Tunable diode laser absorption

Gieseler et al. utilized tunable diode laser absorption spectroscopy to detect water vapor concentrations, gas velocities and mass flow during freeze-drying of pure water at different pressure and shelf temperature settings and of a 5%w/w mannitol solution. The analyzer was interfaced to the spool that connected the dryer chamber to the condenser. The reported method was advantageous in that primary and secondary drying end-point control based upon mass flow rate was independent of freeze-dryer size and configuration. ... 

H. Gieseler, W.J. Kessler, M. Finson, et al.. Evaluation of tunable diode laser absorption spectroscopy for in-process water vapor mass flux measurements during freeze drying, J. Pharm. Sci., 96(7), 1776-1793 (2007). 

Welle, S.D., D.S. Baer, and R. K. Hanson. 1997. Tunable diode-laser absorption measurements of temperature, velocity, and H2O in hypervelocity flows. 33rd Joint Propulsion Conference Proceedings. NY AIAA. AIAA Paper No. 97-3267. 

Brassington, D. J., Tunable Diode Laser Absorption Spectroscopy for the Measurement of Atmospheric Species, in Spectroscopy in Environmental Science (R. J. H. Clark and R. E. Hester, Eds.), pp. 85-148, Wiley, New York, 1995. 

Fox, D. L L. Stockburger, W. Weathers, C. W. Spicer, G. I. Mackay, H. I. Schiff, D. J. Eatough, F. Mortensen, L. D. Hansen, P. B. Shepson, T. E. Kleindienst, and E. O. Edney, Intercomparison of Nitric Acid Diffusion Denuder Methods with Tunable Diode Laser Absorption Spectroscopy, Atmos. Environ., 22, 575-585 (1988). 

Fried, A., S. Sewell, B. Henry, B. P. Wert, T. Gilpin, and J. R. Drummond, Tunable Diode Laser Absorption Spectrometer for Ground-Based Measurements of Formaldehyde, J. Geophys. Res., 102, 6253-6266 (1997). 

Mackay, G. I., H. I. Schiff, A. Wiebe, and K. Anlauf, Measurements of N02, H2CO, and HNO, by Tunable Diode Laser Absorption Spectroscopy during the 1985 Claremont Intercomparison Study, Atmos. Enriron., 22, 1555-1564 (1988). 

Sachse, G. W., G. F. Hill, L. O. Wade, and M. G. Perry, Fast-Response, High-Precision Carbon Monoxide Sensor Using a Tunable Diode Laser Absorption Technique, J. Geophys. Res., 92, 2071-2081 (1987). 

Schiff, H. I G. I. Mackay, and J. Bechara, The Use of Tunable Diode Laser Absorption Spectroscopy for Atmospheric Measurements, Res. Chem. Intermed., 20, 525-556 (1994a). 

Tunable diode laser absorption spectroscopy (TDLAS) has been used to measure oxides of nitrogen during flight (71). By tuning the laser to specific infrared absorption bands, the technique can selectively measure each compound. Detection limits are higher (25-100 pptrv for a 3-min response time) than the best chemiluminescent methods, and the instrumentation is less amenable to aircraft operations than the chemiluminescence techniques because of weight and size. 

Magnetic Resonance Imaging and Tunable Diode Laser Absorption Spectroscopy for In-Situ Water Diagnostics in Polymer Electrolyte Membrane Fuel Cells... 

In-situ measurement technique of water vapor concentration in gas flow channels in PEMFCs using tunable diode laser absorption spectroscopy (TDLAS)31-36 is also shown with fundamental descriptions on its measuring principle and validity of a practical system. Localized current density and through-plane water-back transport index are obtained with variation of vapor concentration along the gas channel taken into account. Demonstrative results showing that effect of the micro porous layer (MPL) on variation of through-plane water-back transport index is shown in an operating PEMFC. 

TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY (TDLAS) AS A DIAGNOSTIC TOOL FOR IN-SITU DETECTION OF WATER VAPOR CONCENTRATION IN PEMFCs... 

