An overmoded 140 GHz, 1 kW quasioptical gyro-twt with an internal mode converter

The design and experimental study of a 140 GHz, 1 kW gyro-traveling wave tube (Gyro-TWT) operating in the HE₀₆ mode of a confocal waveguide is presented. A combination of quasioptical gain sections with dielectric loaded severs enables high gain operation with mode selectivity. A nanosecond-scale 120 mW pulse driver at 140 GHz was demonstrated. This input driver pulse will be amplified by the Gyro-TWT and the resulting output high-power short pulse will be transmitted to an EPR spectrometer probe. A quasioptical mode converter utilized to transform the higher order operating confocal mode into a Gaussian-like beam was designed and cold tested. The simulated and measured Gaussian beam patterns of the output mode converter are in good agreement.