Possibility of a high-power, high-gain FEL amplifier

High-gain FEL amplifiers offer many unique advantages such as robust operation without a high-Q optical cavity and potentially high extraction efficiencies with the use of tapered wigglers. Although a high average power, cw FEL amplifier has not been demonstrated, many key physics issues such as electron beam brightness requirements, single-pass gain, saturation, etc. have been resolved. In this paper, we study the feasibility of a high-power FEL based on the high-gain, tapered-wiggler amplifier. We show that with suitable electron beam parameters, a peak output power of 1 GW and a micropulse energy of 8 mJ can be achieved. We also outline a possible configuration of a high-power, high-gain FEL amplifier with energy recovery.