Hybrid free-electron maser based on the combination of the guiding-center shift and Doppler shift

This is the authors' abstract. We don't add key points for this paper.

A new possible free-electron maser is proposed, which is based on the combination of the guiding-center shift and Doppler shift. In this proposal the electron beam is located at the point where the ordinary gyrotron interaction vanishes, and the initial normalized transverse velocity is chosen to be equal to the reciprocal of its relativistic factor, so as to let the Doppler shift be dominant in the cyclotron resonance condition. Linear analysis of the TEₘₙ mode and nonlinear simulation of the TEmnq mode are presented. The influences of the initial transverse velocity to the axial velocity ratio on the linear growth rate and nonlinear efficiency are discussed in detail. It is found that the hybrid free-electron maser may attain an efficient growth rate and efficiency, and is quite sensitive to the initial transverse velocity to axial velocity ratio.