Study of the E $$_{\alpha }$$ = 395 keV Resonance of the 22Ne(α, γ)26Mg Reaction at LUNA

Abstract

The \(^{22}\)Ne(\(\alpha \),\(\gamma \))\(^{26}\)Mg is the competitor of the \(^{22}\)Ne(\(\alpha \),n)\(^{25}\)Mg in AGB stars, which, in turn, is an efficient source of neutrons for s-processes in medium masses AGB stars. There is a significant uncertainty in the \(^{22}\)Ne(\(\alpha \),\(\gamma \))\(^{26}\)Mg thermonuclear reaction rate. This has been clearly remarked the ChETEC COST Action (CA16117) considering the \(^{22}\)Ne(\(\alpha \),\(\gamma \))\(^{26}\)Mg among the nuclear reactions with major impact on stellar nucleosynthesis. A narrow resonance at an energy \(E_\alpha \) = 395 keV has been claimed in the \(^{22}\)Ne(\(\alpha \),\(\gamma \))\(^{26}\)Mg reaction and it has been studied only with indirect methods leading to a range of possible values for its strength from \(10^{-9}\) to \(10^{-15}\) eV. At LUNA (Laboratory for Underground Nuclear Astrophysics) this resonance can be studied directly, thanks to a high efficiency setup, composed by a 4\(\pi \)-BGO detector and a windowless gas target filled with neon gas enriched in the \(^{22}\)Ne isotope to 99.99%. This setup has been already used in a previous experiment for the study of the \(^{22}\)Ne(p,\(\gamma \))\(^{23}\)Na reaction, and in April-June 2018 a new measurement campaign will be performed. Thanks to its position inside the Laboratory of Gran Sasso, LUNA already benefits from a reduced background and in particular a factor one thousand for the neutron component. Still this remains the most important source of background in the region of interest for the \(^{22}\)Ne(\(\alpha \),\(\gamma \))\(^{26}\)Mg. Therefore a new borated polyethylene shielding will be employed to reduce the neutron contamination due to the environmental background by an additional order of magnitude.