Metascintillator pulse feature and shape analysis to detect photoelectric interactions and energy sharing

Abstract Metascintillators are scintillator topologies whose principle is based on sharing the energy of an impinging gamma ray between their composing materials. These can be a dense crystal such as LYSO or BGO to retain a high gamma absorption probability, and a fast-emitting compound such as BC-422, EJ232 or BaF 2 contributing to its light production kinetics. In this work, we look into the details of metascintillator pulse formation as modelled by a double bi-exponential shape. We analyze the extent of energy sharing through analysis, simulation and experiment in a coincidence timing resolution (CTR) measurement setup, using 3×3×15 mm 3 metascintillators, compared against a LYSO:Ce:Ca 3×3×5 mm 3 reference detector. Features of individual pulses allow us to choose the photoelectric interactions and provide insight into the extent of energy sharing for each gamma interaction. We evaluate the quality of energy sharing surrogates for different metascintillator designs. Different populations of photoelectric interactions are defined based on the extent of energy sharing. These populations have different production rates of fast photons in the first picoseconds and hence significantly different timing capabilities. We benchmark this selection by using the features to apply a timewalk correction. For a 3:1 volume ratio BGO:EJ232 metascintillator, improvement rises up to ∼25% for the whole photopeak, from 280.1 ps to 204.7 ps, while the 10% events with higher production in the fast emitter show a ∼50% improvement, from 106 ps to 54.7 ps. These results are compared with other tested metascintillators. This shows that while metascintillators with comparable light yield components still provide the best alternative, it is possible through simple pulse analysis to measure and isolate the photoelectric interactions in every metascintillator with two components.