Cosmic-ray tomography of shipping containers: A combination of complementary secondary particle and muon information using simulations

TL;DR

This work addresses the challenge of imaging inside shipping containers with cosmic-ray tomography by leveraging complementary information from muon scattering and secondary particle production. It introduces a dual-channel reconstruction workflow (MST+SPA) built on a common 1 dm$^3$ voxel grid and a multi-step fusion process (normalization, Gaussian sharpening, smoothing, filtering, alignment, merging) to compare stand-alone MST/SPA against the combined approach. The study demonstrates that incorporating secondary-particle information yields perceptible improvements across multiple materials and metrics, reducing reconstruction artifacts and enabling more accurate geometry and density representations, though it relies on manual parameter tuning and idealized detector assumptions. The findings highlight the potential of dual-channel CRT for container screening and set the stage for automated, ML-driven optimization and experimental validation with more realistic detectors and geometries.

Abstract

Cosmic-ray tomography usually relies on measuring the scattering or transmission of muons produced within cosmic-ray air showers to reconstruct an examined volume of interest (VOI). During the traversing of a VOI, all air shower particles, including muons, interact with the matter within the VOI producing so-called secondary particles. The characteristics of the production of these particles contain additional information about the properties of the examined objects and their materials. However, this approach has not been fully realized practically. Hence, this work aims to study a novel technique to scan shipping containers by comparing and combining the complementary results from stand-alone secondary particles and muon scattering using simulated simplified scenes with a 1 m3 cube made out of five different materials located inside the container. The proposed approach for a statistical combination is based on a multi-step procedure centered around a clustering and segmentation algorithm. This ensures a consistent evaluation and comparison of the results before and after the combination focusing on dedicated properties of the reconstructed object. The findings of this work show a potential improvement over the results obtained solely through muon scattering due to the utilization of secondary particle information by applying this novel dual-channel cosmic-ray tomography analysis.

Figures (6)

• Figure 1: Visualization of the simulation setup. The detector layers are indicated by the blue planes surrounding the container, in which the target object is located. The trajectory of an air shower particle is represented by the green line, while the pink lines show the paths of secondary particles produced during the depicted interaction of the air shower particle with the target cube.
• Figure 2: Reconstruction of the vanadium cube inside the container using the PoCA method.
• Figure 3: Reconstruction of the vanadium cube inside the container using the ASR method.
• Figure 4: Reconstruction of the vanadium cube inside the container using the SPA method.
• Figure 5: Reconstruction of the vanadium cube inside the container using the PoCA+SPA combination.