Chirped pulse amplification of HGHG-FEL at DUV-FEL facility at BNL

The DUV-FEL facility has been in operation in the High Gain Harmonic Generation (HGHG) mode producing a 266-nm output from 177-MeV electrons for 1 year. In this paper, we present preliminary results of the Chirped Pulse Amplification (CPA) of the HGHG radiation. In the normal HGHG process, a 1-ps electron beam is seeded by a chirped 9 ps long, 800-nm Ti:Sapphire laser. The electron beam sees only a narrow fraction of the seed laser bandwidth. However, in the CPA case, the seed laser pulse length is reduced to 1 ps, and the electron beam sees the full bandwidth. We introduce an energy chirp on the electron beam to match the chirp of the seed pulse, enabling the resonant condition for the whole beam. We present measurements of the spectrum bandwidth for various chirp conditions.