The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Gilles Noguere - One of the best experts on this subject based on the ideXlab platform.
-
New 23Na evaluation in the resolved Resonance Range taking into account both differential and double differential experiments
EPJ Web of Conferences, 2020Co-Authors: Pierre Tamagno, Cyrille De Saint Jean, P. Archier, Gilles NoguereAbstract:In 2012 CEA produced a entire new evaluation of sodium nuclear data for the release of the JEFF-3.2 evaluated nuclear data library. During the evaluation process performed with the CONRAD code, several differential measurements (total and discrete inelastic cross-sections) have been used. However double differential data (elastic angular distribution) that were yet available in the EXFOR database were not incorporated in the analysis at that time. The experimental elastic angular distribution were discarded because of it was impossible to obtain a good agreement for both angle-integrated cross-sections and double differential ones. The underlying cause of this disagreement is expected to be due to the attribution of quantum numbers to Resonance and related channel amplitudes. Indeed these numbers are imposed during the analysis but impact differently angular distributions and angle-integrated cross-sections. An automated search for an accurate set of quantum numbers has been implemented in order to produce a reliable quantum numbers set. In this paper we present a new evaluation of Na-23 taking into account both differential and double differential measurements. The analysis performed with the CONRAD code reached the level of agreement with experimental data for the total and inelastic cross-sections but this time with a significant improvement for the elastic angular distributions. This new evaluation produced in the ENDF-6 format has then been tested and validated on critical facilities calculation (MASURCA and ZPPR) in different configurations (nominal and voided) in order to assess its performances.
-
Measurements of the capture cross sections of natural silver in the Resonance Range with the time of flight technique
EPJ Web of Conferences, 2017Co-Authors: L. Šalamon, Gilles Noguere, B. Geslot, J. Heyse, S. Kopecky, P. Leconte, C. Paradela, P. Schillebeeckx, Luka SnojAbstract:Neutron capture cross section measurements have been performed at the time-of-flight facility GELINA of the EC-JRC-Geel. Prompt gamma rays, originating from a natural silver sample, were detected by a pair of C6 D6 liquid scintillation detectors. The total energy detection principle in combination with the pulse height weighting technique has been used. In this contribution the experimental details together with the data reduction process are described. In addition, first results of calculations with REFIT are presented to verify the quality of recommended cross section data in the resolved Resonance region.
-
From low- to high-energy nuclear data evaluations
The European Physical Journal A, 2015Co-Authors: Pierre Tamagno, Cyrille De Saint Jean, Gilles Noguere, P. Archier, E. Privas, Olivier Bouland, Olivier SerotAbstract:Evaluation of neutron cross sections between 0eV and 20MeV is based on several aspects of nuclear physics such as nuclear reaction and structure models and microscopic and integral measurements. Most of the time, the evaluation process is separately done in the resolved Resonance Range and the continuum. It may give rise to non-physical mismatches of cross sections and large uncertainties at boundaries. It also leads to an absence of cross correlations between high-energy domain and Resonance Range. In addition, integral experiments are sometimes only used to check central values (evaluation is “working fine” on a dedicated set of benchmarks). Eventual reduction of uncertainties on cross sections is not straightforward: “working fine” could be mathematically turned into reduced uncertainties. This paper will present several ideas that could be used to avoid such effects. They are based on basic physical principles, recent advances in terms of covariance evaluation methodologies, intensive use of Monte Carlo methods and High Performance Computing (HPC) and on some newly introduced models. A clear connection is made between Resonance and continuum energy Ranges.
