A Neutron Sensitive Detector Using 3D-Printed Scintillators

TL;DR

This study demonstrates a scalable route to neutron-sensitive detectors by fabricating polystyrene-based scintillators via FDM, doped with p-terphenyl and POPOP and loaded with $^6$Li via LiF to enable neutron sensitivity. The printed scintillators are integrated with a TimePix3-based detector and an image intensifier, enabling high-resolution spatial and temporal readout; a cluster-based discrimination algorithm leverages TimePix3 data to separate neutron events from gamma backgrounds in mixed fields. Geant4 simulations guide design and interpretation, and experiments show a light yield of $30 \pm 5$ photons/MeV, with Li-loaded designs enhancing neutron detection relative to non-loaded geometries, though commercial EJ-420 remains more sensitive. The work highlights a flexible, low-cost path for customizing neutron-sensitive detectors, with future improvements anticipated from dopant innovations such as perovskites to increase light output while maintaining fast decay times.

Abstract

This work reports on the performance of a novel neutron-sensitive scintillating detector fabricated using Fused-Deposition Modelling (FDM) additive manufacturing. FDM is a cost-effective 3D-printing method employing flexible plastic filaments to create custom-shaped components. Scintillating filaments, based on polystyrene doped with \emph{p}-terphenyl and 1,4-bis (5-phenyloxazol-2-yl) benzene, and enriched with $^6$LiF to enable neutron sensitivity were manufactured in house and achieved visible scintillation with a light output of 30$\pm$5~photons per MeV. Printed scintillators were then integrated into a detector system consisting of an image intensified TimePix3 camera, offering high spatial and temporal resolution. The detector performance was compared with Geant4 simulations of the scintillating sensor's response to electrons, gamma-rays, and thermal neutrons. A novel event discrimination algorithm, using the properties of the TimePix3 camera, enabled the separation of neutron signatures from the gamma-ray background.

Figures (8)

• Figure 1: A reel of lithium-containing scintillating filament, fluorescing under UV light
• Figure 2: Figure \ref{['fig:setup1']} shows the filament maker used to produce neutron-sensitive 3D-printer filament, with a diameter of 1.75 mm. The filament is then used to print scintillators using the 3D-printer seen in Figure \ref{['fig:setup2']}
• Figure 3: An example of a lithium-containing 3D-printed scintillator; in this case, a 2 cm by 2 cm by 0.5 cm cuboid.
• Figure 4: The detector system, illuminated with UV light to show the position of the scintillator. The TPX3Cam is on the left, with the image intensifier connected to it. The scintillator is within the light-tight box, glowing under the UV light.
• Figure 5: Two TimePix images of the 3D-printed lithium-packed scintillator, when exposed to a $^{252}$Cf source. Figure (\ref{['fig:neutron_image']}) shows a post-processed and summed image, combining multiple such frames from a 30 minute observation. Note the bright central spot, from the scintillator. Figure (\ref{['fig:single_frame']}), meanwhile, is a single raw output frame, using a 0.5 s integration time, and shows a single neutron-associated photon cluster to the left of the centre, in the red circle. Colours represent photon counts, with purple being a single photon detected in that pixel and blue two photons.