| 41. |
- Balibrea-Correa, J., et al.
(författare)
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First measurement of the 94Nb(n,γ) cross section at the CERN n_TOF facility
- 2023
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 279
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Tidskriftsartikel (refereegranskat)abstract
- One of the crucial ingredients for the improvement of stellar models is the accurate knowledge of neutron capture cross-sections for the different isotopes involved in the s-,r- and i- processes. These measurements can shed light on existing discrepancies between observed and predicted isotopic abundances and help to constrain the physical conditions where these reactions take place along different stages of stellar evolution.In the particular case of the radioactive 94Nb, the 94Nb(n,γ) cross-section could play a role in the determination of the s-process production of 94Mo in AGB stars, which presently cannot be reproduced by state-of-the-art stellar models. There are no previous 94Nb(n,γ) experimental data for the resolved and unresolved resonance regions mainly due to the difficulties in producing highquality samples and also due to limitations in conventional detection systems commonly used in time-of-flight experiments.Motivated by this situation, a first measurement of the 94Nb(n,γ) reaction was carried out at CERN n_TOF, thereby exploiting the high luminosity of the EAR2 area in combination with a new detection system of small-volume C6D6-detectors and a high quality 94Nb-sample. The latter was based on hyper-pure 93Nb material activated at the high-flux reactor of ILL-Grenoble. An innovative ring-configuration detection system in close geometry around the capture sample allowed us to significantly enhance the signal-to-background ratio. This set-up was supplemented with two conventional C6D6-detectors and a highresolution LaCl3(Ce)-detector, which will be employed for addressing reliably systematic effects and uncertainties.At the current status of the data analysis, 18 resonance in 94Nb+n have been observed for the first time in the neutron energy range from thermal up to 10 keV.
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| 42. |
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| 43. |
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| 44. |
- Bevilacqua, Riccardo, et al.
(författare)
-
Light-ion Production from O, Si, Fe and Bi Induced by 175 MeV Quasi-monoenergetic Neutrons
- 2014
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Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 119, s. 190-193
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Tidskriftsartikel (refereegranskat)abstract
- We have measured double-differential cross sections in the interaction of 175 MeV quasimonoenergetic neutrons with O, Si, Fe and Bi. We have compared these results with model calculations with INCL4.5-Abla07, MCNP6 and TALYS-1.2. We have also compared our data with PHITS calculations, where the pre-equilibrium stage of the reaction was accounted respectively using the JENDL/HE-2007 evaluated data library, the quantum molecular dynamics model (QMD) and a modified version of QMD (MQMD) to include a surface coalescence model. The most crucial aspect is the formation and emission of composite particles in the pre-equilibrium stage.
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| 45. |
- Bevilacqua, Riccardo, et al.
(författare)
-
Light-Ion Production in the Interaction of 175 MeV Neutrons with Iron and Bismuth
- 2011
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Ingår i: Journal of the Korean Physical Society. - : Korean Physical Society. - 0374-4884 .- 1976-8524. ; 59:2, s. 1701-1704
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Tidskriftsartikel (refereegranskat)abstract
- We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, (3)He, and a) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20 degrees to 160 degrees, in steps of 20 degrees. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification, fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, (3)He and alpha particles and compare them with model calculations with TALYS-1.2.
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| 46. |
- Bevilacqua, Riccardo, 1974-, et al.
(författare)
-
Light-ion production in the interaction of 175 MeV neutrons with iron and bismuth
- 2011
-
Ingår i: Journal of Korean Physical Society.
-
Konferensbidrag (refereegranskat)abstract
- We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, 3He and α) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20◦ to 160◦, in steps of 20◦. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification,fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, 3He and α particles and compare them with model calculations with TALYS-1.2.
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| 47. |
- Bevilacqua, Riccardo, 1974-, et al.
(författare)
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Medley spectrometer for light ions in neutron-induced reactions at 175 MeV
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 646:1, s. 100-107
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Tidskriftsartikel (refereegranskat)abstract
- We have upgraded the Medley spectrometer to measure neutron-induced double differential cross-sections for light-ion production, with neutron energies up to 175 MeV. Measurements were performed at the quasi-monoenergetic neutron beam line at the The Svedberg Laboratory, in Uppsala (Sweden). Medley is a spectrometer system composed of eight three-element telescope detectors; Delta E-E technique is used for particle identification and total kinetic energy measurement. We have improved particle separation and installed new detectors that fully stop ions with kinetic energy up to 170 MeV. To reduce the contribution of the low energy tail in the quasi-monoenergetic neutron spectrum, we have applied time-of-flight techniques and investigated the results for measurements with 175 MeV neutrons. We have investigated the response function of the CsI(Tl) scintillators and describe a method for efficiency correction. We have studied the signal-to-background ratio of the new configuration of the spectrometer and of the collimation system. A method to obtain absolute cross-section normalization, separating the peak neutrons from the low-energy tail, is proposed. Finally we have characterized the 175 MeV quasi-monoenergetic neutron spectrum with the Medley spectrometer. This upgraded configuration has been used in 2007 and 2009 for light-ion production measurements at 175 MeV from C, Si, O, Fe, Bi and U.
