Experimental and numerical methods are presented to investigate ion emission from laser-produced plasma (LPP) sources of Extreme Ultraviolet (EUV) light, which are relevant for state-of-the-art nanolithography industry, namely. Laboratory tools are carefully calibrated for accurate ion flow measurements, in which the charge state of ions and their angle of emission can be resolved. Experimental ion energy spectra are compared to those produced by single-fluid numerical simulations of laser-produced plasmas, with great match. The association of experimental and numerical studies allows for accurate detection of ions and better understanding of the underlying physics of plasma expansion in vacuum. The thesis contributes to fundamental physics understanding and to development of cleaner EUV sources for the nanolithographic industry.