The fission probability distributions of 232, 233, 234Pa and 231Th have been measured up to an excitation energy of 15 MeV, using the transfer reactions 232Th(3He, t)232Pa, 232Th(3He, d)233Pa, ...232Th(3He, p)234Pa and 232Th(3He, 4He)231Th. From these measurements, the neutron induced fission cross sections of 231Pa, 233Pa and 230Th have been determined from the product of the fission probabilities of 232Pa, 233Pa and 231Th respectively with the calculated compound nucleus formation cross sections in the 231Pa+n, 233Pa+n and 230Th+n reactions. The validity of the applied method has been successfully tested with the existing neutron induced fission cross sections of 230Th and 231Pa. Special emphasis is put on the 233Pa(n, f) reaction which is of importance for thorium fueled nuclear reactors. Based on a statistical model analysis of the neutron induced fission cross section as a function of neutron energy, it has been possible to determine the barrier parameters of the 234Pa fissioning nucleus. Cross sections for the compound nucleus inelastic scatttering 233Pa(n, n′) and radiative capture 233Pa(n, γ) reactions have also been calculated and compared with recent evaluations.
Micromegas type neutron detector for ADS system Pancin, J.; Andriamonje, S.; Aunes, S. ...
2006 IEEE Nuclear Science Symposium Conference Record,
2006-Oct., Letnik:
6
Conference Proceeding
ADS need neutron detectors working on a wide energy range and quite insensitive to X- and gamma-rays. Micromegas technology has been proposed to achieve this goal. The ability of Micromegas to detect ...neutrons has already been demonstrated and this detector is, under certain conditions, insensitive to gamma-rays. A new Micromegas neutron detector has been designed and it gives the possibility to get integrated neutron fluxes on different energy domains. The configuration of the detector will be presented as well as its functioning and the reasons of its insensitivity to gamma-rays. Moreover, some experiments have been realized on a TRIGA reactor at Casaccia in Italy. It is the first time that a Micromegas is placed in a nuclear reactor. The configuration and results of these tests will be shown and some improvements suggested.
Micromegas in CAST and prospects Abbon, P.; Andriamonje, S.; Aune, S. ...
2006 IEEE Nuclear Science Symposium Conference Record,
2006-Oct., Letnik:
6
Conference Proceeding
A low background Micromegas X-ray detector has been used to search for solar axions in the CAST experiment at CERN. The detector has an active area of 7cm times 7cm, excellent spatial resolution ...(~70nm), and good energy resolution. It is built using low radioactivity materials and the obtained background level is below 5times10 -5 counts/keV/cm 2 /s. The detector is being upgraded for the second phase of the experiment (2006-2007) with a reduced active area. A focusing X-Ray optic and improved shielding will be used to further reduce the background by approximately two orders of magnitude.
Astrophysics at n_TOF facility G. Tagliente, U. Abbondanno, G. Aerts, H. Alvarez, F. Alvarez-Velarde, S. Andriamonje, J. Andrzejewski, P. Assimakopoulos, L. Audouin, G. Badurek, P. Baumann, F. Becvar, F. Belloni, E. Berthoumieux, S. Bisterzo, F. Calvino, M. Calviani, D. Cano-Ott, R. Capote, C. Carrapico, P. Cennini, V. Chepel, E. Chiaveri, N. Colonna, G. Cortes, A. Couture, J. Cox, M. Dahlfors, S. David, I. Dillman, C. Domingo-Pardo, W. Dridi, I. Duran, C. Eleftheriadis, M. Embid-Segura, L. Ferrant, A. Ferrari, R. Ferreira-Marques, K. Fujii, W. Furman, R. Gallino, I. Goncalves, E. Gonzalez-Romero, F. Gramegna, C. Guerrero, F. Gunsing, B. Haas, R. Haight, M. Heil, A. Herrera-Martinez, M. Igashira, E. Jericha, F. Kappeler, Y. Kadi, D. Karadimos, D. Karamanis, M. Kerveno, P. Koehler, E. Kossionides, M. Krticka, C. Lamboudis, H. Leeb, A. Lindote, I. Lopes, M. Lozano, S. Lukic, J. Marganiec, S. Marrone, T. Martinez, C. Massimi, P. Mastinu, A. Mengoni, P. M.Milazzo, C. Moreau, M. Mosconi, F. Neves, H. Oberhummer, S. O'Brien, J. Pancin, C. Papachristodoulou, C. Papadopoulos, C. Paradela, N. Patronis, A. Pavlik, P. Pavlopoulos, L. Perrot, M. T. Pigni, R. Plag, A. Plompen, A. Plukis, A. Poch, J. Praena, C. Pretel, J. Quesada, T. Rauscher, R. Reifarth, C. Rubbia, G. Rudolf, P. Rullhusen, J. Salgado, C. Santos, L. Sarchiapone, I. Savvidis, C. Stephan, J. L. Tain, L. Tassan-Got, L. Tavora, R. Terlizzi, G. Vannini, P. Vaz, A. Ventura, D. Villamarin, M. C. Vincente, V. Vlachoudis, R. Vlastou, F. Voss, S. Walter, H. Wendler, M. Wiescher, K. Wisshak
I͡A︡derna fizyka ta enerhetyka,
09/2009, Letnik:
10, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The neutron time of flight (n_TOF) facility at CERN is a neutron spallation source, its white neutron energy spectrum ranges from thermal to several GeV, covering the full energy range of interest ...for nuclear astrophysics, in particular for measurements of the neutron capture cross-section required in s-process nucleosynthesis. This contribution gives an overview on the astrophysical program made at n_TOF facility, the results and the implications will be considered.
The neutron capture cross section of 232Th has been measured relative to σ(n, γ) for 197Au and σ(n,f) for 235U in the energy range from 60 keV to 2 MeV. Neutrons were produced by the 7Li(p,n) and ...T(p,n) reactions at the 4-MV Van de Graaff Accelerator of CEN Bordeaux-Gradignan. The activation technique was used, and the cross section was measured relative to the 197Au(n,γ) standard cross section up to 1 MeV. The characteristic gamma lines of the product nuclei 233Pa and 198Au were measured with a 40% high-purity germanium detector. Above this energy, the reaction 235U(n,f) was also used as a second standard, and the fission fragments were detected with a photovoltaic cell. The results, after applying the appropriate corrections, indicate that the cross sections are close to the JENDL-3 database values up to 800 keV and over 1.4 MeV. For energies in the intermediate range, our values are slightly lower than those from all the libraries. (ANS)
The 151Sm n, gamma 152Sm cross section, which is important for the interpretation of the 151Sm branching as an s-process thermometer, was measured from 1 eV up to 1 MeV at the innovative n_TOF ...facility at CERN. Based on these data, the Maxwellian-averaged cross section at kT=30 keV is found to be 3100pm160 mb. This value can be used to constrain the thermodynamical conditions in Asymptotic Giant Branch (AGB) stars during He-shell burning.
Neutron capture cross sections of the 90,91,92,94,96 Zr have been measured over the energy range from 1 eV to 1 MeV at the spallation neutron facility n_TOF at CERN in 2003. The innovative features ...of the neutron beam, in particular the high instantaneous flux, the high energy resolution and low background, together with improvements of the neutron sensitivity of the capture detectors make this facility unique for neutron-induced reaction cross section measurements with much improved accuracy. The preliminary results of the Zr measurements show capture resonance strengths generally smaller than in previous measurements.
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