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This research investigates the fabrication and analysis of plastic scintillators using an epoxy matrix. Plastic scintillators are widely used in radiation detection because of their low cost, ease of fabrication, resistance to moisture, and rapid decay time. The production process involved dissolving primary and secondary dopants, p-terphenyl (p-TP) and 1,4-bis [2-(phenyloxazolyl)]-benzene (POPOP), respectively, into a low-viscosity of cycloaliphatic amine as hardener B, which was then combined with Bisphenol-A diglycidyl ether as epoxy A. The ratio of primary and secondary dopants was varied in the experiment. The resulting scintillators were characterized using Fourier Transform Infrared Spectroscopy (FTIR) to analyze the functional groups that constitute the epoxy before and after curing. The morphology of the scintillator sample was evaluated using SEM and The thermal properties were evaluated with differential scanning calorimetry (DSC). The optical properties of the scintillator were studied using a UV-Vis Spectrophotometer and a Fluorescence Spectrophotometer. The performance of the scintillator in detecting gamma rays was evaluated using a module comprising a Photomultiplier Tube (PMT) and a Multichannel Analyzer (MCA) with sources of gamma Cesium 137. The results showed that epoxy-based scintillators can provide a detective response to gamma rays. This study demonstrates the potential of epoxy-based plastic scintillators for use in radiation detection. [ABSTRACT FROM AUTHOR]

We would like to present here with the eyes of the chemist the most recent developments of plastic scintillators (PS) for neutron detection. This review covers the period from 2000 to August 2014, and is fragmented in two main chapters. The first chapter deals with the chemical modifications for thermal neutron capture, whereas the second chapter presents the various strategies used to enhance the response to fast neutrons via pulse shape discrimination. For each chapter the theory is also explained. [ABSTRACT FROM AUTHOR]

This paper is devoted to characterizing plastic scintillators with neutron/gamma (n/\gamma ) discrimination abilities and understanding experimentally the photophysical processes downstream. This experimental work is divided into two main studies, neutron sources irradiations and optical photoionization of a range of organic scintillators. Commercial liquid and plastic scintillators, respectively BC-501A from Saint-Gobain and EJ-200 from Eljen Technologies, are used as references in terms of respectively extremely high [C. Guerrero, , “Analysis of the BC-501A Neutron Detector Signals Using the True Pulse Shape,” Nucl. Instrum. Methods Phys. Res. A, Accel. Spectrom. Detect. Assoc. Equip., vol. 597, no. 23, pp. 212–218, 2008] and very poor n/\gamma discrimination efficient scintillators. We have developed a plastic scintillator [P. Blanc , “Neutron/Gamma Pulse Shape Discrimination in Plastic Scintillators: Preparation and Characterization of Various Compositions,”Nucl. Instrum. Methods A, vol. 750, pp. 1–11, Jun. 2014] that shows good discrimination efficiency when compared to plastics that discriminate from literature. We have demonstrated that by exciting with a 70 femtoseconds pulsed laser with energies up to \50~\mu\J at 260 nm, it was possible to simulate nuclear interactions with matter. As a result of the photoionization, we observed a time-delayed light emission when a sufficient energy deposition was optically achieved on a discriminating plastic and none when the plastic showed no discrimination properties. This work is ongoing at CEA in collaboration with the nuclear measurement industry AREVA/Canberra and the Laboratoire de Chimie Physique from Orsay University. [ABSTRACT FROM PUBLISHER]

Abstract: This work deals with the preparation and evaluation of plastic scintillators for neutron/gamma pulse shape discrimination (PSD). We succeeded in developing a plastic scintillator with good neutron/gamma discrimination properties in the range of what is already being commercialized. Several combinations of primary and secondary fluorophores were implemented in chemically modified polymers. These scintillators were fully characterized by fluorescence spectroscopy and under neutron irradiation. The materials proved to be stable for up to 5 years without any degradation of PSD properties. They were then classified in terms of their PSD capabilities and light yield. Our best candidate, 28.6wt% of primary fluorophore with a small amount of secondary fluorophore, shows promising PSD results and is particularly suited to industrial development, because its preparation does not involve the use of expensive or exotic compounds. Furthermore, even at the highest prepared concentration, high stability over time was observed. As a proof of concept, one sample with dimensions 109mm ∅×114mm height (≈1L) was prepared. [Copyright &y& Elsevier]

Abstract: Discrimination between fast neutrons and gamma rays has been successfully achieved using a blue-fluorescing 4-substituted 1,8-naphthalimide in aromatic solvents. As previously stated in the literature, an important solvent effect was observed, but the substitution groups surrounding the core of the naphthalimide also appeared to be extremely crucial. Our system presents the advantages of being based on the use of a single highly soluble solute, exhibiting a large Stokes shift (to avoid self-absorption process) and presenting an emission spectrum fitting well to the photomultiplier (PM) sensitivity. More importantly, we observed that our scintillator was not affected by the concentration of oxygen dissolved in the medium. This observation has no equivalent in commercial liquid scintillators, which are known to be oxygen-sensitive. The discrimination efficiency of our system is described in terms of scintillation performances, figure of merit and the angle between neutrons and gamma lobes visualized in the bi-parametric discrimination spectrum. [Copyright &y& Elsevier]

