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Fission Cross-section Measurements of ^(233)U, ^(245)Cm and ^(241;243)Am at CERN n_TOF Facility
M. Calviani 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Neutron-induced fission cross-sections of minor actinides have been measured using the n_TOF white neutron source at CERN, Geneva, as part of a large experimental program aiming at collecting new data relevant for nuclear astrophysics and for the design of advanced reactor systems. The measurements at n_TOF take advantage of the innovative features of the n_TOF facility, namely the wide energy range, high instantaneous neutron flux and good energy resolution. Final results on the fission cross-section of ^(233)U, ^(245)Cm and ^(243)Am from thermal to 20 MeV are here reported, together with preliminary results for ^(241)Am. The measurement have been performed with a dedicated Fast Ionization Chamber (FIC), a fission fragment detector with a very high efficiency, relative to the very well known cross-section of ^(235)U, measured simultaneously with the same detector.
A Transparent Detector for n_TOF Neutron Beam Monitoring
S. Andriamonje,M. Calviani,Y. Kadi,R. Losito,V. Vlachoudis,E. Berthoumieux,F. Gunsing,A. Giganon,Y. Giomataris,C. Guerrero,R. Sarmento,P. Schillebeeckx,P. Siegler 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
In order to obtain high precision cross-section measurements using the time-of-flight technique, it is important to know with good accuracy the neutron uence at the measuring station. The detector dedicated to these measurements should be placed upstream of the detectors used for capture and fission cross-section measurements. The main requirement is to reduce the material of the detector as much as possible, in order to minimize the perturbation of the neutron beam and, especially, the background produced by the device itself. According to these considerations, a new neutron detector equipped with a small-mass device based on MicroMegas "Micro-bulk" technology has been developed as a monitoring detector for the CERN n TOF neutron beam. A description of the different characteristics of this innovative concept of transparent detector for neutron beam monitoring is presented. The result obtained in the commissioning of the new spallation targetof the n TOF facility at CERN is shown, compared with simulations performed with the FLUKA code.
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.
Past, Present and Future of the n_TOF Facility at CERN
E. Chiaveri,S. Andriamonje,M. Calviani,V. Vlachoudis,M. Brugger,P. Cennini,F. Cerutti,M. Chin,A. Ferrari,Y. Kadi,E. Lebbos,R. Losito,C. Guerrero,V. Becares,D. Cano-Ott,M. Fernandez-Ordonez,E. Gonzalez 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The n_TOF spallation neutron facility is operating at CERN since 2001. Neutrons are produced with a very wide energy range, from thermal up to 1 GeV and with a very high instantaneous flux (10^5n/cm^2/pulse at 200 m from target) thanks to the high intensity (7 × 10^(12) protons/pulse) and low repetition rate of the Proton Synchrotron (PS) which is delivering protons to a lead spallation target. The experimental area is located at 200 m from the target, resulting in a very good energy resolution and beam quality thanks to the adoption of an optimal collimation system. At the end of 2008 the n_TOF facility has resumed operation after a halt of 3 years due to technical issues. This contribution will outline the main physics results obtained by the facility since its inception in 1999, and show the importance of the measured nuclear data in the field of Nuclear Astrophysics and Nuclear Technology. Then it will present the future perspectives of the facility, aiming mainly in the direction of measuring highly radioactive samples, for which the facility has unique capabilities, with a lower background.
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.
The Role of Fe and Ni for S-Process Nucleosynthesis and Innovative Nuclear Technologies
G. Giubrone,J. L. Tain,C. Lederer,A. Pavlik,A. Wallner,S. Andriamonje,M. Brugger,M. Calviani,F. Cerutti,E. Chiaveri,A. Ferrari,Y. Kadi,E. Lebbos,V. Vlachoudis,J. Andrzejewski,J. Marganiec,J. Perkowski 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The accurate measurement of neutron capture cross sections of all Fe and Ni isotopes is important for disentangling the contribution of the s-process and the r-process to the stellar nucleosynthesis of elements in the mass range 60 < A < 120. At the same time, Fe and Ni are important components of structural materials and improved neutron cross section data is relevant in the design of new nuclear systems. With the aim of obtaining improved capture data on all stable iron and nickel isotopes, a program of measurements has been launched at the CERN Neutron Time of Flight Facility n_TOF.
Characterization of the New n_TOF Neutron Beam: Fluence, Profile and Resolution
C. Guerrero,V. Becares,D. Cano-Ott,M. Fernandez-Ordonez,E. Gonzalez-Romero,F. Martin-Fuertes,T. Martinez,E. Mendoza,G. Pina,J. Quinones,V. Vlachoudis,M. Calviani,S. Andriamonje,M. Brugger,F. Cerutti,E 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
After a halt of four years, the n_TOF spallation neutron facility at CERN has resumed operation in November 2008 with a new spallation target characterized by an improved safety and engineering design, resulting in a more robust overall performance and efficient cooling. The first measurement during the 2009 run has aimed at the full characterization of the neutron beam. Several detectors, such as calibrated fission chambers, the n\textunderscore TOF Silicon Monitor, a MicroMegas detector with ^(10)B and ^(235)U samples, as well as liquid and solid scintillators have been used in order to characterize the properties of the neutron fluence. The spatial profile of the beam has been studied with a specially designed "X-Y" MicroMegas which provided a 2D image of the beam as a function of neutron energy. Both properties have been compared with simulations performed with the FLUKA code. The characterization of the resolution function is based on results from simulations which have been verified by the study of narrow capture resonances of ^(56)Fe, which were measured as part of a new campaign of (n, γ) measurements on Fe and Ni isotopes.