Advanced instrumentation for spectral and spatial investigations of high-order laser harmonics

We report on the design and characterization of a grazing-incidence flat-field spectrograph that allows simultaneously the measurement of spectrum, beam divergence, and absolute flux of EUV and soft X-ray radiation for a beam of high-order laser harmonics generated by the interaction between an ultrashort femtosecond laser pulse and a gas jet. The instrument seems a very powerful tool for the understanding of the generation process.