Development of a 3-D Position Sensitive Gamma-ray Imaging Detector based on Multi-layer Ceramic Scintillators with Double-side SiPM Readout

Gamma-ray imaging detectors can provide directional information of the radiation by detecting the interacting points and the deposited energy values of gamma-rays. Scintillator-based imaging detectors are very useful in national and homeland security applications for their high detection efficiency, easy operation and robustness. A 2-D array of long scintillator bars can provide the energy and 3-D position information of multi-site gamma-ray events using the depth of interaction (DOI) technique and independent readout of each scintillator bar. A detector based on such a 2-D array is developed by combining several layers of scintillators. The gap of the adjacent layers can be adjusted for different applications: a nearly zero gap leads to a multi-site event sensitive 3-D detector with 4π field of view; a large gap (e.g., 10-20 mm) can be used in high efficiency high angular resolution Compton imaging. Each layer is a row of sixteen 3.0 mm × 3.0 mm × 48.0 mm ceramic Ce:GAGG scintillator bars, which are independently read out by 32 SiPMs and two 16-ch ASICs (IDEAS IDE3380) from both sides. The use of ceramic scintillators greatly facilitates the processing of the bars. A
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Co source is used to test the basic performances of each unit. The DOI and energy information is derived from the amplitudes of both ends. The DOI resolution is measured to be between 4 mm FWHM with 1 mm slit collimating at different positions. The energy resolution is measured to be 18.5% FWHM at 122 keV without collimating. Monte Carlo simulations are carried out based on the measured DOI and energy resolution. The intrinsic efficiency and angular resolution at certain layer pitch are estimated using different position resolution values.