Study of the beam-wave interaction of a 0.34-THz confocal waveguide gyro-TWT with confocal beam

In this paper, in order to enhance the efficiency of the confocal gyrotron travelling wave tube (confocal gyro-TWT), the confocal beam is first introduced based on the field distribution of the operating mode in the confocal waveguide. Besides, a confocal gyro-TWT with a confocal beam operating at 0.34 THz is simulated and designed based on linear and nonlinear theories. It is verified that the confocal beam can enhance the interaction efficiency and output power significantly through simulation. In addition, the effects of electron beam parameters on output power are also analyzed in this paper. The simulation results indicate that the confocal gyro-TWT can operate at TE06 stably with an output power of 17.3 kW when the beam voltage is 60 kV, beam current is 2 A, input power is 40 mW, and transverse velocity spread is 5%. The corresponding frequency and interaction efficiency are 0.34 THz and 14.4%, respectively.