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| 48. |
- Bevilacqua, Riccardo, et al.
(författare)
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Neutron induced light-ion production from iron and bismuth at 175 MeV
- 2010
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Ingår i: RADIATION MEASUREMENTS. - : Elsevier BV. ; 45:10, s. 1145-1150
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Konferensbidrag (refereegranskat)abstract
- We have measured light-ion (p, d, t, He-3 and alpha) production in the interaction of 175 MeV neutrons with iron and bismuth with low-energy thresholds and for a wide angular range (from 20 degrees to 160 degrees, in steps of 20 degrees). Measurements have been performed with the Medley setup, semi-permanently installed at the The Svedberg Laboratory, Uppsala (Sweden), where a quasi-monoenergetic neutron beam is available and well characterized. Medley is a conventional spectrometer system and consists of eight telescopes, each of them composed of two silicon surface barrier detectors, to perform particle identification, and a CsI(Tl) scintillator to fully measure the kinetic energy of the produced light-ions. We report preliminary double-differential cross sections for production of protons, deuterons and tritons in comparison with model calculations using TALYS-1.0 code. These show better agreement for the production of protons, while the theoretical calculations seem to overestimate the experimental production of deuterons and tritons.
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| 49. |
- Bevilacqua, Riccardo, 1974-
(författare)
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Neutron induced light-ion production from iron and bismuth at 175 MeV
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Light-ions (protons, deuterons, tritons, 3He and α articles) production in the interaction of 175 MeV neutrons with iron and bismuth has been measured using the Medley setup at the The Svedberg Laboratory (TSL) in Uppsala. These measurements have been conducted in the frame of an international collaboration whose aim is to provide the scientific community with new nuclear data of interest for the development of Accelerator Driven Systems, in the range of 20 to 200 MeV. In this Licentiate Thesis I will present the background for the present experiment, the choice of the measured materials (iron and bismuth) and of the energy range. I will then give a short theoretical description of the involved nuclear reactions and of the model used to compare the experimental results. A description of the neutron facility at TSL and of Medley setup will follow. Monte Carlo simulations of the experimental setup have been performed and some results are here reported and discussed. I will present data reduction procedure and finally I will report preliminary double differential cross sections for production of hydrogen isotopes from iron and bismuth at several emission angles. Experimental data will be compared with model calculations with TALYS-1.0; these show better agreement for the production of protons, while seems to overestimate the experimental production of deuterons and tritons.
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| 50. |
- Bevilacqua, Riccardo, 1974-
(författare)
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Neutron-Induced Light-Ion Production from Iron and Bismuth at 175 MeV
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radioactive waste management is one of the key issues in sustainability of nuclear energy production. Geological repositories represent today the most appropriate solution to long-term management of high-level radioactive waste. Strategies such as Partitioning and Transmutation of spent nuclear fuel may offer a positive impact on geological repositories, by reducing the mass of transuranium elements to be disposed and the time scale for their radiotoxicity. In this scenario, Accelerator Driven Systems (ADS) may play a relevant role as dedicated burners towards sustainable nuclear energy. The NEXT project at Uppsala University contributes to a European effort to improve nuclear data knowledge for transmutation, providing the first experimental neutron induced data in the 100 to 200 MeV energy region. This thesis presents measurements of double-differential cross sections for production of light-ions in the interaction of 175 MeV quasi-monoenergetic neutrons with Fe and Bi. Results are compared with model calculations obtained with state-of-the-art nuclear reaction codes; TALYS-1.2, a modified version of JQMD, and MCNP6. Special focus in this work is given to pre-equilibrium emission of composite light-ions. A new energy dependence in the mechanisms described by the Kalbach systematics used in TALYS to account for composite particle emission in the pre-equilibrium stage is proposed. Data show also the need to include multiple pre-equilibrium emission of composite particles, a mechanism now included in TALYS only for protons and neutrons. The JQMD code was recently modified to include a surface coalescence model in the quantum molecular dynamics description of the formation of composite particles. Comparisons of the measured data with results from this modified JQMD code confirm the importance of coalescence mechanisms for the description of the emission spectra of composite particles. Finally, the neutron-induced data are compared with MCNP6 calculations, to contribute to the process of validation and verification of the code.
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