Influence of secondary neutrons on alpha-particle induced reaction cross section measurement below the Coulomb barrier

TL;DR

This study investigates how secondary neutrons affect alpha-particle activation cross section measurements below the Coulomb barrier, revealing their significant impact and emphasizing the need to account for them in such experiments.

Contribution

The paper introduces a method to quantify secondary neutron effects on activation cross sections below the Coulomb barrier using particle transport simulations and cross section libraries.

Findings

Secondary neutrons significantly influence measured cross sections.

Secondary light charged particles have negligible effect.

High measured cross sections are explained by secondary neutron reactions.

Abstract

The influence of the secondary neutrons on measurements of alpha-particle activation cross sections below the Coulomb barrier was studied for the $^\mathrm{nat}$Pt($\alpha$,x)$^\mathrm{195m}$Pt reaction. We characterized the secondary neutron field by using the particle transport simulation code PHITS, and estimated the $^\mathrm{nat}$Pt(n,x)$^\mathrm{195m}$Pt yields by using the characterized neutron spectra and the $^\mathrm{nat}$Pt(n,x)$^{195m}$Pt cross sections in the JENDL-5/A library. We confirmed that the unexpectedly high $^\mathrm{nat}$Pt($\alpha$,x)$^\mathrm{195m}$Pt cross sections below the Coulomb barrier measured by us are explained well by the $^\mathrm{nat}$Pt(n,x)$^\mathrm{195m}$Pt reaction induced by the secondary neutrons. This indicates that the secondary neutron effect is sometimes not negligible even in low energy charged-particle activation cross section measurements. We also studied the influence of the secondary light charged particles by the same approach, and confirmed that their influence is negligible.