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Measurement of the ^(236)U(n, f) Cross Section at n_TOF
R. Sarmento,I. F. Goncalves,P. Vaz,M. Calviani,N. Colonna 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
A precise knowledge of the ^(236)U neutron-induced fission cross-section is required for the development of accelerator-driven systems and reactors based on the Th-U cycle. The evaluated data presently stored in the nuclear data libraries rely on outdated experimental measurements and show large discrepancies in the energy region between 1 keV and 100 keV. More recent measurements made at LANSCE and GELINA yielded results which are in disagreement with the literature for the resonance region and below 10 eV. In order to improve the present knowledge of the ^(236)U(n, f) cross-section, a new measurement was performed at the neutron Time-Of-Flight facility n_TOF at CERN. A Fast Ionization Chamber was used, in which four samples of ^(236)U and two of ^(235)U were mounted. The ^(236)U(n,f) cross-section was determined relative to the standard ^(235)U(n, f) reaction. The contribution from the ^(235)U contamination in the samples was subtracted, together with the alpha-particle background. Finally, the data were corrected for dead-time and detection efficiency. The n_TOF results on the ^(236)U(n, f) cross-section are reported in the neutron energy region from 200 meV to 2 MeV. The present high-resolution data point to several shortcomings in the current evaluated databases in the sub-threshold region. High accuracy cross-sections, important for applications to fast nuclear reactors as well as for fundamental Nuclear Physics, are also reported here.
D. Cano-Ott,F. Alvarez-Velarde,E. Gonzalez-Romero,C. Guerrero,T. Martinez,E. Mendoza,D. Villamarin,M. C. Vicente,U. Abbondanno,N. Colonna,M. H. Meaze,S. Marrone,G. Tagliente,R. Terlizzi,F. Belloni,K. 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The successful development of advanced nuclear systems for sustainable energy production and nuclear waste management depends on high quality nuclear data libraries. Recent sensitivity studies and reports [1][2][3] have identified the need for substantially improving the accuracy of neutron cross-section data for minor actinides. The n_TOF collaboration has initiated an ambitious experimental program for the measurement of neutron capture cross sections of minor actinides. Two experimental setups have been constructed for this purpose: a Total Absorption Calorimeter (TAC) [4] for measuring neutron capture cross-sections of low-mass and/or radioactive samples and a set of two low neutron sensitivity C_6D_6 detectors for the less radioactive materials.
A New 2D-micromegas Detector for Neutron Beam Diagnostic at n_TOF
S. Andriamonje,M. Calviani,Y. Kadi,R. Losito,V. Vlachoudis,E. Berthoumieux,F. Gunsing,Y. Giomataris,T. Papaevangelou,C. Guerrero,N. Colonna,C. Weiss 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
A novel detector for 2D neutron beam diagnostic has been jointly developed by CERN andCEA in the framework of the n TOF Collaboration for investigation of the neutron beam spatial characteristics, namely position and profile as a function of the neutron energy. The detector is based on the already established MicroMegas "Bulk" technology and has been evolved from the one used for the CAST (CERN Axion Solar Telescope) experiment but equipped with an appropriate neutron/charged particle converter for neutron detection. The experimental results obtained in the 2009 commissioning run of the n_TOF facility and a comparison with simulations performed by means of FLUKA code are given, together with future perspectives and possible applications for this original type of neutron detector.
Study of Photon Strength Function of Actinides: the Case of ^(235)U, ^(238)Np and ^(241)Pu
C. Guerrero,F. Alvarez-Velarde,D. Cano-Ott,T. Martinez,E. Mendoza,D. Villamarin,N. Colonna,M. H. Meaze,S. Marrone,G. Tagliente,R. Terlizzi,F. Belloni,U. Abbondanno,K. Fujii,P. M. Milazzo,C. Moreau,G. 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The decay from excited levels in medium and heavy nuclei can be described in a statisticalapproach by means of Photon Strength Functions and Level Density distributions. The study of electromagnetic cascades following neutron capture based on the use of high eciency detectors has been shown to be well suited for probing the properties of the Photon Strength Function of heavy (high level density) and/or radioactive (high background) nuclei. In this work we have investigated for the first time the validity of the recommended PSF of actinides, in particular ^(235)U, ^(238)Np and ^(241)Pu. Our study includes the search for resonance structures in the PSF below S_n and draws conclusions regarding their existence and their characteristics in terms of energy, width and electromagnetic nature.
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.