Bismuth-Loaded Plastic Scintillator Portal Monitors

Plastic scintillators incorporating 8 weight percent elemental Bismuth offer enhanced sensitivity and distinct photopeak spectra in the <1000 keV range typically used in radiation portal monitors. The Bismuth-loaded plastic is based on polyvinyl toluene with standard singlet fluors. It produces similar to 6,000 photons/MeV with a maximum emission at 430 nm and a similar to 10 ns decay. Energy resolution of 49% at 59.5 keV and 16% at 662 keV are obtained for a 14 in(3) Bismuth plastic scintillator plate. Count rates compared to standard plastic scintillator of the same size reveal a sensitivity improvement of >5x in the <200 keV range. Future spectroscopic radiation portal monitors based on the Bismuth plastic scintillator could provide moderate resolution spectroscopy for radioisotope identification. In addition, the Bismuth plastic offers outstanding environmental stability to weathering effects, in contrast with standard plastic scintillator formulations.