Organizations such as the military, hazardous materials units, first responders and industries involved in the processing and manufacture of chemicals all have requirements for specialized whole body protection for those people in their organizations whose job it is to work with toxic chemicals on a day to day basis or in emergency situations. Currently, excluding chemical biological (CB) challenge scenarios, there is no routine monitoring of the possible ingress of toxic chemicals within chemical protective suits. Under existing national standards, swatches of the protective suit fabric are usually tested for chemical breakthrough and if they meet certain criteria, the suit is considered to provide adequate protection to the individual. Despite advances in protection level research provided by full system protective clothing tests, inexpensive, real-time, sensitive and robust chemical monitoring systems for use both under protective clothing and within a challenge environment, remains a technologically deficient area. This paper presents the results of a preliminary assessment of the feasibility of miniature detectors for monitoring real-time volatile organic chemical (VOC) challenges under chemical protective clothing and in closed environments where such suits are used. Nine gas sensors of n-type semiconductor design (Figaro Engineering Inc) were assessed for their response to a dichloromethane concentration of 560 ppm at a temperature of 23 degrees Celsius and relative humidity of 20%. Absolute voltage output, speed of response to dichloromethane exposure, and time required to return to zero, were considered. The top ranked sensor was further evaluated for its calibration response to a range of dichloromethane concentrations up to 560 ppm. Variables that were considered include effect of temperature and relative humidity, hysteresis and repeatability. Increasing RH causes an increase in the zero output of the sensor with an approximate linear relationship. The sensor response was characterized by minimal hysteresis, indicating that calibration values over the short term are very stable. Calibration responses measured on different days were in excellent agreement.

The results of Raman and fluorescence spectra investigations of fluoroorganic aromatic compounds are presented. We present technique for realizing of qualitative and quantitative analysis of fluoroorganic aromatic compounds on the base of Raman and fluorescence spectroscopy. We propose to applicate the pulsed copper vapor laser for exciting of Raman and fluorescence spectra of fluoroorganic samples. The Raman spectra have been received for a number of compounds as: 1- bromoperfluoroocotane, perfluorodecanoic acid, 1,3,5- trifluoromethylbenzene, hexafluorobenzene, pentafluoropyridine, p-fluoro-DL-phenyl-alanine, m-fluoro-DL- phenyl-alanine, o-fluoro-DL-phenyl-alanine, m-fluoro-DL- tyrosine, 6-fluoro-DL-tryptophan, 5-fluorouracil, 5- Fluorouridine, 5-fluoroindole. On the base of our measurements we have worked out the manner of linear molecule C_nF_2n+1Br length recognizing. Thus, presented technique, based on using of the modern laser sources and registration system of Raman and fluorescence spectra, permitted to identify the different fluoroorganic molecules in mixtures and pure samples.

This paper describes the theory and design of a new laser system for monitoring ammonia in human breath to provide information on the clinical course in patients with liver disease. The technique depends upon proper illumination of human breath with radiation from modulated laser sources at selected wavelengths. The wavelength selection is based on the absorption characteristics of ammonia and other interfering sources. The laser radiation transmitted through the breath gases is detected and their signal processing is based on differential absorption laser spectroscopy. This is done in such a way to overcome the performance limitations of conventionally available equipment. The detailed description and operating characteristics of this system are presented.

A novel experimental set-up using laser-induced breakdown spectroscopy (LIBS) for environmental analyses of heavy metals is described in this paper. It is based on state-of-the-art spectroscopic equipment, advanced detectors, and laser atomizers: a 0.75 m spectrometer ARC-750, intensified TE- cooled 256 X 1024 CCD camera, probe with fiber optic guide for signal transportation, and Nd:YAG laser plasma atomizers with two different methods for sample delivery. In the first method the liquid solution containing the atoms to be investigated is drawn into the chamber of the nebulizer. The mixture passes through the nozzle, accompanied by argon gas along with formed aerosol, and enters the plasma plume, which is generated by the laser spark in argon. The second method is based on direct generating of the plasma in the water jet of a continuously circulating sample. LIBS testing of samples containing Al, Cd, Cu, Fe, Pb, Zn, and Cr ions was compared with results using atomic absorption spectrophotometry. Initial indications showed good agreement between these two methods. Detection levels of less than 100 ppb were observed for copper and chromium. The described spectroscopic system exhibits high sensitivity, accumulation of luminescence spectrum in real time; and high dynamic range for concentrations detection from 100 ppb to 1000 ppm.

