New polyvalent low background γ-ray setup at UNamur: Application to S-factor measurements for the 13C(p,γ)14N reaction

The Laboratory of Analysis by Nuclear Reaction (LARN) at the University of Namur (Belgium) is equipped with a low background γ-ray detection system. This setup is made of one ton of lead as passive shielding and plastic scintillators as an anti-cosmic active shielding which covers a large area around a 3.5 × 3.5 inches HPGe detector. This setup makes it possible to reduce the background level from two to three orders of magnitude, depending on the energy range of interest. In this work, this polyvalent detection system is described and used to refine the cross-section measurements of the 13C(p,g)14N nuclear reaction at middle and low
energies. The reaction 13C(p,g)14N plays an important role in the CNO cycle and s-process in stellar evolution. In this work, we studied more precisely the 13C(p,g)14N ground transition (𝐸𝛾= 8.06 MeV) for incident energies ranging from 147 to 574.3 keV in the centre-of-mass system generated by the 2 MV Tandetron accelerator ALTAÏS installed at the LARN. Our measurements performed both in reverse (i.e. 1H(13C,g)14N) and direct kinematics are in good agreement with all the data available in the literature, validating our low background detection system.