Abstract: This paper deals with the scintillation of fluorescent polymeric materials and their utilization in nuclear detection. Despite the importance of its applications, discrimination between fast neutrons and gamma rays in plastic scintillators remains very difficult due to the extreme sensitivity of these detectors to gamma. We have investigated the relevance of different 4-substituted 1,8-naphthalimides as fluorophores, either dispersed in a polymer matrix or copolymerized with styrene or methyl methacrylate to prepare new scintillating materials. Thus, various polymer pellets (Ø 18mm, length 10–15mm) incorporating from 0.05% to 1% of naphthalimide were prepared. The charge comparison method commonly used as discrimination technique in nuclear physics experiments was chosen. This technique lies in identifying neutrons from gamma rays by the shape of the light pulse delivered in the scintillator. Preliminary results indicate that the developed scintillators did not satisfy the discrimination criterion. [Copyright &y& Elsevier]

The aim of our study is to develop a material and associated detector that can provide a quantitative response when exposed to any kind of radionuclide decaying by the emission of alpha, beta, fast neutrons (thermalized by their environment or not) and/or gamma rays, accompanied with the categorization of such incoming radiation. To achieve this, only a single sensor is being used, composed of a three-layered, fully organic phoswich (a morphological stacking of different plastic scintillators) showing various thicknesses and decay times. The detection and sorting of fast, thermal neutrons and gamma-rays are obtained through a thick 6Li-doped scintillator. Beta and alpha detection and counting are performed respectively with thin and ultrathin films manufactured with dedicated thickness and decay times, optimized thanks to simulation studies. A Pulse Shape Discrimination method based on the charge comparison method is used to separate alpha, beta, neutrons and gamma rays contributions. We present the preparation and characterization of various configurations: quintuple discrimination, beta detection and alpha spectrometry (performed on a cocktail of alpha emitters). These experimental results are discussed and expended in the frame of complex multi-source scenarios. This all-purpose concept is trademarked as Omniscinti™. [ABSTRACT FROM AUTHOR]

Since Helium-3 shortage announcement, organic scintillators play a major role in neutron detection. Our laboratory decided to focus on plastic scintillators and their ability to discriminate fast neutrons from gamma rays. In this work, we highlight the influence of the secondary fluorophore in lab-made plastic scintillators. The secondary fluorophore is generally added in the scintillating mixture to shift the emission wavelength towards the transparency domain of the material to improve its attenuation length. Thus, it is considered as a harmless molecule and is barely seen as a key criterion that could enhance the performances of the organic scintillator. In our work, we demonstrate that this molecule, even added at a small concentration (typically in the range 0.02–0.2 wt%), directly impacts the neutron/gamma discrimination ability of plastics. Not only the secondary fluorophore plays a role in self-absorption of the scintillating material, but also the couple it creates with the primary fluorophore has to be carefully chosen, as some specific triplet energy transfers between the two fluorophores can influence the neutron/gamma discrimination abilities of the plastic scintillator. Aside from classical photophysical inconveniences such as self-absorption or diffusion, the possibility that the whole, bulk material was heterogeneous in a photochemical point of view was also checked. Thus, various samples were cut from bulk monoliths and their pulse shape discrimination compared with the parent scintillator in terms of Figure of Merit and light output. • Fast neutrons/gamma discrimination efficiency is usually reduced when the volume of a plastic scintillator is increased. • This effect is studied, first in a morphologically way, then chemically and photophysically. • The secondaray fluorophore has an essential role in the discrimination process. [ABSTRACT FROM AUTHOR]

We report herein the application of a new series of plastic scintillators loaded with lithium tetraborate nanoparticles (Li 2 B 4 O 7) designed for the simultaneous detection of fast neutrons, thermal neutrons and gamma-rays. First, MCNP simulations are performed to highlight the potential benefit of Li 2 B 4 O 7 loading. Then, a nanoparticle-loaded scintillator is prepared and evaluated towards the detection of a partially thermalized neutron/gamma 252-californium source. Several scenarios of radiation/matter interactions are evaluated against the observed results. A detection chamber composed of boron-containing chipboard wood has been specifically designed and a subtraction method was set up to afford the best discrimination pattern. For the first time, a triple discrimination is presented with a nanoparticles-loaded plastic scintillator, where both 6Li(n, α) and 10B(n, α) signatures are observed. A Figure of Merit of 1.40 was calculated between fast neutrons and gamma rays around 480 keVee. The Figure of Merit between fast + thermal neutrons and gamma rays is slightly worse as it is 1.16 at 380 keVee. [ABSTRACT FROM AUTHOR]