Design Consideration on Position Sensitive Detectors Based on LuAG:Pr Scintillators for High Energy X-ray Cargo Inspection

To prevent illegal trade of weapons, X-ray scanning systems are used for non-intrusive inspection of import containers and cargoes at every seaport and airport. Conventional X-ray scanning system for cargoes is based mainly on X-rays of several MeV energy generated by an electron Linac. For high quality X-ray imaging, an X-ray source with good directionality, narrow width of energy spectrum and tunable energy is ideal and a laser Compton scattering (LCS) X-ray source is much more promising one than those generated by the Linac. Thus we propose a cargo scanning system based on the LCS X-ray source. However, the small cross section of LCS sets a limit of the intensity of LCS X-rays, therefore high-density scintillators are suitable for the detector of this system. We adopted LuAG:Pr, which has high density, good energy resolution and high light-yield. The position sensitive detector was designed as stacked thin LuAG:Pr scintillators and their independent readouts. By Monte Carlo simulation, the thickness of the thin LuAG:Pr scintillator was optimized as 0.5 mm. In addition, we measured a response of a prototype detector to LCS X-rays generated with an 800 MeV storage ring at AIST-Tsukuba and experimental results agreed well with the simulation ones.