SEEDING EXPERIMENTS AT SPARC

The SPARC Free Electron Laser can be operated in both SASE and seeded modes. A major part of the second stage of the commissioning, now undergoing, is dedicated to the characterization of the SASE radiation. Simultaneously, we are finalizing the experimental setup for seeding. We present an in-situ characterization of the two input seeds that are foreseen: both are obtained via harmonic generation, the first one in crystal (400 and 266 nm) and the second in rare gas (Argon). We also describe the specific diagnostics implemented for the electron-seed overlap in the undulator, together with the diagnostics for radiation analysis (2D spectrometer and FROG). The seeding will enable the operation of the SPARC FEL in original cascaded configurations