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Description
LiquidO is a radiation-detection technology that moves beyond transparent scintillators. Instead of allowing light to propagate freely through the detector volume, it uses an optically opaque scintillator that strongly scatters scintillation photons [1]. This scattering confines light close to the particle track and preserves local spatial information. A lattice of wavelength-shifting fibres collects this optical signal, enabling intrinsically high-resolution tracking without mechanical segmentation.
Recent prototypes demonstrate this advantage experimentally [2], [3]. A 3 cm opaque-scintillator cube with fibres at 3.2 mm pitch achieved 450 $\mu$m position resolution in one dimension using cosmic-ray muons [3]. This represents roughly a factor-of-two improvement over conventional transparent scintillator detectors with similar readout granularity, and performance comparable to triangular scintillator bar systems.
These results were obtained with non-optimised scintillator composition, fibre layout, and detector geometry. Simulation-validated studies indicate that, by tuning optical properties and fibre pitch, LiquidO detectors could achieve a factor of five to ten improvement in spatial resolution. This gain can be used either to increase imaging performance at fixed channel count and cost, or to achieve the same resolution with fewer channels and lower cost.
LiquidO therefore has strong potential for muon imaging applications. We have built a first planar LiquidO detector with orthogonal fibre planes for muon-tomography studies. The detector is currently taking cosmic-ray data and demonstrates clear track reconstruction capability. Further optimisation and larger-scale prototypes are in development.
[1] LiquidO Collaboration, “Neutrino physics with an opaque detector,” Commun. Phys., vol. 4, no. 1, p. 273, Dec. 2021, doi: 10.1038/s42005-021-00763-5.
[2] LiquidO Collaboration, “Characterization of a radiation detector based on opaque water-based liquid scintillator,” Nucl. Instrum. Methods Phys. Res. A, vol. 1071, p. 170075, Feb. 2025, doi: 10.1016/j.nima.2024.170075.
[3] LiquidO Collaboration, “Muon tracking in a LiquidO opaque scintillator detector,” Journal of Instrumentation, vol. 21, no. 01, p. P01010, Jan. 2026, doi: 10.1088/1748-0221/21/01/P01010.