Recent results from the Los Alamos free-electron laser

In this paper, we review the most recent experimental results of the Los Alamos free-electron laser program. Three major efforts will be described: lasing at improved efficiency over that previously attained, electron beam improvement, and energy recovery. An extraction efficiency of 2 percent was achieved with a wiggler having a 12 percent wavelength taper. The beam has been improved so that limits to its quality are now caused, not by injector performance, but by wake fields related to the high peak currents achieved. Limits to optical power are set by mirror damage. Experiments are described that demonstrate the successful operation of an energy-recovery system.