Chemical threat detection has long been of interest to military, law enforcement, environmental agencies, and forensic investigators. Recently, as the propensity for both foreign and homegrown terrorism, illegal drug manufacture, and concern for environmental regulation continues to grow, the demand for rapid, portable chemical threat detection capabilities has increased dramatically. In particular, the ability to identify chemical threats (explosives, narcotics, toxic industrial chemicals, etc.) at a distance (standoff) is of special interest as it increases the safety of the end user during interrogation. Traditional analytical laboratory techniques such as high-performance liquid chromatography or gas chromatography coupled with mass spectrometry offer excellent sensitivity for detection and identification of trace amounts of threatening material. However, these techniques often lack the portability necessary for remote on-site interrogation as samples must be physically collected and brought to a laboratory for analysis. Vibrational spectroscopic techniques offer both the chemical identification and miniaturization capabilities required for portable, on-site chemical threat detection. Most importantly, spectroscopic techniques are inherently and uniquely standoff, where emitted or scattered photons are collected at some distance from the sample. The challenge then becomes miniaturizing the instrumentation while maximizing the distance at which accurate chemical detection can be made. Here we report on portable chemical threat detection instrumentation developed by Alakai Defense Systems, which employs deep ultra-violet Raman spectroscopy. We discuss the general system aspects such as basic optical design and ambient light rejection techniques. We also present data on the performance capabilities using several substances including actual narcotics and other compounds commonly used as cutting agents. Lastly, we discuss possible future directions including the ability for rapid spectroscopy while maintaining high photon detection sensitivity by employing an intensified scientific CMOS (sCMOS) and the propensity for NIR standoff Raman detection using deep-depletion CCD technology.
Alakai Defense Systems has created two new short range UV Raman standoff explosive detection sensors. These are called the Critical Infrastructure Protection System (CIPS) and Portable Raman Improvised Explosive Detection System (PRIED) and work at standoff ranges of 10cm and 1-10m respectively. Both these systems are designed to detect neartrace quantities of explosives and Homemade Explosives. A short description of the instruments, design trades, and CONOPS of each design is presented. Data includes a wide variety of explosives, precursors, TIC/TIM’s, narcotics, and CWA simulants
Alakai Defense Systems has created a standoff explosive detection sensor called the Check Point Explosives Detection
System for use at military check points. The system is designed to find trace level explosive residues from a standoff
distance to thwart the transport and use of illegal homemade explosives, precursors and related contraband. Because of
its standoff nature, this instrument could offer benefits to those searching for explosives, since it removes the searcher
from harm's way if a detonation occurs. A short description of the instrument, improvements to the system over the past
year, and a brief overview of recent testing are presented here.
In order to stop the transportation of materials used for IED manufacture, a standoff checkpoint explosives detection
system (CPEDS) has recently been fabricated. The system incorporates multi-wavelength Raman spectroscopy and laser
induced breakdown spectroscopy (LIBS) modalities with a LIBS enhancement technique called TEPS to be added later
into a single unit for trace detection of explosives at military checkpoints. Newly developed spectrometers and other
required sensors all integrated with a custom graphical user interface for producing simplified, real-time detection results
are also included in the system. All equipment is housed in a military ruggedized shelter for potential deployment intheater
for signature collection. Laboratory and performance data, as well as the construction of the CPEDS system and
its potential deployment capabilities, will be presented in the current work.
Recent progress has been made on an explosive laser standoff detection system called TREDS-2 constructed from COTS
components. The TREDS-2 system utilizes combination of Laser Induced Breakdown (LIBS), Townsend Effect Plasma
Spectroscopy (TEPS) and Raman spectroscopy techniques with chemometric algorithms to detect hazardous materials.
Extension of the detection capability of the TREDS-2 system on the real-time point detection of chemical, biological,
radioactive, and nuclear threats has been tested and presented in this report.
System performance of surface detection of a variety of CBRNE materials is shown. An overview of improvements to
the explosives detection capabilities is given first. Challenges to sensing some specific CBRN threats are then discussed,
along with the initial testing of TREDS-2 on CBRN surrogates on a limited number of surfaces. Signal processing using
chemometric algorithms are shown as a demonstration of the system's capabilities. A path forward for using the specific
technologies is also provided, as well as a discussion of the advantages that each technology brings to the CBRNE
The present work focuses on a new variant of double pulse laser induced breakdown spectroscopy (DP-LIBS) called
Townsend effect plasma spectroscopy (TEPS) for standoff applications. In the TEPS technique, the atomic and
molecular emission lines are enhanced by a factor on the order of 25 to 300 times over LIBS, depending upon the
emission lines observed. As a result, it is possible to extend the range of laser induced plasma techniques beyond LIBS
and DP-LIBS for the detection of CBRNE materials at distances of several meters.
A fully integrated UV Townsend Effect Plasma Spectroscopy (TEPS)-Raman Explosive Detection System (TREDS-2)
system has been constructed for use of standoff detection. A single 266nm Q-Switched Nd:YAG laser was used for
Raman excitation and TEPS plasma ignition. A nearly simultaneous 10.6μm CO<sub>2</sub> laser was employed for the signal
enhancement in the TEPS measurements. TEPS and Raman spectra have been measured for a wide variety of energetic
samples on several different substrates. Chemometric techniques are presented for analysis and differentiation between
benign and energetic samples. Since these techniques are orthogonal, data fusion algorithms can be applied to enhance
the results. The results of the TEPS and Raman techniques along with their algorithms are discussed and presented.
In-situ trace detection of explosive compounds such as RDX, TNT, and ammonium nitrate, is an important
problem for the detection of IEDs and IED precursors. Spectroscopic techniques such as LIBS and Raman have
shown promise for the detection of residues of explosive compounds on surfaces from standoff distances. Individually,
both LIBS and Raman techniques suffer from various limitations, e.g., their robustness and reliability
suffers due to variations in peak strengths and locations. However, the orthogonal nature of the spectral and
compositional information provided by these techniques makes them suitable candidates for the use of sensor
fusion to improve the overall detection performance. In this paper, we utilize peak energies in a region by fitting
Lorentzian or Gaussian peaks around the location of interest. The ratios of peak energies are used for discrimination,
in order to normalize the effect of changes in overall signal strength. Two data fusion techniques are
discussed in this paper. Multi-spot fusion is performed on a set of independent samples from the same region
based on the maximum likelihood formulation. Furthermore, the results from LIBS and Raman sensors are
fused using linear discriminators. Improved detection performance with significantly reduced false alarm rates is
reported using fusion techniques on data collected for sponsor demonstration at Fort Leonard Wood.