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Laser-based Remote Detection of Explosives

A problem faced by members of certain occupations in today’s society is the lack of an efficient remote detection technique. For example, imagine an employee at waste management facility who has just identified an unfamiliar scent. If this employee could identify the cause of the scent without having to subject themselves to the potentially hazardous source, their health would not have to be jeopardized for the safety of the facility. Similarly, visualize how much safer soldiers would be if they were able to detect explosive residue a distance away from the source.

The desire for standoff detection, that is, the ability to characterize an object from a distance, has led researchers at the University of Maryland Baltimore County (UMBC) to explore the effectiveness of UV-Raman Spectroscopy. In general, spectroscopy is a characterization technique which measures how matter interacts with light. More specifically, the mechanics of Raman spectroscopy involve bombarding a sample with laser light and using a detector to monitor how the light’s frequency changes after it has interacted with the sample. The frequency changes of light provide a great deal of insight into the nature of the sample. In fact, a Raman spectrum (graph generated by conducting Raman spectroscopy) typically provides enough information to characterize the molecular make-up of the sample.

The researchers at UMBC led by Dr. Bradley Arnold have developed an apparatus which is able to conduct Raman spectroscopy with samples up to ten meters away from the detector. This apparatus was largely designed by Dr. Arnold and his graduate student, Christopher Cooper. Undergraduate researcher, Michael Matrona, has worked to overcome alignment issues while also collecting and analyzing data. So far, the collective efforts of the research team have allowed them to generate identifiable spectra at distances of up to 4 meters. The next phase of their project will be to collect Raman spectra of samples placed on silica gel slides. Since silicon is the main constituent of sand, this effort will simulate a soldier using the technique to scan a desert environment for potential hazards.

Quartz

 

A quartz sample holder containing a hazardous

material being irradiated by laser light.