Direct Measurement of the 13 C(a,n)16O Reaction at LUNA

Abstract

The13 C(a,n)16 reaction is the main neutron source for the s-process in low mass AGB stars. Although several direct measurements have been performed, no dataset reaches the Gamow window (140–230�keV) due to the the nearly exponential drop of (E) with decreasing energy. The available dataset didn’t extend to lower energies because of the strong cosmic background and some difficulties to evaluate the target degradation. To study the13 C(a,n)16 cross section at low energies, ancillary measurements to characterize13 C enriched evaporated targets, under an high intensity proton beam (100–200 A), are carried out at Laboratori Nazionali del Gran Sasso (LNGS) in the framework of the LUNA experiment. The preliminary results are reported in this contribution.