Study of a 0.42 THz fourth-harmonic large orbit gyrotron

A 0.42 THz fourth-harmonic large orbit gyrotron (LOG) operating with TE
_4,2
mode is designed and studied. Unlike the widely used TE
_{m, 1}
mode in previous high harmonic (harmonic number s>=4) LOGs, the increase of radial index from 1 to 2 and even larger values bears the potential to enhance the beam-wave interaction efficiency as well as to decrease the cavity wall loss. 3D PIC simulation has shown that an output power of 2 kW corresponding to an efficiency of 2.7% can be achieved.