A full-scale prototype for muon tomography

The technology is particularly advantageous since cosmic muons are available worldwide; display well-known properties at sea level; and can penetrate far deeper into heavy materials than x-rays. As they interact with heavy elements such as nuclear materials, muons are scattered at characteristic angles. Therefore, by comparing the trajectories of muons entering and exiting a material being inspected, researchers can identify these elements, even if they are hidden within large containers. However, since cosmic muons are relatively rare, this technique requires long scanning times to produce suitable levels of sensitivity and image resolution -- limiting its use in large-scale monitoring. Many previous studies have now addressed this issue using advanced muon detection techniques, alongside image reconstruction algorithms.

In this topical issue, Riggi and colleagues used the insights gained through these studies to build a full-scale muon tomograph prototype, with a sensing area of 18m2 -- large enough to inspect a standard cargo container. Their study involved placing light-emitting muon detectors above and below a small lead block. A specialised algorithm then used the data they gathered to estimate the closest approach between nuclei with high atomic numbers within the block, and the muons which were scattered by them -- enabling the researchers to determine the position of the block in 3D. The outcomes of the study pave the way for practical detectors with low sensing times and high image resolutions. Through further improvements, the prototype could soon lead to sophisticated monitoring systems, suitable for use in cargo-handling facilities worldwide.