This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Muons are constantly being created as cosmic rays collide with molecules in Earth's upper atmosphere. With their ability to penetrate far into dense, solid materials, these cosmic muons are often used to image the insides of objects that are otherwise hidden from view.
However, the flow of these natural particles is far too slow for the technique to become both fast and reliable in practical settings. Through new research posted to the preprint server arXiv , a team including Madalina Dobre at the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering in Romania has created images using an artificial muon beam for the first time. Muons share many similarities with electrons—but with masses around 200 times heavier, they lose far less energy as they travel through matter, allowing them to pass through many meters of rock or metal before being absorbed.
By measuring how many muons emerge on the other side of an object, and how their paths have been deflected, researchers can map out its internal structure. Named "muography," this technique has already achieved remarkable feats: revealing a hidden chamber inside the Great Pyramid of Giza in 2023. But because only around one cosmic muon crosses each square centimeter every second, each scan can take months to complete.
The process could be sped up enormously with artificial muon beams—but so far, it has proven difficult to produce muons with enough energy for imaging, while simultaneously separating them from the other particles created alongside them. In their study, Dobre's team used an ultra-powerful laser at the Extreme Light Infrastructure—Nuclear Physics (ELI-NP) facility in Romania. They started by firing the laser into a gas, accelerating electrons to extremely high energies.
When these electrons struck a solid target, they produced bursts of light, which went on to create pairs of muons. To block other unwanted particles, the researchers sent the beam through a large filter made of plastic and paraffin, followed by a 2-meter-thick concrete wall. Portable detectors placed in a van, up to 42 meters from the source, then recorded the shadow cast by a pile of lead bricks.
The shape of this shadow closely matched the known size and position of the bricks. By comparing their measurements with detailed computer simulations, Dobre's team also confirmed that around 90% of the detected particles were muons, carrying energies consistent with their laser-driven source. This makes the new result the first image dominated by artificial, laser-driven muons.
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