Results Of The PALADIN Experiment

PALADIN is a single pass, free electron laser amplifier located at the Lawrence Livermore National Laboratory. This FEL is designed to run at 10.6 um. The 1 -kA, 45 -MeV electron beam is provided by the Advanced Test Accelerator. The wiggler is 25 m long with an 8 cm period. The input optical signal to theamplifier is provided by a conventional CO2 laser, which can produce a peak input power of either 18 kW or 3.6 MW. We have demonstrated 31 dB of gain with the 18 -kW input and 12.9 dB of gain for the 3.6 -MW input,producing over 70 MW of optical power. Using the 18 -kW input, the gain saturated at about 12 m into thewiggler; with the 3.6 -MW input, the gain saturated at about 8 m. Modeling results are shown.INTRODUCTIONIn 1986, the Electron Laser Facility (ELF) at LLNL demonstrated high gain and high extraction efficiency from a tapered -wiggler FEL amplifier.) The ELF experiments were done using microwaves in a waveguide anddid not address some issues pertinent to an optical- wavelength FEL. The PALADIN experiment was designed toexamine the physics pertaining to an FEL operating in the optical regime (10.6 um). The PALADIN wigglerwas designed to be assembled in 5 -m long sections, with a final length of 25 m. Preliminary experimentshave been performed using wiggler lengths of 5 and 15 m (Ref. 2). These earlier experiments have shown thatwe can successfully transport the electron beam through long wigglers without losing beam current into thewalls of the wiggler. The design of the wiggler magnet pole pieces made transport of the electron beam