Exploring the halo structure via near-barrier scattering on 208Pb: the cases of 15C and 17Ne

This thesis dedicated to the preparation, development and analysis of the IS619 and E788S experiments. These experiments can be located in a research framework of weakly- bound light nuclei whose so-called halo structure manifests on their scattering dynamics at energies near the Coulomb barrier. A series of similar studies began in the early 2000s and extends to the present day, gradually reaching more exotic and heavier nuclei as facilities are able to provide better quality and wider variety of beams. Furthermore, detection systems become more sophisticated and theoretical models gain accuracy. The IS619 experiment, proposed in mid-2016 and carried out in August 2017 at the ISOLDE facility of CERN (Geneva, Switzerland), aims to probe the structure of the neutron-rich nucleus 15C through its differential elastic cross section at 4.37 MeV/u on a 208Pb target. The completion of the HIE post-acceleration line of ISOLDE left a door open to perform this measurement with a 15C beam, being IS619 the first experimental study of this nucleus at energies near the Coulomb barrier. The weakly bound nucleus 15C (S(n)= 1218.1(8) keV, S(2n)= 9394.5(8) keV) has been investigated in several experiments at higher energies. Its total interaction cross section is larger than that of the neighboring 14,16C and its momentum distributions for the one-neutron breakup are much narrower than for the rest of the isotopes in the carbon chain. These features suggest the presence of a halo configuration that would be unique, according to its spectroscopic factors, due to the almost pure s1/2 single neutron wave function in the ground state, which could partially compensate the relatively large S(n) value for a halo structure. A complete description of how these studies arise, are experimentally planned and carried out, and how results are obtained will be detailed throughout this thesis. Firstly, a general overview about the aspects of nuclear physics related to this research is given. The most commonly used theories to describe direct nuclear reactions is discussed. The experimental technique and the development of the Monte Carlo simulations are presented. The results and their theoretical interpretation are discussed.