Standoff detector systems are an important part of any chemical/biological defense system. It's critical that the fielded systems meet the requirements of the battlefield commander. This requires criteria checked with sound test protocols. This paper discusses and proposes methods to improve the testing, modeling, and characterizing of standoff detector systems. The described testing protocol will provide information to support testing, evaluation, design, training, and other areas of the acquisition process. The goal of higher information content is achieved at a lower cost than the current generation of systems.

This work describes initial modeling results for a single US Army ICAM (Improved Chemical Agent Monitor). The model is data driven and based on data obtained using pulse inputs to the ICAM from a Chemical Stimulator (a system that presents mixtures, quantifiable in time and concentration, to the input of the ICAM. A third order ARIMA model proved sufficient to model the input-output relationship for this ICAM for inputs of a single chemical. Concentration ranged from 100 ppb to 4000 ppb. Extensions of the model to more complex situations are ongoing.

Experimental chemical detection and radiometric results are presented from recent coherent differential absorption lidar (DIAL) ground tests conducted over four kilometer horizontal path at the Air Force Research Laboratory. Heterodyne data was collected simultaneously with the Laser Airborne Remote Sensing direct detection DIAL sensor for comparison. A brief system description of the bistatic coherent DIAL system is presented. These experiments illustrate some of the technological challenges encountered in the implementation of a wavelength-agile coherent chemical detection system.

To be able to understand and predict the concentration of a target compound in the atmosphere one must understand the atmospheric chemistry involved. The transformation of volatile organic compounds in the troposphere is predominantly driven by the interaction with the hydroxyl and nitrate radicals. The hydroxyl radical exists in daylight conditions and its reaction rate constant with an organic compound is typically very fast. The nitrate radical drives the nighttime chemistry. These radicals can scavenge hydrogen from an organic molecule generating secondary products that are often overlooked in detection schemes. Secondary products can be more stable and serve as a better target compound in detection schemes. The gas phase reaction of the hydroxyl radical (OH) with cyclohexanol (COL) has been studied. The rate coefficient was determined to be (19.0 +/- 4.8) X 10^-12 cm³ molecule^-1 s^-1 (at 297 +/- 3 K and 1 atmosphere total pressure) using the relative rate technique with pentanal, decane, and tridecane as the reference compounds. Assuming an average OH concentration of 1 X 10⁶ molecules cm^-3, an atmospheric lifetime of 15 h is calculated for cyclohexanol. Products of the OH + COL reaction were determined to more clearly define cyclohexanol's atmospheric degradation mechanism. The observed products were: cyclohexanone, hexanedial, 3- hydroxycyclohexanone, and 4-hydroxycyclohexanone. Consideration of the potential reaction pathways suggest that each of these products is formed via hydrogen abstraction at a different site on the cyclohexanol ring.

The motivation for using response to physical perturbation to classify microparticles came from our previous experiments with Dipicolinic Acid (DPA). DPA as a calcium complex is a major component of bacterial spores, constituting more than 5% of their dry weight. It is not commonly found in other natural products and therefore its presence is indicative of the presence of bacterial spores. Previous schemes utilizing the presence of DPA to detect these spores have relied on fluorescence which occurs when lanthanide metals (e.g., terbium) are added to a solution where the presence of DPA is to be determined. We have recently demonstrated that changes in the fluorescence of DPA can be stimulated without the addition of such reagents. Thus after exposure to UV light, a substantial increase of fluorescence emitted by DPA solutions with a peak at 410 nm occurs for excitation light with wavelength less than approximately 305 nm.

A methodology is presented that allows aerosol particle size data to be used to indicate when an abnormal aerosol event may be occurring. Such data can be collected from an array of commercially available particle counter-sizers. The methodology employs two main elements: a detection element that recognizes when an aerosol concentration spike event is occurring; and a classification element that classifies aerosol events as normal (e.g. dust kicked up by wind gust or generated by normal vehicular activity) or abnormal (e.g. mistakenly released non-indigenous aerosol material). The detection element is based on observation of statistically significant rises in the aerosol concentration level, during an appropriate time interval. The classification element uses an new 3D feature space that highlights relevant differences in the aerosol particle size distribution function. The classifier adapts to the local environment by learning the region of the feature space that is occupied by normal aerosol events. Observations which then fall significantly outside this region are classified as abnormal. The methodology was developed using a set of atmospheric aerosol data containing over 600,000 observed aerosol particle size distributions, under both normal conditions, and with intentionally introduced abnormal aerosol. An implementation of the methodology is described. Many abnormal aerosol events in the data set are demonstrated to be distinguishable from normally occurring aerosol events.

