Theoretical and Experimental Investigations on a Gaussian-Like Beam Output System for Ku-Band Gyro-TWT

Theoretical and experimental investigations on an output system, consisting of waveguide horn, phase-shift section, RF window, and monitoring section, capable of outputting a Gaussian-like beam rather than a circular waveguide TE_1,1 mode, for a Ku-band gyrotron-traveling-wave tube, have been carried out. An azimuthally symmetric Gaussian-like beam has been observed at the output port in both the low-power and high-power measurements. The experimental results showed that the mode purity of output Gaussian beam is over 98% from 14.5 to 16.5 GHz. There is no arcing monitored when the output pulse peak power is over 160 kW when the pulsed tube operates with 10% duty cycle. The output Gaussian-like beam can be directly usable for low-loss transmission as well as for effective antenna feeding and no extra mode converter is needed, which can improve the transmission efficiency of the transmission line system and form a compact high-power system.