Intrinsic Evaluation of neutron/gamma Discrimination in Plastic Scintillators

International audienceThis paper is devoted to characterizing plastic scintillators with neutron/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, et al., “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 neutron/gamma discrimination efficient scintillators. We have developed a plastic scintillator [P. Blanc et al., “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 µJ 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