Development of an Event Tracking Feature in OpenMC for Neutron Spectroscopy and Scatter Camera Systems

This paper presents the development and application of an event tracking feature within the OpenMC Monte Carlo code, designed for advanced neutron spectroscopy and scatter camera system simulations. The newly implemented feature enables the tracking of individual neutron collisions, with potential applications in nuclear non-proliferation, reactor physics, and nuclear security. Additionally, the feature holds potential for the calibration of neutron detectors, specifically in converting light output into energy deposited within the detectors. The implementation consists of a set of filters - such as reaction type, energy, cell, and material - that constrain the set of events that are tracked, a tie-in to the Python API to enable simple user input formats, and different file format saving options as OpenMC’s native HDF5-based format or Monte Carlo particle lists (MCPL). This feature is still in development and is not yet part of an OpenMC release; it remains subject to change. The verification of the new feature is performed using a model of an optically segmented scatter camera exposed to a 252Cf source. We apply the time-of-flight analysis technique to extract the neutron spectrum and infer the direction of the incoming source by the simple back-projection method.