A high duty factor electron linac for FEL

An 18-MeV, 433-MHz linac capable of operating at 25% RF duty factor (DF) is being commissioned for FEL applications. Comprising a two-cell RF photocathode injector followed by four new multicell cavities, the linac is an extension of the photoinjector which previously delivered 5 nC at 27 MHz micropulse repetition frequency, and 25% DF. The system is constructed using equipment from the Ground Based Laser and the Average Power Laser Experiment (APLE). The linac can serve as the driver for an infrared FEL or as the preaccelerator for a higher energy linac driving a visible FEL.