Angular distribution of fragments in neutron-induced nuclear fission at energies 1−200 MeV: Data, theoretical models and relevant problems

Alexey Barabanov,Alexei Gagarski,Oleg Shcherbakov,Alexander Vorobyev,Larisa Vaishnene

doi:10.1051/epjconf/202125600003

Abstract

In recent years, investigations of angular distributions of fragments in neutron-induced nuclear fission have been extended to intermediate energies, up to 200 MeV, as well as to a wide range of target isotopes. Using as an example the latest data obtained by our group for the reaction 237Np(n; f), we discuss the specific features of fission fragment angular distribution and present a method for their simulation based on the code TALYS. It is shown that a simplified model reasonably describes energy dependence of the angular distribution in the whole range 1–200 MeV. The ways to improve the model are discussed along with the possibilities to use it for obtaining new information on fission and pre-equilibrium processes in neutron-nucleus interaction. We consider also the relevant problems of describing fission fragment angular distributions.

Highlights

Within the last five years we have studied angular distributions of fragments in neutron induced fission at energies 1–200 MeV for the following isotopes: 232Th, 235U, 238U [1], 209Bi, 233U [2], natPb, 239Pu [3], and 237Np [4]
Angular distributions of fragments in neutron-induced nuclear fission have attracted the attention of researchers for many decades
Invetigations have been extended to intermediate energies, up to 200 MeV, as well as to a wide range of target isotopes

Summary

Introduction

Within the last five years we have studied angular distributions of fragments in neutron induced fission at energies 1–200 MeV for the following isotopes: 232Th, 235U, 238U [1], 209Bi, 233U [2], natPb, 239Pu [3], and 237Np [4] (see [5, 6]). Similar investigations were performed by collaborations n TOF and NEFFTE for target nuclei 232Th [9], 235U, 238U [10] and 235U [11], respectively These studies are of significance because almost all earlier obtained data on fission fragment angular distributions refer to the energy region below 20 MeV; only in the work [12] the angular anisotropy of fragments in neutron induced fission of 232Th and 238U was measured up to the energy 100 MeV. The angular distribution of fragments is among observables, which are the most sensitive to the transition states characteristics, in particular, to the K value This circumstance resulted in intensive experimental studies of fission fragment angular anisotropy during 2–3 decades after discovery of this phenomenon in the energy region below 20 MeV available at that time (see, e.g., [14]). We consider the relevant problems in this field and perspectives for the development

Total fission cross section

Fission fragment angular distribution

C JJKK Q0

Model for angular distribution of fragments

Results and discussion

Summary