Harmonic terahertz gyrotron with a double confocal quasi-optical cavity

To reduce mode competition in a high-harmonic terahertz gyrotron, the gyrotron with a quasi-optical confocal cavity is proposed. Theoretical and experimental investigations demonstrate that the confocal cavity has good-mode selection and is suitable for high-harmonic operation. However, due to the transverse nonuniformity of the radio frequency field, the beam-wave interaction efficiency is low in the confocal cavity. To mitigate this drawback, the double confocal cavity is investigated in this study. Through three-dimensional particle-in-cell simulation on a designed 330-GHz gyrotron with a double confocal cavity, the physical mechanism of beam-wave interactions in a double confocal cavity is analyzed and presented. Published under license by AIP Publishing.