Development of a positron emission particle tracking system

We present the development of a cost-effective detector system for positron emission particle tracking (PEPT) inside dense granular media [1, 2, 3]. The detector is based on the coincident detection of the two back-to-back 511keV gamma rays produced by electron-positron annihilation. In contrast to most PET systems, which typically employ inorganic crystal scintillators, our design uses elongated organic scintillator bars that are read out at both ends by 2 × 2 arrays of silicon photomultipliers (SiPMs). The detector consists of four modular walls, each comprising 22 scintillator bars, surrounding an observation volume of approximately 0.5m × 0.5m × 1m. In this work, the position of a stationary radioactive positron source is reconstructed using the first commissioned detector configuration, consisting of two opposing walls with every second scintillator bar instrumented. The complete detector readout chain and the data processing and reconstruction algorithms are presented in detail. By exploiting precise timing information from the scintillation signals, the annihilation position is reconstructed using consecutive time-of-flight (ToF) analyses. The experimental results are compared with previously published Monte Carlo simulations of the same detector configuration. Although only one quarter of the final detector is currently operational, the reconstructed source position exhibits a root mean square deviation below 3.2mm. These results demonstrate the feasibility of the proposed detector concept and provide a strong experimental foundation for the completion of the full four-wall PEPT system.