Status of the SPARC project

In this paper we report on the final design of the SPARC FEL experiment which is under construction at the Frascati INFN Laboratories by a collaboration between INFN, ENEA, ELETTRA, Un. of Rome (Tor Vergata), CNR and INFM. This project comprises an advanced 150 MeV photo-injector aimed at producing a high brightness electron beams to drive a SASE-FEL experiment in the visible using a segmented 12 m long undulator. The project, finally approved and funded early this year, has a 3 year time span, with the final goal of reaching saturation on the fundamental of the SASE-FEL and studying the resonant non-linear generation of harmonics. Peculiar features of this project are the optimized design of the photo-injector to reach minimum emittances by using flat-top laser pulses on the photocathode, and the use of an uncompressed electron beam of 100 A peak current at very low emittance to drive the FEL. Results of start-to-end simulations carried out to optimize the performances of the whole system are presented, as well as the status of the construction and assembly of the system components. Activities planned for a second phase of the project are also mentioned: these are mainly focused on velocity bunching experiments that will be conducted with the aim to reach higher peak currents with preservation of low transverse emittances.