Tuesday, October 5, 2010

Is the Government X-Raying You While You Drive?


Homeland Security has just purchased mobil X-ray vans that can scan cars, trucks and homes without the drivers even knowing that they're being zapped.

Photo Credit: Adrian Barnes via Flickr
If you have been feeling uneasy about having to be X-rayed by a Transportation Security Administration goon who can look under your clothes every time you fly, consider this: at least you can say no, and agree to be subjected to an old-fashioned full-body search.

No opt-out for the latest in anti-terror technology though, with reports just out in Forbes Magazine and the Christian Science Monitor that the Homeland Security Department has purchased 500 mobil X-ray vans called ZBVs that can scan cars, trucks and homes without the drivers even knowing that they’re being zapped.

These vans, made by a Massachusetts company called American Science & Engineering, are fitted out with what are called Z Backscatter X-ray devices, which aim a focussed X-ray beam that reportedly has the capability of penetrating 14 inches of steel.

In theory, the device is supposed to be safe for human targets, because it is operated at a distance, and because the beam is weakened by penetrating the metal of a vehicle before it reaches a person. But the flaws in this kind of reassuring safety calculus are readily apparent in a photo of a small truck carrying contraband that accompanies the Christian Science Monitor story. The X-ray image, after penetrating the truck cab’s metal body, clearly shows the contraband behind the driver’s seat, but it also just as clearly shows the shadowy outline of the driver of the pickup. Worse yet, even his window is half-way down, so there is no shielding at all of the X-rays hitting his head.

We can expect these mobil X-ray vans to be proliferating around the country soon, if they’re not out there already, but they may be hard to spot. As American Science & Engineering says in a note to investors on the company website:

A breakthrough in X-ray detection technology, AS&E's Z Backscatter Van is the number one selling non-intrusive mobile inspection system on the market. The ZBV system is a low-cost, highly mobile screening system built into a commercially available delivery van.

Prof. Peter Rez, a physicist a Arizona State University who specializes in X-ray technology, and who has been doing research on backscatter X-ray dosages, says that if used properly, the radiation doses received by targeted persons would be very minute, but then he notes that if the government begins a major campaign of surreptitious X-raying on highways and at locations of security concern (the machines are already being used at major sporting events like the Superbowl), there have to be concerns about whether the machines are being maintained in proper working condition (driving them around on America’s run-down highways is subjecting the machines to quite a beating), and about whether the operators are using them properly.

This is even the case with airport X-ray machines, he says, where the doses are very low, but the actual beam is quite powerful. Since X-ray beams cannot be focussed, two moving mechanical parts are used, including a spinning wheel with a small series of holes in it, so that what reaches the targeted individual is just short bursts of X-rays. If either of those moving mechanical parts broke down while a person was being zapped, though, Rez says the person would be “fried” by a major X-ray exposure. “I was assured by the government that the machines have a fail-safe system so they shut down instantly if the moving parts fail,” he says, “but BP had a fail-safe system too, and we saw how well that worked. For my part, I wouldn’t go through an X-ray scanner unless they could show me a very low documented failure rate!”

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