ORCID Profile
0000-0003-1822-6537
Current Organisation
CEA
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Publisher: Elsevier BV
Date: 05-2020
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1668/1/012005
Abstract: Neutron capture cross sections are one of the fundamental nuclear data in the study of the s (slow) process of nucleosynthesis. More interestingly, the competition between the capture and the decay rates in some unstable nuclei determines the local isotopic abundance pattern. Since decay rates are often sensible to temperature and electron density, the study of the nuclear properties of these nuclei can provide valuable constraints to the physical magnitudes of the nucleosynthesis stellar environment. Here we report on the capture cross section measurement of two thallium isotopes, 204 Tl and 205 Tl performed by the time-of-flight technique at the n TOF facility at CERN. At some particular stellar s-process environments, the decay of both nuclei is strongly enhanced, and determines decisively the abundance of two s-only isotopes of lead, 204 Pb and 205 Pb. The latter, as a long-lived radioactive nucleus, has potential use as a chronometer of the last s-process events that contributed to final solar isotopic abundances.
Publisher: MDPI AG
Date: 17-06-2021
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 s le 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.
Publisher: American Physical Society (APS)
Date: 24-02-2022
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1668/1/012001
Abstract: Radiative neutron capture cross section measurements are of fundamental importance for the study of the slow neutron capture (s-) process of nucleosynthesis. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. Particularly relevant are branching nuclei along the s-process path, which are sensitive to the physical conditions of the stellar environment. One such ex le is the branching at 79 Se (3.27 × 10 5 y), which shows a thermally dependent β -decay rate. However, an astrophysically consistent interpretation requires also the knowledge of the closest neighbour isotopes involved. In particular, the 80 Se(n, γ ) cross section directly affects the stellar yield of the “cold” branch leading to the formation of the s -only 82 Kr. Experimentally, there exists only one previous measurement on 80 Se using the time of flight (TOF) technique. However, the latter suffers from some limitations that are described in this presentation. These drawbacks have been significantly improved in a recent measurement at CERN n TOF. This contribution presents a summary of the latter measurement and the status of the data analysis.
Publisher: Springer International Publishing
Date: 2019
Publisher: Springer International Publishing
Date: 2019
No related grants have been discovered for Diego Ramos.