Comparison of plastic and NaI(Tl) scintillators for vehicle portal monitor applications

Experimental data and computer simulations are presented for gamma-ray detection by vehicle portal monitors for homeland security applications at international borders. The experiments and simulations use spectral processing of gamma rays from various sources (²⁴¹Am, ⁵⁷Co, ¹³³Ba, ¹³⁷Cs, ⁶⁰Co) and background to provide data for comparing plastic and NaI(Tl) detectors. The effects of gamma-ray scattering in cargo are also examined. Plastic scintillators are well suited for primary screening of gamma-ray sources because of their large size and low cost. Sodium iodide is preferable to plastic for applications of isotope identification based on gamma-ray spectrometry. Some applications may benefit from integrating features from both types of detectors.