The soft x-ray free-electron laser fermi@elettra

Abstract

FERMI, the Italian free electron laser (FEL) user facility, delivers highintensity ultra-short photon pulses in the 100–4nm range. Adiagnostic section called PADReS (Photon Analysis, Delivery, and Reduction System) follows the two undulator chains, giving informations about the photon beam intensity, transverse distribution and coherence, pointing, and energy spectrum. All these quantities are available during the experiments as they are obtained in a non-invasive way on a shot-to-shot basis. The radiation intensity can also be controlled bymeans of a gas absorber. Moreover, it is possible to split and delay part of the beam to perform auto-correlation measurements determining the pulse length and temporal coherence, as well as to perform pump-probe experiments. Finally, active optics-based systems refocus the photon beam into the endstations.