Detection Of Ethane Research Articles

Vision Fourier transformer empowered multi-modal imaging system for ethane leakage detection

A leak detection is an essential procedure to guarantee reliable functioning during ethane production and transportation with infrared imaging. However, infrared imaging cannot perceive semantic information about objects, such as colors and textures. Visible imaging can provide such information but lacks reliability against bad weather. Multi-modal imaging that utilizes visible and infrared information can be the ultimate solution to compensate for their properties. Thus, this study proposed an innovative multi-modal detection framework, Vision Fourier Transformer-based Ethane Detection (VFTED), to effectively and efficiently fuse visible and infrared information to detect ethane leaks. Specifically, the fast Fourier transform is embedded in the neural network to extract global attention for improved information fusion from VI and IR imaging. Meanwhile, a Fourier multi-layer perceptron (FMLP) is designed to enable neural networks to process complex numbers from Fourier transform. Finally, the fused features are fed into the detector for ethane leak detection. Besides, this article also conveys a new case study to validate the feasibility of the proposed VFTED. Extensive experiments demonstrate the significant improvement brought by the proposed framework over detection’s accuracy and robustness. Hence, the proposed framework enables reliable ethane monitoring with multi-modal imaging.

A homogeneous sampling membrane inlet photoelectron ionization miniature time-of-flight mass spectrometer for on-line determination of ethane

Ethane is the second largest component among natural gas, and the detection of ethane is an effective method for rapid identification of the leakage of the natural gas pipelines. In this work, a homogeneous sampling membrane inlet was developed and coupled with the homemade photoelectron ionization miniature time-of-flight mass spectrometer (PEI-mini-TOFMS) for in situ, on-line and highly sensitive ethane detection. The membrane area of the homogeneous sampling membrane inlet was increased from 490 mm2 to 1256 mm2, gaseous sample is injected from the top port and flowed through the membrane surface and out of the bottom two ports, with the three ports arranged in a triangular shape. The highest average flow velocity of the gas on the surface of the membrane reached 0.4 m s−1, and the optimal gas pressure in the PEI source was enhanced from 2.2 Pa to 4.0 Pa with this new design. The new design improved the comprehensive sensitivity of ethane by a factor of 3.0 compared with that of the traditional two-hole membrane inlet with the membrane area of 490 mm2. The semiconductor cold trap controlled the sample relative humidity (RH) at 10–12%, enabling direct sampling for highly sensitive analysis with RH as high as 70% and temperature from 7 °C to 40 °C. The quantitative range was 1–50 ppmv with a limit of detection (LOD, S/N = 3) lowered to 420 ppbv within 1 min, and zero humidity quantitative calibration with cold trap further reduced the relative standard deviation (RSD) of the signal intensities to 2.84%. The performance of the novel method developed in this work demonstrated a potential application on the above-ground natural gas pipelines leakage monitoring.

Methane, Ethylene, and Ethane Detection by Differential Helmholtz Resonance Spectroscopy Using a 3345 nm Mid-Infrared Tunable Diode Laser Source

Gas detection based on photoacoustic spectroscopy (PAS) has attracted extensive attention due to its high sensitivity and large range of linearity. Herein, to achieve the simultaneous detection of the light carbon gases (CH4, C2H4, and C2H6), a gas detection system was constructed using a single mid-infrared tunable diode laser (central wavelength 3345 nm) source based on differential Helmholtz resonance spectroscopy (DHRS). The detection parameters (driving current, modulation depth, phase angle, etc.) were optimized under ambient pressure using the 1f demodulation method. With an integration time of 2 s, the detection limit reached 98.8 ppb, 252 ppb, and 33 ppb for methane, ethylene, and ethane, respectively. The validation test of the three-component mixture shows that the cross-interference can be effectively reduced by multiwavelength linear regression, and single wavelength linear regression causes large errors in the quantification of methane and ethylene.

Methane and ethane detection from natural gas level down to trace concentrations using a compact mid-IR LITES sensor based on univariate calibration

A gas sensor based on light-induced thermo-elastic spectroscopy (LITES) capable to detect methane (C1) and ethane (C2) in a wide concentration range, from percent down to part-per-billion (ppb), is here reported. A novel approach has been implemented, exploiting a compact sensor design that accommodates both a custom 9.8 kHz quartz tuning fork (QTF) used as photodetector and the gas sample in the same housing. The resulting optical pathlength was only 2.5 cm. An interband cascade laser (ICL) with emission wavelength of 3.345 µm was used to target absorption features of C1 and C2. The effects of high concentration analytes on sensor response were firstly investigated. C1 concentration varied from 1% to 10%, while C2 concentration varied from 0.1% to 1%. These ranges were selected to retrace the typical natural gas composition in a 1:10 nitrogen dilution. The LITES sensor was calibrated for both the gas species independently and returned nonlinear but monotonic responses for the two analytes. These univariate calibrations were used to retrieve the composition of C1-C2 binary mixtures with accuracy higher than 98%, without the need for further data analysis. Minimum detection limits of ∼650 ppb and ∼90 ppb were achieved at 10 s of integration time for C1 and C2, respectively, demonstrating the capability of the developed LITES sensor to operate with concentration ranges spanning over 6 orders of magnitude.

