This PhD thesis is focused on the AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) antimatter experiment. The main work consisted in the design, realization and characterization of an electron beam. This machine, now fully operational, will be used for ageing measurements of positron to positronium converters for the AEGIS experiment. In addition, I have been working on the design of the final AEGIS positron source and participating in the studies and modelling needed for the choice of the appropriate converter for the experiment. Finally, I made measurements of positronium formation in liquid scintillators, of interest for solar neutrino detectors.