Muon

Muon technology uses naturally occurring, highly penetrating cosmic-ray particles (muons) as a non-invasive radiation source to perform density-based imaging, functioning as a deep-reading, geological CT scanner.

Muons are fundamental subatomic particles, over 207 times the mass of an electron, generated when cosmic rays strike Earth’s atmosphere. This gives them exceptional penetrating power: they travel miles through rock before decaying (lifetime: 2.2 microseconds). The technology, called muography or muon tomography, detects the flux attenuation or scattering of these particles (approximately one muon hits every square centimeter per minute at sea level) to map internal density structures. Applications are diverse and high-stakes: they range from historical archaeology (e.g., locating hidden chambers in the Egyptian pyramids) to national security (detecting shielded nuclear materials in cargo) and geophysics (imaging volcanoes, monitoring carbon sequestration sites, or mapping mineral deposits).

https://www.energy.gov/science/doe-explainsmuons