What is "muography"

Muography is an imaging technique that produces a projectional image of a target volume by recording elementary particles, called muons, either electronically or chemically with materials that are sensitive to charged particles such as nuclear emulsions. Cosmic rays from outer space generate muons in the Earth’s atmosphere as a result of nuclear reactions between primary cosmic rays and atmospheric nuclei. They are highly penetrative and millions of muons pass through our bodies everyday.

Muography utilizes muons by tracking the number of muons that pass through the target volume to determine the density of the inaccessible internal structure. The X-ray is a similar technique in principle to muography, one of the differences being that much larger objects can be surveyed. Since muons are less likely to interact, stop and decay in low density matter than high density matter, a larger number of muons will travel through the low density regions of target objects in comparison to higher density regions. The apparatuses record the trajectory of each event to produce a muogram that displays the matrix of the resulting numbers of transmitted muons after they have passed through hectometer to kilometer-sized objects. The internal structure of the object, imaged in terms of density, is displayed by converting muograms to muographs.