-
Contributions to the study of the unresolved Resonance Range of neutron-induced reactions
2014Co-Authors: Gilles NoguereAbstract:This document presents the statistical description of neutron cross sections in the unresolved Resonance Range. The modeling of the total cross section and of the "shape - elastic" cross section is based on the "average R-Matrix" formalism. The partial cross sections describing the radiative capture, elastic scattering, inelastic scattering and fission process are calculated using the Hauser-Feshbach formalism with width fluctuation corrections. In the unresolved Resonance Range, these models depend on the average Resonance parameters (neutron strenght function Sc, mean level spacing Dc, average partial reaction widths, channel radius ac, effectif radius R' and distant level parameter). The codes (NJOY, CALENDF...) dedicated to the processing of nuclear data libraries (JEFF, ENDF\B, JENDL, CENDL, BROND... ) use the average parameters to take into account the self-shielding phenomenon for the simulation of the neutron transport in Monte-Carlo (MCNP, TRIPOLI... ) and deterministic (APOLLO, ERANOS...) codes. The evaluation work consists in establishing a consistent set of average parameters as a function of the total angular momentum J of the system and of the orbital moment of the incident neutron l. The work presented in this paper aims to describe the links between the S-Matrix and the "average R-Matrix" formalism for the calculation of Sc, ac and R'.
-
Estimation of Nuclear Reaction Model Parameter Covariances and the Related Neutron Induced Cross Sections with Physical Constraints
Nuclear Data Sheets, 2014Co-Authors: Cyrille De Saint Jean, P. Archier, E. Privas, Gilles NoguereAbstract:Abstract In neutron induced reactions between 0 eV and 20 MeV, a general problem arises during the evaluation of cross sections. Most of the time, the evaluation work is done independently between the resolved Resonance Range and the continuum, giving rise to mismatches for the cross sections, larger uncertainties on boundary and no cross-correlations between high energy domain and Resonance Range. This paper will present several methodologies that may be used for avoiding such effects. A first idea based on the use of experiments overlapping two energy domains appeared in the near past. It will be reviewed and extended to the use of systematic uncertainties (normalization for example). In addition, we propose a methodology taking into account physical constraints on an overlapping energy domain where two nuclear reaction models are used (continuity of both cross sections or derivatives for example). The use of LagRange multipliers (related to these constraints) in a classical generalized least square procedure will be presented and some academic examples will be detailed.
Danilo Giulietti - One of the best experts on this subject based on the ideXlab platform.
-
intense gamma ray source in the giant dipole Resonance Range driven by 10 tw laser pulses
Physical Review Letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, P Doliveira, M Galimberti, J Galy, Andrea Gamucci, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
-
intense γ ray source in the giant dipole Resonance Range driven by 10 tw laser pulses
Physical Review Letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, P Doliveira, M Galimberti, J Galy, Andrea Gamucci, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
-
Intense γ-Ray Source in the Giant-Dipole-Resonance Range Driven by 10-TW Laser Pulses
Physical review letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, M Galimberti, J Galy, Andrea Gamucci, P. D’oliveira, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
Cyrille De Saint Jean - One of the best experts on this subject based on the ideXlab platform.
-
New 23Na evaluation in the resolved Resonance Range taking into account both differential and double differential experiments
EPJ Web of Conferences, 2020Co-Authors: Pierre Tamagno, Cyrille De Saint Jean, P. Archier, Gilles NoguereAbstract:In 2012 CEA produced a entire new evaluation of sodium nuclear data for the release of the JEFF-3.2 evaluated nuclear data library. During the evaluation process performed with the CONRAD code, several differential measurements (total and discrete inelastic cross-sections) have been used. However double differential data (elastic angular distribution) that were yet available in the EXFOR database were not incorporated in the analysis at that time. The experimental elastic angular distribution were discarded because of it was impossible to obtain a good agreement for both angle-integrated cross-sections and double differential ones. The underlying cause of this disagreement is expected to be due to the attribution of quantum numbers to Resonance and related channel amplitudes. Indeed these numbers are imposed during the analysis but impact differently angular distributions and angle-integrated cross-sections. An automated search for an accurate set of quantum numbers has been implemented in order to produce a reliable quantum numbers set. In this paper we present a new evaluation of Na-23 taking into account both differential and double differential measurements. The analysis performed with the CONRAD code reached the level of agreement with experimental data for the total and inelastic cross-sections but this time with a significant improvement for the elastic angular distributions. This new evaluation produced in the ENDF-6 format has then been tested and validated on critical facilities calculation (MASURCA and ZPPR) in different configurations (nominal and voided) in order to assess its performances.
