Observation of Dynamic Interactions between Fundamental and Second-Harmonic Modes in a High-Power Sub-Terahertz Gyrotron Operating in Regimes of Soft and Hard Self-Excitation

摘要

Dynamic mode interaction between fundamental and second-harmonic modes has been observed inhigh-power sub-terahertz gyrotrons [T. Notake et al., Phys. Rev. Lett. 103, 225002 (2009); T. Saito et al.Phys. Plasmas 19, 063106 (2012)]. Interaction takes place between a parasitic fundamental or firstharmonic(FH) mode and an operating second-harmonic (SH) mode, as well as among SH modes. Inparticular, nonlinear excitation of the parasitic FH mode in the hard self-excitation regime with assistanceof a SH mode in the soft self-excitation regime was clearly observed. Moreover, both cases of stable twomodeoscillation and oscillation of the FH mode only were observed. These observations and theoreticalanalyses of the dynamic behavior of the mode interaction verify the nonlinear hard self-excitation of theFH mode.