Infrared spectroscopy is an important technique for measuring airborne chemicals, for pollution monitoring and to warn of toxic compound releases. Infrared spectroscopy provides both detection and identification of airborne components. Computer-assisted classification tools, including pattern recognition and artificial neural network techniques, have been applied to a collection of infrared spectra of organophosphorus compounds, and these have successfully discriminated commercial pesticide compounds from military nerve agents, precursors, and hydrolysis products. Infrared spectra for previous tests came from a commercial infrared library, with permission, from military laboratories, and from defense contractors. In order to further test such classification tools, additional infrared spectra from the NIST gas-phase infrared library were added to the data set. These additional spectra probed the tendency of the trained classifiers to misidentify unrelated spectra into the trained classes.

This paper extends our earlier work in developing statistically optimal algorithms for estimating the range- dependent concentration of multiple vapor materials using multiwavelength frequency-agile lidar with a fixed set of wavelength bursts to the case of a time series processor that recursively updates the estimates as new data become available. The concentration estimates are used to detect the presence of one or more vapor materials by a sequential approach that accumulates likelihood in time for each range cell. A Bayesian methodology is used to construct the concentration estimates with a prior concentration smoothness constraint chosen to produce numerically stable results at longer ranges having weak signal return. The approach is illustrated on synthetic and actual field test data collected by SBCCOM.

This paper presents a maximum likelihood based algorithm capable of estimating the concentration of one or more aerosol clouds as a function of range. The traditional Differential Scattering technique does not optimally utilize all the information available with tunable LIDAR sensors. For this reason, the authors have investigated alternative approaches that may better handle the general multi-material multi-wavelength scenario. This algorithm was tested using data that was generated to simulate the response of the Army's FAL sensor. The algorithm is shown to be able discriminate between three materials.

Anthrax has been recognized as a highly likely biological warfare or terrorist agent. The purpose of this work was to design a culture technique to rapidly isolate and identify `live' anthrax. In liquid or solid media form, 3AT medium (3-amino-L-tyrosine, the main ingredient) accelerated germination and growth of anthrax spores in 5 to 6 hours to a point expected at 18 to 24 hours with ordinary medium. During accelerated growth, standard definitive diagnostic tests such as sensitivity to lysis by penicillin or bacteriophage can be run. During this time, the bacteria synthesized a fluorescent and thermochemiluminescent polymer. Bacteria captured by specific antibody are, therefore, already labeled. Because living bacteria are required to generate the polymer, the test converts immunoassays for anthrax into viability assays. Furthermore, the polymer formation leads to the death of the vegetative form and non-viability of the spores produced in the medium. By altering the formulation of the medium, other microbes and even animal and human cells can be grown in it and labeled (including viruses grown in the animal or human cells).

We are developing (U.S. Air Force, SBIR) a proprietary technology, based on the enzyme Q-beta replicase, to very rapidly detect and identify microorganisms (rRNA), virions (particularly RNA-based), and proteins of interest for pathogen detection. This enzyme is known to amplify a specific RNA signal one billion-fold in less than fifteen minutes at a constant temperature of 37 degree(s)C. RNA probes are made in `halves' that are joined to each other after their terminal ends are brought into proximity mediated by the binding to the target. Only such a full-length molecule can be amplified. We have demonstrated specific examples of recognition of RNA target sequences of interest in species of Bacillus and are investigating methods for overcoming the well-known promiscuity of the enzyme so that this recognition feature can be utilized with confidence, even in the presence of dirty backgrounds.

We are studying ways to improve the performance of evanescent wave biosensors for use in detecting chemical and biological agents. We show a beam-propagation simulation that is used to determine the optimum fiber profile to achieve the desired propagation parameters. The model parameters can then be used to fabricate polymer fibers using an in-house fiber drawing apparatus. We also demonstrate a simple method of comparing the optical performance of different waveguides for use in such sensors.

