DOE's super-sensitive explosives detector
http://www.defensesystems.com/news/gcn/daily-updat [2008-7-22]
Tag : Tributyl Phosphate
The Energy Department’s Oak Ridge National Laboratory can nowdetect explosives at distances exceeding 20 yards using newphotoacoustic spectroscopy methods that use a laser and a devicethat converts reflected light into sound.
The technique involves illuminating a target sample with aneye-safe, pulsed light source and allowing the scattered light tobe detected by a quartz crystal tuning fork. The method enabledresearchers to detect trace explosive residue using lasers 100times less powerful than those of competing technologies. By usinglarger collection mirrors and stronger illumination sources,researchers believe they can achieve detection at distancesapproaching 109 yards.
"We match the pulse frequency of the illuminating light with themechanical resonant frequency of the quartz crystal tuning fork,generating acoustic waves at the tuning fork's air-surfaceinterface," said Charles Van Neste of Oak Ridge’s BiosciencesDivision. "This produces pressures that drive the tuning fork intoresonance."
The vibration’s amplitude is proportional to the intensity ofthe scattered light beam falling on the tuning fork which, becauseof the nature of quartz, creates a piezoelectric voltage.Piezoelectricity is the ability of some materials, such as crystalsand some ceramics, to generate voltage across the material inresponse to applied mechanical stress.
The method is a variation of photoacoustic spectroscopy, in whichmaterials exposed to rapidly interrupted light transform the energyinto sound. Plotting the sound against the light wavelength createsa photoacoustic spectrum of a sample that can be used to identifythe absorbing components of the sample.
The new method overcomes a number of problems associated with thetechnique. Most notably, agency researchers are able to probe andidentify materials in open air instead of having to introduce apressurized chamber, which renders photoacoustic spectroscopyvirtually useless for security and military applications.
Researchers believe the new technology can be an inexpensive andmore exact technique for detecting explosives in the field than iscurrently available.
Researchers tested the technology using tributyl phosphate andthree explosives—cyclotrimethylenetrinitromine,trinitrotoluene (better known as TNT) and pentaerythritoltetranitrate.
The Energy Department’s Oak Ridge National Laboratory can nowdetect explosives at distances exceeding 20 yards using newphotoacoustic spectroscopy methods that use a laser and a devicethat converts reflected light into sound.
The technique involves illuminating a target sample with aneye-safe, pulsed light source and allowing the scattered light tobe detected by a quartz crystal tuning fork. The method enabledresearchers to detect trace explosive residue using lasers 100times less powerful than those of competing technologies. By usinglarger collection mirrors and stronger illumination sources,researchers believe they can achieve detection at distancesapproaching 109 yards.
"We match the pulse frequency of the illuminating light with themechanical resonant frequency of the quartz crystal tuning fork,generating acoustic waves at the tuning fork's air-surfaceinterface," said Charles Van Neste of Oak Ridge’s BiosciencesDivision. "This produces pressures that drive the tuning fork intoresonance."
The vibration’s amplitude is proportional to the intensity ofthe scattered light beam falling on the tuning fork which, becauseof the nature of quartz, creates a piezoelectric voltage.Piezoelectricity is the ability of some materials, such as crystalsand some ceramics, to generate voltage across the material inresponse to applied mechanical stress.
The method is a variation of photoacoustic spectroscopy, in whichmaterials exposed to rapidly interrupted light transform the energyinto sound. Plotting the sound against the light wavelength createsa photoacoustic spectrum of a sample that can be used to identifythe absorbing components of the sample.
The new method overcomes a number of problems associated with thetechnique. Most notably, agency researchers are able to probe andidentify materials in open air instead of having to introduce apressurized chamber, which renders photoacoustic spectroscopyvirtually useless for security and military applications.
Researchers believe the new technology can be an inexpensive andmore exact technique for detecting explosives in the field than iscurrently available.
Researchers tested the technology using tributyl phosphate andthree explosives—cyclotrimethylenetrinitromine,trinitrotoluene (better known as TNT) and pentaerythritoltetranitrate.
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