Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides

D Ramos,X Derkx,C Paradela,T Roger,C Schmitt,A Dijon,M Rejmund,D Cortina,B Jacquot,L Audouin,A Navin,O Delaune,F Farget,M Caamaño,J Benlliure,D Doré,E Casarejos,A Heinz,M D Salsac ,C Rodríguez‐Tajes ,E Clément ,B Fernández–Domínguez

doi:10.1051/epjconf/201611110001

Abstract

Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a U-238 beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of Cf-250, Cm-244, Pu-240, Np-239 and U-238 are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.

Highlights

The fission of the nucleus is a complex process where intrinsic excitation energy transforms into a large deformation until the nucleus splits
Data on five different fissioning systems are reported in this work: 250Cf, produced in fusion reactions with a well-defined excitation energy of 46 MeV, 244Cm,240Pu, 239Np, and 238U, produced in transfer reactions with distributions of excitation energy centered at 23 MeV, 10.7 MeV, 7.5 MeV, 7.4 MeV respectively, with a full width at half maximum of approximately 8 MeV [7]
The reconstruction of the fission-induced reactions and the isotopic identification of their fission products show the evolution of the characteristics of the fragments as a function of the available excitation energy of the fissioning system

Summary

Introduction

The fission of the nucleus is a complex process where intrinsic excitation energy transforms into a large deformation until the nucleus splits. The present work, based on the use of inverse kinematics, provides a new set of measurements that relates the excitation energy of the fissioning system, produced either by fusion or transfer reactions, to the characteristics of the full isotopic fragment distribution. These new measurements for fissioning systems, some of them not accessible with any other technique, provide nuclear data, important for nuclear energy applications, such as the development of next-generation nuclear reactors or the recycling of radioactive waste

Experimental Setup

Fission Products

Conclusions and outlook