-
From low- to high-energy nuclear data evaluations
The European Physical Journal A, 2015Co-Authors: Pierre Tamagno, Cyrille De Saint Jean, Gilles Noguere, P. Archier, E. Privas, Olivier Bouland, Olivier SerotAbstract:Evaluation of neutron cross sections between 0eV and 20MeV is based on several aspects of nuclear physics such as nuclear reaction and structure models and microscopic and integral measurements. Most of the time, the evaluation process is separately done in the resolved Resonance Range and the continuum. It may give rise to non-physical mismatches of cross sections and large uncertainties at boundaries. It also leads to an absence of cross correlations between high-energy domain and Resonance Range. In addition, integral experiments are sometimes only used to check central values (evaluation is “working fine” on a dedicated set of benchmarks). Eventual reduction of uncertainties on cross sections is not straightforward: “working fine” could be mathematically turned into reduced uncertainties. This paper will present several ideas that could be used to avoid such effects. They are based on basic physical principles, recent advances in terms of covariance evaluation methodologies, intensive use of Monte Carlo methods and High Performance Computing (HPC) and on some newly introduced models. A clear connection is made between Resonance and continuum energy Ranges.
-
Estimation of Nuclear Reaction Model Parameter Covariances and the Related Neutron Induced Cross Sections with Physical Constraints
Nuclear Data Sheets, 2014Co-Authors: Cyrille De Saint Jean, P. Archier, E. Privas, Gilles NoguereAbstract:Abstract In neutron induced reactions between 0 eV and 20 MeV, a general problem arises during the evaluation of cross sections. Most of the time, the evaluation work is done independently between the resolved Resonance Range and the continuum, giving rise to mismatches for the cross sections, larger uncertainties on boundary and no cross-correlations between high energy domain and Resonance Range. This paper will present several methodologies that may be used for avoiding such effects. A first idea based on the use of experiments overlapping two energy domains appeared in the near past. It will be reviewed and extended to the use of systematic uncertainties (normalization for example). In addition, we propose a methodology taking into account physical constraints on an overlapping energy domain where two nuclear reaction models are used (continuity of both cross sections or derivatives for example). The use of LagRange multipliers (related to these constraints) in a classical generalized least square procedure will be presented and some academic examples will be detailed.
-
A Monte Carlo Approach to Nuclear Model Parameter Uncertainties Propagation
Nuclear Science and Engineering, 2009Co-Authors: Cyrille De Saint Jean, Benoit Habert, Gilles Noguere, Bertrand IoossAbstract:AbstractThe evaluation of neutron cross sections in the low energy Range (electron volt, mega-electron-volt) is based on formal nuclear models having different types of parameters. Some of them may be fitted to reproduce experimental datasets giving rise to an adjusted covariance matrix. In this paper, a Monte Carlo method is presented to properly consider the influence of the remaining parameters, having a priori uncertainties, on the fitted parameters covariances. This method is based on an exact mathematical description using conditional probabilities. To explain the key points of the methodology, an academic example of average parameters evaluation in the unresolved Resonance Range is presented using Hauser-Feshbach model calculations.
-
Generalization of the SPRT Method for the Modeling of the Neutron Cross Sections in the Unresolved Resonance Range
Nuclear Science and Engineering, 2009Co-Authors: E. Rich, Cyrille De Saint Jean, Gilles Noguere, A. TudoraAbstract:For the modeling of the neutron cross sections, three energy Ranges can be distinguished. The resolved Resonance Range can be interpreted in terms of single-level, multilevel, Reich-Moore, or R-matrix parameters. The unresolved Resonance Range (URR) is described with the average R-matrix and Hauser-Feshbach formalisms. For the high energies ("continuum"), optical model parameters are used in association with statistical and preequilibrium models. One of the main challenges of such a work is to study the consistency of the average parameters obtained by these different calculations. With the ESTIMA and SPRT methods, we provide a set of parameters for partial s-waves and p-waves (strength functions S l and effective potential scattering radius R'). However, accurate analysis of the URR domain needs more information than parameters R' and S l associated with orbital moments l = 0 and l = 1. Using links between the average R-matrix formalism and the optical model calculations, we propose a generalization of the SPRT method for I > 1 and a new description of the URR domain in terms of S l and R ∞ lJ .
