Using CGMF to estimate corrections for fission yields measured via γ-ray spectroscopy

P Jaffke,N Fotiades,P Talou,M Devlin

doi:10.1051/epjconf/202024203003

Abstract

Fission product yields have been inferred using γ-ray spectroscopy for several decades. Typically, these efforts have focused on even-Z even-A fission products as their nuclear structure are less complicated. To further simplify the situation, it is often assumed that no side-feeding to the ground-state occurs and multiplicity cuts have a negligible effect on the inferred yields. Using CGMF, a Hauser-Feshbach statistical decay model for the primary fission fragments, we estimate the impact of these assumptions and determine corrections for specific fission product yields. We report on these corrections and investigate their sensitivity to various nuclear parameters, specifically the spin distribution of the fission fragments and the assumed nuclear structure. Our results indicate that even in the simplest of cases, say the 2+ → 0+ transitions in even-Z even-A fragments, average level corrections are on the order of 75%.

Highlights

Gamma-ray spectroscopy has been utilized to infer fission yields for a variety of nuclear reactions [1,2,3,4]
Prompt γ-ray emissions are sensitive to the independent fission product yields, while later γ-ray emissions after β-decay are more sensitive to cumulative yields
The open squares show the inferred yields from a summation of the 4+ → 2+ transition photopeak over all CGMF events for each even-Z even-A fission product for 235U(nth, f ). These results take into account the typical energy resolution of a Ge detector and utilize a νγT ≥ 3 multiplicity cut, a conservative estimate in Ge detector arrays not spanning a 4π solid angle [26]

Summary

Introduction

Gamma-ray spectroscopy has been utilized to infer fission yields for a variety of nuclear reactions [1,2,3,4]. Experimental assumptions and corrections must be applied to the data in order to properly account for energy resolution, nuclear transition strengths, and multiplicity cut effects. For prompt γ rays, fission products are generated with a distribution in excitation energy and spin. This distribution further complicates the necessary corrections. We present preliminary calculations of three potential corrections required for prompt γ-ray spectroscopy and outline a procedure for a given experimental setup. The multiplicity correction arises when experimental cuts are applied to either reduce the data rate or provide more assurance of a fission coincidence.

Hauser-Feshbach de-excitation

Corrections for prompt γ rays

Results

Conclusion