An Ultrahigh Compression Ratio Sheet Beam Electron-Optical System for 0.66-THz Traveling-Wave Tubes

A stable sheet beam electron-optical system for 0.66-terahertz (THz) traveling-wave tubes (TWTs) is presented in this article. An electron gun with an ultrahigh-compression ratio (over 110) is carried out employing the Pierce design method. A three-stage beam focus electrode (BFE) is used to achieve the ultrahigh beam-area compression ratio without deteriorating the beam quality. When the operating voltage is set to 19 kV, this electron gun could generate a 28.9-mA current with a 5.6-A/cm2 emission density, simulated and confirmed by the CST Particle Tracking Solver. To confine the sheet electron beam (SEB), a uniform magnet (UM) system is presented, providing over 0.9-T $z$ -axis magnet field. Focused by this magnet, the joint simulation shows that the SEB can smoothly transmit through a $180\,\,\mu \text{m}\,\,\times 65\,\,\mu \text{m}\,\,\times30$ mm tunnel without interception with the wall. The error sensitivities of this electron-optical system are analyzed and discussed to make the design more practical.