Physicists in Romania have made muons with a laser and used them to take a picture. The beam cast a shadow of lead bricks that matched their real size and position. It is the first image made with an artificial muon beam, according to the team led by Madalina Dobre of the Horia Hulubei National Institute for Physics and Nuclear Engineering.
Muons are heavier cousins of electrons that pass through rock and metal. Scientists already use the muons that cosmic rays create in the sky to look inside large objects such as pyramids, a method called muography. The trouble is supply: only about one cosmic muon crosses each square centimeter every second. Finding a hidden chamber in Egypt's Great Pyramid in 2023 took months of scanning.
How the laser does it
The team used the ultra-intense laser at the Extreme Light Infrastructure for Nuclear Physics, ELI-NP. The laser sped electrons up to very high energies. When they hit a solid target, they made bursts of light, and that light produced pairs of muons.
Plastic, paraffin and a 2-meter concrete wall filtered out the other particles. Detectors stood up to 42 meters away. Measurements and simulations show that about 90 percent of the particles they caught were muons, the team says.
Early days
The image is still rough, and the work is a preprint that other scientists have not yet reviewed. The authors see on-demand muon beams as a future tool for inspecting infrastructure or finding shielded nuclear material at borders.
For now, they have one clear shadow of a stack of lead.
