EuNPC2015

Asymptotic Giant Branch (AGB) stars play a fundamental role in the determination of the observed abundances of light mass elements. Despite great efforts, model predictions for AGB yields are rather uncertain due to the complex physical structure and the weakly constrained mass-loss rates and convection efficiencies. In addition, the poor knowledge of the cross sections of the relevant proton capture reactions diminishes the reliability of the model predictions particularly for light element yields. The reaction 23Na(p,g)24Mg links the NeNa and the MgAl cycles of stellar burning, hence the precise knowledge of its cross section is crucial. For a resonance of this reaction at 138 keV only an upper limit of 5.17 neV (95% confidence limit) could be established for its strength, with indications of a signal at (2.15+-1.29) neV (68% confidence level) [1]. Measurements at LUNA, the Laboratory Underground for Nuclear Astrophysics, are aimed at a direct observation of this resonance with a segmented bismuth germanium oxide (BGO) detector [2] to determine the resonance strength more precisely or to provide an improved upper limit. Compared to previous experimental efforts, LUNA benefits from an increased sensitivity thanks to reduced backgrounds due to its location underground at the Gran Sasso National Laboratories (LNGS) and a massive shielding. The current status of the experimental efforts will be presented, covering the setup and the preliminary results of studies and measurements. [1] J.M. Cesaratto et al., Phys. Rev. C 88, 065806 (2013). [2] C. Casella et al., Nucl. Instr. Meth. A 489, 160 (2002).