Detector Technology 

A small-scale prototype system has been constructed in Glasgow and has successfully validated the technique by imaging several test sceanrios. A model of the modular system consisting of two modules above, and two below, the assay volume is shown opposite. Each module is comprised of orthogonal layers (in the x and y directions) of 128 2mm-pitch scintillating fibres from Saint Gobain coupled to Hamamatsu H8500 Multi-Anode PhotoMultiplier Tube (MAPMT).

Identification of the struck fibre in each layer allows the reconstruction of a single interaction point, called a space point, on each module (opposite). From the two space points above and below the assay volume, the incoming and Coulomb-scattered muon trajectories can be reconstructed. These can then be used to determine the most-likely scattering location within the assay volume and the associated scattering density, which is dependent on the atomic number Z of the material.

Per detection layer, two scintillating fibres are optically coupled to one pixel of a 64-pixel H8500 MAPMT (opposite). With the identification of the signal pixel on each MAPMT, and via a dedicated decoupling algorithm, the correct fibre per layer is identified in offline data analysis.

The process from cosmic ray to image reconstruction using the small-scale prototype system is simplified below.