ORCID Profile
0000-0001-8358-9217
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Publisher: Institute of Physics, Polish Academy of Sciences
Date: 04-2021
Publisher: EDP Sciences
Date: 2017
Publisher: American Physical Society (APS)
Date: 22-09-2021
Publisher: Elsevier BV
Date: 05-2020
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023901008
Abstract: The neutron induced fission of 235 U is extensively used as a reference for neutron fluence measurements in various applications, ranging from the investigation of the biological effectiveness of high energy neutrons, to the measurement of high energy neutron cross sections of relevance for accelerator driven nuclear systems. Despite its widespread use, no data exist on neutron induced fission of 235 U above 200 MeV. The neutron facility n_TOF offers the possibility to improve the situation. The measurement of 235 U(n,f) relative to the differential n-p scattering cross-section, was carried out in September 2018 with the aim of providing accurate and precise cross section data in the energy range from 10 MeV up to 1 GeV. In such measurements, Recoil Proton Telescopes (RPTs) are used to measure the neutron flux while the fission events are detected and counted with dedicated detectors. In this paper the measurement c aign and the experimental set-up are illustrated.
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023901009
Abstract: Neutron capture on 241 Am plays an important role in the nuclear energy production and also provides valuable information for the improvement of nuclear models and the statistical interpretation of the nuclear properties. A new experiment to measure the 241 Am(n, γ ) cross section in the thermal region and the first few resonances below 10 eV has been carried out at EAR2 of the n_TOF facility at CERN. Three neutron-insensitive C 6 D 6 detectors have been used to measure the neutron-capture gamma cascade as a function of the neutron time of flight, and then deduce the neutron capture yield. Preliminary results will be presented and compared with previously obtained results at the same facility in EAR1. In EAR1 the gamma-ray background at thermal energies was about 90% of the signal while in EAR2 is up to a 25 factor much more favorable signal to noise ratio. We also extended the low energy limit down to subthermal energies. This measurement will allow a comparison with neutron capture measurements conducted at reactors and using a different experimental technique.
Publisher: Springer Science and Business Media LLC
Date: 07-2019
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023905004
Abstract: The study of neutron-induced reactions on actinides is of considerable importance for the design of advanced nuclear systems and alternative fuel cycles. Specifically, 230 Th is produced from the α-decay of 234 U as a byproduct of the 232 Th/ 233 U fuel cycle, thus the accurate knowledge of its fission cross section is strongly required. However, few experimental datasets exist in literature with large deviations among them, covering the energy range between 0.2 to 25 MeV. In addition, the study of the 230 Th(n,f) cross-section is of great interest in the research on the fission process related to the structure of the fission barriers. Previous measurements have revealed a large resonance at E n =715 keV and additional fine structures, but with high discrepancies among the cross-section values of these measurements. This contribution presents preliminary results of the 230 Th(n,f) cross-section measurements at the CERN n_TOF facility. The high purity targets of the natural, but very rare isotope 230 Th, were produced at JRC-Geel in Belgium. The measurements were performed at both experimental areas (EAR-1 and EAR-2) of the n_TOF facility, covering a very broad energy range from thermal up to at least 100 MeV. The experimental setup was based on Micromegas detectors with the 235 U(n,f) and 238 U(n,f) reaction cross-sections used as reference.
Publisher: American Physical Society (APS)
Date: 30-08-2021
Publisher: American Physical Society (APS)
Date: 02-10-2020
Publisher: Springer Science and Business Media LLC
Date: 2019
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2017
Publisher: IOP Publishing
Date: 10-2020
DOI: 10.1088/1742-6596/1668/1/012013
Abstract: The idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely (n, γ) cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how advances in instrumentation have led to the assessment of new aspects of s-process nucleosynthesis and to the progressive refinement of stellar models. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with γ-ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates.
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 10-2017
Publisher: American Physical Society (APS)
Date: 20-10-2020
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Physical Society (APS)
Date: 24-07-2018
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2017
Publisher: American Physical Society (APS)
Date: 27-04-2021
Publisher: EDP Sciences
Date: 2017
Publisher: American Physical Society (APS)
Date: 24-05-2018
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: EDP Sciences
Date: 2017
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: 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: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023901024
Abstract: The neutron-induced fission cross section of 235 U, a standard at thermal energy and between 0.15 MeV and 200 MeV, plays a crucial role in nuclear technology applications. The long-standing need of improving cross section data above 20 MeV and the lack of experimental data above 200 MeV motivated a new experimental c aign at the n_TOF facility at CERN. The measurement has been performed in 2018 at the experimental area 1 (EAR1), located at 185 m from the neutron-producing target (the experiment is presented by A. Manna et al. in a contribution to this conference). The 235 U(n,f) cross section from 20 MeV up to about 1 GeV has been measured relative to the 1 H(n,n) 1 H reaction, which is considered the primary reference in this energy region. The neutron flux impinging on the 235 U s le (a key quantity for determining the fission events) has been obtained by detecting recoil protons originating from n-p scattering in a C 2 H 4 s le. Two Proton Recoil Telescopes (PRT), consisting of several layers of solid-state detectors and fast plastic scintillators, have been located at proton scattering angles of 25.07° and 20.32°, out of the neutron beam. The PRTs exploit the ΔE-E technique for particle identification, a basic requirement for the rejection of charged particles from neutron-induced reactions in carbon. Extensive Monte Carlo simulations were performed to characterize proton transport through the different slabs of silicon and scintillation detectors, to optimize the experimental set-up and to deduce the efficiency of the whole PRT detector. In this work we compare measured data collected with the PRTs with a full Monte Carlo simulation based on the Geant-4 toolkit.
