Muon Tomography 

The field of Muon Tomography (MT) is one of the fastest-growing areas in applied physics research. This imaging technique exploits the physical properties of naturally-occurring muons produced when cosmic rays impact upon the Earth's atmosphere. Since the discovery of cosmic radiation by Hess (1912), and the muon by Anderson & Neddermeyer (1936), there has been a wealth of applications using these fundamental, charged particles to image large and/or shielded structures. Several of these are summarised on the timelines below.

These applications make use of either the energy loss of the muon as it interacts with atomic electrons or the Coulomb scattering from atomic nuclei as it passess through a material. For the application of nuclear waste characterisation, the latter is exploited.

For the application of nuclear waste characterisation, the latter is exploited. As the muon passes through a material, it undergoes multiple Coulomb scatters (illustrated opposite). The scattering angle has an inherent dependence on the atomic number Z (i.e. the number of protons within the nucleus) of the material. Muons typically scatter through larger scatter angles from higher Z materials such as uranium. It is this dependence that allows the discrimination of different materials within a shielded volume.