A novel spectrometer device using a single monolithic optical component and a detector array has been developed. The device is compact, rugged, and has good spectral purity and resolving power. The device size is 1.4 X 1.4 X 0.6 inches. Current designs work both in the visual and near infrared. Potential applications are manufacturing control, agricultural screening, medical instrumentation, and color measurement.

Ultrasensitive optical spectroscopy technologies for environment monitoring, and in general, for gas analysis in the near Infrared are mainly based on the following spectroscopic methods: diode laser spectroscopy with multipass cells, with or without frequency modulation, photoacoustic spectroscopy, and since very recently, difference frequency spectroscopy with diode lasers. One of the most important issues of any monitoring technology, as important as the sensitivity, is its ability to provide absolute absorption coefficients without the need of complicated and cumbersome calibration procedures. Until now, two of the most sensitive optical spectroscopic technologies capable of providing this absolute information, Cavity Ringdown Spectroscopy and Intracavity Laser Absorption Spectroscopy have practically no use in this field. Due to recent advances, these two methods can now provide low-cost very compact field instruments working in the spectral range from 0.8 to 2.5 microns, with the smallest detectable absorption down to 10^-10 (one over 10 billions) per one centimeter of the absorption path. This would result in the sub-ppb detection limit for moisture for example. Experimental results obtained with prototype field instruments developed by our group will be presented. Future perspectives will be discussed.

Fibertek is currently under contract to the US Army Soldier and Biological Chemical Command (SBCCOM) at Aberdeen Proving Ground, MD to develop a multi-wavelength lidar system. Under this effort, Fibertek will deliver a system that is capable of detecting the presence of biological aerosols. The SR-BSDS has successfully demonstrated the ability to detect and track a biological aerosol cloud while discriminating between biological and non-biological aerosols and hard targets. The SR-BSDS is an active standoff detection system with both ultraviolet (UV) and infrared (IR) capability. The UV wavelengths can provide near real time detection and ranging of a particulate cloud with demonstrated discrimination capability. Recent enhancements to the IR capability extended the cloud detection range and acquisition capability as well as providing an autonomous operation mode of operation. The SR-BSDS can be operated in one of two modes, manual or autonomous. In the manual mode the operator selects the desired scan field of view, resolution, wavelength, and degree of pulse coadding, then instructs the system to start scanning. The system will monitor its own performance and display information to the operator to indicate proper operation. The system will monitor cloud data and warn the operator when the sensor is aimed at an aerosol of interest. If a biological cloud of interest is found, an audible alarm will sound, and the operator can examine cloud imagery while the system continues to automatically monitor and track all clouds in the field-of-view. The scanning parameters can also be changed easily upon aerosol detection, if desired. In the autonomous mode, the operator selects the desired scan field of view. The system automatically scans for aerosol clouds with the IR beam. This is accomplished in a rapid, single pulse laser firing mode. Once a cloud with specified characteristics is acquired, the system automatically switches over to an UV beam for discrimination interrogation. System status, data and discrimination interrogation results will be transmitted over a wireless modem to a Command Post. All the above will continue to operate without additional operator intervention. The autonomous operation feature was recently demonstrated at Dugway Proving Ground in July of 1999. Field testing to date, both at Aberdeen Proving Ground, MD and Dugway Proving Ground, UT in 1998 and 1999 successfully demonstrated the system's detection, discrimination, scanning functions and autonomous operation. With the initial field testing and system demonstration testing successfully complete, emphasis is on several areas of enhancements in preparation for additional DPG testing and system delivery for field implementation in 2000.

