First lasing of FERMI FEL-2 (1° STAGE) and FERMI FEL-1 recent results

The FERMI@Elettra seeded Free Electron Laser (FEL) is based on two complementary FEL lines, FEL-1 and FEL-2. FEL-1 is a single stage cascaded FEL delivering light in the 80-20 nm wavelength range, while FEL-2 is a double stage cascaded FEL where the additional stage should extend the frequency up-conversion to the spectral range of 20-4 nm. The FEL-1 beam line is in operation since the end of 2010, with user experiments carried on in 2011 and 2012. During 2012 the commissioning of the FEL-2 beam line has started and the first observation of coherent light from the first stage of the cascade has been demonstrated. In the meanwhile, the commissioning of a number of key components of FERMI, as the laser heater, the X-Band cavity for the longitudinal phase space linearization and the high energy RF deflector, has been completed. The additional control on the longitudinal phase space and a progressive improvement in the machine optics optimization, had a significant impact of FEL-1 performances, which has reached the expected specifications. In addition, emission of radiation at very high order conversion factors (up to 29) has been observed from FEL-1 and schemes based on double stage cascades have been preliminarily tested, with the observation of coherent radiation up to the 65 harmonic of the seed drive laser, at about 4.1 nm in the water window.