Direct Measurement of the (formula presented) Reaction at LUNA

Abstract

The (formula presented) 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 exponential drop of the cross section (formula presented)(E) with decreasing energy. The reaction rate becomes so low that the strong cosmic background would become predominant. In order to measure the (formula presented) cross section at low energies, ancillary measurements to understand the behaviour of 99% enriched (formula presented) evaporated targets, under a high intensity alpha beam (100–200 (formula presented)A). These measurements were carried out in deep underground laboratories of Laboratori Nazionali del Gran Sasso (LNGS) in the framework of the LUNA experiment. The preliminary results are reported in this contribution.