12 May 2016 Portable low power cavity ring-down spectrometer for precise measurement of carbon dioxide, methane and water vapor
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The necessity for monitoring of changing levels of greenhouse gases (GHGs) is clearly evident now more than ever. This has led to large deployments of analytical devices to most remote locations as well as the most densely populated regions around the world. Both large and small scale projects have forced new and old technologies to be pushed to their limits to obtain the highest performing measurements while maintaining a cost effective way to remotely monitor changes in atmospheric concentrations. In order to accomplish these strict guidelines, we present a low-power cavity ring-down spectrometer that measures Carbon Dioxide, Methane and water vapor which can achieve measurements with precisions lower than 20ppb of CO2 and 50ppt of CH4. Comparing to hundreds of watts needed in conventional CRDS design, we demonstrate that the high performance can be achieved with less than 25W. Stability of these measurements has allowed for averaging times of up to 3hr, yielding measurements of methane concentrations with precisions down to 40ppt. This is accomplished utilizing an FSR based frequency scale to determine an absolute frequency scale for these absorption features. Taking advantage of this faster, and less costly measurement technique of CRDS shows future promise with applications spanning scientific and industrial analyses, from isotopes to trace gases.
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Derek Fleck, Derek Fleck, John Hoffnagle, John Hoffnagle, Sze Tan, Sze Tan, Yonggang He, Yonggang He, } "Portable low power cavity ring-down spectrometer for precise measurement of carbon dioxide, methane and water vapor", Proc. SPIE 9855, Next-Generation Spectroscopic Technologies IX, 98550H (12 May 2016); doi: 10.1117/12.2229642; https://doi.org/10.1117/12.2229642

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