Metascintillator pulse shape analysis for optimizing energy and timing
measurements
Abstract
The working principle of metascintillators is based on sharing the
energy of an impinging gamma ray between their composing materials. Such
can be a dense crystal such as LYSO or BGO to maximize the gamma
stopping potential and a fast organic or inorganic compound such as
BC-422, EJ232 or BaF2 for its light production kinetics. In this work we
look into the details of metascintillator pulses as modelled through a
double bi-exponential model. We analyze the extent of energy sharing, as
understood through analysis, simulation and experiment in a coincidence
timing resolution (CTR) measurement setup, using 3x3x15 mm3
metascintillators, against a reference detector. Features of individual
pulses allow choosing the photoelectric interactions and provide insight
on the energy sharing extent of each gamma interaction. We evaluate the
quality of energy sharing surrogates for different metascintillator
designs. Different populations of photoelectric interactions depending
on the extent of energy sharing are defined, that have different
contribution of fast photons in the first picoseconds and hence
different timing. We benchmark this selection through using these
features to apply a timewalk correction on an event-to-event basis. A
significant improvement is demonstrated in all cases, while for a 3:1
volume ratio BGO:EJ232 metascintillator this improvement rises up to
~25% for the whole photopeak (204.7 ps), while the 10%
events with higher production in the fast emitter show a
~50% improvement to 54.7 ps. 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