Optimization studies of the fermi at elettra FEL design

The FERMI at ELETTRA project at Sincrotrone Trieste involves two FEL's, each based upon the principle of seeded harmonic generation and using the existing ELET-TRA injection linac at 1.2 GeV beam energy. Scheduled to be completed in 2008, FEL-1 will operate in 40-100 nm wavelength range and will involve one stage of harmonic up-conversion. The second undulator line, FEL-2, will begin operation two years later in the 10-40 nm wavelength range and use two harmonic stages operating as a cascade. The FEL design assumes continuous wavelength tunability over the full wavelength range, and polarization tunability of the output radiation including vertical or horizontal linear as well as helical polarization. The design considers focusing properties and segmentation of realizable undulators and available input seed lasers. We review the studies that have led to our current design. We present results of simulations using GENESIS and GINGER simulation codes including studies of various shot-to-shot fluctuations and un-dulator errors. Findings for the expected output radiation in terms of the power, transverse and longitudinal coherence are reported.