Bochum 2009 – wissenschaftliches Programm

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HK: Fachverband Hadronen und Kerne

HK 50: Nuclear Astrophysics

HK 50.7: Vortrag

Mittwoch, 18. März 2009, 15:45–16:00, H-ZO 60

Direct Measurements of low energy resonances in ²⁵Mg(p,γ) ²⁶Al — •Benedetta Limata — INFN Napoli, Italy

The direct observation of the 1.809 MeV γ-ray line following the β⁺ and EC of ²⁶Al from COMPTEL and INTEGRAL instruments provides an evidence that ²⁶Al production is still active on a large scale. Stellar nucleosynthesis studies have not yet identified which one of the possible ²⁶Al sources could explain the observed evidences. Hence, solving the controversy for different astrophysical production sites of ²⁶Al demands a better understanding of the rates for the nuclear reaction ²⁵Mg(p,γ) ²⁶Al, which in turn is the slowest reaction of the Mg-Al cycle. The ²⁵Mg(p,γ) ²⁶Al reaction has been investigated down to the astrophysical relevant low energy resonances at E_R = 93, 130, and 189 keV at the 400 kV accelerator of the LUNA facility at the Laboratori Nazionali del Gran Sasso, Italy taking advantage of the strong suppression of cosmic-ray background in the underground lab. As a γ-ray detection system a six fold segmented 4π BGO detector was used. In addition to the high efficiency the segmented detector allows for detecting a full sum spectrum as well as single spectra from each of the six crystals which provides additional information on the decay scheme. The low energy resonance at E_R = 93 keV of the reaction ²⁵Mg(p,γ) ²⁶Al could be detected for the first time in a direct experiment. The results of the project will be presented and astrophysical consequences will be discussed as well as the potential of this experimental approach for future measurements in an underground lab.