Neutron capture reactions on Lu isotopes at DANCE

O Roig,J.-M Daugas,T.A Bredeweg,V Méot,J.L Ullmann,W.A Taylor,R.C Haight,R.S Rundberg,A.J Couture,P Morel,J.M O’Donnell,E.M Bond,A.L Keksis,D.J Vieira,M Jandel,J.M Wouters

doi:10.1051/epjconf/20100205003

Abstract

The DANCE (Detector for Advanced Neutron Capture Experiments) array located at the Los Alamos national laboratory has been used to obtain the neutron capture cross sections for the 175 Lu and 176 Lu isotopes with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process in astrophysics and for applications as in reactor physics or in nuclear medicine. Three targets were used to perform these measurements. One was nat Lu foil and the other two were isotope-enriched targets of 175 Lu and 176 Lu. The cross sections are obtained for now through a precise neutron flux determination and a normalization at the thermal neutron cross section value. A comparison with the recent experimental data and the evaluated data of ENDF/B-VII.0 will be presented. In addition, resonances parameters and spin assignments for some resonances will be featured.

Highlights

Neutron capture cross sections are of current interest in nuclear astrophysics and for the nuclear reaction models
The reaction rates needed for s-process nucleosynthesis are amenable to experimental investigation as the s process follows the valley of beta-stability, making most of the reactions of interest take place on stable isotopes. 175Lu is an important waiting point while 176Lu exhibits a thermally enhanced beta decay rate, making it a sensitive branch point, both for estimating neutron densities as well as temperatures at the nucleosynthesis site [1,2]
The neutron capture reaction rates are obtained by measuring the neutron capture cross section using a neutron spectrum similar to a Maxwell-Boltzmann distribution at a given stellar temperature [3]

Summary

Introduction

Neutron capture cross sections are of current interest in nuclear astrophysics and for the nuclear reaction models. Nuclear data for both topics are crucial to improve the predictive capabilities of the models. The reaction rates needed for s-process nucleosynthesis are amenable to experimental investigation as the s process follows the valley of beta-stability, making most of the reactions of interest take place on stable isotopes. This kind of experiments provides the opportunity to further constraint reaction models obtaining nuclear structure information like resonance spin assignement and level density [4] or testing the gammarays strenght functions [5,6]. To check the predictive capabilities of nuclear reaction models, we have envisaged to pursue performing such experiments on some Lu unstable isotopes as the 173Lu

Methods

Results

Conclusion