Smith–Purcell free electron laser based on a semi-conical resonator

We investigate a Smith–Purcell free electron laser composed of an electron gun, a semi-conical resonator, a metallic grating and collector. The semi-conical resonator could reflect all Smith–Purcell radiation with emission angle θ, and with random azimuthal angles, back onto the electron beam and causes the electrons to be modulated. Tunable coherent far-infrared Smith–Purcell radiation with a high output peak power at millimeter wavelengths can be generated.