A prototype of an unattended ground sensor has been developed for detection of biological agent aerosols. This point sensor uses ultraviolet laser induced fluorescence (UV LIF) to detect aerosol biological microorganisms collected on filter media. The concept can be designed to be compact, low power, and hardened to survive harsh delivery environments such as airdrop. The prototype consists of an air sampling system, a filter exchange mechanism, an Nd:YAG microlaser that is frequency tripled and quadrupled to generate 355-nm and 266-nm excitation wavelengths, a spectrometer, an intensified CCD detector, and a data acquisition and control system. The analysis utilizes a spectral database of fluorescence signatures of biological organisms and common interferents measured by Sandia for the Army's Edgewood Research and Development Engineering Center (ERDEC) and the Department of Energy's Chemical and Biological Non-proliferation (DOE CBNP) program. The analysis algorithms are based on algorithms developed by Sandia for an airborne UV LIF lidar system.

Several workers have reported the development of systems which allow the measurement of intrinsic fluorescence from particles irradiated with ultra-violet radiation. The fluorescence data are frequently recorded in conjunction with other parameters such as particle size, measured either as a function of optical scatter or as an aerodynamic size. The motivation for this work has been principally the detection of bioaerosols within an ambient environment. Previous work by the authors has shown that an analysis of the scattering profile of a particle, i.e.: the spatial distribution of light scattered by the particle carried in a sample air-stream, can provide an effective means of particle characterization and classification in terms of both size and shape parameters. Current work is aimed at the simultaneous recording of both spatial scattering and fluorescence data from individual particles with a view to substantially enhanced discrimination of biological aerosols. A prototype instrument has recently been completed which employs a cw 266 nm laser source to produce both elastic (spatial scattering) and inelastic (fluorescence) signals from individual airborne particles. The instrument incorporates a custom designed high-gain multi- pixel hybrid photodiode (HPD) to record the spatial scattering data and a single photomultiplier to record total fluorescence from the illuminated particle. Recorded data are processed to allow the classification of airborne particles on the basis of size, shape, and fluorescence for both biological and non- biological aerosols.

Effective defense against biological warfare (BW) agents requires rapid, fieldable and accurate systems. For micro- organisms like bacteria and viruses, ribosomal RNA (rRNA) provides a valuable target with multiple advantages of species specificity and intrinsic target amplification. Vegetative and spore forms of bacteria contain approximately 10⁴ copies of rRNA. Direct detection of rRNA copies can eliminate some of the interference and preparation difficulties involved in enzymatic amplification methods. In order to apply the advantages of rRNA to BW defense, we are developing a fieldable system based on 16S rRNA, physical disruption of the micro-organism, solid phase hybridization, and fluorescence detection. Our goals include species-specific identification, complete operation from raw sample to identification in 15 minutes or less, and compact, fieldable instrumentation. Initial work on this project has investigated the lysis and hybridization steps, the species-specificity of oligonucleotides probes, and the development of a novel electromagnetic method to physically disrupt the micro- organisms. Target bacteria have been Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). Continuing work includes further development of methods to rapidly disrupt the micro-organisms and release the rRNA, improved integration and processing, and extension to bacterial and mammalian viruses like MS2 and vesicular stomatitis virus.

The Chemical Weapons Convention prohibits the development, production, stockpiling, and use of warfare agents (chemical and biological), and requires their destruction. Yet their use persists and has been included in the terrorist's arsenal. Currently, a number of analytical methods are being developed to perform rapid measurements of trace agents to ensure treaty compliance, as well as safe environments for military personal and the public at large. We have been investigating the ability of surface-enhanced Raman spectroscopy to detect bacterial nucleic acid-base pairs with sufficient sensitivity and selectivity to eliminate the need for enumeration used in polymerase chain reactions and culture growth, required by other measurement techniques. The design of a small volume, fiber optic coupled, electrolytic sample cell is presented along with analysis of DNA and RNA separated from non-toxic bacteria.

Real-time methods which is reagentless and could detect and partially characterize bioaerosols are of current interest. We present a technique for real-time measurement of UV-excited fluorescence spectra and two-dimensional angular optical scattering (TAOS) from individual flowing biological aerosol particles. The fluorescence spectra have been observed from more than 20 samples including Bacillus subtilis, Escherichia coli, Erwinia herbicola, allergens, dust, and smoke. The S/N and resolution of the spectra are sufficient for observing small lineshape differences among the same type of bioaerosol prepared under different conditions. The additional information from TAOS regarding particle size, shape, and granularity has the potential of aiding in distinguishing bacterial aerosols from other aerosols, such as diesel and cigarette smoke.

