CO_2 laser-based differential absorption lidar system for range-resolved and long-range detection of chemical vapor plumes

Abstract

A dual CO(2) laser-based differential absorption lidar (DIAL) system has been constructed and demonstrated for range-resolved mapping of chemical vapor plumes. The system acquires high range resolution through the use of plasma-shutter pulse clippers that extinguish the nitrogen tail of the CO(2)-laser output. Aprogrammable servomotor-driven scanner allows full hemispherical coverage of the interrogated field. A high-speed direct-detection receiver subsystem is used to gather, process, and display vapor-concentration data in near real time. Data demonstrating range-resolved detection of low concentrations of chemical plumes from ranges of 1 to 2 km are presented. In the column-content detection mode, trace levels of secondary vapors from various organophosphate liquids were monitored. Detection of an SF(6) vapor plume released 16 km from the DIAL system is also adduced.