FERMI is the seeded Free Electron Laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, an upgrade plan for increasing the Linac energy from 1.5 GeV to 2.0 GeV is actually going on. After the successful testing of the short prototype of the new high gradient (HG) S-band accelerating structure up to an accelerating gradient of 40 MV/m, two full-length 3.0 m HG structures have been built and installed at the FERMI linac. In this paper, we report the low power measurement, conditioning results, and commissioning with the beam of the first HG module.

The upgrade of the single cascade FEL-1 of the FERMI free-electron laser, aiming at implementing operation either in Echo Enabled Harmonic Generation (EEHG) or in High Gain Harmonic Generation (HGHG) mode, has started. We have recently modified the layout in order to crate the space required for the installation of the large dispersive section needed for the EEHG scheme. As a result, the radiator has been separated by a 10-meter long drift from the modulator, where the interaction between electron bunch and seed laser takes place. The setup will be completed by the end of the first semester of 2023 and users operations are expected to start shortly afterwards. In this contribution, we present a status report of the FEL-1 upgrade process, focusing in particular on the results obtained during the commissioning.

We present an overview of the FERMI seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste, Italy. FERMI, in operation with both FEL lines FEL-1 and FEL-2 since 2012, covers the spectral range between 100 nm and 4 nm with light characterized by variable polarization, narrow spectral width, stable intensity and central wavelength. A series of infrastructure upgrades have been proposed in recent years to keep the facility in a world-leading position. The upgrade includes profound modifications of the linac and the two FERMI FELs with the ambition to extend the performance of the FEL and the control of the light produced to include the K edges of N and O and the L edges of transition metals. Recently, new accelerating section allowed an increase of the beam energy of about 100 MeV and the configuration of the first FEL-1 has been revamped. The FEL has been changed into an echo-enabled harmonic-generating FEL, and commissioning of this new FEL is underway.