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Evaluation of neutron cross sections of^(48)Ti based on the Unified-Monte-Carlo-B method

Chinese Physics C 2024年第7期48卷 118-130页

作者：夏候琼续瑞瑞刘萍 Roberto Capote 田源陶曦吴小飞张玥葛智刚舒能川冯松 China Nuclear Data Center China Institute of Atomic EnergyBeijing 102413China NAPC–Nuclear Data Section P.O.Box 100Vienna International CentreA-1400ViennaAustria School of Nuclear Science and Technology University of South ChinaHengyang 421001China

A cross section evaluation of neutron induced reactions on^(48)Ti is undertaken using the Unified Monte Carlo-B(UMC-B)*** evaluation concentrates on estimating the covariance and the use of the UMC-B allows avoiding the deficiencies of linear regression brought by the traditional least squares *** main neutron and charged particle emission reactions from n+^(48)Ti in the fast neutron energy region below 20 MeV are studied in this *** posterior probability density function(PDF)of each neutron cross section is obtained in a UMC-B Bayesian approach by convoluting the model PDFs sampled based on model parameters and the likelihood functions for the experimental *** model parameters including level density,pair corrections,optical model and Kalbach matrix element parameter are stochastically sampled with the assumption of normal distributions to estimate the model *** Cholesky factorization approach is applied to consider potential parameter ***,the posterior covariance matrices are generated using the UMC-B generated *** new evaluated results are compared with the CENDL-3.2,ENDF/B-VIII.0,JEFF-3.3,TENDL-2021 and JENDL-5 evaluations and differences are discussed.

关键词： covariance Unified Monte Carlo B(UMC-B) ^(48)Ti neutron cross sections Cholesky factor-ization approach

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Examination of static fission properties of U and Th using Cassinian oval parametrization within the macroscopic–microscopic approach

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The European Physical Journal A 2024年第8期60卷 1-8页

作者： Jachimowicz, P. Capote, R. Kowal, M. Institute of Physics University of Zielona Góra Zielona Góra Poland NAPC-Nuclear Data Section International Atomic Energy Agency Vienna Austria National Centre for Nuclear Research Warsaw Poland

We have conducted a thorough analysis of the potential energy surfaces (PES) in $$^{236}$$ U and $$^{233}$$ Th using the Cassini-ovals parameterization within the macro–micro approach. We employed the state-of-the-art immersion water flow (IWF) method to study the saddles on four-dimensional energy grids encompassing reflection-asymmetric shapes. For $$^{233}$$ Th, we computed the adiabatic potential energy surfaces by minimizing configurations with one blocked neutron within ten levels below and above the Fermi level. Our results show satisfactory agreement with empirical and experimental estimates for both nuclei, specifically regarding the first and second fission barriers. This suggests that our method holds promise in efficiently describing non-compact shapes while reducing the dimensionality of the space without sacrificing accuracy. Interestingly, employing Cassinian oval parameterization fails to reveal a pronounced, hyper-deformed third minimum in the potential energy landscape. Instead, only a shallow third minimum is observed for $$^{233}$$ Th, while in $$^{236}$$ U, this minimum ultimately vanishes. This finding holds significant importance when considering the modeling of fission cross-sections.

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High-energy neutron emission in thermal neutron-induced fission of U235

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Physical Review C 2024年第5期109卷 054616-054616页

作者： Martin Schulc Michal Kostal Roberto Capote Jan Simon Evzen Novak Tomas Czakoj Research Centre Rez Husinec-Rez 130 250 68 Czech Republic NAPC–Nuclear Data Section International Atomic Energy Agency A-1400 Vienna Austria

Spectrum-averaged cross-section (SACS) ratio measurement showing reduced uncertainties of measured SACS in two independent fission neutron fields is presented. The used prompt fission neutron fields correspond to the Cf252(sf) and U235(nth,f) fission neutrons. The employed SACS in the U235(nth,f) prompt fission neutron spectrum (PFNS) were measured using three different light water reactors: LR-0 and VR-1 zero power reactors and the LVR-15 10 MWt reactor. The employed SACS in the Cf252(sf) prompt fission neutron field were measured using a certified high-flux neutron source. Existing correlations among measured SACS in the two different neutron fields are estimated and used to reduce the uncertainty of measured SACS ratio for IRDFF dosimetry reactions. The derived set of measured SACS ratios with reduced uncertainty extends previous works into the higher-energy fission neutron range up to 20–30 MeV. The SACS ratio in Cf252(sf) and U235(nth,f) PFNS can be used to probe the high-energy tail of the U235(nth,f) fission neutron spectrum as the Cf252(sf) reference neutron spectrum is relatively well known. Derived experimental SACS ratio data. featuring low uncertainty are compared to the calculated dosimetry SACS ratio using the IRDFF-II dosimetry cross sections and the U235(nth,f) ENDF/B-VII.1, ENDF/B-VIII.0, or JEFF-3.3 PFNS evaluations. The ENDF/B-VIII.0 evaluation of the U235(nth,f) PFNS agrees well with derived SACS ratio data within quoted uncertainties. Other libraries predict a significantly lower fraction of U235(nth,f) fission neutrons above 11 MeV of the outgoing neutron energy.

