Measurement of neutron-capture cross sections of ^70,72Ge using the DANCE facility

Journal Article · Wed Aug 03 00:00:00 EDT 2022 · Physical Review. C

DOI:https://doi.org/10.1103/physrevc.106.025802· OSTI ID:1883810

Laminack, A. ^[1]; Blackmon, J. C. ^[2]; Couture, A. ^[3]; Greene, J. P. ^[4]; Krtička, M. ^[5]; Macon, K. T. ^[6]; Mosby, S. ^[3]; Prokop, C. ^[3]; Ullmann, J. L. ^[3]; Valenta, S. ^[5]

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1. Louisiana State University, Baton Rouge, LA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Louisiana State University, Baton Rouge, LA (United States)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
4. Argonne National Lab. (ANL), Argonne, IL (United States)
5. Charles University, Prague (Czech Republic)
6. University of Notre Dame, IN (United States)

We report approximately half of all atomic nuclei heavier than iron are synthesized by the slow neutron-capture process. The weak component of this process is not well understood and the reaction rates of each isotope in the s-process path affect nucleosynthesis abundances downstream. To measure the neutron-capture cross sections of two weak s-process nuclei, ^70,72Ge , using the neutron time-of-flight technique. Measuring the capture cross sections for isotopes in this region of the chart of nuclides has proven challenging due to dominant scattering cross sections. Samples consisted of pellets made of pressed enriched metallic powders. The ^70,72Ge neutron-capture cross sections were measured as a function of neutron energy using the Detector for Advanced Neutron Capture Experiments at Los Alamos National Laboratory. Neutron-capture cross sections were measured from 10 eV to 1 MeV. These are the first measurements for ^70,72Ge between 300 keV and 1 MeV neutron energy. Maxwellian-averaged cross sections were calculated in the astrophysically relevant neutron energy range (5 keV ≤ kT ≤ 100 keV). Their value at kT = 30 keV was found to be 89 ± 11 mb for ⁷⁰Ge and 58 ± 5 mb for ⁷²Ge. Both values are in agreement with recent time-of-flight measurements at n_TOF (neutron Time-Of-Flight facility at the European Organization for Nuclear Research). The average cross section results from this work for ⁷⁰Ge show minor (< 1σ) disagreement with a recent measurement by the n_TOF collaboration at higher neutron energies. This corresponds to the neutron energy region that had previously never been measured ( > 300 keV). Two reaction library databases underestimate the ⁷²Ge average cross section below 30 keV according to n_TOF and DANCE. This is likely due to capture resonances that are missing from the theoretical cross sections in the databases that were identified in both time-of-flight measurements. Additionally, a rudimentary analysis of the impact of both cross section measurements on stellar nucleosynthesis abundances using the NETZ nucleosynthesis tool is presented.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); Czech Science Foundation
• Grant/Contract Number: AC05-00OR22725; 89233218CNA000001; FG02-96ER40978
• OSTI ID: 1883810
• Journal Information: Physical Review. C, Journal Name: Physical Review. C Journal Issue: 2 Vol. 106; ISSN 2469-9985
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
hydrostatic stellar nucleosynthesis
nuclear astrophysics
nuclear reactions
radiative capture
s process