Versatile multipass cell for laser spectroscopic trace gas analysis

Manninen, Albert; Tuzson, Béla; Looser, Herbert; Bonetti, Yargo; Emmenegger, Lukas

doi:10.1007/s00340-012-4964-2

Cited by 49 publications

(33 citation statements)

References 30 publications

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“…Using an appropriate focusing lens, the light from the EC-QCL was coupled to a circular multi-pass cell (MPC, IR Sweep, IRcell-4M) [3] with an effective path length of 3.99 m (51-reflections), a volume of 38 ml and a specified, lowest achievable fringe-level of 0.39‰ rms of the dc intensity. The output beam of the MPC was focused on a midinfrared photodetector (VIGO System, PVI-2TE-5-1×1).…”

Section: Experimental Tdlas Setup and Breath Samplermentioning

confidence: 99%

“…quantum cascade lasers (QCLs) and interband cascade lasers (ICLs), suitable optical sensors can be realized based on tunable diode laser absorption spectroscopy (TDLAS) or cavity-enhanced methods [1,2]. In TDLAS, high sensitivity is achieved employing multi-pass cells (MPCs) [3] for path length enhancement and modulation techniques, e.g. wavelength modulation spectroscopy (WMS) [4], for noise reduction.…”

Section: Introductionmentioning

confidence: 99%

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Real-time breath gas analysis of CO and CO2 using an EC-QCL

Ghorbani

Schmidt

2017

Appl. Phys. B

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Section: Experimental Tdlas Setup and Breath Samplermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-time breath gas analysis of CO and CO2 using an EC-QCL

Ghorbani

Schmidt

2017

Appl. Phys. B

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“…Solutions for the limitations of low SNR can be mitigated by adding a beam stabiliser [9,26], but which cannot eliminate other instrumental noise. SNR issues can be improved by using multi-pass cells, often at the expense of spatial resolution [27][28][29][30]. As alternatives, cavity ring-down spectroscopy (CRDS) [14,[31][32][33][34][35][36] and multi-pass tunable diode laser absorption spectroscopy (TDLAS) absorption methods [37][38][39][40][41][42][43][44][45][46] have been developed to obtain high SNR when concentrations are very small.…”

Section: Introductionmentioning

confidence: 99%

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

et al. 2015

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Accurate measurement techniques for in situ determination of soot are necessary to understand and monitor the process of soot particle production. One of these techniques is line-of-sight extinction, which is a fast, low-cost and quantitative method to investigate the soot volume fraction in flames. However, the extinction-based technique suffers from relatively high measurement uncertainty due to low signal-to-noise ratio, as the single-pass attenuation of the laser beam intensity is often insufficient. Multi-pass techniques can increase the sensitivity, but may suffer from low spatial resolution. To overcome this problem, we have developed a high spatial resolution laser cavity extinction technique to measure the soot volume fraction from low-soot-producing flames. A laser beam cavity is realised by placing two partially reflective concave mirrors on either side of the laminar diffusion flame under investigation. This configuration makes the beam convergent inside the cavity, allowing a spatial resolution within 200 μm, whilst increasing the absorption by an order of magnitude. Three different hydrocarbon fuels are tested: methane, propane and ethylene. The measurements of soot distribution across the flame show good agreement with results using laser-induced incandescence (LII) in the range from around 20 ppb to 15 ppm.

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“…For example, the absorbance of CH 4 at 1.646 µm is 1.800 × 10 −5 ppm −1 m −1 compared to the H 2 S absorbance of 5.573 × 10 −7 ppm −1 m −1 at 1.601 µm (factor 32) [12]. A way to overcome this drawback is to increase the interaction path length by using multipass gas cells [13][14][15][16]. This generally adds to the bulkiness of the systems, and hence, a small size is hardly achieved with H 2 S TDLAS sensors.…”

Section: Introductionmentioning

confidence: 99%

Cantilever-enhanced photoacoustic detection of hydrogen sulfide (H2S) using NIR telecom laser sources near 1.6 µm

Moser

Lendl

2016

Appl. Phys. B

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concentrations as low as 500 pptv manifesting in the characteristic odor of rotten eggs can already be detected by the human olfactory sense, the total loss of olfactory sensation starts at 150-200 ppmv [3]. Because of the wide occurrence of H 2 S in industrial processes and its often negative impact on process stabilities and product quality, its concentration needs to be tightly monitored. Furthermore, safety considerations and legal concentration limits also necessitate the accurate determination of H 2 S levels. In practice, concentrations ranging from sub-ppm levels at low pressures to several per cents at atmospheric conditions need to be monitored. Due to such diverse requirements, H 2 S analyzers based on different measurement technologies have been developed and are in industrial use. Apart from spectroscopic techniques based on absorption measurements, a range of other analytical techniques such as pulsed UV fluorescence [4], sulfur chemiluminescence [5], colorimetry employing a lead acetate tape [6], flame photometry as detector in gas chromatography [7] as well as electrochemical detection techniques ranging from potentiometric, galvanic, coulometric and amperometric detection [8] is frequently employed. It is interesting to note that in the petrochemical industry the lead acetate tape method is still in frequent use. Also, gas chromatographic methods are popular as they can be used to detect several components almost simultaneously, but this technique requires preparation and extraction of the sample gas leading to a time-consuming measurement. A general drawback of nonspectroscopic techniques is the fact that they do not allow for direct measurements. This, however, also applies to H 2 S detection based on UV fluorescence as this technique requires sample combustion as well as detection by chemoluminescence, where addition of reagents is required.Most of the spectroscopic techniques are based on the detection of the absorption spectrum of the molecules in Abstract Sensitive detection of hydrogen sulfide (H 2 S) at different pressure levels using a cantilever-enhanced photoacoustic detector in combination with a telecom NIR L-band laser source is reported. Amplitude and wavelength modulation schemes for photoacoustic signal generation are compared. A detection limit (3σ) of 8 ppmv was achieved for amplitude modulation mode with a 50-s averaging time for the H 2 S absorption near 1.6 µm. As compared to simulated spectra, the cantilever-enhanced photoacoustic detection approach in combination with the sufficiently stable and narrow bandwidth NIR laser is able to reproduce the rotationally resolved H 2 S spectrum at low pressures of 300 mbar.

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Versatile multipass cell for laser spectroscopic trace gas analysis

Cited by 49 publications

References 30 publications

Real-time breath gas analysis of CO and CO2 using an EC-QCL

Real-time breath gas analysis of CO and CO2 using an EC-QCL

High spatial resolution laser cavity extinction and laser-induced incandescence in low-soot-producing flames

Cantilever-enhanced photoacoustic detection of hydrogen sulfide (H2S) using NIR telecom laser sources near 1.6 µm

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