21 April 2008 Extinction and backscatter cross sections of biological materials
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Abstract
Aerosol backscatter and extinction cross-sections are required to model and evaluate the performance of both active and passive detection systems. A method has been developed that begins with laboratory measurements of thin films and suspensions of biological material to obtain the complex index refraction of the biological material from the UV to the LWIR. Using that result with particle size distribution and shape information as inputs to T-matrix or discrete dipole approximation (DDA) calculations yields the extinction cross-section and backscatter cross section as a function of wavelength. These are important inputs to the lidar equation. In a continuing effort to provide validated optical cross-sections, measurements have been made on a number of high purity biological species in the laboratory as well as measurements of material released at recent field tests. The resulting observed differences between laboratory and field measurements aid in distinguishing between intrinsic and extrinsic effects, which can affect the characteristic signatures of important biological aerosols. A variety of biological and test aerosols are examined, including Bacillus atrophaeus (BG), and Erwina, ovalbumin, silica and polystyrene.
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M. E. Thomas, M. E. Thomas, D. V. Hahn, D. V. Hahn, A. K. Carr, A. K. Carr, D. Limsui, D. Limsui, C. C. Carter, C. C. Carter, N. T. Boggs, N. T. Boggs, J. Jackman, J. Jackman, } "Extinction and backscatter cross sections of biological materials", Proc. SPIE 6954, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing IX, 69540Y (21 April 2008); doi: 10.1117/12.777650; https://doi.org/10.1117/12.777650
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