Microwave System of Transverse Output for a High-Power ${W}$ -Band Gyro-TWT

A conceptual design and the results of concrete simulations of the output microwave system of a W-band gyrotron traveling-wave tube (gyro-TWT) with a predicted output pulse power of more than 300 kW are presented. A distinctive feature of this system is the transverse (relative to the translational velocity of the electrons in the gyro-TWT) extraction of the output power. The designed microwave circuit includes a waveguide mode converter and a set of quasi-optical mirrors. An oversized hole in the first 45° inclined mirror enables a lossless transport of the electron beam to the collector. The ring-like distribution of microwave radiation on the mirror is formed by a profiled waveguide mode converter and provides minimal radiation diffraction loss. For the synthesis of the mode converter, particle swarm optimization (PSO) method was used. The system of external quasi-optical mirrors provides the transformation of the ring-like beam into the HE1,1 mode of a corrugated waveguide with an efficiency of more than 94% in the frequency range 92-98 GHz. The mirror profiles were synthesized using the Katsenelenbaum-Semenov iterative procedure.