SEMINAR      Thursday, 16 December 2004 - h. 15:00  Auditorium B. Touschek     M. Ferrario & The SPARC Team  (LNF-INFN) A Free Electron Laser Project at Frascati Abstract Free Electron Lasers (FEL) driven by high brightness Linac are a promising source to produce short wavelength radiation. These new facilities consist of a long undulator, driven by a high-quality electron beam with high charge density, low emittance and low energy spread. The interaction of the spontaneous undulator radiation with the electron beam leads to a longitudinal charge density modulation such that millions of electrons radiate in phase without using mirrors – this effect is called Self-Amplified Spontaneous Emission (SASE). In a FEL a wide spectral range from micrometer to Ångström wavelengths can be covered by varying the electron beam energy and the magnetic period and field of the undulator. The high quality electron beams required for these FELs, however, cannot be generated in electron storage rings but rather require linear accelerators and special photocathode radiofrequency (RF) guns together with emittance compensation and bunch compression techniques. After an introductory description of the FEL process, recent advances in the understanding of high brightness beam production will be discussed. Present and future activities at LNF in this field will be also emphasized.