Event coincidences in 3D gamma ray semiconductor detector

• Published in: IEEE conference record - Nuclear Science Symposium & Medical Imaging Conference. p. 1
• Main Authors: Terenzi, L., Rieger, E., Danielsson, M.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 26.10.2024
• Subjects: Estimation; Gamma-rays; Hardware; Kinematics; Microwave integrated circuits; Semiconductor detectors; Three-dimensional displays
• ISSN: 2577-0829
• DOI: 10.1109/NSS/MIC/RTSD57108.2024.10657658

This work investigates event coincidences in a three-dimensional semiconductor detector for gamma rays with energy 140 keV and 510 keV using GEANT4 for activities ranging from 5 MBq to 500 MBq. The semiconductor detector is assumed to have an area of 400 \mathrm{~cm}^{2} and a thickness of either 2 cm or 5 cm. We further assumed a point like source 15 cm from the detector embedded in a water cylinder with diameter 30 cm, while the voxel size in the semiconductor detector was set to be 25 \times 25 \times 700 \mu^{3}. Given the recoil electron track estimations, it was also possible to estimate in each interaction the corresponding hit map for the voxels. The events used for the analysis in this work are determined by a gamma ray interacting at least once in the detector, concluding its track with either a photoabsorption or an escape. Each event volume was approximated with a sphere centered in the centroid of the interaction points, having as radius the distance between such center and the furthest interaction from it. Then each temporal coincidence of two events was divided in three different cases: overlap of the volumes, surface of the spheres closer than 2 cm, or than 5 cm. This was done to estimate how many temporally coincident events could be spatially separated as distinct events with a future algorithm and kinematic considerations. The resulting number of events not resolved due to temporal coincidence remained below 26 \% even at 500 MBq, while this percentage can be further reduced up to less than 4 \%, with the spatial volume analysis. The results are important input to future hardware development of three-dimensional gamma ray detectors.