Studies of fission fragment yields via high-resolution γ-ray spectroscopy

¹ Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex, France
² European Commission, Joint Research Centre, Directorate G for Nuclear Safety and Security, Unit G.I.5, Postfach 2340, 76215 Karlsruhe, Germany
³ Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA 94550, USA
⁴ Subatech/Ecole des Mines, 4 rue Alfred Kastler, 44307 Nantes, France
⁵ Department of Physics, University of Surrey, Guildford, GU2 7XH, UK
⁶ Institute for Nuclear and Radiation Physics, KU Leuven, 3000 Leuven, Belgium
⁷ Irfu, CEA, Université Paris Saclay, 91191 Gif-sur-Yvette Cedex, France
⁸ CSNSM Orsay, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
⁹ INFN Laboratori Nazionali di Legnaro, Viale dell'Universita, 2, 35020 Legnaro, Italy
¹⁰ Institut für Kernphysik, Zülpicher Strasse 77, 50937 Köln, Germany
¹¹ University of Oslo, Department of Physics, P.O. Box 1048, Blindern 0316 Oslo, Norway
¹² National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
¹³ LMU München, Schellingstrasse 4, 80799, Munich, Germany
¹⁴ CEA/DAM, DIF, Bruyères-le-chètel, 91297 Arpajon, France
¹⁵ CENBG Bordeaux, Chemin du Solarium, Le Haut Vigneau, BP. 120, 33175 Gradignan, France
¹⁶ Extreme Light Infrastructure - Nuclear Physics (ELI-NP), 077125 Bucharest-Magurele, Romania
¹⁷ European Commission, Joint Research Centre, Directorate G for Nuclear Safety and Security, Unit G.2, 2440 Geel, Belgium
¹⁸ CEA Cadarache, 13108 Saint-Paul-lez-Durance, France
¹⁹ University of Manchester, Dept. Of Physics, Oxford Road, Manchester, M13 9PL, UK

Published online: 6 March 2018

Abstract

Precise spectroscopic information on the fast neutron induced fission of the ²³⁸U(n,f) reaction was recently gained using a new technique which involved coupling of the Miniball high resolution y-ray spectrometer and the LICORNE directional neutron source. The experiment allowed measurement of the isotopic fission yields for around 40 even-even nuclei at an incident neutron energy of around 2 MeV where yield data are very sparse. In addition spectroscopic information on very neutron-rich fission products was obtained. Results were compared to models, both the JEFF-3.1.1 data base and the GEF code, and large discrepancies for the S1 fission mode in the Sn/Mo isotope pair were discovered. This suggests that current models are overestimating the role played by spherical shell effects in fast neutron induced fission. In late 2017 and 2018 the nu-ball hybrid spectrometer will be constructed at the IPN Orsay to perform further experimental investigations with directional neutrons coupled to a powerful hybrid Ge/LaBr3 detector array. This will open up new possibilities for measurements of fission yields for fast-neutron-induced fission using the spectroscopic technique and will be complimentary to other methods being developed.