High-sensitivity detection of ethane and ethylene using gamma-irradiated ZnO chemiresistors

Gamma irradiated ZnO chemical sensors showed highly sensitive and selective responses to 1.2 ppm of ethane and ethylene. Scanning electron microscopy images showed the formation of nanosized features on the surface of ZnO after irradiation. The porosity, crystallite size, and points defects (mainly oxygen and zinc vacancies) of the studied ZnO thin films were found to increase with increase in gamma irradiation. The sensitivity of ZnO chemical sensors increased with increase in the radiation dose. The ZnO sensors exhibited approximately 440 and 730% enhancements in the sensitivity to ethane and ethylene, respectively after irradiation with 200 kGy. The sensitivity and selectivity of the ZnO sensors to ethane and ethylene were interpreted from the radiation-induced changes in surface morphology that led to higher surface area and changes in surface chemistry with abundance of oxygen and zinc vacancies.

Near-Infrared Dual-Gas Sensor System for Methane and Ethane Detection Using a Compact Multipass Cell

In this invited paper, a compact dense-pattern multipass cell-based near-infrared sensor system was demonstrated for detection of parts-per-billion in volume (ppbv)-level methane (CH4) and ethane (C2H6). The dimension size of the fabricated gas cell is 18.5 × 8 × 9 cm3 with an absorption path length of 9.39 m. CH4 measurement was realized within a spectral range of 6,046–6,048 cm−1 and an absorption line of 6,046.95 cm−1. The spectral range for C2H6 detection is 5,951–5,953 cm−1 with an absorption line of 5,951.73 cm−1. Allan deviation analysis was used for evaluating the dual-gas sensing performance, and a detection limit of 78 ppbv for CH4 and 190 ppbv for C2H6 were achieved, respectively, with an averaging time of 0.8 s. Furthermore, CH4 measurement in the indoor and outdoor atmosphere was both performed to verify the field sensing capability of the sensor system. Compared with two separate sensor systems for CH4/C2H6 sensing, the proposed dual-gas sensor system using two near-infrared lasers and one multipass cell has the advantages of low-cost, compact-size without decreasing the selectivity and sensitivity.

Geological, geophysical, and geochemical characteristics of deep-routed fluid seepage and its indication of gas hydrate occurrence in the Beikang Basin, Southern South China Sea

Deep-routed fluid seepage conduits are widely distributed in the Southern South China Sea (SSCS), and gas hydrates have been discovered inside these conduits through drilling and logging. Due to a lack of integrated geological, geophysical, and geochemical data, deep-routed fluid seepage conduits and their relationship to gas hydrate occurrence are still unclear. In this study, a comprehensive investigation of fluid seepage was conducted through systematic analysis of high-resolution 2-D seismic data, multibeam bathymetry data, headspace gas and carbon isotope components, authigenic carbonates, pore water, biomarkers, and hydrate phase equilibrium simulation. Multiple types of deep-routed conduits—which typically manifested as mud volcanoes, diapirs, fluid-escape pipes, and paleo-uplift associated faults—were identified. These manifestations were generally accompanied by Bottom Simulating Reflectors (BSRs), blanking zones, locally enhanced reflections, "pulled-up" reflections, pockmarks, mounds, and gas plumes, which indicated fluid seepage and possible gas hydrate accumulation. The Sulfate Methane Transition Zone (SMTZ) in the fluid seepage sites occurred at relatively shallow depths of 325–660 cmbsf (centimeter below the seafloor), suggesting a high methane flux and sufficient gas supply. The carbon isotope composition of the methane (−92.6‰ < δ13C < −50.2‰) and the detection of ethane, propane, and n-butane, as well as multiple geological configuration biomarkers, all indicate that deep-sourced hydrocarbons and thermogenic gas have migrated into the shallow layer through deep-routed conduits. Several geological and geochemical anomalies, including gas expansion, gas bubbling in piston core sediments, negative pore water chloride anomalies, and δ18O enrichment (3.8‰ < δ18O < 4.1‰) in the cold seep carbonates, provide evidence of hydrate dissociation during core recovery. The deep-routed fluid seepage and the accompanying hydrocarbon gas supply have a significant influence on the potential thermogenic gas-sourced hydrate accumulation and evolution. Overall, the co-existence of fracture-filling hydrates and pore-filling hydrates formed from the same supply of thermogenic gas and biogenic gas was inferred through comprehensive study and comparison with adjacent hydrate drilling areas. This article is the first systematic study of the characteristics of hydrate accumulation under the fluid seepage background in the Beikang Basin, and it provides a favorable reference for revealing the relationship between deep-sourced fluid seepage and hydrate formation. However, more exploration work needs to be conducted to confirm the above assumptions.

