Development and operation of a 6LiF:ZnS(Ag)-scintillating plastic capture-gated detector

We report on the design, construction, and operation of a capture-gated neutron detector based on a heterogeneous scintillating structure comprising two scintillator types. A flat, 500 µm thick sheet composed of a mixture of lithium-6-fluoride capture agent, 6LiF, and zinc sulfide phosphor, ZnS(Ag), is wrapped around scintillating polyvinyl toluene (PVT) in a form of cylinder. The 6LiF: ZnS(Ag) sheet uses an aluminum foil backing as a support for the scintillating material and as an optical reflector, and its optical properties have been characterized independently. The composite scintillator was tested using 252Cf, DD fusion, 137Cs, and 60Co sources. The intrinsic detection efficiency for neutrons from an unmoderated 252Cf source and rejection of gammas from 137Cs were measured to be 3.6% and 10−6, respectively. A figure of merit for pulse shape discrimination of 4.6 was achieved, and capture-gated spectroscopic analysis is demonstrated.