Benchmarking Geant4 for Simulating Galactic Cosmic Ray Interactions Within Planetary Bodies

TL;DR

This paper evaluates the accuracy of the Geant4 simulation code in modeling galactic cosmic ray interactions within planetary bodies by comparing its results to lunar neutron data, highlighting the importance of physics assumptions.

Contribution

It provides a systematic benchmarking of Geant4 against lunar neutron data and explores how different physics models affect simulation accuracy.

Findings

Geant4 over-predicts lunar neutron data generally.

Some physics lists in Geant4 perform better than others.

MCNP6 results are similar to Geant4 simulations.

Abstract

Galactic cosmic rays undergo complex nuclear interactions with nuclei within planetary bodies that have little to no atmosphere. Radiation transport simulations are a key tool used in understanding the neutron and gamma-ray albedo coming from these interactions and tracing these signals back to geochemical composition of the target. We study the validity of the code Geant4 for simulating such interactions by comparing simulation results to data from the Apollo 17 Lunar Neutron Probe Experiment. Different assumptions regarding the physics are explored to demonstrate how these impact the Geant4 simulation results. In general, all of the Geant4 results over-predict the data, however, certain physics lists perform better than others. In addition, we show that results from the radiation transport code MCNP6 are similar to those obtained using Geant4.