A 0.33-THz second-harmonic frequency-tunable gyrotron
Li Zheng-Di1, 2, Du Chao-Hai3, Qi Xiang-Bo3, Luo Li1, 2, Liu Pu-Kun3, †,
       

Starting oscillation currents of cavity modes near the operating mode TE−3,4,1 as a function of magnetic field, where dashed lines represent fundamental-harmonic modes while solid lines refer to second-harmonic modes with beam parameters: Vb = 12 kV and α = 1.75.