The FERMI@Elettra free-electron-laser source for coherent x-ray physics: photon properties, beam transport system and applications

FERMI@Elettra comprises two free electron lasers (FELs) that will generate short pulses (tau similar to 25-200 fs) of highly coherent radiation in the XUV and soft x-ray region. The use of external laser seeding together with a harmonic upshift scheme to obtain short wavelengths will give FERMI@Elettra the capability of producing high-quality, longitudinally coherent photon pulses. This capability, together with the possibilities of temporal synchronization to external lasers and control of the output photon polarization, will open up new experimental opportunities that are not possible with currently available FELs. Here, we report on the predicted radiation coherence properties and important configuration details of the photon beam transport system. We discuss the several experimental stations that will be available during initial operations in 2011, and we give a scientific perspective on possible experiments that can exploit the critical parameters of this new light source.