|Acquisition Program: ||Joint Biological Point Detection System (JBPDS) Increment 2|| Objective: ||We are seeking novel approaches to demonstrate feasibility of a compact, long-wave infrared (LWIR, 8-12 micron), point bio sensor with advanced algorithms, with extension to combined chemical detection, for manportable and small ground and airborne vehicle deployment.
|| Description: ||It was recently discovered in field testing with the FAL (Frequency Agile Laser) sensor that bio agent simulants and interferents could be detected and discriminated by their differential backscatter signatures in the 9-11 ƒÝm band using a CO2 TEA (transversely excited atmospheric) laser transmitter. The FAL had been used successfully for chemical vapor detection which suggests that a single transmitter/sensor could be used for both chem and bio detection. The FAL laser emits pulses composed of a 150 ns spike followed by a 1 ƒÝs low intensity tail. The pulse rate is typically 200 Hz and pulse energy is on the order of 100 mJ which allows a standoff detection range on the order of 2.5 km. Importantly, laser wavelength can be rapidly shifted at a 200 Hz rate among about 60 lines within the 9-11 ƒÝm band. This wavelength diversity is essential to biological and chemical agent detection/discrimination. For an LWIR point sensor, other transmitter types with wavelength diversity should be considered, including (but not limited to) the miniature CO2 waveguide, the micro CO2 TEA, the quantum cascade laser, and diode-pumped solid state crystal types with OPO (optic parametric oscillators). The concept of this topic is analogous to the previous extension of Laser Induced Fluorescence (LIF) from standoff to point configurations.
Point sensors for airborne bio agents have utilized various air flow mechanisms to capture samples and concentrate them for enhanced signal strength as in the case of vortex compactors. Point sensors based on LIF (laser induced fluorescence) use precision air metering systems to channel particles at the focus of a UV (ultraviolet) laser. Cavity ringdown spectroscopy (CRS) has been used for chemical detection based on the phenomenology of differential absorption. It may also be of interest to apply CRS to the case of differential scattering.
It would be of interest to extend the capability of the point sensor to include operation at very short standoff range for rapid scanning within and around relatively confined spaces such as rooms and between buildings and as a tool for developing a differential backscatter data base within the laboratory. It is also of interest to consider extension of the backscatter phenomonelogy to the 3-5 ƒÝm band for detection of TICs (Toxic Industrial Chemicals).
Advanced algorithms have been applied to the case of bio detection by long wave IR (infrared) backscatter and to chemical detection by differential absorption. It is of interest to further integrate the algorithms with both detection phenomenologies and to develop a data base for algorithm quantification and validation.
|| ||PHASE I: Perform analysis and systems study to show feasibility of a 1-cubic-foot point sensor approach and develop a demonstration sensor conceptual design.
|| ||PHASE II: Develop a sensor detailed design. Fabricate and test the detection and discrimination capabilities of the point biological sensor, to include advanced algorithms. Investigate combined biological and chemical detection.
|| ||PHASE III|| ||DUAL-USE APPLICATIONS: In Phase III, a prototype point sensor system can be built for biological and chemical detection field trials. This would lead to a combined chemical and biological sensor suitable for deployment. Development of such a sensor would be of great benefit in homeland defense applications and for environmental pollution monitoring.
|| References: ||1. R. Vanderbeek, ¡§Aerosol Backscatter Field Measurements Of Chem-Bio Simulants Using A Windowless Vortex Chamber¡¨, Proceedings Sixth Joint Conference On Standoff Detection For Chemical and Biological Defense, Williamsburg, VA October 25-29, 2004
2. R. E. Warren, ¡§Discriminating Aerosols By Multi-Wavelength Lidar¡¨, Proceedings Sixth Joint Conference On Standoff Detection For Chemical and Biological Defense, Williamsburg, VA October 25-29, 2004
3. D. B. Cohn, ¡§Compact CO2 TEA Lasers and Chemical Sensors¡¨, Proceedings Sixth Joint Conference On Standoff Detection For Chemical and Biological Defense, Williamsburg, VA October 25-29, 2004
4. D. Cohn, J. Fox and C. Swim, "Frequency agile CO2 laser for chemical sensing", SPIE Proceedings, Los Angeles, California, vol. 2118, p 72, (Jan 1994).
|Keywords: ||chemical, biological, detection, sensors|