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Muons are subatomic particles created when very high- energy cosmic-ray particles from outer space collide with atomic nuclei in the upper layers of the Earth’s atmosphere. Once created, muons travel at nearly the speed of light and rain down on the Earth’s surface from random locations and in random directions; every second, 100 muons hit each square yard of the Earth’s surface. Their tremendous energy enables them to penetrate most objects and even travel hundreds of feet into the Earth’s crust. Yet, muons compose fewer than 10 percent of all background radiation and are harmless to people. Muons continuously scatter as they move through material; they scatter more in very heavy materials than in lighter materials. Uranium and plutonium, which are heavy, cause the largest scattering angles, albeit no more than a few degrees. Lighter elements, such as iron, cause smaller angles, and even-lighter elements, such as oxygen, cause little or no scattering. So, measuring the scattering angle reveals the identity of the material that caused the scattering. Just as important, the angle also reveals the location of the material. In that way, muons can be used to “see” materials deep inside closed containers . . . or inside damaged reactors. Los Alamos’s unique muon vision measures muon scattering and “sees” materials otherwise hidden from view. To interrogate the inside of a shipping container, Decision Sciences International Corporation (DSIC) has commercialized muon vision. DSIC uses two specially designed detectors placed above and below the container. The system records a muon’s path through the top detector (before it enters the container) and then measures its path through the bottom detector (after it exits the container). Highly sophisticated software then traces the entry and exit paths back to where they meet inside the container— the point of intersection is the location of a material. If the lines meet at a very slight angle, the muon struck a lighter element. If the lines meet at a larger angle, the muon struck a heavy material. By detecting enough scattered muons, the computer software can also identify the shape of the heavy material— a particularly important feature if a material has melted. The software can even translate the data into a real-time, 3D digital image, color-coded to indicate different heavy materials. As shown in the infographic below, a lead box can be differentiated from smuggled uranium within it and from the sacks of cement that surround it inside a shipping container. ~Necia Grant Cooper Cargo passes through a Computer constructs muon detector the muon pathways. and the muon paths are virtually detected. Points of intersection are then measured and marked with a 3D color-coded pixel. uranium ALERT!!! In a minute or less, National Security Science December 2016 potential threats can be detected. 39