Power generation in a resonant cavity using a beam bunched at 35 GHz by a free electron laser

An intense beam of relativistic electrons (800A, 6.7MeV) has been bunched at 35GHz by a free-electron laser, in which output power levels exceeding 100MW were obtained. The beam was then extracted and transported through a resonant cavity, that was excited by its passage. Microwave power levels of 10MW were extracted from the cavity, in reasonable agreement with a simple formula which relates power output to known properties of the both beam and cavity.