Recoil separator ERNA: Measurement of 3He7Be

The reaction He 3 ( α , γ ) Be 7 plays a key role for the understanding of the production of 7Li in Big Bang nucleosynthesis as well as for the high energy component of the solar neutrino spectrum. The uncertainty in its absolute cross-section arises from systematic differences of the available data sets. In various experiments the cross-section was measured by the detection of the prompt γ -rays or by the off-line observation of the γ -rays following the 7Be electron capture; in a few cases both observations were carried out. ort on a new approach based on the use of the recoil separator ERNA (European Recoil separator for Nuclear Astrophysics) to detect directly the 7Be recoils as well as the prompt γ -rays in coincidence with the recoils. We present technical details of the experimental setup, such as a recirculating 3He gas target, a TOF-E end detector, and a NaI detector array. In addition, the measurement of the separator acceptance is discussed and compared to the expected recoil emittance. The feasibility of the approach is demonstrated by sample spectra, indicating cross-section determinations of He 3 ( α , γ ) Be 7 in the energy range E cm = 0.7 – 3.3 MeV with high precision and accuracy.