop a practical BOS with sufficient passing rate is an urgent but difficult task for the development of the 220 GHz FW BWO. Using theoretical method and numerical tool, the three parts were designed one by one, to satisfy the requirement proposed by earlier analysis on beam-wave interaction. Based on the design results and error analysis, the sample tube of BOS was preliminarily developed and tested. The experiment data show that the BOS can generate an electron beam with a beam voltage of 15.4 kV, a beam current of 22 mA to pass a beam tunnel with a diameter of 0.19 mm, a length of 30 mm, where the passing rate is over 80%.