High-accuracy Geant4 simulation and semi-analytical modeling of nuclear resonance fluorescence

Abstract

Nuclear resonance fluorescence (NRF) is a photonuclear interaction that enables highly isotope-specific measurements in both pure and applied physics scenarios. High-accuracy design and analysis of NRF measurements in complex geometries is aided by Monte Carlo simulations of photon physics and transport, motivating Jordan and Warren (2007) to develop the G4NRF codebase for NRF simulation in Geant4. In this work, we enhance the physics accuracy of the G4NRF code and perform improved benchmarking simulations. The NRF cross section calculation in G4NRF, previously a Gaussian approximation, has been replaced with a full numerical integration for improved accuracy in thick-target scenarios. A high-accuracy semi-analytical model of expected NRF count rates in a typical NRF measurement is then constructed and compared against G4NRF simulations for both simple homogeneous and more complex heterogeneous geometries. Agreement between rates predicted by the semi-analytical model and G4NRF simulation is found at a level of ∼1% in simple test cases and ∼3% in more realistic scenarios, improving upon the ∼20% level of the initial benchmarking study and establishing a highly-accurate NRF framework for Geant4.

Monte Carlo Simulation of γ − γ Correlation Functions

“…For example, Jordan and Warren [7] and Hayakawa et al [8] developed a Monte Carlo simulation for the NRF process. More recently, Vavrek et al [9,10] have upgraded the simulation model of Jordan and Warren to enhance its accuracy. They have tested the simulation model, which lowered the discrepancy between the simulation and experiment to approximately 15%.…”