Linear and Nonlinear Analyses of a 0.34-THz Confocal Waveguide Gyro-TWT

In this paper, the dispersion relation of the beam wave interaction of the confocal waveguide gyrotron-traveling-wave tube (confocal gyro-TWT) is derived from kinetic theory for the first time; according to this dispersion relation, we can make the linear analysis of confocal gyro-TWT as well as the cylindrical waveguide gyro-TWT. At the same time, a numerical code based on the self-consistent nonlinear theory is written to simulate the behavior of electron beam and electromagnetic wave during beam wave interaction. When neglecting the spread of velocity and guiding center, the gain and growth rate calculated by the nonlinear theory code makes great agreement with that of linear theory in the small-signal region.