Köln 2025 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 22: Nuclear Astrophysics III

HK 22.1: Group Report

Tuesday, March 11, 2025, 15:45–16:15, SR 0.03 Erw. Physik

Neutron activations for nuclear astrophysics — •Tanja Heftrich — Goethe-Universität Frankfurt

About 50% of heavy elemental abundances are produced in the slow neutron capture process (s-process). The main component of the s-process takes place in low-mass thermally pulsing asymptotic giant branch (TP-AGB) stars during the He-shell burning phase. The weak component refers to massive pre-supernova stars during convective C-shell burning. In AGB stars, neutron densities of 10¹⁰ cm⁻³ and temperatures of k_BT = 5 and 25 keV are reached, whereas in massive stars neutron densities of 10¹² cm⁻³ at temperatures of up to k_BT = 30 and 90 keV during C-shell burning are reached.
The activation method is a strong tool to investigate neutron capture measurements corresponding to the stellar sites of the s-process. Stellar neutron spectras are produced by accelerating protons with an energy of 1912 keV onto a metallic lithium target. The resulting neutron spectrum refers to temperatures of k_BT = 25 keV. We developed this working horse method further to measure neutron capture cross section at lower temperatures of k_BT = 5 keV and even higher temperatures of k_BT = 90 keV to cover the whole s-process temperature regime.

Keywords: s-process; AGB stars; massive stars; activation experiments; Lithium target