Beam Physics Highlights of the Fermi@elettra Project*

The electron beam dynamics in the Fermi Linac has been studied in the framework of the design of a singlepass free electron laser (FEL) based on a seeded harmonic cascade. The wakefields of some accelerating sections represent a challenge for the preservation of a small beam emittance and for achieving a small final energy spread. Various analytical techniques and tracking codes have been employed in order to minimize the quadratic and the cubic energy chirps in the longitudinal phase space, since they may cause a degradation of the fel bandwidth. As for the transverse motion, the beam breakup (BBU) instability has been recognized as the main source of emittance dilution; the simulations show the validity of local and non-local correction methods in order to counteract the typical “banana” shape distortion of the beam caused by the instability.