Search for cosmic ray origins by the study of supernova remnants associated with molecular clouds with HESS and test of HESS II sampling system.

The H.E.S.S. telescop (High energy Stereoscopic System), located in Namibia, is currently the most efficient for the observation of very high energy (VHE) gamma-ray sources. It is composed of 4 large diameter telescops working in stereoscopic mode and allows an unequaled survey of the galactic plane at these extreme wavelenghts. The H.E.S.S. experiment showed the presence of high energy particles up to 100 TeV within supernova remnant. This astrophysical objects are believed to be the main particle accelerator within the Galaxy. However, the particle nature remains unclear. This thesis presents a new observationnal approach in order to show hadronic particles acceleration through diffusive shock within supernova remnant. A search of supernova remnant associated with molecular cloud have been led within the HESS source catalog and the H.E.S.S. observations. An analysis of the new VHE gamma-ray source in Monoceros and its interpretation are presented. As well, the analysis and interpretation of new observations of the unidentified source HESS J1745-303 are presented. The multi-wavelength analysis of the new source HESS J1714-385, coincident with the supernova remnant CTB37A is presented. A contribution to the H.E.S.S. phase II building is also presented. This second phase consists in the building of a fifth telescop at the center of the existing system. The series tests of the new camera sampling system are reported.