Design of an atmospheric muon tomographer for material identification based on CORSIKA+GEANT4 simulations

TL;DR

This work proposes a portable atmospheric muon tomographer based on plastic scintillator planes read by SiPMs to identify materials inside large or inaccessible objects. A two-stage simulation pipeline using CORSIKA for muon flux and GEANT4 for detector-object transport quantifies two differentiation methods: absorption via transmitted muon fraction and scattering via the Gaussian width of deflection angles. Lead is consistently distinguishable from most materials, with absorption delivering larger discrimination and shorter observation times to reach $3\sigma$ significance. The results demonstrate a feasible path toward field-deployable muon tomography for security, archaeology, and geology, supported by quantitative sigma-based significance and a configurable rotating detector geometry.

Abstract

In recent years, muon tomography has turned into a powerful and innovative technique for non-invasive imaging of large and small structures with applications in different areas like geology, archaeology, security, etc. We present the design and simulation of a transportable and easy to construct detector based on plastic scintillator and Silicon photomultipliers current technology. From a flux of cosmic rays reaching the atmosphere we simulated atmospheric muons at ground using CORSIKA. The detector and the object to analyze are simulated with GEANT4, where the previously obtained muon flux is transported. We use two methods for muon tomography to differentiate objects made of different materials: absorption and scattering. The statistical differences for several object sizes and materials are quantified. Using a threshold of 3 $σ$ in the first method, we conclude that materials made of lead can be differentiated from objects made of other materials. The observation time needed to differentiate an object made of lead from one of aluminum was 4.9 and 9.9 days using the first and second method, respectively. In general, the absorption method gives the best results.

Figures (13)

• Figure 1: Detector design and measurement geometry in GEANT4.
• Figure 2: Energy distribution of secondary particles arriving at ground generated by the input primary cosmic ray composition.
• Figure 3: GEANT4 measurement setup showing 10 particles coming from one shower with the second sub-detector turning $\approx90^{\circ}$ around the central point. Red lines are negative charged particles (e.g. muon tracks and electrons), blue lines are positive particles (e.g. antimuons tracks and positrons), while green lines are photons.
• Figure 4: Absorption Method: fraction of particles detected in the sub-detector after the object and those that should have arrived after passing through air for different materials as a function of the object width.
• Figure 5: Number of sigma deviations between the material stated on top of each plot compared with those in the legend.