A paper by Dr. Boyd V. Hunter, Chief Technical Officer, Kestrel Corporation, USA; Jason M. Cox, Kestrel Corporation, USA; Paul Harrison, Kestrel Corporation, USA; William P. Walters, Kestrel Corporation, USA; and Dr. Michael A. Miller, Institute Scientist, Southwest Research Institute, USA

Reliable detection of chemical, biological and explosive threats is the first step in a successful interdiction and control operation. In a laboratory environment, there are many techniques that can be used to identify unknown materials. In a non-laboratory environment, the detection process is compromised by the presence of various backgrounds and interferents. These materials are problematic because their responses have similarities with the materials to be interdicted; confusion of the detection algorithms results, which produces false positive and false negative identifications. If the error rate is large enough, first responders and security forces will refuse to use instrument.
For the past few years, Kestrel Corporation has been developing a new spectroscopic technique called Differential Excitation Spectroscopy (DES) (patent pending). DES is a new pump-probe detection technique which characterizes molecules based on a multi-dimensional parameterization of the rovibrational excited state structure, pump and probe interrogation frequencies, as well as the lifetimes of the excited states. Under appropriate conditions, significant modulation of the ground state can result, providing a robust signal-to-noise ratio. The technique does not require special conditions—operation in both laboratory and outdoor environments has been shown to work equally well. While it is easy to understand how DES results provide a unique, simple mechanism to validate and understand various molecules in support of relevant science, the technique was developed to support the chemical detection and identification mission. The DES multi-dimensional parameterization provides an identification signature that is highly unique and has demonstrated high levels of immunity from common interferents and backgrounds, providing significant practical value for high-specificity material identification. The immunity of the technique may be
understood on the basis of the several parameters that must be correct to force the molecule into the excited state; the greater the number of factors that must be correct, the harder it is to generate a false positive signal.
In this paper, recent research using DES for identification of threat materials is reviewed. Results for common explosive materials such as AN, UN, RDX and TNT (in laboratory conditions as well as in the presence of interferents/backgrounds) are presented1. Testing on chemical warfare simulants such as DMMP and thiodiglycol illustrates the applicability of the technology to this class of threats2. Finally, ongoing work to detect vapors emitted by environmental hazards (solvents such as benzene, dichloroethylene, trichloroethylene, tetrachloroethane, chloroform and carbon tetrachloride) and physical security threats (such as sulfur dioxide, ethylene oxide, nitrogen dioxide and boron trifluoride) will be discussed. The threat classes that will be discussed are precisely the same materials or types of materials that would be controlled and interdicted in the on-going effort to control domestic or international terrorist activities, ensure the safety of facilities and individuals, as well as address current environmental safety requirements. DES provides a
high-specificity detection technique well-suited to the CBe mission.

Please access the Full Paper by clicking on the following link: Hunter – NCT CBRNe USA 2015

The Full Paper by Hunter, Cox, Harrison, Walters and Miller will be presented during NCT CBRNe USA Innovation Stream, taking place from April 29 to May 1.


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