Estimating the range dependence of vapor concentration with range-resolved lidar is a challenging problem because of the weak returns provided by atmospheric aerosols and the rapid decrease in signal-to-noise ratio with range. This paper summarizes an earlier approach for constructing a statistically optimal estimator for the range dependent vapor concentration using data from multiwavelength frequency-agile lidar. The estimates of path-integrated concentration from this algorithm are compared with those made using a previously derived Kalman filter on data collected by topographic backscatter from a mountain range. In addition, the range- resolved concentration estimation algorithm is generalized to the case of multiple vapor materials. The algorithms are illustrated on a combination of synthetic and field test data collected recently by SBCCOM at the Department of Energy Nevada Test Site.

Range-resolved lidar measurements of chemical vapor output from a smokestack were conducted using a moderate-power (100 millijoules per pulse) frequency-agile CO₂ differential absorption lidar (DIAL) system. A 70-foot non-industrial smokestack, erected for the purpose of studying effluent emissions, was used in the experiment. These measurements were conducted for the purpose of obtaining real data to support development of advanced chemical and biological (CB) range- resolved vapor detection algorithms. Plume transmission measurements were made using natural atmospheric backscatter from points at the mouth of the stack and several positions downwind. Controlled releases of triethyl-phosphate (TEP), dimethyl-methylphosphonate (DMMP), and sulfur-hexaflouride (SF₆) were performed. Test methodology and experimental results are presented. Effective application of ground-based lidar to the monitoring of smokestack effluents, without the use of fixed targets, is discussed.

The Air Force Research Laboratory (AFRL) Active Remote Sensing Branch has developed the Laser Airborne Remote Sensing (LARS) system for long standoff range chemical detection using the differential absorption lidar (DIAL) technique. The system is based on a high-power CO₂ laser which uses either the ¹²C¹⁶O₂ or the ¹³C¹⁶O₂ carbon dioxide isotopes as the lasing medium, and has output energies of up to 5 J on the stronger laser transitions. The lidar system is mounted on a flight-qualified optical breadboard designed for installation in the AFRL Argus C-135E optical testbed aircraft. This paper will present chemical detection results and issues arising from ground tests of the system performed from September to December 1998. Recent advances in implementing a frequency-agile heterodyne receiver to further increase the standoff range of the DIAL system will also be presented.

In this work the spectral characteristics of a new type of mid-infrared diode laser are discussed and an application for CO trace gas detection is demonstrated. The InGaAsSb/AlGaAsSb QW diode lasers operating in the spectral range of 2.0 - 2.7 micrometer in continuous wave (CW) regime at room temperature (RT) were developed last year. Earlier, the spectral range of RT CW operation for diode lasers was limited by 2.0 - 2.1 micrometer. The extension of wavelength to 2.7 micrometer was achieved for InGaAsSb/AlGaAsSb quantum well (QW) lasers by employing for QWs new quasi-ternary InGaSb(As) compositions that are out of the miscibility gap for InGaAsSb materials. Single spatial mode ridge lasers emitting at 2.2 - 2.7 micrometer have parameters similar to those of the infrared lasers with (lambda) less than 2 micrometer widely used for spectroscopic application. At operating currents about 80 - 200 mA and temperatures up to +50 degrees Celsius, these lasers emit CW output power of several milliwatts. Investigation of the laser spectra has revealed the current and temperature ranges where a single longitudinal mode dominates with side mode suppression of 22 - 25 dB. The dominant mode can be tuned in wavelength by varying current or temperature. The lasers were used to record high-resolution CO absorption lineshapes (2v band near 2.3 micrometer) in a static cell (14.9-cm path). Probed CO transitions were selected for applications to in situ measurements in high- temperature combustion flows. In general, the measured CO absorption lineshapes agreed with theoretical Voigt profiles calculated using the HITRAN database to within 2%. For a minimum detectable absorbance of 0.01% and a 1-meter long path, the CO measurement sensitivity for the probed R30 transition near 2.302 micrometer was 5 - 10 ppm at 1000 K. This value is about two orders of magnitude better than the sensitivity reported for CO detection with conventional diode lasers that probe transitions in the 3v band near 1.56 micrometer.