Destruction of the cosmic γ -ray emitter Al 26 in massive stars : Study of the key Al 26 (n,p) reaction

The Al26(n,p)Mg26 reaction is the key reaction impacting on the abundances of the cosmic γ-ray emitter Al26 produced in massive stars and impacts on the potential pollution of the early solar system with Al26 by asymptotic giant branch stars. We performed a measurement of the Al26(n,p)Mg26 cross section at the high-flux beam line EAR-2 at the n_TOF facility (CERN). We report resonance strengths for eleven resonances, nine being measured for the first time, while there is only one previous measurement for the other two. Our resonance strengths are significantly lower than the only previous values available. Our cross-section data range to 150 keV neutron energy, which is sufficient for a reliable determination of astrophysical reactivities up to 0.5 GK stellar temperature.