Gadolinium and terbium-covered bismuth-loaded plastic scintillators for thermal neutron detection

Jonathan Nicolas Dumazert (1) , Romain Coulon (1) , Mathieu Hamel (1) , Stéphane Normand (1) , Laurence Méchin (2) , Guillaume H. V. Bertrand (1)

1 LCAE (CEA, LIST) - Laboratoire Capteurs et Architectures Electroniques (CEA, LIST)
2 Equipe Electronique - Laboratoire GREYC - UMR6072

This paper describes the simulation-based scaling of the sensors and insulation of measurement channels, the synthesis of bismuth-loaded plastic scintillators, the experimental energy calibration of these scintillators, the nonlinear smoothing of the raw counting signals and the setting of a hypothesis test to discriminate the signal generated by the radiative signature of thermal neutron captures in gadolinium from statistical fluctuations over the compensation of both independent channels. The neutron measurement by compensation carried out over two gadolinium- and terbium-covered bismuth-loaded plastic scintillators has allowed the detection of a neutron activity in the photon radiation background of the californium-252 source at the exit of the HDPE block (estimated about 1.2 μSv.h-1 with a standard radiameter, which matches the typical constraints of a “monitored area” in the context of radioprotection applications), thus validating the concept of a new neutron detection system, robust to “controlled area” typical photon background, portable, compatible with online implementation, and whose cost-effectiveness advantageously compare to inorganic, silicon-based compensation schemes. In order to increase the counting rates, as well as the precision associated to them, future works will be turned towards a scale-up over the loaded scintillating samples, with all the known challenges associated to such a process: homogeneity issues with the loading and self-absorption of the scintillator to quote the more obvious of them.

Mots clés: instrumentation; nuclear instrumentation; sensor; electronic architecture; plastic scintillator; calibration; signal processing; radioactivity; ionizing radiation; thermal neutrons; neutrons; Neutron-gamma discrimination

Domaines: Micro et nanotechnologies/Microélectronique

Jonathan Nicolas Dumazert, Romain Coulon, Mathieu Hamel, Stéphane Normand, Laurence Méchin, et al.. Gadolinium and terbium-covered bismuth-loaded plastic scintillators for thermal neutron detection. Information System on Occupational Exposure (ISOE 2016), European Technical Centre of Brussels, Jun 2016, Bruxelles, Belgium. ⟨hal-01641690⟩