Abstract
The Am241(n,γ) cross section has been measured at the n_TOF facility at CERN with the n_TOF BaF2 Total Absorption Calorimeter in the energy range between 0.2 eV and 10 keV. Our results are analyzed as resolved resonances up to 700 eV, allowing a more detailed description of the cross section than in the current evaluations, which contain resolved resonances only up to 150–160 eV. The cross section in the unresolved resonance region is perfectly consistent with the predictions based on the average resonance parameters deduced from the resolved resonances, thus obtaining a consistent description of the cross section in the full neutron energy range under study. Below 20 eV, our results are in reasonable agreement with JEFF-3.2 as well as with the most recent direct measurements of the resonance integral, and differ up to 20–30% with other experimental data. Between 20 eV and 1 keV, the disagreement with other experimental data and evaluations gradually decreases, in general, with the neutron energy. Above 1 keV, we find compatible results with previously existing values.8 MoreReceived 31 January 2018DOI:https://doi.org/10.1103/PhysRevC.97.054616Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNeutron physicsNuclear reactorsRadiative capturePropertiesA ≥ 220Nuclear Physics
Highlights
To improve the design of new advanced nuclear reactors and for determining their performance in the transmutation of nuclear waste, it is important to reduce the present neutron cross section uncertainties of minor actinides [1,2,3]
Ctot(En) − Cbkg(En), ε(En)φ(En) where En is the neutron energy, Ctot(En) and Cbkg(En) are the number of total and background counts registered by the Total Absorption Calorimeter (TAC), respectively, under certain Esum and mcr cuts, ε(En) is the corresponding detection efficiency, and φ(En) is the intensity of the neutron beam intercepted by the sample
Background events in the 241Am(n,γ ) measurement can be attributed to two contributions: (i) events coming from neutron reactions in the 241Am nuclei, i.e., fission and elastic scattering, and (ii) the rest of the background, which results from the environmental background, the activity of the BaF2 crystals, the sample activity, and the interaction of the neutron beam with all the materials except the 241Am nuclei
Summary
To improve the design of new advanced nuclear reactors and for determining their performance in the transmutation of nuclear waste, it is important to reduce the present neutron cross section uncertainties of minor actinides [1,2,3]. In addition there are several other measurements, both TOF and integral, which present significant discrepancies among one another. It is not surprising that there are large discrepancies among the evaluated libraries. The 241Am(n,γ ) cross section measurement presented in this paper was performed at the n_TOF facility at CERN [7] using the n_TOF Total Absorption Calorimeter (TAC). Capture cross section data were obtained for incident neutron energies between 0.2 eV and 10 keV.
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