关键词： Fission Neutron physics nuclear reactors Nucleon induced nuclear reactions A ≥ 220

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Cross-section measurements of ( , ) reactions on zinc isotopes using the 4 -summing method for astrophysics applications

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The European Physical Journal Plus 2025年第5期140卷 1-22页

作者： Harissopulos, S. Provatas, G. Foteinou, V. Axiotis, M. Becker, H.-W. Lagoyannis, A. Vagena, E. Dimitriou, P. TANDEM Laboratory Institute of Nuclear and Particle Physics NCSR “Demokritos” Athens Greece Rujer Bošković Institute Zagreb Croatia RUBION Ruhr-Universität Bochum Bochum Germany Nuclear Data Section NAPC IAEA Vienna Austria

The cross sections of the ( $$\alpha$$ , $$\gamma$$ ) reactions on 64Zn, 66Zn, and 68Zn were measured using the 4 $$\pi$$ $$\gamma$$ -summing method at center-of-mass energies relevant to the $${ p}$$ -process nucleosynthesis, ranging from 4.756 to 9.352 MeV, with isotopically enriched targets. The paper also reports the analysis procedure for the current and previous measurements, through which the uncertainty of the absolute efficiency of the employed 4 $$\pi$$ $$\gamma$$ -summing NaI(Tl) detector was significantly reduced to $$\approx$$ 4%. This allowed for testing existing global models of the $$\alpha$$ -particle-nucleus optical model potential with increased sensitivity. The experimental cross-section data and resulting astrophysical S factors were compared with corresponding statistical model calculations performed using version 2.0 of the nuclear reaction code TALYS. The conclusions drawn from this comparison are presented and discussed. Additionally, the reaction rates of the three reactions investigated were calculated and compared with well-established and widely used reaction-rate databases.

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How to explain ENDF-6 to computers: A formal ENDF format description language

arXiv

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arXiv 2023年

作者： Schnabel, Georg Aldama, Daniel Lopez Capote, Roberto NAPC–Nuclear Data Section International Atomic Energy Agency Vienna Austria Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear Havana Cuba

The ENDF-6 format, widely used worldwide for storing and disseminating nuclear data, is managed by the Cross sections Evaluation Working Group (CSEWG) and fully documented in the ENDF-6 formats manual. This manual employs a combination of formal and natural language, introducing the possibility of ambiguity in certain parts of the format specification. To eliminate the possibility of ambiguity, this contribution proposes a generalization of the formal language used in the ENDF-6 formats manual, which is precisely defined in extended Backus-Naur form (EBNF). This formalization also offers several other advantages, notably reducing the complexity of creating and updating parsing and validation programs for ENDF-6 formatted files. Moreover, the availability of a formal description enables the automatic mapping of the low-level ENDF-6 representation, provided by a sequence of numbers, to a more human-friendly hierarchical representation with variable names. Demonstrating these advantages, almost the entire ENDF-6 format description has been translated into the proposed formal language, accompanied by a reference implementation of a parser/translator. This implementation leverages the formal format specification to enable reading, writing, and validating ENDF-6 formatted files. © 2023, CC BY-SA.

关键词： Specifications

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Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions

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Physical Review C 2023年第4期107卷 044608-044608页

作者： T. Kawano A. E. Lovell S. Okumura H. Sasaki I. Stetcu P. Talou Los Alamos National Laboratory Los Alamos New Mexico 87545 USA NAPC–Nuclear Data Section International Atomic Energy Agency Vienna A-1400 Austria

Prompt and β-delayed fission observables, such as the average number of prompt and delayed neutrons, the independent and cumulative fission product yields, and the prompt γ-ray energy spectra for the photonuclear reactions on U235,238 and Pu239, are calculated with the Hauser-Feshbach fission fragment decay (HF3D) model and compared with available experimental data. In the analysis of neutron-induced fission reactions to the case of photo-induced fission, an excellent reproduction of the delayed neutron yields supports a traditional assumption that the photo fission might be similar to the neutron-induced fission at the same excitation energies regardless of the spin and parity of the fissioning systems.

