Effects of microscopic transport coefficients on fission observables calculated by Langevin equation and its systematics

Mark Usang,Chikako Ishizuka,Satoshi Chiba,Fedir Ivanyuk,A Plompen,P Siegler,S Oberstedt,J Heyse,S Kopecky,W Mondelaers,P Schillebeeckx,F.-J Hambsch

doi:10.1051/epjconf/201714604025

Abstract

The Langevin dynamical description of fission observables is inspired by the random evolution of shape parameters across the potential surface. In these work, we shall use mass and friction tensors inspired from Linear Response Theory (microscopic transport coefficients) and obtain the fission observables associated with these calculations. We compare these microscopic results with calculations using hydrodynamical mass tensor and wall-window friction tensor (macroscopic transport coefficients). We are able to calculate the fission product yield, Coulomb kinetic energy and prescission kinetic energy from the Langevin calculation. This allows us to observe the systematic of average light and heavy mass fission product yield calculated using both microscopic and macroscopic calculations. We also compare the results of microscopic and macroscopic calculation total kinetic energy (TKE) with Viola's TKE systematics. In the case of 236,239 U compound nucleus, we do the microscopic calculation for several excitation energy up to 30 MeV and afterwards compare it to the TKE of experimental data and corresponding macroscopic TKE. Reasonable agreement of microscopic TKE to experiment is obtained which shows decreasing TKE with increasing excitation energy. Macroscopic TKE however, is independent of excitation energy and thus contrary to experimental data.

Highlights

Linear response theory [1,2,3,4] allowed us to obtain microscopic mass and friction tensor for a nucleus under perturbation such as in nuclear fission from the response function of these perturbations
[9], we have shown for 236U detailed analysis of the fission observables calculated using Langevin equation with microscopic transport coefficients
We are able to show that the total kinetic energy (TKE) of 239,236U compound nucleus at various excitation energy are roughly consistent with experimental results at various incident energy by assuming that the excitation energy of the compound nucleus for the actinides in experimental is Kinetic Energy, MeV

Summary

Introduction

Linear response theory [1,2,3,4] allowed us to obtain microscopic mass and friction tensor for a nucleus under perturbation such as in nuclear fission from the response function of these perturbations. The coefficient gμν is related to friction tensor and temperature via the Einstein relation gμσ gσ ν = T γμν. We call this temperature the local temperature to differentiate it with the transport temperature, Ttr which is used in the calculation of microscopic mass, mμν and friction tensor, γμν. Eint is related to the excitation energy, Ex and level density parameter, a using the relationship, The collective coordinates; z0 is the elongation of the nucleus, R0 the radius of spherical compound nucleus, δ is the deformation of fragments, and α is the mass asymmetry. [9], we have shown for 236U detailed analysis of the fission observables calculated using Langevin equation with microscopic transport coefficients

Mass yield systematics

Total kinetic energy systematics

Excitation energy dependence

Conclusion