Muon detection with an opaque scintillator detector prototype

LiquidO is an innovative scintillator-based radiation detector concept. The core idea is to achieve the self-segmentation of a detector by exploiting stochastic light confinement in a highly scattering medium. Key components include an opaque scintillator with short scattering and long absorption lengths, along with a wavelength-shifting fibre lattice for efficient collection of scintillation light, enabling confining and collecting light near its creation point. At the University of Sussex, the focus is on investigating the performance of the LiquidO technology on cosmic-ray muons detection. We developed the design of a 3D-printable 64 fibres cube. The cube has a length of a few centimetres and contains an $8 x 8$ grid of optical fibres along one direction, with a 3-millimetre pitch, read-out by silicon photomultipliers. Wax-based opaque liquid scintillators are used to fill the cube. Using this LiquidO detector, ‘ light cylinders” produced by cosmic-ray muons in a LiquidO detector are observed. The distinct LiquidO event topology is used to identify and reconstruct the muons track. A sub-millimetre one-dimensional position resolution is demonstrated, surpassing the capability of a physically segmented detector with identical pixel pitch. Room for improvements to further enhance the position resolution of the 64 -fibre cube comprises tuning the scintillator properties, supported by the study of the setup in Monte Carlo simulations. Additionally, a ten times larger prototype with 256 fibres along two perpendicular directions is being commissioned and will soon be used to acquire cosmic-ray muons data. These results demonstrate the potential of LiquidO detectors in muons imaging techniques and advance the understanding of the novel LiquidO technology. Finally, these prototypes constitute a fundamental step towards the first large-scale detector under development by the LiquidO consortium, CLOUD (Chooz LiquidO Ultra-near Detector).