Optimizing the Position of Inorganic Scintillators in a Handheld Dual Particle Imager

This work details an optimization process for incorporating inorganic scintillators into a stilbene-based handheld dual particle imager (H2DPI). A prototype H2DPI composed of eight stilbene pillars with dimensions of 6 x 6 x 50.5 mm3 coupled to silicon photomultipliers has been built and is capable of imaging both neutrons and gamma rays emitted by special nuclear material. Gamma-ray imaging with the prototype was performed using an approximate Compton imaging method due to lack of photoelectric absorption of gamma rays in stilbene. Incorporation of inorganic scintillators significantly increases the probability of photoelectric absorption, allowing for Compton imaging. Simulations were made for several geometries where the placement of CeBr3 scintillators was varied to analyze how the system geometry impacts the image quality of simulated measurements. These were compared to a step function using a structural similarity index to determine which system geometry produced the optimal images. It was found that placing the CeBr3 scintillators in the corners of the system produced the best gamma-ray images while maintaining high neutron double-scatter efficiency.