关键词： Fission nuclear reactions Photonuclear reactions

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Dispersive optical model analysis of nucleon scattering on Zr90

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Physical Review C 2023年第6期107卷 064606-064606页

作者： Xiuniao Zhao Wenqing Du R. Capote E. Sh. Soukhovitskiĩ College of Physical Science and Technology Bohai University Jinzhou 121013 China NAPC-Nuclear Data Section International Atomic Energy Agency Vienna A-1400 Austria Joint Institute for Energy and Nuclear Research Minsk-Sosny 220109 Belarus

Zr90 is a double-magic spherical nucleus. Nucleon scattering on such a nucleus can be well described by spherical optical model potentials. Nucleon scattering data including neutron total cross section, elastic scattering angular distributions and analyzing powers, and low-energy scattering observables are used to derive a new Lane-consistent spherical optical model potential that obeys dispersive constraints, features nonlocality of the real part, and considers the shell gap in the potential. It is shown that the derived dispersive optical potential gives a good description of the energies of the bound single-particle states of the target nucleus Zr90.

关键词： Nucleon induced nuclear reactions Optical, coupled-channel & distorted wave models 90 ≤ A ≤ 149 nuclear reactions Shell model

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Low-Energy Reactions of the n+233U nuclear Compound System and Its Initial Validation

Low-Energy Reactions of the n+233U Nuclear Compound System a...

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2021 Transactions of the American nuclear Society Winter Meeting, ANS 2021

作者： Pigni, Marco T. Capote, Roberto Trkov, Andrej Nuclear Data Group Oak Ridge National Laboratory P.O. Box 2008 Oak RidgeTN37831 United States NAPC-Nuclear Data Section International Atomic Energy Agency Vienna Austria Jožef Stefan Institute Jamova cesta 39 Ljubljana1000 Slovenia

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Consideration of memory of spin and parity in the fissioning compound nucleus by applying the Hauser-Feshbach fission fragment decay model to photonuclear reactions

arXiv

引用

arXiv 2022年

作者： Kawano, T. Lovell, A.E. Okumura, S. Sasaki, H. Stetcu, I. Talou, P. Los Alamos National Laboratory Los AlamosNM87545 United States NAPC Nuclear Data Section International Atomic Energy Agency ViennaA-1400 Austria

Prompt and β-delayed fission observables, such as the average number of prompt and delayed neutrons, the independent and cumulative fission product yields, and the prompt γ-ray energy spectra for the photonuclear reactions on 235,238U and 239Pu are calculated with the Hauser-Feshbach Fission Fragment Decay (HF3D) model and compared with available experimental data. In the analysis of neutron-induced fission reactions to the case of photo-induced fission, an excellent reproduction of the delayed neutron yields supports a traditional assumption that the photo-fission might be similar to the neutron-induced fission at the same excitation energies regardless of the spin and parity of the fissioning systems. Copyright © 2022, The Authors. All rights reserved.

关键词： Gamma rays

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Multi-step Direct Reaction Models Including Collectivity in Nucleon Induced Reactions 6th

Multi-step Direct Reaction Models Including Collectivity in ...

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6th International Workshop on Compound-nuclear Reactions and Related Topics, CNR 2018

作者： Chimanski, E.V. Capote, R. Carlson, B.V. Koning, A.J. Aeronautics Institute of Technology São José dos Campos Brazil NAPC-Nuclear Data Section International Atomic Energy Agency Vienna Austria Instituto Tecnológico da Aeronáutica São José dos Campos SP Brazil

ISBN: (纸本)9783030580810

Pre-equilibrium nuclear reactions occur on an intermediate time scale when compared to fast direct reactions and to the slow process of compound nucleus evaporation. They dominate the reaction spectra in a large range of energy, especially for fast incident projectiles. The quantum models developed so far describe the process as multiple collisions of an incident leading particle with the target nucleus. The low-energy excited states of the target can have several components forming a collective state. We present here, preliminary results on the description of such a state in the Random Phase Approximation that considers long and short range residual interactions beyond mean field. We have investigated the contributions of different particle–hole modes to the low-lying excited states of the target nucleus. In addition, a simplified model for the particle–hole basis is studied. © 2021, This is a U.S. government work and not under copyright protection in the U.S.;foreign copyright protection may apply.

关键词： nuclear reactions

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