Three-dimensional particle-in-cell simulation of sub-terahertz high-power gyrotron

High power sub-terahertz pulsed gyrotrons are being developed for Collective Thomson Scattering (CTS) diagnostics of fusion plasmas. The typical target parameters are: output power 100~200 kW, operation frequency of 300 GHz, and pulsed length > 10 us. In order to support experimental development, numerical simulations have been carried out by using three dimensional particle-in-cell (PIC) code, "MAGIC". The oscillation modes of the electromagnetic radiation was selected as TE_15,2 and TE_17,2, for which the beam parameters and cavity dimensions was determined accordingly. So far, in the TE_15,2 mode, the simulation results showed maximum power of ~ 156 kW at oscillation frequency of 295.10 GHz, with oscillation efficiency of ~ 24.04 %. Also, in the TE_17,2 mode, the simulation results have showed maximum power of ~ 223 kW at oscillation frequency of 295.16 GHz, with conversion efficiency of ~ 34.42 %.