Study on the Multi-Modes, Multi-Harmonics Behavior of a THz Large-Orbit Gyrotron

A large orbit gyrotron capable of operating from the 4th to the 9th harmonic is investigated. With the assistance of the 3-D particle-in-cell simulation, the beam-wave interaction dynamics and high harmonics operation regimes are studied. It is shown that by tuning the external magnetic field intensity, successive excitation of the oscillation at a number of neighboring harmonics can be achieved, corresponding to radiation frequencies between 240 GHz to 460 GHz. Then, a study of the competition among the 7th, 8th and 9th harmonics are conducted, providing an insight into the multi-modes, multi-harmonics behavior of the high-harmonic LOG.