Photoacoustic phase shift as a chemically selective spectroscopic parameter

Kosterev, Anatoliy A.; Bakhirkin, Yury A.; Tittel, Frank K.; Blaser, Stéphane; Bonetti, Yargo; Hvozdara, L.

doi:10.1007/s00340-004-1519-1

Cited by 48 publications

(18 citation statements)

References 9 publications

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“…Also, the gain in signal to noise ratio (SNR) from I-QEPAS as compared to 2f-WM QEPAS is given. The figures of merit for CO detection are adversely influenced by optical saturation as well as slow V-T relaxation [4,47]. However, despite strong optical saturation, the sensitivity is increased by a factor of 57 as compared to 2f-WM QEPAS without power enhancement.…”

Section: Sensing Performancementioning

confidence: 99%

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

et al. 2019

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The sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) can be drastically increased using the power enhancement in high-finesse cavities. Here, low noise resonant power enhancement to 6.3 W was achieved in a linear Brewster window cavity by exploiting optical feedback locking of a quantum cascade laser. The high intracavity intensity of up to 73 W mm −2 in between the prongs of a custom tuning fork resulted in strong optical saturation of CO at 4.59 µm. Saturated absorption is discussed theoretically and experimentally for photoacoustic measurements in general and intracavity QEPAS (I-QEPAS) in particular. The saturation intensity of CO's R9 transition was retrieved from power-dependent I-QEPAS signals. This allowed for sensing CO independently from varying degrees of saturation caused by absorption induced changes of intracavity power. Figures of merit of the I-QEPAS setup for sensing of CO and H 2 O are compared to standard wavelength modulation QEPAS without cavity enhancement. For H 2 O, the sensitivity was increased by a factor of 230, practically identical to the power enhancement, while the sensitivity gain for CO detection was limited to 57 by optical saturation.

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Section: Sensing Performancementioning

confidence: 99%

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

et al. 2019

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“…Thus, this rate or the related phase shift can be used as an additional spectroscopic parameter to distinguish species with overlapping absorption spectra. Such an approach was used in [120] to measure trace CO impurity concentrations in 100% propylene.…”

Section: Quartz-enhanced Photoacoustic Spectroscopymentioning

confidence: 99%

“…Hence, while slow spectral scans can be performed and are actually useful for laboratory studies, field-application oriented sensors are designed to have the laser locked to the absorption line of the target gas and to continuously monitor the signal resulting from the optical absorption at that wavelength. The first QEPAS based trace gas sensing experiments using QCLs and ICLs were performed in 2004 [118][119][120]. In [119], a liquid nitrogen cooled CW DFB QCL at 4.55 lm was used to detect N 2 O (2195.633 cm À1 absorption line) and CO (2196.664 cm À1 ).…”

Section: Quartz-enhanced Photoacoustic Spectroscopymentioning

confidence: 99%

Quantum cascade lasers in chemical physics

Curl¹,

Capasso²,

Gmachl³

et al. 2010

Chemical Physics Letters

500

250

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“…This functionality can be used as an additional spectroscopic parameter for discrimination between QEPAS signals originating from molecular species with overlapping absorption spectra [Kosterev, Bakhirkin, Tittel, Blaser, Bonetti, Hvozdara 2004]]. For many target gases the 32.8 kHz frequency represents an optimum choice in terms of providing a time scale of the energy transfer processes in gases and as electric noise decreases at higher frequencies.…”

Section: Qepas Based Gas Sensing Technologymentioning

confidence: 99%

SS: Advances in Flexible Riser Technology: Fiberoptic Gas Monitoring Of Flexible Risers

et al. 2009

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This paper presents a new advancement within the field of optical gas measurement with applications to the monitoring of gases inside the annulus of flexible risers used in the offshore industry. This advancement is based on the novel Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) technology. Specifically, we report on the first demonstation of such a gas sensor system using a spectraphone (a module for detecting laser-induced sound) consisting of a quartz tuning fork (QTF)/microresonator assembly and two commercial single frequency diode lasers operating at λ =1.58 μm for detecting H 2 S as well as CO 2 and at 1.65 μm for detecting CH 4 . A minimum detectable H 2 S concentration of 10 ppmv (parts per million by volume) at the 1σ level was obtained for t=1 s averaging time, scaling down as 1/t ½ up to 1000 s (verified) This implies that a 100 s sampling time will result in a minimum detectable concentration of 1 ppm. For CO 2 and CH 4 , the minimum detectable concentrations were 270 and 1.5 ppm, respectively. The measurement technique will be described and test results will be presented along with implications for the field of riser condition monitoring.This system will allow continuous monitoring of the annulus chemical environment in flexible risers. Current gas monitoring solutions are either offline with a low sampling frequency or require cumbersome EX protection near the pipe (gas chromatography). By contrast, the proposed technique will allow a compact sensing unit connected only with fiberoptics that can monitor annulus gas levels continuously and with high accuracy.Laboratory test results show a high level of measurement accuracy even over short timescales. These results show a clear advantage over conventional systems due to the real-time sampling, and the compact final design being free of electrical leads allows for a compact bolt-on solution which can be installed almost anywhere without compromising working space. This also minimises the number of work-hours necessary near the pipe to maintain the monitoring system. Wells may change fluid composition in a way which brings the problem of corrosion fatigue to a riser never intended for these conditions. For example, wells which initially were sweet may become sour over time. Having a gas monitoring solution in place will allow for real-time risk assessment as well as a warning system for changes in riser annulus conditions. For sour service pipes, a gas monitoring solution will allow up-to-date and highly precise corrosion fatigue calculations. Combining the input from gas monitoring with the data from other sources, such as strain and temperature monitoring, will give unprecedented insight into the field service conditions of a riser, yielding a far greater level of operating safety than previously feasible.

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Photoacoustic phase shift as a chemically selective spectroscopic parameter

Cited by 48 publications

References 9 publications

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy

Quantum cascade lasers in chemical physics

SS: Advances in Flexible Riser Technology: Fiberoptic Gas Monitoring Of Flexible Risers

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