Systematic study of the de-excitation of neutron-rich nuclei produced in different fission reactions

¹ Extreme Light Infrastructure - Nuclear Physics (ELI-NP) / Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 077125 Bucharest-Magurele, Romania
² Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
³ European Commission, DG Joint Research Centre, Directorate G - Nuclear Safety and Security, Unit G.2 Standards for Nuclear Safety, Security and Safeguards, 2440 Geel, Belgium
⁴ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91406 Orsay, France
⁵ Institut Pluridisciplinaire Hubert Curien, 23 rue du Loess, B.P. 28, 67037 Strasbourg Cedex 2, France

^* e-mail: andreas.oberstedt@eli-np.ro

Published online: 15 December 2021

Abstract

In this paper we present results from two recent studies, both related to the emission of prompt fission γ rays. Firstly, we have analyzed data from the reaction ²³⁵U(n, f) induced by fast neutrons of average energy E̅_n = 1.7 MeV. The deduced spectral characteristics are an average multiplicity M̅_γ = 7.11 ± 0.44 γ rays per fission and an average total γ-ray energy release in fission E̅_γ,tot = 5.51 ± 0.46 MeV, corresponding to an average γ-ray energy ɛ̅_γ = 0.77 ± 0.08 MeV. Secondly, we have addressed – and answered – the question how those characteristics in general depend on the width of the chosen prompt time window and the timing resolution, determined by the employed detectors and electronics. The conclusion is that once this is known, it is possible to compare results from different experiments in a more meaningful way.