FEASIBILITY STUDIES FOR SINGLE STAGE ECHO-ENABLED HARMONIC IN FERMI FEL-2∗

Recently, the second FEL line of the FERMI FEL has been modified in order to extend its tuning range down to 4 nm. In order to reach such a short wavelength start-ing from the UV seed laser the FERMI FEL-2 system re-lies on a double cascade of high gain harmonic generation (HGHG). In this work we study the possibility of using the present FEL-2 layout with minor modifications to generate GW soft x-ray radiation using the recently proposed echo-enabled harmonic generation (EEHG) technique. The final aim is to cover the expected spectral range of FEL-2 with a single stage. The performance of the EEHG in FERMI FEL-2 is estimated by means of FEL simulations with stan-dard FEL codes