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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$221.5~^{\circ }$ </tex-math></inline-formula>C and 0.173 mm when the convection coefficient of the heat dissipation base plate is set to be 25 W/m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}~^{\circ }$ </tex-math></inline-formula>C.