Dept. of Radiological Science/석사Muon tomography is a useful method for monitoring special nuclear materials (SNMs) using multiple Coulomb scattering of muons. Tracking the incoming and outgoing trajectories of muons enables the detection of SNMs and shielding materials. We designed a muon tomography system consisting of four detector modules. The incident and scattered muon tracks were calculated by two top and two bottom detectors, respectively. The degree of the scattering angle represented the atomic number of the material. The proposed detector module for the muon tomography system was composed of a plastic scintillator, wavelength-shifting (WLS) fiber arrays placed on the top and bottom of the scintillator orthogonally, and a position-sensitive Photomultiplier (PSPMT). Light photons in the scintillator were absorbed by the WLS fibers, and the re-emitted green lights were guided to the PSPMT. The light distribution among WLS fibers determined the position of the muon interaction. 3-D tomographic images were obtained by extracting the crossing points of each muon track with a point-of-closest-approach algorithm. The aim of this study was to optimize the design parameters of a muon tomography system using DETECT2000 and GEANT4 and to experimentally evaluate the performance of the proposed detector. The detector module consisted of a 10 x 10 cm2 plastic scintillator (BC-408 equivalent, Epic-crystal), 0.2 x 0.2 x 50 cm3 WLS fibers (BCF-91A, Saint-Gobain), and a PSPMT (H7546A-300 MOD, Hamamatsu). The images were obtained using a 420 nm laser light source. The experimental results agreed well with simulation. These results indicate that the detector module is feasible for a muon tomography system, and they verify the Z-discrimination capability of the muon tomography system.ope
