Superradiant Undulator Radiation of Periodic Intense Electron Bunches in a Cavity

Considered is superradiant undulator radiation emitted at grazing resonance by intense electron bunches periodically injected into a resonating cavity. Compared to a single bunch in a long waveguide, cumulative interaction of periodic bunches in a cavity allows much higher saturated efficiency induced by superradiant stimulated emission of radiation. Simulations in the saturation regime show that the self-field of intense bunches tends to reduce the efficiency by obstructing nonlinear bunching. When energy gain is balanced by cavity loss, the emitted radiation finds a steady state in which the radiation pulse persists with no dispersion. At that state, the cavity works as a stable oscillator, supplying periodic bursts of radiation via output coupling.