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RISS 인기검색어
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- 저자 : Domingo-pardo (검색결과 2 건)
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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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Neutron Capture on <SUP>209</SUP>Bi: Determination of the Production Ratio of ^(210m)Bi/^(210g)Bi
F. Gunsing,E. Berthoumieux,A. Borella,T. Belgya,L. Szentmiklosi,P. Schillebeeckx,J. C. Drohe,R. Wynants,N. Colonna,S. Marrone,G. Tagliente,R. Terlizzi,C. Domingo-pardo,J. Tain,T. Martinez,C. Massimi,P 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Neutron capture on ^(209)Bi produces either an isomeric state ^(210m)Bi with a half life of 3×10^6 years, or the ground state ^(210g)Bi which decays with a half life of 5 days to the alpha emitter ^(210)Po. Therefore the neutron capture cross section ratio ^(209)Bi(n,γ) ^(210m)^(Bi)/^(210g)Bi plays an important role in predicting the short- and long-term radio-toxicity produced by ^(209)Bi under neutron irradiation. This ratio is dependent on the neutron energy. We have measured this ratio for cold neutrons at the cold neutron beam facility of the Budapest Neutron Centre by observing the population of the ground- and the metastable state using high resolution gamma-ray spectroscopy. The same technique hasbeen used at the pulsed white neutron source GELINA of the IRMM, Geel in combination with the neutron time-of-flight technique. Results for the neutron-energy dependent branching ratio will be presented. In addition we performed simulations using a statistical decay code.
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