利用三维粒子模拟仿真软件，对共焦波导结构的0.4 THz回旋行波管进行了注波互作用的模拟研究。以共焦波导的冷腔色散以及衍射损耗入手，最终选定HE06模作为互作用工作模式。为了对寄生振荡进行抑制，在互作用结构中引入了截断。在模拟过程中，通过调节束压、束流、工作磁场、电子束横纵速度比，得到了最优的工作参数。最终，在束压34 kV、磁场14.25、束流2 A、横纵速度比0.75的工作参数下，当输入信号为1 W时，得到了最高2.76 kW的功率输出，增益超过34 dB，3 dB带宽为8 GHz，效率达到4%。

With the help of 3D PIC software, the beam-wave interaction for a 0.4 THz confocal gyro-traveling-wave tube was simulated. With the consideration of cold dispersion characteristics and diffraction loss of the confocal waveguide, HE06 mode is chosen as the interaction working mode. For the purpose of suppressing competing mode, a sever structure is used. In the simulation process, with the adjusting of beam voltage, beam current, working magnetic field, and velocity ratio, the optimized working parameters are found. At last, the operating parameters are chosen as 34 kV beam voltage, 14.25 T magnetic field, 2 A beam current, 0.75 velocity ratio, and with the input power of 1 W, 2.76 kW output power is achieved. The gain exceeds 34 dB, the 3 dB bandwidth achieves 8 GHz, and the efficiency achieved 4%.