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Application of an all-solid-state diode-laser-based sensor for carbon monoxide detection by optical absorption in the 4.4 ? 4.8 µm spectral region

by Rodolfo, Barron Jimenez

Abstract (Summary)
An all-solid-state continuous-wave (cw) laser system for mid-infrared absorption measurements

of the carbon monoxide (CO) molecule has been developed and demonstrated. The single-mode, tunable

output of an external-cavity diode laser (ECDL) is difference-frequency mixed (DFM) with the output of a

550-mW diode-pumped cw Nd:YAG laser in a periodically-poled lithium niobate (PPLN) crystal to

produce tunable cw radiation in the mid-infrared. The wavelength of the 860-nm ECDL can be coarse

tuned between 860.78 to 872.82 nm allowing the sensor to be operated in the 4.4 ? 4.8 µm region. Results

from single-pass mid-IR direct absorption experiments for CO concentration measurements are discussed.

CO measurements were performed in CO/CO2/N2 mixtures in a room temperature gas cell that allowed the

evaluation of the sensor operation and data reduction procedures. Field testing was performed at two

locations: in the exhaust of a well-stirred reactor (WSR) at Wright-Patterson Air Force Base and the

exhaust of a gas turbine at Honeywell Engines and Systems. Field tests demonstrated the feasibility of the

sensor for operation in harsh combustion environments but much improvement in the sensor design and

operation was required. Experiments in near-adiabatic hydrogen/air CO2-doped flames were performed

featuring two-line thermometry in the 4.8 µm spectral region. The sensor concentration measurement

uncertainty was estimated at 2% for gas cell testing. CO concentration measurements agreed within 15%

of conventional extractive sampling at WSR, and for the flame experiments the repeatability of the peak

absorption gives a system uncertainty of 10%. The noise equivalent CO detection limit for these

experiments was estimated at 2 ppm per meter, for combustion gas at 1000 K assuming a SNR ratio of 1.

Bibliographical Information:

Advisor:Caton, Jerald A.; Lucht, Robert P.; Phares, Denis; Welch, George R.

School:Texas A&M University

School Location:USA - Texas

Source Type:Master's Thesis

Keywords:optical sensor laser spectroscopy frequency conversion carbon monoxide infrared sources

ISBN:

Date of Publication:12/01/2004

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