Simultaneous Gyrotron Operation at Several Cyclotron Harmonics: Theory and Experiment

The results of theoretical and experimental studies of simultaneous gyrotron operation at several cyclotron harmonics are presented. Based on numerical simulations we consider possible effects in the beam-wave interaction which can be responsible for the nonlinear excitation of a parasitic fundamental-harmonic mode in a second-harmonic gyrotron. Contrariwise, we determine optimal conditions for efficient 2nd harmonic generation which can accompany the radiation at a fundamental one due to frequency multiplication. Results of numerical simulations are in a good agreement with experiments in which 2nd harmonic radiation power of 80 mW was obtained in a 0.263 THz gyrotron.