Study of a High-Efficiency Depressed Collector for 0.22 THz Traveling Wave Tube Amplifiers

A three-stage depressed collector with significant features of high collection efficiency and low back-streaming rate is designed for a 220 GHz sheet beam traveling wave tube (SB-TWT). To make the simulation model close to the realistic situation, the spent electron beam was obtained from the end of the beam-wave interaction system based on the actual electron optics system (EOS) rather than the ideal one. However, if the extracted spent electron beam is directly used for the design of a collector, it will greatly increase the simulation time and even make the simulation collapse. To address this issue, multiple samplings of the spent electron beams are employed. Based on the position and energy distribution of the sampled spent electron beam, the collector is designed by using computer simulation technology (CST). Simulation results show that the collection efficiency and back-streaming rate for the case having considered secondary electrons are up to 95.7% and 0.07%, respectively. In addition, the thermal analysis has been conducted for the designed collector by using ANSYS software. Simulation results show that the maximum temperature and deformation of the collector are $221.5~^{\circ }$ C and 0.173 mm when the convection coefficient of the heat dissipation base plate is set to be 25 W/m $^{2}~^{\circ }$ C.

I. Introduction

The terahertz (THz) technology has an abundance of promising applications, including high-data-rate communications, high-resolution radar, security imaging, plasma diagnostics, and biomedical sciences, making it become an important research hotspot in recent decades [1], [2]. The THz radiation source is one of the most important devices for the THz application systems. Among different kinds of THz radiation sources, the THz-band sheet beam traveling wave tube (SB-TWT) has gained a lot of attention due to its significant advantages of high output power and wide bandwidth [3], [4], [5].