Development of an Open-Path, Laser Dispersion Spectroscopy (LDS) for Methane Emissions Monitoring

If you're looking for professional advice on methane analysis by means of an open-path laser-absorption spectrometer, follow the link for the relevant e-Learning. Similarly, if you're in need of information on hyperspectral infra-red imaging for any-state methane, take a look at Jean-Phillipe Gagnon of Telops Inc.'s lecture on the topic. Finally, click through to find an overview of new sensor technologies for methane analysis.

Laser Dispersion Spectroscopy (LDS), is a new gas sensing technique that applies a novel approach to tuneable diode laser spectroscopy. Established laser absorption techniques depend on measuring detected intensity to derive concentration. This significantly impacts measurements in "dirty" environments where detected intensity of the transmitted light is bound to fluctuate. MIRICO's LDS-based instrument derives concentration using the phase of light. This makes it highly immune to intensity fluctuations received at the photodetector. The instrument enables precise, real time measurements of trace gas molecules in demanding environments. Furthermore, compared to absorption techniques, the analyser can measure gas concentrations within a very wide dynamic range (typically about five to six orders of magnitude), meaning for example from parts per billion all the way to sub-percent concentrations without the requirement for dilution.

In a long open-path, multi-direction configuration, coupled with a retroreflector array, and anemometer, the LDS analyser is capable of measuring methane concentrations associated with large area sources, and locating and quantifying point source emissions within said area. Here we describe the principle of LDS, and the development of a field-deployable instrument. In addition, we introduce the basic configuration required for mapping applications.

For further techological developments in laser-dispersion spectroscopy, check out an e-Learning that investigates a mid-infrared variation of the technique.