Very sensitive explosives detector created

OAK RIDGE, Tenn., June 26 (UPI) -- U.S. government scientists say they've used a laser and a device that converts reflected light into sound to create a super-sensitive explosives detector.

Researchers at the U.S. Department of Energy's Oak Ridge National Laboratory say the device can detect explosives at distances exceeding 20 yards by utilizing a variation of photoacoustic spectroscopy.

The technology, originally created by Alexander Graham Bell during the late 1880s, then necessitated the use of a pressurized chamber, making it nearly useless for security or military purposes. The ORNL device is able to probe and identify materials in open air by illuminating the target sample with an eye-safe pulsed light source and allowing the scattered light to be detected by a quartz crystal tuning fork.

"We match the pulse frequency of the illuminating light with the mechanical resonant frequency of the quartz crystal tuning fork, generating acoustic waves at the tuning fork's air-surface interface," said researchers Charles Van Neste. "This produces pressures that drive the tuning fork into resonance."

While the researchers have been able to detect explosives at 66 feet, they say they can eventually achieve detection at distances approaching 330 feet.

The research is reported in the journal Applied Physics Letters.