Novel polysiloxane-based scintillators for neutron detection

Abstract

Polysiloxane-based scintillators are promising for employment in harsh environments, owing to their outstanding radiation resistance and thermal properties over the traditional plastics (polyvinyltoluene and polystyrene). In this work, cross-linked polydimethyl-co-diphenylsiloxane (PMPS) scintillators with 22% molar percentage of diphenylsiloxane units have been synthesised. 2,5-Diphenyloxazole and Lumogen Violet (BASF) were employed as primary and secondary fluor, respectively. Thermal neutrons sensitivity was achieved through the addition of 3% wt of ortho-carborane. Scintillation yield measurements were made by exciting with (241)Am alpha source samples with different concentrations of dye molecules. PMPS-based scintillators with ∼50% light yield as compared with the commercial plastic scintillator EJ212 were produced. The scintillation yield of the B-loaded samples under thermal neutrons was tested with a moderated Am-Be source and compared with the commercially available EJ254 (5% wt B). 2.2 MeV neutrons were produced by irradiating with a 4.0 MeV proton beam an LiF target, thus exploiting the reaction (7)Li(p,n)(7)Be. Time-of-flight measurements were performed to distinguish pulses due to neutrons or gamma. A similar test was performed with an EJ254 commercial scintillator for comparison. Using the same set-up, polyethylene bricks were used as a moderator to produce low-energy neutrons for testing B-loaded samples.