Speaker
Description
The use of radioactive materials has been expanding across various fields, increasing the risk of radiation accidents, such as loss or theft. In such cases, a monitoring system capable of both source localization and radionuclide identification is essential [1]. However, conventional directional radiation monitoring systems are limited by a narrow field of view and difficulty in real-time monitoring of multiple sources. To overcome these limitations, we propose a depth-of-interaction (DOI)-based directional radiation monitoring system that provides real-time radionuclide identification and directional information for multiple sources over a 360° field of view [2]. In this study, we experimentally evaluate the feasibility of the proposed system using a fabricated prototype and simplified accident scenarios.
The system consists of a 1″×4″ CsI:Tl scintillator, two photomultiplier tubes (PMTs) attached to both ends, and a multi-slot lead collimator (Fig. 1(a)). Each collimator slot was designed with a specific height and direction. Gamma rays passing through a slot interact at a specific depth in the scintillator, and the interaction position is determined using a dual-ended DOI method based on the amplitude ratio of the two PMT signals. Measured events are classified according to interaction depth, and the resulting energy spectra and distribution images are used to infer the source direction.
Feasibility was evaluated through experiments involving multiple sources of the same radionuclide placed at different directions and intensities. Analysis of the acquired data using energy spectra and radiation distribution maps demonstrated that individual source directions could be distinguished even under multiple-source conditions. This enabled identification of relative directions and intensity differences between sources (Fig. 1(b)), verifying the feasibility of the proposed system for directional radiation detection.