Simulation of high-efficiency gyrotron with the system of multistage energy recovery

The results of simulations of helical electron beam formation and collecting, as well as high frequency wave-particle interaction processes, in the moderate-power experimental gyrotron with the frequency of 74.2 GHz are presented. Various methods of beam quality and electron efficiency improvement via optimization of electric and magnetic field distributions in the cathode region were realized. In the optimal operating regime with high pitch ratio and low velocity spread, the electron efficiency of about 46 % was calculated for the gyrotron with the magnetron injection gun including a control electrode and a cathode with sectioned emission. In the gyrotron collector region, a system of 4-stage electron energy recovery was used for enhancement of total efficiency of the device. By improving the quality of the electron beam and efficient energy recovery in the collector region, the total efficiency of the gyrotron equal to 71.8% was achieved.