X-ray devices

Discovered in 1895 by W. C. Roentgen, x-rays are a form of invisible, highly penetrating electromagnetic radiation. Because of their ability to pass through most material, x-rays are used in a variety of applications, including security settings. Since the events of September 2001, the U.S. government has been investing enormous amounts of money and effort in technology to prevent future terrorist attacks, especially in U.S. transportation systems.
Currently, the Transportation Security Administration (TSA) is field-testing a noninvasive x-ray system known as a “backscatter portal” that can see items hidden on a person’s body, concealed in vehicles, or secretly stashed in cargo containers. The system’s signals interact with explosives, plastics, and metals, revealing their shape and form and thereby making them easy to visually identify.
The backscatter technology works by measuring the solar radiation reflected by the person or object under scrutiny. The system is sensitive enough to detect metal objects, plastic explosives and weapons, nonmetallic handguns, and drugs. In vehicle inspections, the driver briefly exits while the screening van slowly passes by the target, screening for contraband. When a person is screened, the individual steps into the refrigerator-sized machine, and the technology performs a virtual strip search, which provides inspectors with a clear view of what is underneath the person’s clothes—skin or weapons. Whether the technology is used to screen a vehicle or a person, TSA claims that the process takes less than a minute and asserts that the technology is physically harmless; however, critics purport that generating such a realistic image of an individual’s naked body violates privacy rights.
The TSA is aware of the revealing nature of the images. It is working with companies to create software that would substitute a generic body but leave in place the outlines of the suspected contraband. The TSA’s proposed goal for using this technology is to reduce the long queues in airports and to reduce security threats posed by vehicles containing explosives.
The devices are currently used by U.S. Customs agents at 12 airports to screen suspected drug smugglers, at London’s Heathrow Airport, and in London’s underground subway tube since the July 2005 bombings. Furthermore, the backscatter technology is being used as part of the Secure Automobile Inspection Lanes (SAIL) test project, which screens for explosives on automobiles boarding the Cape May-Lewes Ferry in Cape May, New Jersey, the Golden Gate Ferry in San Francisco, California, and several other designated locations.