Simulation of nuclear resonance fluorescence in Geant4

Ongoing research at Pacific Northwest National Laboratory (PNNL) is assessing the utility of exploiting nuclear resonance fluorescence (NRF) to detect bulk samples of special nuclear materials, high explosives, and related illicit cargo constituents in a variety of cargo inspection scenarios. PNNL has developed a Monte Carlo radiation transport simulation capability for studying the NRF signal response in order to facilitate computational studies of these inspection scenarios. The simulation framework implements NRF as a new physics process, "G4NRF," in the Geant4 modeling toolkit, and leverages the Evaluated Nuclear Structure Data File (ENSDF) database of nuclear level properties to determine isotope-specific parameters of the NRF response model in general cargo constituents. The G4NRF package has been benchmarked against bremsstrahlung photon-beam data collected at the University of California at Santa Barbara's 5.3 MeV accelerator. A series of cargo-inspection scenario studies utilizing the NRF simulation package is currently in progress.