Detection of ethane, methane, formaldehyde and water vapor in the 3.33 μm range

Detection of ethane, methane, formaldehyde and water vapor in the 3.33 μm range

Sub parts-per-billion detection of ethane in a 30-meters long mid-IR Antiresonant Hollow-Core Fiber

In this work, we present the first demonstration of a gas sensor utilizing the Wavelength Modulation Spectroscopy technique and a mid-IR guiding Antiresonant Hollow-Core Fiber with a record length of 30 m. The self-fabricated ARHCF was used as an air-tight, low-volume absorption cell delivering an extended laser-gas molecules interaction path within the sensor’s setup, which enabled it to efficiently detect ethane at 2996.88 cm−1. Benefiting from the unique guidance properties of the ARHCF, the sensor reached a minimum detection limit of 670 parts-per-trillion by volume for 14 s integration time, which is at a level comparable to the bulk optics-based systems utilizing more complex detection techniques or multipass cells with tens of meters long optical path lengths. The obtained results confirm that ARHCF-based gas sensors can successfully compete with or even outperform bulk optics-based mid-IR gas sensor configurations. The obtained results show the potential for the development of novel, low-volume, compact, and reliable types of gas detectors allowing precise analysis of various gaseous substances at their trace concentration level.

Ethane detection with mid-infrared hollow-core fiber photothermal spectroscopy.

We report a compact mid-infrared (MIR) photothermal spectroscopic ethane (C2H6) sensor with a hollow-core negative-curvature-fiber (HC-NCF) gas cell. The HC-NCF supports low-loss transmission of an MIR pump (3.348 µm) and a near-infrared (NIR) probe (1.55 µm). The pump and probe laser beams are launched into the gas cell from the opposite ends of the HC-NCF, allowing independent MIR pump delivery and NIR fiber-optic probe circuitry. The use of Fabry-Perot as the probe interferometer simplifies the sensor design and suppresses the common-mode noise in the lead in/out single-mode fiber. With a 14-cm-long HC-NCF, an ethane sensor system with the limit of detection (LOD) of 13 parts-per-billion (ppb) is achieved with 1 s lock-in time constant. The LOD goes down to 2.6 ppb with 410 s average time, which corresponds to noise equivalent absorption (NEA) of 2.0×10-6 and is a record for the hollow-core fiber MIR gas sensors. The system instability is 2.2% over a period of 8 hours.

Occurrence and origin of groundwater methane in the Stellarton Basin, Nova Scotia, Canada

Groundwater methane (CH4) in areas of fossil fuel development has been a recent focus of study as high CH4 concentrations pose water quality concerns and potential explosive hazards. In 2013, a provincial study in Nova Scotia identified areas with elevated groundwater CH4. However, due to limited data, the specific sources and local distribution of CH4 in those areas remain unknown. In this study, we examined the Stellarton Basin in central Nova Scotia, Canada, a region with an abundance of coal formations, numerous abandoned coal mines, and an active open pit coal mine. Methane was detected in 94% of water samples that were sampled from 45 private water wells. Six water wells exceeded the 28 mg/L hazard mitigation threshold with CH4 levels of up to 72.7 mg/L. The δ13CCH4 (−85.5 to −48.5‰) and the δ2HCH4 (−280 to −88‰) indicated that >95% of samples had CH4 of microbial origin. However, the detection of ethane (C2H6) up to 2.97 mg/L and propane (C3H8) up to 0.008 mg/L, as well as the δ13CC2H6 values (−30.1 to −15.6‰) suggested a mixture of microbial CH4 with trace thermogenic gas, likely migrated from Stellarton coals (δ13CC2H6 of −27.6 to −15.35‰). A mobile greenhouse gas analyzer survey was conducted within the perimeter of residences and off-gassing from taps had atmospheric CH4 measurements as high as 66 ppmv. This study integrates multiple sampling and monitoring methods to investigate groundwater CH4 in a coal-bearing region. The findings advance the understanding of the origin and occurrence of CH4 in complex groundwater systems. The data acquired in this study may be used as a pre-drill baseline for groundwater CH4 concentrations and origins should coal-bed methane operations in Nova Scotia proceed in the future.

