Rf stability in the Los Alamos free-electron laser energy-recovery experiment

The energy-recovery experiment (ERX) successfully completed at Los Alamos recently was designed to demonstrate efficiency improvement of a radio-frequency (rf) linac-driven free-electron laser. In the ERX, most of the power in the residual electron beam, after the wiggler, is extracted in a decelerator and is then coupled by bridge couplers to the accelerator for new beam-acceleration power. In this paper, the authors present an equivalent-circuit analysis of the rf stability for the ERX system. The authors' results indicate that the aperture of the beam-transport line imposes a severe limit on the system's stability. They also discuss the effect of phasing between the decelerated beam and the rf field