Development of muon radiography system using a three-layer muon tracker

Cosmic-ray muon radiography has been utilized as a tool for the non-destructive testing (NDT) method for evaluating internal density distributions and structural integrity in large-scale and high-density structures. In this study, a prototype muon radiography system employing a three-layer muon tracker was fabricated, and the 2D image reconstruction performance was experimentally validated. Each detector layer of a muon tracker consisted of a 50 × 50 × 0.5 cm 3 BC-408 monolithic plastic scintillator, a 1D array of 64 wavelength-shifting (WLS) fibers (0.3 × 50 × 0.3 cm 3 ), and 0.3 × 0.3 cm 2 silicon photomultipliers (SiPMs) coupled to one end of the WLS fibers. A PETsys Electronics TOFPET-based data acquisition system was employed to simultaneously acquire and process signals from 192 channels, and coincidence counting was performed using a 100 ns timing window. The detection efficiency and spatial resolution performances of detector layer were validated using a 90 Sr source. The 2D muon radiography images were reconstructed from 50 hours of measurement acquired under both Open-sky (target-absent) and Target (target-present) conditions. These experimental results demonstrate that the proposed muon radiography system, based on a three-layer muon tracker, can detect and image high-density targets against the background.