Spectral and intensity diagnostics of the SPARC free-electron-laser

We describe the instrument that is used for the spectral and intensity diagnostics of the SPARC free-electron-laser facility in Frascati (Italy). The instrument hosts three interchangeable gratings to cover the 50-550 nm spectral region and an EUV-enhanced CCD detector to acquire the spectrum in the single-shot operation with high resolution. The spectral resolution is in the range 2000-10000. The design, characterization and calibration of the instrument are presented and some results obtained at SPARC are discussed.