A Multi-Stage Depressed Collector for 0.22 THz Sheet Beam Traveling-Wave Tubes

In this paper, in order to improve the device efficiency of 0.22 THz traveling-wave tubes (TWTs), a multi-stage depressed collector (MDC) is investigated. For the purpose of designing a suitable collector structure and reasonable collector voltages, the energy distributions of the spent sheet beam is analyzed, and then the information of the energy distribution of the sheet beam is obtained. Through the theoretical calculations, the design scheme of a four-stage depressed collector is determined, and the maximum collector efficiency (98.11%) and the corresponding collector voltages (21.70 kV, 22.25 kV, 23.35 kV, and 24.40 kV) under ideal conditions are obtained. An elliptical four-stage depressed collector is accordingly designed by CST. After simulation optimization, it is finally determined that the collector voltages of each stage are 21.3 kV, 22.3 kV, 23.3 kV, and 24.4 kV, respectively. The collector efficiencies without and with considering the secondary electrons are 95.19% and 91.74%, respectively. These results are important for the design of the MDC for the 0.22 THz sheet beam TWTs.