Abstract : This manuscript describes the experiments performed from 1998 to 2008 on the metastable helium setup. Since my arrival in the group, we have decided to look for the Bose-Einstein condensation of metastable helium. This atom has indeed one asset: its metastability. Its internal energy of 20 eV is high enough for the atom to be detected efficiently by a microchannel plate. The single atom capability of the detector has opened studies in quantum atom optics. Moreover, the ionization during two or three-body inelastic collisions leads to a new in-situ diagnostic tool of the atomic density. My researches could be split in three periods. From 1998 to 2004, we obtained the Bose-Einstein condensation and studied its collisional properties. From 2004 to 2007 we measured the two-body correlation properties of atomic clouds above or below the quantum degeneracy, thanks to an improvement on our detection setup. Since 2006, we have started studies on quantum atom optics and a first experiment on correlated atomic pairs has already been performed.