Direct cross-section measurement of 13C(α,n)16O in the s-process Gamow peak

The main neutron source for the slow neutron capture process in low mass Asymptotic Giant Branch stars is the 13C(α,n)16O reaction. This reaction is responsible for the production of half of the natural heavy elements in the Universe. Up to now, no direct measurements have reached the energy region of interest for astrophysics, the so called Gamow window, which lies between 140 and 230 keV in the center of mass. In this paper we describe the experiment carried out at the LUNA experiment at the Laboratori Nazionali del Gran Sasso and present first preliminary results.