First observation of minimum ionising particle tracks in the RIPTIDE detector

RIPTIDE is a novel fast-neutron detector that determines neutron energy and direction via n-p elastic scattering, imaging recoil-proton tracks in a plastic scintillator through a lens, MCP-PMT intensifier, and fast CMOS camera. We present the first experimental characterisation of the HiCAM FLUO camera with minimum-ionising particles (MIPs) using a simplified single-arm setup in which a mirror provides a simultaneous second view of the scintillator within a single frame. Two cubic scintillators are tested, BC-408 and CsI(Tl): muon tracks are clearly observed in CsI(Tl) while no track-like signal is detected in BC-408, in quantitative agreement with Monte Carlo simulations. A weighted RANSAC algorithm for reconstructing 3D track directions from the dual projections is presented. These results constitute a preliminary analysis on a limited data sample, providing a proof-of-principle for the full RIPTIDE fast-neutron detection chain.