Pulsed quantum cascade laser instrument with compact design for rapid, high sensitivity measurements of trace gases in air |
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Authors: | JB McManus JH Shorter DD Nelson MS Zahniser DE Glenn RM McGovern |
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Institution: | (1) Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821, USA |
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Abstract: | We have developed a compact instrument for sensitive, rapid and continuous measurement of trace gases in air, with results
presented here for methane (CH4), nitric oxide (NO), nitrous oxide (N2O) and ammonia (NH3). This instrument takes advantage of recent technology in quantum cascade (QC) lasers and infrared detectors, which allows
high sensitivity without cryogenic liquids, e.g., 0.2 ppb (0.2×10-9) of NH3 in air in 1 s. One may substitute a QC laser operating at a different wavelength to measure other gases. The instrument operates
continuously, requiring little operator attention, and web-based remote access is provided for instrument control, calibration
and data retrieval. The instrument design includes a thermoelectrically (TE) cooled pulsed distributed feedback (DFB) QC laser,
a low volume (0.5 l) multipass cell offering 76 m absorption path length and a TE cooled detector. Integrated software for
laser control and data analysis using direct absorption provides quantitative trace gas measurements without calibration gases.
The instrument may be applied to field measurements of gases of environmental concern.
PACS 07.57.Ty; 42.62.Fi; 92.70.Cp |
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