Compact laser-plasma accelerator can generate muons on demand for imaging

Sanjukta Mondal
contributing writer

Gaby Clark
scientific editor

Robert Egan
associate editor

Muon beams can now be created in a device that is the length of a ruler.
Researchers at Berkeley Lab presented a foot-long (30 cm) compact laser-plasma accelerator (LPA) that can generate and detect highly directional muon beams. It works by using intense laser pulses to accelerate electron beams, which then create muons in significantly higher numbers and with greater directionality, providing a powerful new alternative for non-destructive imaging of large or concealed objects.
Conventional artificial muon sources are bulky and expensive, which has left many imaging applications reliant on naturally occurring, scarce, and unreliable cosmic rays. The new LPA overcomes these constraints by producing significantly higher muon yields, slashing exposure times from months to minutes, according to the study in Âé¶¹ÒùÔºical Review Accelerators and Beams.
Unlike X-rays, which are easily absorbed, muons lose energy gradually, allowing them to pass through large or hidden structures made up of hundreds of meters of rock or dense materials like lead and steel. Thanks to this exceptional penetration power, muon imaging has revealed hidden chambers in the Great Pyramid of Giza, probed the interiors of volcanoes, and inspected nuclear waste.

Cosmic rays constantly shower Earth with muons. About 147 muons pass through every square meter of the surface each second, and trillions pass through each of us over a lifetime. However, imaging applications that require muons from specific directions, which is why traditional muon imagery requires months of exposure to collect enough data for a clear image.
The need for a compact device that can be carried on-site led researchers to LPAs. Several studies had theorized that LPAs could potentially generate muons as a byproduct of colliding laser plasma generated electron beams with high-Z targets; Z here stands for atomic number of an element. Most of these were only computational predictions, with no experimental backing.
At Berkeley Lab's BELLA Facility, researchers have achieved the first detection and characterization of directional muon beams produced by a laser–plasma accelerator (LPA). Using the laser, the researchers accelerated electrons to extremely high (multi-GeV) energies in a 30 cm plasma channel.
These high-energy electrons then collided with a high-Z target (lead), where they emitted photons as they were deflected by atomic nuclei. When these energetic photons struck the target nuclei, they produced muon–antimuon pairs. The resulting muons formed a highly directional, collimated beam along the original electron path, with energies reaching several GeV.

Simulations and experiments reveal two distinct muon populations: high-energy, directional muons concentrated along the central beam axis, and lower-energy, nondirectional muons dominating the regions away from the central beam.
The LPA also generated muon fluxes more than 40 times higher than cosmic rays for horizontal imaging. Instead of relying on the sparse trickle of muons from cosmic sources, the system delivered over 20 muons per shot within the imaging aperture, offering exceptional resolution at unprecedented speed.
The researchers note that the experiment establishes LPA-generated electron beams as practical muon sources, paving the way for future applications built around high-energy beams and detectors optimized for muon scattering image reconstruction.
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More information: Davide Terzani et al, Measurement of directional muon beams generated at the Berkeley Lab Laser Accelerator, Âé¶¹ÒùÔºical Review Accelerators and Beams (2025).
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