Development of Aircraft Borne 13CH4 Analyzer Using a Continuous Wave Quantum Cascade Infrared Laser Spectrometer

Methane is the second most important atmospheric greenhouse gas after CO2, yet its global sources and sinks are still inadequately characterized. Recent observations that industrial plants may account for a substantial fraction of atmospheric methane have lead to an increased emphasis on studies of ecosystem CH4 fluxes, with particular interest in using isotopic composition to identify specific production pathways. Field deployable instruments for direct measurements of 13CH4, having sufficient precision without sample pre-concentration, do not yet exist. Recent advances in quantum cascade laser technology have made available continuous wave operation near room temperature without cryogenic cooling. With such devices, it is now feasible to develop a compact portable instrument with sufficient sensitivity for direct measurements of 13CH4. The portability would allow deployment from light aircraft to assess sources of methane in remote areas of the world. Phase I will design and test a prototype optical system to demonstrate the ability to directly detect the ratio of 13CH4 to 12CH4, with a precision of 0.5 parts per thousand (0.5 ¿) in an averaging time of 30 seconds. Key design issues ¿ including laser line width, mode purity, required path length, temperature and pressure control ¿ will be quantitatively assessed. A preliminary designs for an aircraft-borne instrument will be developed, and measurement opportunities for aircraft deployment will be identified. Commercial Applications and other Benefits as described by the awardee: The instrument should be an attractive addition to existing atmospheric trace gas detectors, since it will be able to operate without cryogenic cooling of either the laser or the detector. Other applications would include air pollution monitoring, human breath analysis, and industrial process monitoring. The technology will provide a significant societal benefit though improved understanding and mitigation of global warming and global climate change.