Linear theory of large-orbit gyrotron traveling wave amplifiers with misaligned electron beam

A linear theory of large-orbit gyrotron traveling wave amplifiers (gyro-TWAs), which can be applied to analyze the effect of electron beam misalignment, is developed by specializing the corresponding theory of small-orbit gyro-TWAs. The linear theory is validated by comparing with a nonlinear theory. The theory can also be used to evaluate the starting conditions of a gyrotrn backward wave oscillation (gyro-BWO). It is shown that beam misalignment can break the limitation of mode-selective condition and make the instability problem more complex.