Parametric Studies of Fluorescence Lidar for Detection of Biological Warfare Agents in the Atmosphere

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14-2-2.jpg

Parametric Studies of Fluorescence Lidar for Detection of Biological Warfare Agents in the Atmosphere

9.95

Author(s): Anil Kumar Maini; S. Veerabuthiran
No pages: 8
Year: 2011
Article ID: 14-2-2
Keywords: lasers, lidar, surveillance and target acquisition
Format: Electronic (PDF)

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Abstract: Bioaerosol weapons pose a severe threat to the safety and security of military forces and civilians. During an attack, these weapons release into the atmosphere biological warfare agents, which form stratified cloud layers over a small area. Detection of such bioaerosol clouds at safe standoff distances from the location of a sensor is very important for timely deployment of countermeasures. LIDAR is the only standoff technique that can detect and identify the composition of the clouds in near real time. In this paper, we present the parametric studies of a fluorescence LIDAR system for detection of bioaerosol clouds for given conditions. The elastic backscattered and induced fluorescence signals as a function of range, concentration and optical background levels have been simulated for given system parameters. We considered a Nd:YAG laser at the quadrupled wavelength of 266 nm as a transmitter and a Cassegrain telescope as a receiver with two detection channels namely: a Mie channel (elastic signal), and a fluorescence channel. The performance of various combinations of system design parameters comprising laser pulse energies and receiver telescopes have been determined to detect a bioaerosol cloud located at 1–2 km during day and night time. Our analysis revealed that fluorescence LIDAR with a pulse energy of 100 mJ and receiver telescope diameter of 300 mm can detect the presence of tryptophan containing bioaerosols clouds of 200m thickness and concentration of 8107 particles/litre (ppl) up to a distance of 1.5 km during daytime. We also estimated the sensitivity of the system in terms of minimum detectable concentration with respect to number of transmitted laser pulses. The averaging of 1,000 pulses (equal to the detection time of 50 seconds) resulted in the fluorescence detection range of 520m for a lethal infective dose of ~10,000 ppl.