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.