Study of cross sections of nuclear reactions with astrophysical interest around Coulomb barrier and effects on star models

The energy radiated by stars is given by thermonuclear reactions occurring meanly within these stellar bodies. To have a better understanding of stars' evolution, one has to know precisely nuclear reactions arising in it and particularly their reaction rate. This one can be obtained from the cross sections measured in labs by nuclear physicists. The project developed in this work consists in studying reactions of CNO cycle during which a proton is consumed as in 13C(p,γ)14N and 14N(p,γ)15O. We are studying these reactions in reverse kinematics, this means that we accelerate ions like carbon or nitrogen towards a target containing some hydrogen (1H). The target is realised by ion implantation of hydrogen in materials like silicon. These nuclear reactions are investigated in an energy range for which they occur preferentially in stars (Gamow peak). The results obtained are compiled in existing star models. This allows to infer some consequences about their evolution and then about the isotopic composition of the universe.