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RISS 인기검색어
- 검색키워드
- 저자 : A. Mengoni (검색결과 3 건)
- 무료
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- 유료
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Neutron-capture Studies on ^(235)U and ^(238)U via AMS
A. Wallner,K. Buczak,F. Quinto,P. Steier,T. Belgya,L. Szentmiklosi,M. Bichler,I. Dillmann,F. Kappeler,A. Mengoni 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Major nuclear data libraries exhibit some discrepancies for the neutron capture reactions ^(235)U(n,γ) and ^(238)</SUP>U(n,γ) at keV energies. These differences reflect also the scatter of experimental data that are primarily based on time-of-flight measurements (TOF) with detection of prompt γ-rays. We report here on an independent approach for studying such reactions: Neutron activations with subsequent accelerator mass spectrometry (AMS) measurement represent an independent technique, where interference from fission is completely excluded. Activations of natural uranium samples were performed with cold neutrons (Budapest), thermal (Vienna) and with neutrons of 25 and 500 keV (Karlsruhe) for the measurement of ^(235)U(n,γ) and ^(238)U(n,γ). The produced long-lived ^(236)U and the decay product of ^(239)U, ^(239)Pu, respectively, were subsequently counted by AMS at the Vienna Environmental Research Accelerator. This method for measuring the neutron capture cross section has the advantage that the involved systematic uncertainties are in no way correlated with those inherent to the TOF technique. Preliminary data for these neutron energies indicate good agreement with evaluations and seem to support in the keV energy range the reported lower cross-section values for both capture reactions.
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Results from the IAEA Benchmark of Spallation Models
S. Leray,J. C. David,M. Khandaker,G. Mank,A. Mengoni,N. Otsuka,D. Filges,F. Gallmeier,A. Konobeyev,R. Michel 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Spallation reactions play an important role in a wide domain of applications. In the simulation codes used in this field, the nuclear interaction cross-sections and characteristics are computed by spallation models. The International Atomic Energy Agency (IAEA) has recently organised a benchmark of the spallation models used or that could be used in the future into high-energy transport codes. The objectives were, first, to assess the prediction capabilities of the different spallation models for the different mass and energy regions and the different exit channels, and, second, to understand the reason for the success or deficiency of the models. Results of the benchmark concerning both the analysis of the prediction capabilities of the models and the first conclusions on the physics of spallation models are presented.
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Neutron Studies for Dating the Universe
F. Kappeler,A. Mengoni,M. Mosconi,K. Fujii,M. Heil,C. Domingo-pardo,The n_TOF Collaboration 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The neutron capture cross sections of ^(186)Os and ^(187)Os are of key importance for defining the s-process abundance of ^(187)Os at the formation of the solar system. This quantity can be used to determine the radiogenic abundance component of ^(187)Os from the decay of ^(187)Re (t_(1/2) = 41.2 Gyr) and to infer the time-duration of the nucleosynthesis in our galaxy (Re/Os cosmochronometer). The neutron capture cross sections of ^(186)Os, ^(187)Os, and ^(188)Os have been measured at the CERN n_TOF facility from 1 eV to 1 MeV, covering the entire energy range of astrophysical interest. From these data Maxwellian averaged capture cross sections have been calculated with uncertainties between 3.3 and 4.7%. Additional information was obtained by measuring the inelastic scattering cross section of ^(187)Os at the Karlsruhe 3.7 MV Van de Graaff accelerator and by neutron resonance analyses of the n TOF capture data to establish a comprehensive experimental basis for the Hauser-Feshbach statistical model. Consistent HF calculations for the capture and inelastic reaction channels were performed to determine the stellar enhancement factors, which are required to correct the Maxwellian averaged cross sections for the effect of thermally populated excited states. The consequences of this analysis for the s-process component of the ^(187)Os abundance and the related impact on the evaluation of the time-duration of Galactic nucleosynthesis via the Re/Os cosmo-chronometer are discussed.
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