The war on terror is shrinking

Bryn Nelson Columnist

The fight against terror is shrinking.

As science races to confront terrorism with new technology, researchers are unveiling a new generation of devices featuring ever-more sophisticated sensors to quickly detect explosives, radiation, chemicals and biological agents.

Most share the promise of doing more with far less bulk, suggesting a future in which radiation from a dirty bomb is detected by a commuter’s iPhone, a laptop warns of explosives more than a football field’s length away, a hand-held unit spots airborne anthrax spores within seconds and a device no bigger than a matchbox sniffs out a tiny release of hazardous chemicals.

“We’d all like to have the tricorder on ‘Star Trek’ where you point it at something and it says, ‘Oh, it’s this,’” said Larry Senesac, a physicist at Oak Ridge National Laboratory in Oak Ridge, Tenn. If science isn’t quite ready to “boldly go where no man has gone before,” he agrees that researchers have made huge strides from the days of relatively immobile sensors. And as the devices have shrunk in size, costs have dropped as well.

For detecting explosives, “you’d like to screen people, you’d like to screen their luggage, you’d like to screen packages and ship containers,” Senesac said. “You’d also like to detect these improvised explosive devices that have been showing up all over, but particularly in Iraq.”

Oak Ridge National Laboratory’s new technology, known as standoff photoacoustic spectroscopy, allows people to literally stand off at a distance and detect hazards, suggesting a not-too-distant scenario “where vehicles could drive down the street at a reasonable speed and screen for these explosives,” Senesac said. In a lab setting, he and colleagues detected residue from TNT and two other types of explosives more than 20 yards away — “not just explosives, but we can tell which explosives they are.”

The method, described earlier this year in the journal Applied Physics Letters, has its origins in observations first made by Alexander Graham Bell in the 1880s about how certain frequencies of light can produce sound waves when pulsed onto a surface. Importantly, the version devised by Oak Ridge researchers lets them identify materials out in the open instead of within a pressurized chamber that would have undermined the technique’s usefulness. Essentially, the instrument illuminates a target with pulses of laser light. The light reflected off the target’s surface generates a signature sound when it becomes a vibration through an interaction with a tiny quartz crystal tuning fork.

Because every molecule has a unique spectroscopy signal, the acoustic form of the signal can be used like a fingerprint to identify a hazardous compound. With a broader spectrum of laser light illuminating the target, the resolution increases just like observing more of a person’s fingerprint allows a more accurate identification. With stronger lasers, Senesac said, researchers could potentially push their detection range to more than 100 yards. In the future, he said, drug enforcement agents might use a similar approach to scan the door handle of a house for traces of crystal meth or other illicit drugs.

As for size, off-the-shelf components can decrease costs while improving portability. Each quartz tuning fork, for example, cost the lab less than 16 cents. Currently, the prototype sensor fits into a cart you might push around a kitchen. “But most of the components could be easily made to fit into the size of a handheld calculator,” Senesac said. Including the laser and a controller, he figures a laptop-sized device is definitely within reach.

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