A High-Power Free Electron Laser Using a Short Rayleigh Length

Free Electron Lasers (FELs) have always had the potential for high average power, since the laser medium cannot be damaged, is transparent to all wavelengths, and the exhaust heat is removed at the speed of light. At MW power levels, the resonator mirrors of the oscillator are vulnerable to damage because of the small beam size in the undulator. We present a description of an FEL that uses a resonator with a short Rayleigh length in order to increase the mode area at the mirrors and reduce the intensity. The corresponding undulator must also be short. The whole FEL system is designed to be compact and efficient, producing about 1 MW of power at 1 mu-m infrared wavelengths using an electron beam of about 100 MeV with about 1 ampere of recirculating average current