Mercogliano, Daniela (2025) Experimental study of 22Ne(α, n)25Mg near-threshold energy states and cross section for nuclear astrophysics. [Tesi di dottorato]

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Abstract

The reaction 22Ne(a,n)25Mg is one of the main neutron source in stars, providing the neutron flux for the weak component of the s-process in massive stars and partially contributing to the s-process in AGB stars. For these reasons, its reaction rate is crucial in nuclear astrophysics. However, the limited availability of experimental data in the energy range of astrophysical interest still leads to significant uncertainties in the reaction rate and in nucleosynthesis predictions. The SHADES project addresses this long-standing lack of data in the energy region relevant to stellar He-burning, which spans from the neutron threshold up to a strong resonance at Ecm ≈ 706 keV, which remains the only one accessible on surface. The main novelty of SHADES is to directly study the 22Ne(a,n)25Mg in the deep underground environment provided by the Laboratori Nazionali del Gran Sasso (INFN-LNGS), thus exploiting the advantages of a highly reduced-background environment to enhance sensitivity to the weak neutron signals characteristic of this reaction. This thesis illustrates the development and optimization of the SHADES experimental setup, the strategies adopted throughout the various data-taking phases, and the first results obtained from the investigation of the astrophysically relevant energy region.

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