Abstract
An accurate measurement of the 140Ce(n,γ) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the 140Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in 140Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the 140Ce Maxwellian-averaged cross-section.
Highlights
It has been well ascertained since the late 1950s that the vast majority of the elements above the iron peak are synthesized in stars, via sequences of neutron captures and βdecays [1,2]
In order to calculate the 140 Ce capture yield, the official neutron flux was used, which is known with an uncertainty better than 1% below 3 keV and within
The preliminary 140 Ce data allowed resolving and performing the resonance shape analysis (RSA) of 81 of the 102 resonances reported by the library JENDL-4.0 below 65
Summary
It has been well ascertained since the late 1950s that the vast majority of the elements above the iron peak are synthesized in stars, via sequences of neutron captures and βdecays [1,2]. High-quality nuclear data are required in order to determine the final abundances of all the elements produced in stellar interiors This holds in particular for neutron capture cross-sections. In order to clarify the discrepancy that emerged in [9] and to produce a more accurate evaluation of the MACS, a new measurement of the 140 Ce(n,γ) cross-section was performed at the n_TOF facility in 2018
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