Speaker
Description
Fast-neutron imaging offers unique capabilities for the nondestructive investigation of dense and compositionally heterogeneous objects, particularly those containing both light and heavy elements. However, its wider application is limited by the efficiency of existing detection technologies. Conventional scintillator screens typically combine hydrogen-rich polypropylene (PP) with luminescent ZnS microparticles. Their heterogeneous structure limits the conversion of recoil-proton energy into scintillation light and introduces optical scattering that compromises spatial resolution.
Here, we demonstrate fast-neutron imaging using a monocompound organic-inorganic metal halide scintillator, tetraphenylphosphonium manganese bromide (TPP$_2$MnBr$_4$). Its structure combines hydrogen-rich organic cations and luminescent inorganic units within a single compound, enabling more efficient conversion of recoil-proton energy into visible light. Fast-neutron experiments performed at the NEUTRA beamline of the Paul Scherrer Institute demonstrate approximately 1.5 times higher light output from a 1.8 mm-thick TPP$_2$MnBr$_4$ screen compared to a commercial 2.5 mm-thick PP/ZnS reference. Moreover, the light yield normalized to neutron absorption is nearly four times higher. Radiographic experiments with polymer and mixed-material objects demonstrate a spatial resolution of approximately 1 line pair per millimeter, comparable to commercial screens.
These results highlight the potential of monocompound metal halide scintillators for improving the efficiency of fast-neutron imaging while maintaining high spatial resolution.
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| Figure caption | Schematic of fast-neutron and X-ray detection using a monocompound TPP$_2$MnBr$_4$ scintillator, with representative radiographs demonstrating the complementary imaging contrast of a plastic bolt and metal nut. Scale bars: 1 cm. |