Experimental Investigation of a Dual-Beam Traveling Wave Tube

A multibeam-based traveling wave tube (TWT) system aims to concurrently amplify multiple RF sources with a compact size. However, the practical implementation of this multibeam-based TWT system encounters a challenge as the electron beam traverses a radial magnetic field. The most noticeable effect of this radial magnetic field is a consequential shift in the beam center position. This leads to a degradation in the transmission characteristics of the electron beam within the interaction circuit, consequently yielding a diminished efficiency for the TWT amplifier. In addition, the radial magnetic field worsens the quality of the electron beam, resulting in increased emittance and a decreased axial velocity. In this article, we undertake an investigation and development of a dual beam-based TWT system designed for operation within the 81–87 GHz frequency range. Notably, due to experimental constraints, only one cathode was available for the experiment. The experimentally achieved performance of this dual beam-based TWT includes an output power of 1047 mW at 81.5 GHz, with a corresponding gain of 13.39 dB. Furthermore, the impact of the radial magnetic field on the electron beam is explored through the CST particle-in-cell (PIC) simulations. Our findings contribute to a better understanding of the challenges posed by the radial magnetic field, providing insights that can guide the optimization of multibeam TWT systems.