Polysiloxane scintillators for neutron and gamma-ray pulse shape discrimination

Plastic scintillators offer a cost-effective and scalable option for detection of special nuclear materials. Traditional plastic scintillators are based on thermoplastics such as poly(vinyl toluene) (PVT) and polystyrene. When over-doped with select fluorescent molecules, PVT and polystyrene scintillators are capable of distinguishing between neutrons and gamma ray via pulse shape discrimination (PSD). While this formulation has been extensively studied and commercialized, the resulting scintillators are restricted to applications involving rigid thermoplastics. In order to achieve flexible and elastomeric properties, a new class of elastomer scintillators based on polysiloxanes has been explored. This work details elastomeric polysiloxane scintillators based on a commercial resin and a commercial primary dopant, 2,5-diphenyloxazole (PPO) and a synthesized dopant, 9,9-dimethyl-2-phenyl fluorene (PhF). PPO-polysiloxane scintillators showed PSD capabilities surpassing commercial thermoplastic analogues at low concentrations of PPO (FoM 1.33 ± 0.03 at 450 keVee for 5wt% PPO). PhF-polysiloxane scintillators were also capable of PSD, comparable to the commercial sample, but notably had a high light yield, of 144% EJ-299-33. This work serves as a proof of concept that polysiloxane scintillators can be capable of good PSD and high light yield at low dopant loadings.