Localized remote sensing for chemical compositions in operating PEMFC can be performed by tunable diode laser absorption spectroscopy (TDLAS). Measurement of water vapor and carbon dioxide has been reported by using TDLAS.31-36 In TDLAS measurement, the absorption of the laser beam passing through the gas sample is expressed with the partial pressure of the absorbing species, Pa (atm), by Beer s law,... 

Chapters 4-6 address specific diagnostic methods in PEFCs. Martin et al. provide a detailed review of methods for distributed diagnostics of species, temperature, and current in PEFCs in Chapter 4. In Chapter 5, Hussey and Jacobson describe the operational principles of neutron radiography for in-situ visualization of liquid water distribution, and also outline issues related to temporal and spatial resolution. Tsushima and Hirai describe both magnetic resonance imaging (MRI) technique for visualization of water in PEFCs and tunable diode laser absorption spectroscopy (TDLAS) for measurement of water vapor concentration in Chapter 6. 

Surface acoustic wave Semiconductor Target Radiation Radar Surface acoustic wave Electrophoresis Electrochemical Paramagnetic Chemi/bioluminescence Tunable diode laser absorption... 

Figure 1. Optical arrangement for tunable diode laser absorption spectroscopy...

These experiments demonstrate that tunable diode laser absorption spectroscopy is well suited for in situ measurements of species concentrations in combustion flows, when a line-of-sight technique is appropriate, and for accurate measurements of spectroscopic parameters needed to characterize high-temperature absorption lines. The technique is sensitive, species specific and applicable to a large number of important combustion species including reactive intermediates, and hence it should prove to be a useful tool in future studies of combustion chemistry. The potential of tunable laser absorption spectroscopy in particleladen flows should also be noted (12), in that modulation of the laser wavelength on and off an absorption line allows simple discrimination against continuum extinction by particles. 

The advantages of Tunable Diode Laser Absorption Spectrometry (TDLAS) for measuring trace atmospheric gases are universality positive identification good sensitivity and rapid response time. An instrument is described which can measure two gases simultaneously under automatic computer control with detection limits better than 100 parts per trillion and with response times better than 5 minutes. Procedures have been established for the measurement of NO N0a, HNOa NH3 HbQb and HCHO. These species have been measured under a variety of conditions in smog chambers and in ambient air from mobile laboratories and from aircraft. 

The tunable diode laser absorption spectrometer has been shown to be a very versatile system for measuring trace atmospheric gases from mobile laboratories and from aircraft under a number of ambient and smog chamber air conditions. Its high specificity good sensitivity and rapid response time makes it a very suitable standard against which other less definitive methods can be compared. 

Schiff, H.I. Mackay, G.I. "The Development of a Method for Measuring H2O2 in Real Air Using a Tunable diode Laser Absorption Spectrometer", Final Report of Research Project RP 2023-5, prepared by Unisearch Associates, Inc., for the Electric Power Research Institute, 1984. 

Schiff HI, Mackey GI, Mayne LK, et al. 1986. Tunable diode laser absorption spectrometer measurement of HNO3, HCHO and NO2 and luminox NO, measurements in Claremont CA, September 1985 [Abstract]. Abstr Pap Am Chem Soc 192 ENVR 112. 

Gas phase component concentrations A number of standard gas analysers are routinely available for determination of gaseous mixing ratio of CH4, CO, O3, NO, NO2 and SO2 at moderate atmospheric concentrations. GC determination of a limited number of NMHC species is also available for appropriate experiments. An Aerodyne Quantum Cascade Tunable Diode Laser Absorption Spectrometer (QC-TDLAS) is periodically available for NH3 measurements using tiie line at 967 cm and for NO2 measurement at 1606 cm . There are several potential experiments which may benefit from measurement of other trace species. The Differential Optical Absorption Spectrometer (DOAS) described below may be used for determination of lO, OIO, BrO, NO3, HCHO, SO2 and other trace species. 

Principles of Tunable Diode Laser Absorption Spectroscopy.312... 

Tunable diode laser absorption spectroscopy involves measuring the attenuation of a beam from a diode laser... 

Farooq, A., Jeffries, J. B., and Hanson, R. K. "In Situ Combustion Measurements of HjO and Temperature near 2.5 xm using Tunable Diode Laser Absorption." Measurement Science and Technology 19 (2008) 075604. 

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