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Plastic scintillators (PS) allow design of portative lightweight devices for quantification of low‐activity radiation sources. We have recently suggested a new type of organic fluorophores based on triphenyl pyrazoline (PZ) derivatives with high fluorescence quantum yield showing high radioluminescence when combined with a polyvinyltoluene (PVT) matrix. In this publication we report on radioluminescence properties of the PZ−X family with various halogen substitution (X=F, Cl, Br, I), or having vinyl functional group (vPZ, X=vinyl). PS based on such fluorophores and PVT matrix can be prepared as bulk samples, micrometer size beads or cladding on optical fibers. Application of fluorophores with vinyl functional groups enabled their enhanced interaction with the matrix due to covalent bonding between the components. We demonstrate high performance of PZ−X fluorophores and especially vPZ fluorophore in fabrication of nanocomposites for detection of various types of radiation. Scintillators have enhanced gamma ray detection capabilities with an addition of triphenyl Bi, or Gd2O3 nanoparticles. High fluorescence quantum yield and luminosity of PZ fluorophores allows dramatical reduction of their content in PS systems. Mechanisms of energy transfer and conversion during scintillation process are discussed. Special consideration is given to enhancement of α/β and neutron/gamma (n/γ) pulse shape discrimination (PSD) function of the developed scintillators. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations were used to investigate the correlation between luminosity parameters and pulse shape discrimination (PSD) and subsequently compared with experimental results from CsI:Tl. Luminosity intensity parameters Af, As (fast and slow initial luminosities) and temporal luminosity parameters \tauf, \taus (fast and slow decay time constants) of a dual decay mode scintillator were applied to create a dynamic model with Crystal Ball simulation system. The simulated pulses were analyzed with charge comparison (CC) and constant time discrimination (CTD) PSD methods followed by quantification of the histogrammed pulse data with Figure of Merit (FoM) and spillover (pulse misclassification). Performance in terms of FoM and spillover is compared with that of fixed reference pulses set at (Af \tauf/As \taus)\gamma = 1 and (Af \tauf/As \taus)\gamma = 0.1. For the CC method, independent of the reference pulse characteristics [(Af \tauf/As \taus)\gamma = 1\ {\or} = 0.1], \taus is the most influential parameter for PSD as compared with Af, As, and \tauf. For the CTD method, Af and As are seen to have less influence over the PSD compared to \tauf and \taus when (Af \tauf/As \taus)\gamma = 1 and \tauf is the most influential parameter for both reference pulses. Using both methods with either reference pulse applied, the scintillator having luminosity parameters such that 0.1 < (Af \tauf/As \taus)\alpha/\gamma < 2 is classified as having poor PSD. Excellent correlation is observed between the simulation and the experimental results with CsI:Tl, which is known for very good \alpha/\beta (\gamma) pulse shape discrimination. This study is useful for describing how the luminosity parameters affects PSD. [ABSTRACT FROM PUBLISHER]

Abstract: The absolute total and absolute peak detection efficiencies of gamma ray detector materials NaI:Tl, CdZnTe, HPGe, HPXe, LaBr3:Ce and LaCl3:Ce were simulated and compared to that of polyvinyltoluene (PVT). The dimensions of the PVT detector were 188.82cm×60.96cm×5.08cm, which is a typical size for a single-panel portal monitor. The absolute total and peak detection efficiencies for these detector materials for the point, line and spherical source geometries of 60Co (1332keV), 137Cs (662keV) and 241Am (59.5keV) were simulated at various source-to-detector distances using the Monte Carlo N-Particle software (MCNP5-V1.30). The comparison of the absolute total detection efficiencies for a point, line and spherical source geometry of 60Co and 137Cs at different source-to-detector distance showed that the absolute detection efficiency for PVT is higher relative to the other detectors of typical dimensions for that material. However, the absolute peak detection efficiency of some of these detectors are higher relative to PVT, for example the absolute peak detection efficiency of NaI:Tl (7.62cm diameter×7.62cm long), HPGe (7.62cm diameter×7.62cm long), HPXe (11.43cm diameter×60.96cm long), and LaCl3:Ce (5.08cm diameter×5.08cm long) are all greater than that of a 188.82cm×60.96cm×5.08cm PVT detector for 60Co and 137Cs for all geometries studied. The absolute total and absolute peak detection efficiencies of a right circular cylinder of NaI:Tl with various diameters and thicknesses were determined for a point source. The effect of changing the solid angle on the NaI:Tl detectors showed that with increasing solid angle and detector thickness, the absolute efficiency increases. This work establishes a common basis for differentiating detector materials for passive portal monitoring of gamma ray radiation. [Copyright &y& Elsevier]