³He(α,γ)⁷Be cross section measured using complementary techniques

The astrophysical S-factor for the ³He(α,γ)⁷Be reaction plays an important role in the Solar Standard Model and in the Big Bang Nucleosynthesis scenario but experimental values found in the literature show strong discrepancies. In order to resolve the experimental discrepancies and to constrain the theoretical model extrapolations, 2 experiments using complementary techniques have been performed by our collaboration aiming to determine the cross section at C.M. energies between 1 and 3 MeV. The first technique is the activation method. The ⁷Be recoils are unstable nuclei and decay by electron capture (EC) with a half life of 53.22(6) days. Therefore, instead of measuring directly either the recoils or the prompt-γ from the reaction, the reaction products can be collected and the subsequent EC-delayed γ radiation can be measured. The second technique is the direct recoil detection method which consists in counting ⁷Be recoils directly. Our preliminary results with the Direct Recoil Method show agreement with the activation method up to 2 MeV