The
muon radiography
technique takes advantage of natural cosmic rays, and the technique of multiple scattering radiography developed in
Los Alamos for proton radiography, in order to inspect cross-border shipping for contraband material. The earth is continuously bombarded by muons produced by cosmic rays striking the upper atmosphere. At the surface of the Earth, energetic muons arrive at a rate of about 10,000 per square meter per minute. These muons are highly penetrating and able to go through tens of meters of rock; shielding cannot stop them. This flux could be used to inspect vehicles and containers entering the U.S. This effort draws on capabilities and infrastructure developed under the LAMPF program at LANL. Cargo traffic into the United States is immense, and enters via multiple modes including aircraft, trucks, and containers. It is impossible to search all of them. A zero-dose means of cargo and vehicle inspection that scans every vehicle interior could open new eyes on what enters this country. An important target for this technique will be shielded nuclear material hidden in normal cargo. A muon imaging system could be deployed at major checkpoints. With it, every vehicle or shipping container entering the U.S. could be scanned while moving through at a low speed, and objects with large, unexplained masses, especially of high-Z material, could be pinpointed.