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The FERMI Free Electron Laser (FEL) in Trieste, Italy operates in the extreme ultraviolet and soft x rays (EUV-SXR) wavelength range delivering high-fluence, stable, ultra-short pulses. Its unique design based on a seeded scheme and on tunable undulators allows unprecedented control of pulse parameters such as wavelength, phase, polarization, synchronization, pulse duration and implementation of multi-color FEL schemes. Both FEL-1 and FEL-2 lines with nominal wavelength range 100-20 nm and 20-4 nm, respectively, are open to users. We report on the unique features of FERMI, in particular those that have evolved beyond the original design, and on their application to pioneering experiments. We also present the upgrades that are planned to further expand the capabilities of this unique light source.

In this work an optical pump‐probe set‐up is used to study the photo‐induced non‐equilibrium dynamics of a superconducting underdoped Bi2212 single crystal in a strong excitation regime (10

To accommodate increasing interest in soft x‐ray inelastic scattering, a new spectrometer has been designed, constructed and commissioned at Elettra. This instrument uses as the dispersive element one of two interchangeable Variable Line Spacing (VLS) spherical gratings. The energy scan is performed by a 7 cm linear translation of a back illuminated CCD which also collects the zero order light, facilitating alignment and calibration. The two gratings have the same radius of curvature while the groove densities and the groove density variations differ by a factor four. Thus the energies focused by the gratings at a particular position differ by a factor of four. The total length of the instrument is 60 cm, the energy range covered is roughly 25–1000 eV and the expected resolving power ranges from 1000 to 5000. The spectrometer is now operating on the beamline Bach. It takes advantage of the small size of the photon spot in the experimental chamber and of the possibility to control the polarization of the incoming radiation. The small spot constitutes the virtual entrance slit, and the spectrometer collects the photons emitted in a solid angle of about 30×10 mrad2. The instrument, named ComIXS (Compact Inelastic X‐ray Spectrometer), has been routinely operating since October 2002. Several experiments have already been carried out, and some results illustrating the characteristics of the instrument are described. The manufacture and testing of the blaze gratings are also discussed.

BACH, the new soft x‐ray beamline for polarization dependent experiments at the Italian synchrotron radiation facility ELETTRA, has been commissioned, characterized and opened to external users. Based on two APPLE II undulators, it covers an energy range between 35 eV and 1600 eV with the control of the light polarization. The monochromator works either in high resolution or high flux mode. Resolving powers of 16000 at 50 eV, 12000 at 90 eV, more than 12000 at 400 eV, 15000 at 534 eV and 6600 at 867 eV have been achieved with the three high resolution gratings. The resolving powers of the high flux grating, which covers the 290 – 1600 eV range, have been measured reaching 7000 at 400 eV and 2200 at 867 eV. The fluxes, in the high resolution mode, range between 4⋅1011 photons/s at 125 eV and 2⋅1010 photons/s at about 1100 eV. Using the high flux grating with the best resolution achievable 1.7⋅1011 photons/s impinge on the sample at 900 eV. Two branches are installed after the monochromator allowing the set‐up of two different experimental stations. One of them, besides several facilities for surface preparation and analysis, hosts a compact inelastic soft x‐ray spectrometer (ComIXS) dedicated to x‐ray emission experiments exploiting the small spot (10 μm in the vertical direction) on the sample. The other branch hosts a liquid helium cryostat equipped with a superconducting coil to perform absorption and transmission experiments with temperatures down to 2 K and magnetic field up to ±7 T.