Cargo scanning

[5] Gamma-ray radiography systems capable of scanning trucks usually use cobalt-60 or caesium-137[6] as a radioactive source and a vertical tower of gamma detectors.

[6][7] The systems provide good quality images which can be used for identifying cargo and comparing it with the manifest, in an attempt to detect anomalies.

All three systems are based on neutron interactions with the inspected items and examining the resultant gamma rays to determine the elements being radiated.

[13] The method was re-discovered and improved upon by a research team at Los Alamos National Laboratory,[14][15] muon tomography is completely passive, exploiting naturally occurring cosmic radiation.

This makes the technology ideal for high throughput scanning of volume material where operators are present, such as at a marine cargo terminal.

In these cases, truck drivers and customs personnel do not have to leave the vehicle or exit an exclusion zone during scanning, expediting cargo throughput.

Multi-mode passive detection systems (MMPDS), based upon muon tomography, are currently in use by Decision Sciences International Corporation at Freeport, Bahamas,[16] and the Atomic Weapons Establishment in the United Kingdom.

Systems currently used in US ports (and steel mills) use several (usually 4) large PVT panels as scintillators and can be used on vehicles moving up to 16 km/h.

[19] They provide very little information on energy of detected photons, and as a result, they were criticized for their inability to distinguish gammas originating from nuclear sources from gammas originating from a large variety of benign cargo types that naturally emit radioactivity, including bananas, cat litter, granite, porcelain, stoneware, etc.