Fission Fragment Angular Distribution measurements of ²³⁵U and ²³⁸U at CERN n_TOF facility

¹ Universidade de Santiago de Compostela (USC), Spain
² Centre National de la Recherche Scientifique/IN2P3 - IPN, Orsay, France
³ Johann-Wolfgang-Goethe Universität, Frankfurt, Germany
⁴ Uniwersytet Lódzki, Lodz, Poland
⁵ Istituto Nazionale di Fisica Nucleare, Bari, Italy
⁶ Centro de Investigaciones Energeticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
⁷ Charles University, Prague, Czech Republic
⁸ Commissariat à l’Énergie Atomique (CEA) Saclay - Irfu, Gif-sur-Yvette, France
⁹ European Organization for Nuclear Research (CERN), Geneva, Switzerland
¹⁰ University of Manchester, Oxford Road, Manchester, UK
¹¹ Department of Physics, Faculty of Science, University of Zagreb, Croatia
¹² Universitat Politecnica de Catalunya, Barcelona, Spain
¹³ CTN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Lisboa, Portugal
¹⁴ Universidad de Sevilla, Spain
¹⁵ National Technical University of Athens (NTUA), Greece
¹⁶ Instituto de Física Corpuscular, CSIC-Universidad de Valencia, Spain
¹⁷ Paul Scherrer Institut, Villigen PSI, Switzerland
¹⁸ Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro Italy
¹⁹ Aristotle University of Thessaloniki, Thessaloniki, Greece
²⁰ Bhabha Atomic Research Centre (BARC), Mumbai, India
²¹ Atominstitut, Technische Universität Wien, Austria
²² University of York, Heslington, York, UK
²³ Karlsruhe Institute of Technology, Campus Nord, Institut für Kernphysik, Karlsruhe, Germany
²⁴ Department of Physics, University of Oslo, N-0316 Oslo, Norway
²⁵ University of Vienna, Faculty of Physics, Austria
²⁶ Dipartimento di Fisica, Università di Bologna, and Sezione INFN di Bologna, Italy
²⁷ Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile (ENEA), Bologna, Italy
²⁸ Istituto Nazionale di Fisica Nucleare, Trieste, Italy
²⁹ Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH) Bucharest-Magurele, Romania
³⁰ IRMM, European Commission JRC, Retieseweg 111, B-2440 Geel, Belgium
³¹ Department of Physics and Astronomy - University of Basel, Basel, Switzerland
³² Department of Physics and Astronomy, Uppsala University, Sweden
³³ JAEA, Japan
³⁴ CAR, School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
³⁵ Research School of Physics and Engineering, Australian National University, Australia

^a e-mail: esther.leal@usc.es

Published online: 15 March 2016

Abstract

Neutron-induced fission cross sections of 238U and 235U are used as standards in the fast neutron region up to 200 MeV. A high accuracy of the standards is relevant to experimentally determine other neutron reaction cross sections. Therefore, the detection effciency should be corrected by using the angular distribution of the fission fragments (FFAD), which are barely known above 20 MeV. In addition, the angular distribution of the fragments produced in the fission of highly excited and deformed nuclei is an important observable to investigate the nuclear fission process.

In order to measure the FFAD of neutron-induced reactions, a fission detection setup based on parallel-plate avalanche counters (PPACs) has been developed and successfully used at the CERN-n_TOF facility. In this work, we present the preliminary results on the analysis of new ²³⁵U(n,f) and ²³⁸U(n,f) data in the extended energy range up to 200 MeV compared to the existing experimental data.