A Giulietti - One of the best experts on this subject based on the ideXlab platform.
-
intense gamma ray source in the giant dipole Resonance Range driven by 10 tw laser pulses
Physical Review Letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, P Doliveira, M Galimberti, J Galy, Andrea Gamucci, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
-
intense γ ray source in the giant dipole Resonance Range driven by 10 tw laser pulses
Physical Review Letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, P Doliveira, M Galimberti, J Galy, Andrea Gamucci, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
-
Intense γ-Ray Source in the Giant-Dipole-Resonance Range Driven by 10-TW Laser Pulses
Physical review letters, 2008Co-Authors: A Giulietti, N Bourgeois, Tiberio Ceccotti, X Davoine, S Dobosz, M Galimberti, J Galy, Andrea Gamucci, P. D’oliveira, Danilo GiuliettiAbstract:A {gamma}-ray source with an intense component around the giant dipole Resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the {gamma}-ray yield in the giant dipole Resonance region (8
Andrej Trkov - One of the best experts on this subject based on the ideXlab platform.
-
Fluctuations Above the Resonance Range in Evaluated Data of 55Mn
Nuclear Data Sheets, 2014Co-Authors: Andrej Trkov, Roberto Capote, Luiz C Leal, D.w. Muir, E. Sh. SoukhovitskiiAbstract:Abstract The evaluation procedures for 55 Mn are elaborated, focusing on the issues related to the fluctuations in the cross sections above the resolved Resonance Range. Smooth cross sections are defined in the unresolved Resonance Range, based on the resolution-broadened total cross section measurements, where relevant. Above this energy fluctuations in the measured total cross section are introduced by scaling all reaction cross sections, but preserving the resolution-broadened total cross section. Special procedures are designed to match the observed structure in the average cosine of scattering by adjusting the ratio of the shape-elastic and compound-elastic contributions to the elastic scattering cross sections. The evaluated data file is being assembled and subjected to rigorous testing, verification and validation.
-
evaluation of tungsten nuclear reaction data with covariances
Nuclear Data Sheets, 2008Co-Authors: Andrej Trkov, Ivan Aleksander Kodeli, Roberto Capote, L C LealAbstract:As a follow-up of the work presented at the ND-2007 conference in Nice, additional fast reactor benchmarks were analyzed. Adjustment to the cross sections in the keV region was necessary. Evaluated neutron cross section data files for 180,182,183,184,186W isotopes were produced. Covariances were generated for all isotopes except 180W. In the Resonance Range the retro-active method was used. Above the resolved Resonance Range the covariance prior was generated by the Monte Carlo technique from nuclear model calculations with the Empire-II code. Experimental data were taken into account through the GANDR system using the generalized least-squares technique. Introducing experimental data results in relatively small changes in the cross sections, but greatly constrains the uncertainties. The covariance files are currently undergoing testing.
-
evaluation of tungsten isotopes in the fast neutron Range including cross section covariance estimation
INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY 2007; NICE FRANCE; 20070422 through 20070427, 2007Co-Authors: Roberto Capote, Andrej Trkov, M Herman, B V Carlson, P. ObložinskýAbstract:New evaluations for the tungsten isotopes {sup 180,182,183,184,186}W in the neutron energy Range up to 60 MeV were produced. In the Resonance Range only minor adjustments to the Resonance parameters were made due to a lack of adequate experimental data. Evaluations in the fast energy region were based on nuclear model calculations using the EMPIRE-2.19 code. Recently derived dispersive coupled-channel optical model potentials for W and Ta isotopes were instrumental to achieve a very good description of the available microscopic cross-section database. Model covariance data were generated with the Monte Carlo technique to produce a prior estimate for the covariance matrix. Experimental data were introduced through the GANDR system. The evaluated files were tested on selected fusion neutronics benchmarks and showed marked improvement compared to other existing evaluations.