Development of a Submillimeter Portable Gamma-Ray Imaging Detector, Based on a GAGG:Ce—Silicon Photomultiplier Array
In this study we present the development of a gamma-ray detector based on 1 mm pixel Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillators and a silicon photomultiplier array (ArraySL-4) for possible applications in medical imaging detectors (with focus in PET applications) as well as in personal gamma radiation monitoring applications (with focus on 137Cs radioisotope recognition). A 12 × 12 matrix of pixellated scintillators is coupled to a 4 × 4 pixel elements of a SIPM array covering an active area of 13.4 mm2. Experimental evaluation was carried out with 22Na and 137Cs radioactive sources and the parameters studied were intrinsic spatial resolution, energy resolution and peak-to-valley ratio. ArraySL-4 is a commercially available, 4 × 4 array detector covering an active area of 13.4 mm2. The GAGG:Ce scintillator array used in this study has 1 × 1 × 10 mm3 pixel size elements with 0.1 mm thickness white BaSO4 reflector material between the crystals. A symmetric resistive charge division matrix was applied reducing array’s 16 outputs to 4 position signals. A Field Programmable Gate Array (FPGA) Spartan 6 LX150T was used for triggering and signal processing of the signal pulses digitized using free running Analog to Digital Converters. Raw images and horizontal profiles of the 12 × 12 GAGG:Ce scintillator array produced under 511 keV and 662 keV excitation are illustrated. Moreover, the energy spectra obtained with 22Na and 137Cs radioactive sources are shown. All GAGG:Ce central pixels were separated in the 2-dimensional position histograms providing submillimeter intrinsic spatial resolution with an average peak-to-valley (P/V) ratio of 1.75 for 511 keV and P/V ratio 1.85 for 662 keV. The energy resolution was 16.9% for 511 keV and 14% for 662 keV. Those encouraging results, prove that this system could build up to a compact miniature 137Cs spectrometer (with 2D isotope mapping capability) for homeland security applications as well as can be used in small animal imaging PET detector systems.
This research is implemented through IKY scholarships programme and co-financed by the European Union (European Social Fund—ESF) and Greek national funds through the action entitled” Reinforcement of Postdoctoral Researchers”, in the framework of the Operational Programme” Human Resources Development Program, Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) 2014–2020.
We would like to thanks Prof. S. Majewski who has provided us the GAGG:Ce matrix as well as Dr. L. Fysikopoulos and Dr. M. Georgiou for their contribution in read out signal processing and front end electronics.
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