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HK: Fachverband Physik der Hadronen und Kerne

HK 22: Nuclear Astrophysics III

HK 22.3: Vortrag

Dienstag, 11. März 2025, 16:30–16:45, SR 0.03 Erw. Physik

Direct Measurements of Neutron Capture Rates in Unstable Astrophysical Nuclei: A New Frontier — •Abdallah Karaka¹, Timm-Florian Pabst¹, Devin Hymers¹, Erik Strub², Gereon Weingarten¹, Markus Schiffer¹, Martin Mueller¹, Michael Weinert¹, Stefan Heinze¹, Tom Sittig¹, and Dennis Muecher¹ — ¹Institute of Nuclear Physics, University of Cologne, Germany — ²Institute of Nuclear Chemistry, University of Cologne, Germany

The intermediate neutron capture process (i-process) likely occurs in AGB stars and is crucial for explaining elemental abundances in certain CEMP stars. While most aspects of the i-process are well-constrained, neutron capture rates and cross sections remain significant unknowns in nuclear physics.

Indirect measurements have high uncertainties, while direct measurements are challenging as many key nuclei are a few neutrons away from stability and hence unstable.

This talk explores direct measurements of neutron capture cross sections for selected long-lived nuclei to better understand the i-process dynamics. We present the status and initial tests of a beamline designed to produce a high-density secondary neutron beam at the CologneAMS-6MV tandetron. The cross sections will be measured using a novel activation technique based on detection of beta-decay electrons, suited to suppress the high activity of the initial sample by six orders of magnitude. The first physics case is the ¹³⁷Cs(n_st,γ)¹³⁸Cs stellar neutron capture cross section, constraining the unusual Lanthanum over Barium abundance ratios observed in many CEMP stars.

Keywords: i-process; neutron capture cross sections; neutron source at Cologne 6MV tandetron; Activation technique; AGB stars