First lasing of the regenerative amplifier FEL

The regenerative amplifier free-electron laser (RAFEL) is a high-gain RF-li nac FEL capable of producing high optical power from a compact design. The combination of a high-gain and small optical feedback enables the FEL to re ach saturation and produce a high optical power and high extraction efficie ncy without the risk of optical damage to the mirrors. This paper summarize s the first lasing of the regenerative amplifier FEL and describes recent e xperimental results. The highest optical energy achieved thus far at 16.3 m u m is 1.7 J over a train of 900 micropulses. We infer pulse energy of 1.9 mJ in each 16 ps micropulse, corresponding to a peak power of 120 MW. (C) 1 999 Published by Elsevier Science B.V. All rights reserved.