研究目的
Simultaneous detection of atmospheric methane and water vapor with spatial and temporal distribution in field measurements for better understanding of global warming, climate change.
研究成果
A compact, sensitive and selective sensor system based on a single CW DFB laser was developed for simultaneous detection of CH4 and H2O by using calibration-free DAS method. Allan deviation analysis indicates that MDLs of 1 ppb for CH4 and 10.4 ppm for H2O with an integration time of 102 s were achieved at an optimum pressure of 50 Torr. Such a sensitive, low cost, simple, and compact CH4 and H2O sensor is very suitable for application in balloon- or UAV-embedded observation.
研究不足
The performance of TDLAS-based sensors highly depends upon the availability of spectrally monomode lasers emitting at desired wavelengths for sensitive and selective gas sensing.
1：Experimental Design and Method Selection:
A TDLAS method combined with a DP-MPC was utilized for simultaneous dual-gas detection. The calibration-free direct absorption spectroscopy approach was adopted for data generation and processing.
2：Sample Selection and Data Sources:
Laboratory ambient air was injected into the DP-MPC at the optimal pressure of 50 Torr.
3：List of Experimental Equipment and Materials:
A DFB laser (Nanoplus GmbH) with a central emitting wavelength of 3.38 mm, a compact, low-noise laser driver (Model 0520), a fast thermoelectrically cooled mid-infrared detector (Vigo, PVI-4TE-4), a data acquisition card (National Instrument, USB6356), and a pressure controller (MKS Instruments, Type 640B).
4：38 mm, a compact, low-noise laser driver (Model 0520), a fast thermoelectrically cooled mid-infrared detector (Vigo, PVI-4TE-4), a data acquisition card (National Instrument, USB6356), and a pressure controller (MKS Instruments, Type 640B).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The laser diode current and temperature were controlled, and the frequency tuning was performed by sweeping the diode laser current. The emitted laser beam was collected and collimated, then coupled to the DP-MPC. The out-coming beam from the absorption cell is collected and sent to a detector.
5：Data Analysis Methods:
The acquired spectrum of CH4 and H2O was processed by averaging raw spectra, frequency calibration, baseline correction, and retrieving concentrations using the Levenberg-Marquardt non-linear least-squares routine.
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