Monte Carlo modeling of neutron and gamma-ray imaging systems

Abstract

Detailed numerical prototypes are essential to the design of efficient and cost-effective neutron and gamma-ray imaging systems. We have exploited the unique capabilities of an LLNL-developed radiation transport code (COG) to develop code modules capable of simulating the performance of neutron and gamma-ray imaging systems over a wide range of source energies. COG allows us to simulate complex, energy-, angle-, and time-dependent radiation sources, model 3D system geometries with 'real world' complexity, specify detailed elemental and isotopic distributions and predict the responses of various types of imaging detectors with full Monte Carlo accuracy. COG references detailed, evaluated nuclear interaction databases allowing users to account for multiple scattering, energy straggling, and secondary particle production phenomena which may significantly effect the performance of an imaging system but may be difficult or even impossible to estimate using simple analytical models. In this work we will present examples illustrating the use of these routines in the analysis of industrial radiographic systems for thick target inspection, non-intrusive luggage and cargo scanning systems, and international treaty verification.