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Proceedings Paper

Backscatter and depolarization measurements of aerosolized biological simulants using a chamber lidar system
Author(s): David M. Brown; Evan P. Thrush; Michael E. Thomas; Josh Santarpia; Jason Quizon; Christopher C. Carter
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Paper Abstract

To ensure agent optical cross sections are well understood from the UV to the LWIR, volume integrated measurements of aerosolized agent material at a few key wavelengths is required to validate existing simulations. Ultimately these simulations will be used to assess the detection performance of various classes of lidar technology spanning the entire range of the optical spectrum. The present work demonstrates an optical measurement architecture based on lidar allowing the measurement of backscatter and depolarization ratio from biological aerosols released in a refereed, 1-m cubic chamber. During 2009, various upgrades have been made to the chamber LIDAR system, which operates at 1.064 μm with sub nanosecond pulses at a 120 Hz repetition rate. The first build of the system demonstrated a sensitivity of aerosolized Bacillus atrophaeus (BG) on the order of 5×105 ppl with 1 GHz InGaAs detectors. To increase the sensitivity and reduce noise, the InGaAs detectors were replaced with larger-area silicon avalanche photodiodes for the second build of the system. In addition, computer controlled step variable neutral density filters are now incorporated to facilitate calibrating the system for absolute back-scatter measurements. Calibrated hard target measurements will be combined with data from the ground truth instruments for cross-section determination of the material aerosolized in the chamber. Measured results are compared to theoretical simulations of cross-sections.

Paper Details

Date Published: 5 May 2010
PDF: 12 pages
Proc. SPIE 7665, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XI, 766506 (5 May 2010); doi: 10.1117/12.850361
Show Author Affiliations
David M. Brown, The Johns Hopkins Univ. Applied Physics Lab. (United States)
Evan P. Thrush, The Johns Hopkins Univ. Applied Physics Lab. (United States)
Michael E. Thomas, The Johns Hopkins Univ. Applied Physics Lab. (United States)
Josh Santarpia, The Johns Hopkins Univ. Applied Physics Lab. (United States)
Jason Quizon, The Johns Hopkins Univ. Applied Physics Lab. (United States)
Christopher C. Carter, The Johns Hopkins Univ. Applied Physics Lab. (United States)


Published in SPIE Proceedings Vol. 7665:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XI
Augustus Way Fountain; Patrick J. Gardner, Editor(s)

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