We have successfully evaluated and incorporated ferrocene- based polymers as sensing elements in a novel tapered optical fiber device. Preliminary studies have shown that certain gases can modify the refractive index of these polymers. We have used these polymers as cladding over a tapered region of single-mode fibers. The device behaves as a modal interferometer with a beat length that is controlled by the diameter of the tapered region and the refractive index of the cladding. We have shown that a small variation in the refractive index of the polymer has a direct influence on the transmission characteristic of the tapered region. The responses of several sensors to ammonia, carbon dioxide, and nitrous oxide have been examined. We have fabricated several sensors with different sensitivities by tuning their beat length. Reusability and selectivity of several sensors have also been investigated. A novel, computer based, analysis has been developed to predict the behavior of these devices. A reasonable agreement has been obtained between the experiments and the theory. These sensors can be fabricated inexpensively and operated in harsh environment. A few potential applications are pollution detection, hazardous waste analysis, exhaust analysis of internal combustion engines, and explosive gas monitoring.

We have developed a new and widely-applicable chemical sensing technology based on the coordinated detection of photo-induced charge movements (PICM) of reporter molecules embedded in polymer films. This general technique has been successfully applied to the detection of biomolecules such as sugars as well as other biochemicals. By detecting specific pathogen derived biomolecules, a pathogen-specific sensor can be constructed. We have shown the feasibility of this approach by fabricating a sensor sensitive to the presence of molecules of bacterial origin. These sensors can have a real-time response. They are also inexpensive to manufacture and can be made disposable. We are developing a miniature array of such sensors that may be able to concurrently determine a variety of analytes. Besides biomolecules, this sensing technology can also be applied to the quantification of other organic and inorganic chemicals such as oxygen and ions. The ability of oxygen as well as other molecules to interact with singlet states of molecules and quench fluorescence can also affect the mechanisms that product PICM. For some molecules the quenching of PICM can be shown to follow typical Stern-Volmer quenching. We have investigated the oxygen-sensitivity of several families of compounds known to produce PICM, including the fullerenes.

We report herein on the development of a dual receptor detection method for enhanced biosensor monitoring. The proposed scheme requires the integration of a chemical transducer system with two unique protein receptors that bind to a single biological agent. Optical transduction occurs because the two protein receptors are tagged with special molecular groups. When bound to a single biological agent, these fluorescently labeled proteins undergo a change in fluorescence. This `fluorescent switching' relies on the well-known mechanisms of fluorescent resonance energy transfer (FRET). The paper focuses on the investigation and optimization of the chemical transduction system (FRET). A number of FRET dye pairs were tested in a spectrofluorimeter, and promising FRET pairs (FITC/TRITC and DMACA/FITC) were further tagged to the protein, avidin and its ligand, biotin. Due to their affinities, the FRET-tagged biomolecules combine in solution, resulting in a stable, fluorescent signal from the acceptor FRET dye with a simultaneous decrease in fluorescent signal from the donor FRET dye. The results indicate that the determined FRET pairs can be utilized in the development of dual receptor sensors.

This presentation will describe the design, fabrication, and testing of 2-element, and 8-element micro-Chemical Analysis Array ((mu) CANARY) sensor chips and address electronics. The detailed performance characterization of (mu) CANARY sensors for vapor and liquid phase detection will be presented. For vapor detection, NRL has applied polymer receptor coatings targeted at detection of chemical weapon agents, and has performed extensive chemical vapor exposure tests using two chemical weapon simulants and four vapor phase interferents. Data describing temperature dependence, long term/short term drift stability, detection limits, detection linearity, and vapor selectivity will be presented.

Most microorganisms evolve a suite of volatile metabolites. Some microorganism cultures evolve distinctive odors suggesting that the volatile compounds produced by microorganisms might be used to quickly distinguish microorganism types. We have measured infrared spectra of volatiles from common soil microorganisms. FTIR measurements were performed using the Bomem MB157 Fourier transform infrared spectrophotometer with ZnSe optics, using a MCT detector (500 cm^-1 cut off). Spectral signatures of cultures dominated by coccus microorganisms differed from those with bacillus microorganisms. With improved infrared detection, IR signatures of microbial volatiles may be useful to characterize microorganism consortia and the predominant metabolite.

