Ultra-High Precision Laser Isotope Monitor for 13CO2, CO180 and CO170

Greenhouse gas (GHG) emissions to the atmosphere are primary drivers of global climate change and hence there is a crucial need to quantify their sources and sinks. A general technique to constrain source and sink strengths is the analysis of the relative proportions of isotopic variants of GHG's. These measurements must be performed with extremely high precision. The gold standard technique, isotope ratio mass spectrometry, is limited by laborious sample processing requirements, high capital cost and impracticality of field deployment. Aerodyne Research has developed an alternative approach based on tunable laser infrared spectroscopy that avoids these limitations. Our commercial isotope monitor for the most important GHG gas, carbon dioxide, very nearly meets the measurement precision specified in Sub-Topic 8.3.1 for δ13C (0.01%0) and δ180 (0.02%0). The current instrument is designed for fast response continuous flow measurements whereas the solicitation calls for the measurement of discreet samples with ultra-high precision. We will improve the measurement precision to routinely exceed the solicitation requirements while measuring small discreet samples (60 ml or less). This will be accomplished with two innovations: a small volume, high vacuum multiple-pass cell and a rapid sample switching method to promote long term signal averaging without drift.