Design of 94 GHz second-harmonic complex cavity gyrotron with gradual transition

A code used to analyze beam-wave interaction in complex cavity is written based on the self-consistent nonlinear beam-wave interaction theory. The code is used to optimize cavity and electromagnetic parameters of a gradual transition complex cavity with second-harmonic waves of TE021-TE031 mode group. Simulations using the software Magic show a good agreement with calculations. Based on the calculations and simulations, a second-harmonics complex-cavity gyrotron is developed. Experiments show that the gyrotron delivers steadily peak power of 156 kW with an efficiency of 27.1% and output of TE01 mode at frequency 94 GHz, voltage 57.5 kV and current 10 A. Data of calculations and simulations are consistent with those from the experiments.