In the comics, the Phantom is a masked crime fighter who protected the innocent from pirates, hijackers and other evildoers. While not as dashing or exciting as its costumed namesake, an electromagnetic phantom - a carbon and polymer mixture that simulates the human body - is being readied by the National Institute of Standards and Technology (NIST) for its upcoming role as a different kind of protector. The NIST phantom serves as a mannequin in a standardized performance test for walk-through metal detectors (WTMDs), such as those used at airports.
Metal detectors are currently evaluated by using "clean testers," human subjects who walk through the detector adorned with different types of innocuous metal objects such as eyeglasses, belt buckles, watches, jewelry and coins, or by a piece of plywood pushed through the metal detector with the same items mounted on it. The disadvantage of using human subjects is that person-to-person variability in physical makeup and walking style at each pass makes standardization impossible. The second method is reproducible, but it can't tell evaluators how a human body may impact the WTMD's ability to discriminate between weapons and innocuous objects.
The solution for both problems came from the lab. Researchers in NIST's Electromagnetics Division mixed a polymer with carbon black - a fine powder made almost entirely of elemental carbon - to yield a low-cost, easily molded compound that can mimic the average electrical conductivity of the human body. The material is shaped into brick-like blocks and then arranged on a non-conductive fiberglass frame in a form that simulates the mass and height of the average American adult male.
