Explosives Detection

Responding to the Improvised Explosive Threat

During Operation Iraqi Freedom, improvised explosive devices (IEDs) posed an increasing operational challenge to coalition forces. In response to this challenge, the office of the Director of Defense Research and Engineering (DDR&E) commissioned a study at Lincoln Laboratory to explore possible technical solutions for locating and/or mitigating roadside IEDs.

The Lincoln Laboratory study noted that the dearth of knowledge regarding the magnitude and composition of IED chemical signatures limited the ability to project the potential utility of chemical-based sensors. In response, the Laboratory made the strategic decision to invest experimental resources to begin measuring the chemical signatures of IEDs and to apply the new information to detailed trade studies on different potential sensing options. This science-based approach represented a departure from other requirements-based sensor development efforts and would ultimately help Lincoln Laboratory become an important contributor to the nation's chemical-sensing counter-IED community.

A comprehensive response to the IED threat requires the ability to perform experiments involving all aspects of their deployment. These photos show an experiment  involving a vehicle-borne IED.A comprehensive response to the IED threat requires the ability to perform experiments involving all aspects of their deployment. These photos show an experiment involving a vehicle-borne IED.

Experimental work by the Chemical, Microsystem, and Nanoscale Technologies Group began in 2005 with quantitative measurements of chemical signatures from IEDs and IED-related activities. The effort expanded to include numerous measurement campaigns at ranges in Edgefield, South Carolina; Yuma Proving Ground, Yuma, Arizona; the National Training Center, Fort Irwin, California; and Twentynine Palms Marine Base, Twentynine Palms, California. As the work became more widely recognized, support expanded from DDR&E (which is now the offfice of the Assistant Secretary of Defense for Research and Engineering) to also include the Joint Improvised Explosive Device Defeat Organization, the Defense Advanced Research Projects Agency (DARPA), the Army, and the Department of Homeland Security (DHS), and led to a close collaboration with the U.S. Army Forensic Analytical Center at the Edgewood Chemical and Biological Center at Aberdeen Proving Ground, Maryland. This information was disseminated to numerous agencies within both the DoD and DHS. In 2010, the work was expanded to include homemade explosives, such as those encountered during Operation Enduring Freedom in Afghanistan and threatening the U.S. homeland.

With a broad IED signature database then in hand, Lincoln Laboratory was able to evaluate the potential capabilities of the various proposed detection schemes. One detection method, called photodissociation followed by laser-induced fluorescence (PDLIF) and first reported in open literature in 2001, appeared most promising on the basis of that analysis. Starting in 2006, a Lincoln Laboratory effort refined and improved the PDLIF detection method. In this technique, a single ultraviolet laser pulse photodissociates the explosive molecule to create vibrationally excited nitrogen oxide (NO), and that same laser pulse also induces a unique fluorescence signal from the vibrationally excited NO. A prototype PDLIF system was successfully field tested at Fort Irwin, California, in April 2009.

In 2008, the Chemical, Microsystem, and Nanoscale Technologies Group was asked by the DHS Science and Technology Directorate to provide supporting science to assist them in the development and deployment of the next generation of explosive trace detection systems. This request led to the establishment of a state-of-the art mass spectrometry facility that includes triple-quadrupole, ion trap, and time-of-flight instruments all equipped with an array of atmospheric-pressure ionization sources.

As this work continues, IEDs still remain a threat to U.S. interests and will continue to be for the foreseeable future. Defense against such a persistent and adaptive threat requires the establishment of a long-term commitment to understand, detect, and counteract it. The effort in explosives trace-chemical signature studies and detection has complemented other in-house counter-IED initiatives and has positioned the Chemical, Microsystem, and Nanoscale Technologies Group at Lincoln Laboratory at the forefront of IED defeat technologies.

 

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