High extraction efficiency experiments with the Los Alamos free electron laser

Abstract The injector, radio-frequency power system, beam transport, and cavity optics of the Los Alamos free electron laser system have been significantly improved. We report here on experiments to determine the effects of these improvements on extraction efficiency and to demonstrate performance comparable to that found in amplifier experiments and in reasonable agreement with simulations. The experiments used wigglers with 12% and 30% wavelength taper. Measurements were made with and without a prebuncher and with sideband suppression accomplished by cavity-length detuning. The free electron laser produced extraction efficiencies up to 4.4% and showed well-defined buckets of decelerated electrons.