A security guard spots an abandoned briefcase at an airport. A terrorist bomb? In such cases the police typically evacuate the area and destroy the package, although they rarely eliminate anything more than some misplaced papers. Such disruptions may soon be a thing of the past. Grant Lockwood, a physicist at Sandia National Laboratories, is developing a robotic X-ray machine that rolls up to suspicious packages to identify their contents.
Police use X-rays now, but they must put a piece of film behind the suspected bomb--a risky procedure. With Lockwood's system, a laptop computer linked to the robot constructs images without film from X-rays that scatter back from the target. Some materials scatter X-rays better than others: plastics scatter a lot, metals very little. The computer converts the signals into detailed images. Says Lockwood: "We can see batteries, egg timers, or other devices used in terrorist or homemade, crackpot-type bombs."
