Scientists use outer space particles to examine the fortress wall of Xi’an city: What are muons and how are they used to analyse large structures?

February 7, 2023

Scientists are using outer space particles called muons to examine the fortress wall of Xi’an city, an ancient city in China.
They used a muon detector, called CORMIS (Cosmic Ray Muon Imaging System), to examine the wall of Xi’an city.

What are Muons?

Muons are subatomic particles raining from space. They are created when the particles in Earth’s atmosphere collide with cosmic rays — clusters of high-energy particles that move through space at just below the speed of light.
- Atom is the smallest unit of matter and is made up of smaller units known as subatomic particles i.e. protons, neutrons and electrons.

Muons vs Electrons

Muons are similar to electrons but weigh more than 207 times as much, equivalent to the difference between an adult person and a small elephant. Therefore, they are sometimes called “fat electrons”.
Muons are so heavy, they can travel through hundreds of metres of rock or other matter in comparison, electrons can penetrate through only a few centimetres.
Muons exist for only 2.2 microseconds before they decay into an electron and two kinds of neutrinos.

Muography

Muography (or muon radiography) is a technique that exploits the penetration capability of muons. The measurement of their absorption in matter allows the imaging of the inner structure of large bodies.
Muography is conceptually similar to X-ray but capable of scanning much larger and wider structures, owing to the penetration power of muons.
As these high-energy particles are naturally produced and ubiquitous, all one needs to do is place a muon detector underneath, within or near the object of interest.

Applications

Archaeology
Detecting Volcanic Eruptions
Nuclear Plants
Application in various studies: Muons applications in studies of superconductors, molecular systems and chemical reactions, novel battery materials and a variety of organic systems.