Stellar s -process neutron capture cross sections on 78,80,84,86Kr determined via activation, atom trap trace analysis, and decay counting

Journal
Date Issued
2021
Author(s)
Tessler, M.
•
Zappala, J.
•
•
Roberti, L.
•
Paul, M.
•
Halfon, S.
•
Heftrich, T.
•
Jiang, W.
•
Kijel, D.
•
Kreisel, A.
•
•
Lu, Z. -T.
•
Müller, P.
•
Purtschert, R.
•
Reifarth, R.
•
Shor, A.
•
Veltum, D.
•
•
Weigand, M.
•
Weissman, L.
DOI
Abstract
We present a detailed account of neutron capture experiments of astrophysical relevance on 78,80,84,86Kr (n ,γ ) reactions at the border between weak and main s process. The experiments were performed with quasi-Maxwellian neutrons from the Liquid-Lithium Target (LiLiT) and the mA-proton beam at 1.93 MeV (2-3 kW) of the Soreq Applied Research Accelerator Facility (SARAF). The setup yields high-intensity ≈40 keV quasi-Maxwellian neutrons (3-5 ×1010 n /s) closely reproducing the conditions of s -process stellar nucleosynthesis. A sample of 100 mg of atmospheric, pre-nuclear-age Kr gas contained in a Ti spherical shell was activated in the LiLiT neutron field. The abundances of long-lived Kr isotopes (81,85 gKr) were measured by atom counting via atom trap trace analysis (ATTA) at Argonne National Laboratory and low-level counting (LLC) at University of Bern. This work is the first measurement of a nuclear cross section using atom counting via ATTA. The activities of short-lived Kr isotopes (79,85 m,87Kr) were measured by γ -decay counting with a high-purity germanium detector. Maxwellian-averaged cross sections for s -process thermal energies are extracted. By comparison to reference values, our nucleosynthesis network calculations show that the experimental cross sections have a strong impact on calculated abundances of krypton and neighboring nuclides, in some cases improving agreement between theory and observations.

Volume
104
Issue
1
Start page
015806
Uri
Url
Issn Identifier
2469-9985
Ads BibCode
2021PhRvC.104a5806T
Rights
open.access
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