Simulation study on event positioning algorithm of fast neutron imaging detector based on scintillating fiber and SiPM array

A miniaturized fast neutron imaging detector based on scintillating fiber (Sci-Fi) is designed to adopt a SiPM array as its photoelectric conversion component. The center of gravity (CoG) method, widely used for neutron event positioning, demonstrates limited effectiveness when applied to signals originating from the peripheral regions of the array. To address this issue, the present study conducted a simulation analysis of the light output distribution characteristics from both the Sci-Fi and the associated light guide using the Geant4 toolkit. The photon distribution functions fitted for various regions all exhibited correlation coefficients exceeding 0.99. Furthermore, this work categorized the deviations encountered during the operation of the imaging detector into three principal types: inherent deviations, hardware-induced deviations, and algorithmic deviations. Focusing on algorithmic deviations, scintillation photon events randomly distributed within the Sci-Fi array were simulated. An inversion method, developed based on the photon distribution function, employed an iterative computational approach to accurately determine event positions by optimizing the fit. Compared to the CoG method, the inversion technique achieves a reduction in average positional deviation by over 13%, sustains robust positioning performance for events occurring near the array edges, enhances the effective utilization of the SiPM array, and is well-suited for applications demanding higher spatial resolution and an expanded field of view.