Simulation studies of a possible multi-stage XFEL at ELETTRA

Presently there is strong interest in developing a fourth-generation light source at VUV and soft X-ray wavelengths at the ELETTRA facility at Trieste. One proposal centers around using the existing linac at 1.0 GeV energy with a new photocathode and bunch compression to achieve an output beam at 600 A current, 2–4 mm mrad normalized emittance and 0.05% instantaneous energy spread. To achieve output radiation in the 10–40-nm-wavelength region, we consider a multi-stage device which is initiated by a coherent seed laser operating at 200 nm. We present numerical simulations of various undulator/optical-klystron configurations, seeking to optimize the overall output power level while minimizing the total length of undulator sections needed. Our results suggest that multi-MW instantaneous powers are possible at 10-nm wavelengths.