Publisher: American Physical Society (APS)
Date: 12-2017
Publisher: American Physical Society (APS)
Date: 04-06-2018
Publisher: Elsevier BV
Date: 07-2020
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023907003
Abstract: The (n, γ ) cross sections of the gadolinium isotopes play an important role in the study of the stellar nucleosynthesis. In particular, among the isotopes heavier than Fe, 154 Gd together with 152 Gd have the peculiarity to be mainly produced by the slow capture process, the so-called s-process, since they are shielded against the β -decay chains from the r-process region by their stable samarium isobars. Such a quasi pure s-process origin makes them crucial for testing the robustness of stellar models in galactic chemical evolution (GCE). According to recent models, the 154 Gd and 152 Gd abundances are expected to be 15-20% lower than the reference un-branched s-process 150 Sm isotope. The close correlation between stellar abundances and neutron capture cross sections prompted for an accurate measurement of 154 Gd cross section in order to reduce the uncertainty attributable to nuclear physics input and eventually rule out one of the possible causes of present discrepancies between observation and model predictions. To this end, the neutron capture cross section of 154 Gd was measured in a wide neutron energy range (from thermal up to some keV) with high resolution in the first experimental area of the neutron time-of-flight facility n_TOF (EAR1) at CERN. In this contribution, after a brief description of the motivation and of the experimental setup used in the measurement, the preliminary results of the 154 Gd neutron capture reaction as well as their astrophysical implications are presented.
Publisher: Elsevier BV
Date: 03-2019
Publisher: Springer Science and Business Media LLC
Date: 04-1970
Publisher: American Physical Society (APS)
Date: 03-10-2016
Publisher: Elsevier BV
Date: 04-2018
Publisher: American Physical Society (APS)
Date: 12-10-2021
Publisher: Elsevier BV
Date: 05-2018
Publisher: Springer International Publishing
Date: 2019
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2017
Publisher: American Physical Society (APS)
Date: 17-10-2019
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2017
Publisher: EDP Sciences
Date: 2018
DOI: 10.1051/EPJCONF/201718402005
Abstract: The slow neutron capture process (s-process) is responsible for producing about half of the elemental abundances heavier than iron in the universe. Neutron capture cross sections on stable isotopes are a key nuclear physics input for s-process studies. The 72 Ge( n, γ ) cross section has an important influence on production of isotopes between Ge and Zr during s-process in massive stars and therefore experimental data are urgently required. 72 Ge( n, γ ) was measured at the neutron time-of-flight facility n_TOF (CERN) for the first time at stellar energies. The measurement was performed using an enriched 72 GeO 2 s le at a flight path of 185m with a set of liquid scintillation detectors (C 6 D 6 ). The motivation, experiment and current status of the data analysis are reported.
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023905014
Abstract: Feasibility, design and sensitivity studies on innovative nuclear reactors that could address the issue of nuclear waste transmutation using fuels enriched in minor actinides, require high accuracy cross section data for a variety of neutron-induced reactions from thermal energies to several tens of MeV. The isotope 241 Am (T 1/2 = 433 years) is present in high-level nuclear waste (HLW), representing about 1.8 % of the actinide mass in spent PWR UOx fuel. Its importance increases with cooling time due to additional production from the β -decay of 241 Pu with a half-life of 14.3 years. The production rate of 241 Am in conventional reactors, including its further accumulation through the decay of 241 Pu and its destruction through transmutation/incineration are very important parameters for the design of any recycling solution. In the present work, the 241 Am(n,f) reaction cross-section was measured using Micromegas detectors at the Experimental Area 2 of the n_TOF facility at CERN. For the measurement, the 235 U(n,f) and 238 U(n,f) reference reactions were used for the determination of the neutron flux. In the present work an overview of the experimental setup and the adopted data analysis techniques is given along with preliminary results.
Publisher: Springer International Publishing
Date: 2019
Publisher: EDP Sciences
Date: 2017
Publisher: American Physical Society (APS)
Date: 21-07-2020
Publisher: Springer International Publishing
Date: 2019
Publisher: American Physical Society (APS)
Date: 06-02-2018
Location: Switzerland
No related grants have been discovered for Jorge Lerendegui-Marco.