A millimeter wave FEL driven by a photocathode rf linac

Abstract We present the design of a millimeter wave FEL based on the UCLA photocathode rf linac. The linac energy can be varied between 5 and 18 MeV. The electron pulse duration is 2 ps FWHM, with a peak current exceeding 150 A. The FEL is designed to operate in the high gain Compton regime, controlling the slippage with the propagating radiation in a waveguide. The design will permit the exploration of the basic FEL physics in this regime, including the exploration of saturation and lethargy in the superradiant and steady state regime.