Neutron/γ discrimination by an emission-based phoswich approach

Particle discrimination in a mixed radiation field using scintillators is a challenging topic in radiation detection research. We propose a novel approach relying on the possibility of identifying particles interacting in a phoswich detector from the emission spectrum of the produced scintillation signal. As a proof of concept, we focus on the discrimination between neutrons and gamma rays. Lu3Al5O12:Pr and Gd3Al2Ga3O12:Ce thin single crystal scintillators, coupled to two different silicon photomultipliers equipped with optical filters, are simultaneously used in the same phoswich detector. Their optical emissions peak at approximately 310 nm and 545 nm respectively, and thus they can easily be distinguished by optical filtering. While both crystals are sensitive to gamma rays, neutrons interact only with the Gd3Al2Ga3O12:Ce thanks to the presence of Gd acting as neutron converter. Optical filtration and an anti-coincidence algorithm are therefore used to perform particle discrimination, rejecting coincidence signals arising from gamma rays, which simultaneously deposit energy in both crystals, and counting anti-coincidence signals due to neutrons, which deposit energy only in the Gd3Al2Ga3O12:Ce. The simple neutron counter developed here is intended to be a proof of the principle of the feasibility of the color-based particle discrimination technique.