Feasibility study of the 13C(α, n)16O reaction at LUNA

The 13 C( α, n) 16 O reaction determines the dominant neutron source of the sprocess in thermally pulsing, low-mass, asymptotic giant branch (TP-AGB) stars. The temperature during the s-process in the 13 C pocket of 90×10 6 K corresponds to a Gamow window of 140-230 keV. Since this energy is far below the Coulomb barrier, the cross section of this reaction is extremely small and its rate can only be extrapolated from the measurements at higher energies. At present, the cross section at Gamow peak is uncertain by almost one order of magnitude.An experimental campaign aimed at measuring low energy cross section in 13 C( α n) 16 O is scheduled at the underground LUNA-400 accelerator in Gran Sasso Laboratory, Italy. The unique underground location of this facility offers significant improvement in sensitivity compared with previous investigations. It will allow to establish the interference pattern of the resonances and the absolute scale of this reaction.