Nonlinear theory of quasi-optical gyrotron with an electron beam at an oblique angle

In the quasi-optical gyrotron with a Fabry-Perot cavity, one can inject the electron beam at an oblique angle with respect to the optical axis of the cavity. This angle has a great influence on the gain mechanism, Doppler frequency shift, and saturation length of interaction. Numerical simulations show that two regimes of operation exist when the angle changes from 0° to 90°. When the angle is small (including 0°), the Doppler-shifted regime is identified with small negative optimized detuning and small optimized E-field amplitude. When the angle is large (including 90°), the gyrotronlike regime is identified with large negative optimized detuning and large optimized E-field amplitude. The quasi-optical gyrotron is quite efficient for harmonic operation