The Muon Portal Double Tracker to Inspect Travelling Containers

The Muon Portal Project goal is the design and construction of a working detector prototype in scale 1:1, to inspect the content of travelling containers by means of the secondary cosmic-ray muon radiation and recognize high-Z hidden materials (U, Pu or other fissile samples). The radiographic image is obtained by reconstructing the input and output trajectories of each muon and consequently the scattering angle, exploiting two trackers placed above and below the container. The scan is performed without adding any external radiation, in a reasonable time (a few minutes) and with a good spatial and angular resolution. The detector consists of 8 planes segmented in 6 identical modules. Each module is made of scintillating strips with two WaveLength Shifting fibers (WLS) inside, coupled to Silicon photomultipliers. The customized readout electronics employs trading programmable boards. Thanks to a smart read-out system, the number of output channels is reduced by a factor 10. The signals from the front-end modules are sent to the read-out boards, in order to convert the analog signal to a digital signal, by a comparison to a threshold. The data are pre-analyzed and stored into a data acquisition PC. Actually, an intense measurement and simulation campaign is in progress to characterize carefully the detector components. The first detection modules (1 x 3 m(2)) is now under construction. The detector architecture with a particular attention to the used electronics and the main preliminary results will be presented.