Measurement of the α ratio and (n, γ) cross section of 235U from 0.2 to 200 eV at n_TOF

J. Balibrea-Correa, E. Mendoza, D. Cano-Ott, E. González, R. Capote, M. Krtička, S. Altstadt, J. Andrzejewski, L. Audouin, V. Bécares, M. Barbagallo, F. Bečvář, F. Belloni, E. Berthoumieux, J. Billowes, V. Boccone, D. Bosnar, M. Brugger, M. Calviani, F. Calviño, C. Carrapiço, F. Cerutti, E. Chiaveri, M. Chin, N. Colonna, G. Cortés, M. A. Cortés-Giraldo, M. Diakaki, C. Domingo-Pardo, R. Dressler, I. Durán, C. Eleftheriadis, A. Ferrari, K. Fraval, V. Furman, K. Göbel, M. B. Gómez-Hornillos, S. Ganesan, A. R. García, G. Giubrone, I. F. Gonçalves, A. Goverdovski, E. Griesmayer, C. Guerrero, F. Gunsing, T. Heftrich, A. Hernández-Prieto, J. Heyse, D. G. Jenkins, E. Jericha, F. Käppeler, Y. Kadi, D. Karadimos, T. Katabuchi, V. Ketlerov, V. Khryachkov, N. Kivel, P. Koehler, M. Kokkoris, J. Kroll, C. Lampoudis, C. Langer, E. Leal-Cidoncha, C. Lederer, H. Leeb, L. S. Leong, J. Lerendegui-Marco, R. Losito, A. Mallick, A. Manousos, J. Marganiec, T. Martínez, C. Massimi, P. Mastinu, M. Mastromarco, A. Mengoni, P. M. Milazzo, F. Mingrone, M. Mirea, W. Mondelaers, C. Paradela, A. Pavlik, J. Perkowski, A. J.M. Plompen, J. Praena, J. M. Quesada, T. Rauscher, R. Reifarth, A. Riego-Perez, M. Robles, C. Rubbia, J. A. Ryan, M. Sabaté-Gilarte, R. Sarmento, A. Saxena, P. Schillebeeckx, S. Schmidt, D. Schumann, P. Sedyshev, G. Tagliente, J. L. Tain, A. Tarifeño-Saldivia, D. Tarrío, L. Tassan-Got, A. Tsinganis, S. Valenta, G. Vannini, V. Variale, P. Vaz, A. Ventura, M. J. Vermeulen, V. Vlachoudis, R. Vlastou, A. Wallner, T. Ware, M. Weigand, C. Weiss, T. Wright, P. Žugec

We measured the neutron capture-to-fission cross-section ratio (α ratio) and the capture cross section of U235 between 0.2 and 200 eV at the n_TOF facility at CERN. The simultaneous measurement of neutron-induced capture and fission rates was performed by means of the n_TOF BaF2 Total Absorption Calorimeter (TAC), used for detection of γ rays, in combination with a set of micromegas detectors used as fission tagging detectors. The energy dependence of the capture cross section was obtained with help of the Li6(n,t) standard reaction determining the n_TOF neutron fluence; the well-known integral of the U235(n,f) cross section between 7.8 and 11 eV was then used for its absolute normalization. The α ratio, obtained with slightly higher statistical fluctuations, was determined directly, without need for any reference cross section. To perform the analysis of this measurement we developed a new methodology to correct the experimentally observed effect that the probabilities of detecting a fission reaction in the TAC and the micromegas detectors are not independent. The results of this work have been used in a new evaluation of U235 performed within the scope of the Collaborative International Evaluated Library Organisation (CIELO) Project, and are consistent with the ENDF/B-VIII.0 and JEFF-3.3 capture cross sections below 4 eV and above 100 eV. However, the measured capture cross section is on average 10% larger between 4 and 100 eV.

Isotope Physics
External organisation(s)
Centro de Investigaciones Energeticas Medioambientales y Tecnológica, Charles University Prague, Johann Wolfgang Goethe-Universität Frankfurt am Main, University of Lodz, Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Fisica Nucleare (INFN), Roma, Université Paris-Saclay, University of Manchester, European Organization for Nuclear Research (CERN), University of Zagreb, Universitat Politècnica de Catalunya, Universidad de Sevilla, National Technical University of Athens (NTUA), Universitat de València, Paul Scherrer Institute, Universidade de Santiago de Compostela (USC), Aristotle University of Thessaloniki, Dubna, Bhabha Atomic Research Centre, Obninsk, Technische Universität Wien, European Commission JRC, York University, Karlsruher Institut für Technologie, Tokyo Institute of Technology (TIT), Oak Ridge National Laboratory , Università degli Studi di Catania, Università degli Studi di Bologna, Istituto Nazionale di Fisica Nucleare (INFN), Legnaro, Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Perugia, ENEA Centro Ricerche Bologna, Università degli Studi di Trieste, Horia Hulubei Natl Inst R&D Phys & Nucl Engn IFIN, Horia Hulubei National Institute of Physics & Nuclear Engineering, Extreme Light Infrastruct Nucl Phys, Universität Basel, Australian National University, International Atomic Energy Agency (IAEA), Instituto Superior Técnico, Associação EURATOM/IST
Physical Review C
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103014 Nuclear physics
ASJC Scopus subject areas
Nuclear and High Energy Physics
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