Now that we've gotten the gist of the structures, let's see how they produce images of you.īackscatter machines use rotating collimators to generate X-rays, which pass through a slit and strike a passenger standing inside. Two stacks of disc-shaped transmitters, each surrounded by a curved protective shell known as a radome, sit inside the wall of the structure and pivot 180 degrees around a central point. Two of its six panels are open to serve as an entrance and an exit, while four of the panels sport transparent glass or plastic. The two units face each other with a gap between them big enough to accommodate a person.Ī millimeter wave scanner, however, looks a lot like an oversized, hexagonal telephone booth. Each radiation source is housed in a rectangular structure resembling a large industrial freezer. In terms of construction, a single backscatter machine includes two radiation sources so that both the front and the back of the person can be imaged without producing any blind spots. In other words, the waves emitted by mmw scanners are much larger and therefore have less impact on small structures, such as human proteins and nucleic acids. Millimeter wave scanners produce a special type of microwaves with wavelengths that fall in a range exactly between 0.001 meters (1 millimeter) and 0.01 meters (10 millimeters). Backscatter machines produce low-energy X-rays, which have a wavelength on the order of 0.0000000001 meters, or 0.0000001 millimeters. These waves travel through space and come in various sizes, or wavelengths. With that in mind, we're going to compare and contrast the two technologies across a variety of parameters, starting with the kind of energy they emit.īoth types of scanners give off energy in the form of electromagnetic radiation, which exists in nature as waves of energy made from both electric and magnetic fields. And many more feel a bit lost trying to understand how the machines work and how they're different. Still, many people remain skeptical that airport scanners, in any shape or form, are completely safe. And they've taken steps to protect passenger privacy by installing software that either creates generic outlines of people or blurs certain regions of the image. In the U.S., the TSA and the vendors that manufacture the scanners – such as Rapiscan for backscatter and L-3 Communications for millimeter wave - continue to assure the public about the safety of the devices. That ban complies with a law in several European countries that says people shouldn't be exposed to X-rays except for medical reasons. The European Union has addressed these questions decisively: It bans any body scanners that use X-ray technology. How much radiation do these machines produce? Is it enough to increase cancer rates in the general population? And can TSA agents see intimate details we'd rather they didn't? As soon as the TSA began installing the scanners in 2010, passengers, pilots and public health officials began firing off questions.
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