Now a new, better way to detect explosives

Scientists have found a new way to detect explosives - the Optical Dynamic Detection (ODD) solution. Currently, spectroscopy has been used for the purpose.
"Spectroscopy is good, but it only gets you so far," said Eric Houser, a program manager in the Explosives Division of the Department of Homeland Security's Science and Technology Directorate (SnT).
The wave of the future may lie in a technology called optimal dynamic detection (ODD), which overcomes many of spectroscopy's limitations. Spectroscopy uses the colour spectrum to shed light on a package's makeup.
This method presents two problems. First, there's distance. Many threat detection methods require either the person or the detector to be physically near the bomb, making spectroscopy extremely dangerous.
Second, approaches like spectroscopy, which rely on reflected light, often are not sensitive or selective enough, especially in the real world where chemical signatures may overlap or be contaminated.
The researchers are aiming to develop a portable prototype in the next three years that can be field-tested.
Here's how ODD works-a bomb technician beams a "raw" laser pulse toward a suspicious bag, looking for a specific explosive.
The pulse passes through an electro-optical filter, gaining clarity as it is bent through lenses, reflected by mirrors and amplified by chips. When the technician tunes the laser to a new frequency, the filter reshapes the laser's pulse. As it is bent, reflected, and electronically processed, the pulse changes amplitude.
The shaped pulse hits the chemical environment around the lunchbox and excites the energy state of the material of interest, emitting an energy "signature." Since the pulse was precisely defined, so is the signature.
A second laser, called an analyzing "probe," is beamed through the excited molecules, measuring its spectrum. The probe beam passes into an electro-optical detector stationed on the other side of the target.
The pulse laser's final shape is stored and analyzed. If the signature looks like that of an explosive, it can conclusively be traced to the explosive molecules that emitted it, which may be found on the bag's fabric or zipper.
In this way, ODD reduces background signals, which interfere with the identification process of a potential bomb, and amplifies the return signal, which illuminates the threat.
The light energy going in is precisely defined, which makes it easier than spectroscopy to read the energy coming out.
"In evaluating a potential bomb, you're looking for a needle in a haystack. ODD helps bring the needle to the forefront," explained Houser.

Source : Click

No comments: