Measurement of 3He(α, γ)7Be with ERNA recoil separator

The 3He(α, γ)7Be reaction plays an important role in the interpretation of the results of the solar neutrino experiments, since the estimate of the oscillation parameters relies on the solar neutrino spectrum, calculated by solar models. The high energy component in this spectrum is mainly produced by the decay of 7Be and 8B. The uncertainty in the 3He(α, γ) 7Be cross section is also one of the largest contributions to the uncertainty on the predicted primordial 7Li abundance in Big Bang Nucleosynthesis calculations. Previous measurements of the 3He(α, γ)7Be cross section have been performed detecting the capture γ-rays or, alternatively, measuring the activity of the synthesized 7Be. While the results of the two different approaches agree on the energy dependence of the astrophysical S factor, they disagree in the extrapolated S34(0) value at a 3σ level. A novel approach uses the European Recoil separator for Nuclear Astrophysics (ERNA) to detect directly the 7Be ions produced in the reaction and, additionally, the coincident detection of the capture γ-rays. © 2006 American Institute of Physics.