Central Alliance has collaborated with Geoptic to pioneer the use of muon tomography in infrastructure investigations in the UK. Cosmic ray muons are subatomic particles that are generated by high energy radiation hitting the Earth’s atmosphere. By detecting cosmic ray muons, we can map density changes providing valuable insights that traditional technologies cannot match. Cosmic rays that were created millions of years ago in deep space and have since been on a collision course with the Earth are utilised for this technique. When cosmic rays hit the Earth’s outer atmosphere, they disperse into sub-atomic particles known as muons. Muons continue at high velocity toward the Earth. Highly penetrating, they travel deep into the Earth’s surface and through any structures built on, or in the Earth. These muons hit the earth at an average rate of 10’000 per m2 every minute. 

We can detect muons at depth using specially developed muon detectors. Using the simple concept of monitoring muon flux and by considering direction and angle of detected muons, we can make assessments of density anomalies within the substrate above the detector. Similar to X-rays, the muons are scattered as they travel through dense material, making them ideal for mapping large or dense structures. 


This innovative technique has been successfully used to detect voids above railway tunnels, with a high degree of confidence. By taking readings over several night shifts this was achieved with no disturbance to the operation of the railway. 

Work is currently underway to detect ore deposits around existing mining sites. The use of muon tomography as an exploratory tool was used in Wales to identify new resources and assist with the delineation of existing zones of mineralisation at the mine.


Muon Radiography

By comparing the muon rate inside or below a structure, to an open sky measurement it is possible to detect changes in density. This method is called “Muon Radiography”.


Instrumentation & Monitoring