Performance improvement of a sub-THz traveling-wave tube by using an electron optic system with a converging sheet electron beam

Abstract

Many applications, such as high-data-rate wireless communications, spectroscopy, high-resolution radar, biomedical imaging, security, etc. require compact high-power sources of sub-THz radiation. Traveling wave tube (TWT) amplifiers are the most promising candidates for such sources combining 10–100 W power and wide bandwidth. Here we present the results of design and simulation of a 0.2-THz TWT with a grating slow-wave structure (SWS) and electron-optical system (EOS) with a converging sheet electron beam. The designed EOS provides substantial improvement of the amplifier performance as compared with the EOS with straight beam immersed in a uniform magnetic field. In particular, it facilitates beam focusing and allows reduce of the focusing magnetic field and cathode current density. The latter allows increase of lifetime and makes possible operation in a continuous-wave mode. In addition, decrease of the beam thickness allows reduce of the beam tunnel height accordingly, which leads to nearly 2.5-times increase of the Pierce coupling impedance resulting in increase of gain and decrease of the required driving power. The simulation predicts small-signal gain over 30 dB in 180–200 GHz frequency band and over 80 W saturated power. Keywords: Traveling-wave tube, Sheet electron beam, Electron gun, Slow-wave structure, Terahertz band