Spectrometer for single-shot X-ray emission and photon diagnostics

We present the design and characterization of a compact and portable spectrometer realized for photon in-photon out experiments (in particular X-Ray Emission Spectroscopy, XES), in particular tailored to be used at the FERMI free-electron-laser (FEL) at ELETTRA (Italy). The spectrometer can be installed on different end stations at variable distances from the target area both at synchrotron and FEL beamlines. Different input sections can be accommodated in order to fit the experimental requests, with/without an entrance slit and with/without an additional relay mirror. The design is compact in order to realize a portable instrument within a total footprint of less than one square meter. The instrument is based on the use of two flat-field grazing-incidence gratings and an EUV-enhanced CCD detector to cover the 25-800 eV spectral range, with spectral resolution better than 0.2%. The absolute response of the spectrometer, has been measured in the whole spectral region of operation, allowing calibrated measurements of the photon flux. The characterization on the Gas Phase beamline at ELETTRA Synchrotron as instrument for XES and some experimental data of the FEL emission taken at EIS-TIMEX beamline at FERMI, where the instrument has been used for photon beam diagnostics, are presented.