Development of an OPO wavelength conversion scheme is currently in progress that converts the 1 micrometers output from a diode-pumped laser, to the 8 - 12 micrometers spectral region for remote chemical sensing applications. Preliminary results from the non-optimized first stage OPO, which uses an x-cut KTA crystal, show a 21% energy conversion efficiency from 1 micrometers to 2.59 micrometers . The 2.59 micrometers output will then be used to pump a CdSe OPO to generate tunable 8 - 12 micrometers idler wave output.

A 100 Hz, optical parametric oscillator (OPO) lidar breadboard is designed, built and tested for remote chemical sensing in the 8 - 12 micrometers range. Continuous tuning is achieved by angle tuning a type II, silver gallium selenide (AgGaSe₂) OPO crystal pumped in a single step by a 2.088-micrometers pump laser. The pump source for the OPO consists of a temperature stabilized, continuously pulsed, resonantly pumped Ho:YAG (2.088-micrometers ) laser, end-pumped by a diode- end-pumped Tm:YLF (1.9-micrometers ) laser. The 9 mm X 5 mm X 25 mm-long OPO crystal was mounted on a computer-controlled galvanometer scanner for rapid wavelength tuning (1.5 micrometers between shots). Continuous tunability was demonstrated from 7.9 to 12.6 micrometers with energies in the 50 - 400 (mu) J range. Quantum slope conversion efficiencies up to 40% were obtained. Far-field beam divergence measurement showed the output of the OPO to be 2.6 times diffraction limit. The improved OPO beam quality over previous studied tandem OPO systems is attributed to the reduced Fresnel number of the OPO cavity (idler resonating) and the better beam quality of the pump source. A LabWindows based data collection and analysis system is implemented. The effectiveness of the OPO as a source for chemical sensing is demonstrated by the collection of the absorption spectrum of ammonia.

The WILDCAT sensor is being developed to provide long range, laser standoff detection of chemical agent vapor and aerosol clouds by DIAL and range-resolved cloud mapping by DISC. The sensor is composed of two major subsections, including a telescope/gimbal assembly and a laser/beam diagnostics section that are held in alignment with a surrounding truss system and electrically-actuated, closed-loop mirrors. The entire assembly is integrated into a transportable, 30 ft long container that is field operable. The laser is a pulsed CO₂ type with output energies of 1 J at a repetition rate of 100 Hz and it uses an agile grating to access approximately 60 lines over the 9.2 - 10.7 micrometers band, also at a 100 Hz rate. The telescope/gimbal subsection is composed of a 60 cm dia telescope mounted to a yoke gimbal which provides for full hemispherical scans. The sensor includes a data acquisition system composed of 12 bit, 30 MHz analog-digital converters and a digital signal processor that maintains a running average data stream for each range bin. Algorithms allow for real-time data processing and radar displays of chemical concentration.

US Army Soldier and Biological Chemical Command (SBCCOM) at Aberdeen Proving Ground, MD, with contractor Fibertek, Inc., Herndon, VA, is developing a multiwavelength lidar system to provide detection and discrimination ofpotential Biological Warfare (BW) clouds at standoff distances of several kilometers. Under this effort, a prototype system using Light Detection and Ranging (LIDAR) technology has been designed, fabricated and successftilly tested against a range ofBW simulants at the Dugway Proving Ground, UT. The system, known as the Short Range Biological StandoffDetection System (SR-BSDS), has demonstrated the capability of detecting biological aerosols using infrared LIDAR while discriminating between biological and non-biological using ultraviolet LIDAR. The SR-BSDS is a component ofthe Joint Biological Remote Early Warning System (JBREWS) Advanced Concept Technology Demonstration (ACTD) program. This paper describes the technology and the hardware and presents recent field testing results.

A lightweight, compact sensor breadboard demonstrator is being developed that will be capable of detecting chemical agents in the 8 - 12 micrometers band by DIAL for ranges on the order of 4 km. Engineering analysis shows that the overall sensor size and weight would be approximately 1 cu. ft. and 35 lbs., respectively. The sensor is composed of a 12.5 cm diameter, off-axis paraboloid receive telescope and a 300 Hz repetition rate solid-state laser transmitter. The transmitter is based on a diode-pumped, 1.06 micrometers laser with an output energy of 20 mJ and two cascaded OPO stages that shift the laser wavelength to the far IR bands. The first stage OPO is configured in an arrangement that shifts the laser output to beyond 2 micrometers . The second stage OPO completes the shift to the 8 - 12 micrometers band, giving an overall 1.06 (mu) $m yields 8 - 12 micrometers conversion efficiency of 2% and a sensor output power of 0.1 W.

