Design of a muonic tomographic detector to scan travelling containers

Abstract

The Muon Portal Project aims at the construction of a large volume detector to inspect the content of travelling containers for the identification of high-Z hidden materials (U, Pu or other fissile samples), exploiting the secondary cosmic-ray muon radiation. An image of these materials is achieved reconstructing the deviations of the muons from their original trajectories inside the detector volume, by means of two particle trackers, placed one below and one above the container. The scan is performed without adding any external radiation, in a few minutes and with a high spatial and angular resolution. The detector consists of 4800 scintillating strips with two wavelength shifting (WLS) fibers inside each strip, coupled to Silicon photomultipliers (SiPMs). A smart strategy for the read out system allows a considerable reduction of the number of the readout channels. Actually, an intense measurement campaign is in progress to carefully characterize any single component of the detector. A prototype of one of the 48 detection modules (1 × 3 m 2 ) is actually under construction. This paper presents the detector architecture and the preliminary results.

Fabrication, characterization and testing of silicon photomultipliers for the Muon Portal Project

“…While a small sample was fully characterized to determine the optical and electrical properties, the measurement of the I-V characteristics is performed on each device in order to reject those silicon photomultipliers not satisfying the requirements imposed by the read-out electronics that will properly combine signals in groups of ten, thus reducing the number of output channels without loss of information [11]. Fig.…”

“…The detection planes are segmented into strips of extruded plastic scintillators with wavelength-shifting (WLS) fibres (Kuraray Y11(200)M [6]) to transport the light produced in the extruded scintillator material (produced by AMCRYS-H company [7]) to the photo-sensors at one of the fibre ends, in order to optimize the amount of collected photons, still maintaining at a reasonable level the cost and the size of the detection setup [8][9][10][11].…”

Multiparametric approach to the assessment of muon tomographic results for the inspection of a full-scale container

“…This is achieved by the use of the two WLS fibers embedded in each strip, optically coupled to an equal number of SiPMs. A proper combination of the signals originating from ten channels grouped together (giving the Tens and the Units) was used to identify the interested strip [15]. Although this largely reduced the amount of electronics required, a net effect is observed on the light collection efficiency, since the scintillation photons produced in each strip are shared between the two fibers.…”

“…As part of a local project we have built a full-scale prototype (18 m 2 sensitive area) of a muon tomograph with all features to be potentially employed for the inspection of a standard Twenty-Foot Equivalent (TEU) container, a volume of about 6 m × 2.4 m × 2.6 m. A description of this facility and several aspects of its construction and test have been reported in previous papers [12][13][14][15][16][17][18][19][20][21][22]. The main aim of this project was to explore all the main aspects of a large-scale installation for muon tomography, especially the ones related with building a detector with a large sensitive area and a modular structure, operating a large number of photosensors and electronic channels (O(10 4 )), controlling the data flow and the operational conditions even by remote, testing simulation procedures of the entire setup and comparing different reconstruction and imaging strategies.…”

The Muon Portal Project: A large-area tracking detector for muon tomography

“…A considerable amount of simulations and experimental tests on the individual components (scintillators, WLS fibres, photosensors, frontend electronics,...) have been already done. Different reconstruction and visualization algorithms have been implemented and have demonstrated the feasibility of this Project, with several papers reporting specific aspects [3][4][5][6][7][8].…”