Modification on thermal motion in Geant4 for neutron capture simulation in Gadolinium loaded water

TL;DR

This paper addresses discrepancies in neutron capture simulation in Geant4 by modifying thermal motion modeling, resulting in improved accuracy aligned with nuclear data and experimental observations.

Contribution

The study introduces a manual modification to Geant4's thermal motion implementation, enhancing neutron capture simulation accuracy in Gadolinium-loaded water.

Findings

Modified Geant4 aligns with nuclear data calculations

Improved neutron detection efficiency simulation

Good agreement with SK-Gd observational data

Abstract

Neutron tagging is a fundamental technique for electron anti-neutrino detection via the inverse beta decay channel. A reported discrepancy in neutron detection efficiency between observational data and simulation predictions prompted an investigation into neutron capture modeling in Geant4. The study revealed that an overestimation of the thermal motion of hydrogen atoms in Geant4 impacts the fraction of captured nuclei. By manually modifying the Geant4 implementation, the simulation results align with calculations based on evaluated nuclear data and show good agreement with observables derived from the SK-Gd data.