A compact (2'6' X 2'5' X 1'1') 3.30 - 3.47-micrometers DIAL lidar has been constructed for base remediation and chemical monitoring. The lidar system is designed for short range (0.5 km maximum) aerosol backscatter detection of light hydrocarbons with sensitivities at parts-per-million level in a 30-m ranging bin. The system can also operate in the topographic mode. The on-line and off-line wavelengths are produced sequentially using a dual crystal intra-cavity KTA OPO. Detection is by means of an 8-in Newtonian telescope coupled to a Stirling cycle cooled InSb detector. The system incorporates an onboard digital signal processor and controller, operator's interface is furnished by a laptop PC. Results of initial tests using diesel fuel and a solvent are presented.

Here we describe the development of a tunable ultraviolet LIDAR we use as an exploratory tool for fluorescence data acquisition and performance modeling of standoff bio- sensors. The system was developed around a Continuum model ND 6000 dye laser. The laser has a pulse repetition frequency of 10 Hertz and is tunable from 276 to 292 nanometers with a peak fluence of 75 milliJoules per pulse. The receiver consists of a 16-inch Dall-Kirkham telescope optically coupled, in free space mode, to two photomultipliers. The photomultipliers detect direct laser scatter and the resulting fluorescence. We will also describe the results of field trials conducted at Battelle's West Jefferson facility and chamber trials conducted at Aberdeen Proving Grounds.

Artificial odor recognition system is developed in order to mimic the human sensory test in cosmetics, parfum and beverage industries. The developed system however, lacks of ability to recognize the unknown type of odor. To improve the system's capability, a hybrid neural system with a supervised learning paradigm is developed and used as a pattern classifier. In this paper, the performance of the hybrid neural system is investigated, together with that of FALVQ neural system.

In developing high temperature incendiary weapons, the temperature and duration required to inactivate spores is needed information. Three common biowarfare simulants, Bacillus anthracis var Sterne, Bacillus thuringiensis var Kurstaki and Bacillus globigii var niger have been studied for their susceptibility to heat. The spores of all three simulants lose viability when exposed to temperatures between 250 and 300 degree(s)C for 1 second. Bacillus globigii is perhaps the most heat resistant of the three simulants studied, with Bacillus anthracis and Bacillus thuringiensis having similar susceptibilities to heat. Low temperature experiments requiring longer durations were also conducted; over a period of days at 90 degree(s)C. Bacillus anthracis spores can be inactivated. Thermodynamic and kinetic analysis were also performed. An important implication for any high temperature incendiary is the amount of heat or energy the spores absorb between ambient temperatures and 100 degree(s)C. A phase transition occurs centered at 184 degree(s)C for Bacillus thuringiensis. This is also the beginning of a massive weight loss from the spores, as well as a point at which the kinetics of the kill seem to change.

Dynamic responses a photothermal detector based on bimetallic cantilevers with large aspect ratio are modeled and compared with the experimental data. Photothermal spectrum of polymer epoxy coating is demonstrated in the near infrared region.

An experimental study has been carried out using a Miniature Quadrupole Mass Spectrometer (MicroQuad) for gas analysis. Conventional quadrupole rods have been replaced with a micromachined mass filter made from silicon with Au metallized specially drawn glass fibers of length 30 mm and diameter 0.5 mm. A standard hot filament ion source and both Faraday detection and a channel electron multiplier have been used. The effect of ion focus voltage has also been modeled by SIMION simulation. Conventional electronics were adapted to run at 6 to 8 MHz and mass spectra in the range 0 - 50 a.m.u. The results indicate a good valley separation between O, OH, H₂O and Ar²⁺ and a best resolution at 10% peak height of 0.9 a.m.u. at mass 40 with the multiplier. Application of a static magnetic field transversely to the body of the mass filter is shown to improve resolution howbeit at the expense of ion transmission through the filter.