Quartz-Enhanced Photoacoustic Detection of Ethane in the Near-IR Exploiting a Highly Performant Spectrophone

In this paper the performances of two spectrophones for quartz-enhanced photoacoustic spectroscopy (QEPAS)-based ethane gas sensing were tested and compared. Each spectrophone contains a quartz tuning fork (QTF) acoustically coupled with a pair of micro-resonator tubes and having a fundamental mode resonance frequency of 32.7 kHz (standard QTF) and 12.4 kHz (custom QTF), respectively. The spectrophones were implemented into a QEPAS acoustic detection module (ADM) together with a preamplifier having a gain bandwidth optimized for the respective QTF resonance frequency. Each ADM was tested for ethane QEPAS sensing, employing a custom pigtailed laser diode emitting at ~1684 nm as the exciting light source. By flowing 1% ethane at atmospheric pressure, a signal-to-noise ratio of 453.2 was measured by implementing the 12.4 kHz QTF-based ADM, ~3.3 times greater than the value obtained using a standard QTF. The minimum ethane concentration detectable using a 100 ms lock-in integration time achieving the 12.4 kHz custom QTF was 22 ppm.

Widely-tunable mid-infrared ring cavity pump-enhanced OPO and application in photo-thermal interferometric trace ethane detection.

The development of a broadly and accurately tunable single-frequency mid-infrared laser source and its application to a sensitive laser absorption detection method are described. Photo-thermal interferometric spectroscopy is employed as a phase-sensitive method to detect the minute refractive index change caused by the heating of a gas under laser radiation. A separate probe beam allows for the spectrally-interesting mid-infrared region to be examined whilst utilizing low cost, high detectivity photodetectors in the visible/near-infrared region. We also describe the implementation of a Sagnac interferometer to minimize the effects of environmental perturbation and provide inherent passive stability. A continuous-wave ring-cavity pump-enhanced OPO has been developed to provide excitation light from 3-4 µm at 140 mW with the ability to mode-hop tune continuously over 90 cm-1 in 0.07 cm-1 steps. Complementary use of both detection apparatus and excitation source has allowed for presence of ethane to be detected down to 200 parts per billion.

MEMS sensor array-based electronic nose for breath analysis—a simulation study

The paper presents a simulation study of breath analysis based on theoretical models of microelectromechanical structure (MEMS) cantilever sensor array. The purpose of this study is to suggest a methodology for the development of MEMS electronic nose (e-nose) for monitoring disease-specific volatiles in exhaled breath. Oxidative stress and diabetes are taken as case studies for the assessment of e-nose designs. The detection of ethane for general oxidative stress, isoprene for hypoxia, and acetone for diabetes are considered for targeted detection. A number of volatiles concurrently present in the exhaled breath are taken as interferents. The MEMS cantilevers are coated with volatile-selective polymers and are analyzed in both the static and dynamic modes. The sensor array is defined by polymer selections based on three data mining methods: principal component analysis (PCA), fuzzy c-means clustering (FCM), and fuzzy subtractive clustering (FSC). This utilizes vapor/polymer partition coefficients as a database. Analyses are carried out to find optimal combinations of the polymer selection method and cantilever sensing mode. Virtual breath analysis experiments are analyzed by PCA for target discrimination. It is found that no single combination works best in all conditions. The acetone (diabetes) detection is best in both sensing modes with the polymers selected by FSC; the isoprene (hypoxia) is detectable only in static sensing mode with polymers selected by FCM clustering; and the ethane (oxidative stress) detection is possible by all sensing modes and polymer selections, provided the breath samples are preconcentrated. This study suggests that it is difficult to realize a single general-purpose MEMS breath analyzer. The dedicated analyzers for specific disease indications can however be made with an optimal combination of sensing mode and polymer coatings.

Photoacoustic Measurement of Ethane with Near-Infrared DFB Diode Laser

A compact resonant photoacoustic sensor based on a near-infrared distributed-feedback (DFB) diode laser was developed for detection of ethane (C2H6). A DFB laser emission at 5937.25 cm−1 with a power of ∼5 mW was used as an excitation light source for generating the photoacoustic signal. Wavelength modulation and second harmonic detection scheme were employed. Modulation frequency and modulation amplitude were optimized for getting optimum performance. Performance evaluation based on the linearity response of the PAS sensor system with respect to C2H6 concentration levels was performed, and a good linear dependence of the PAS signal on the C2H6 concentration was obtained. A minimum detectable concentration of 9 ppmv was achieved for detection of C2H6 with a lock-in time constant of 10 ms.

Ppb-level mid-infrared ethane detection based on three measurement schemes using a 3.34-μm continuous-wave interband cascade laser

A ppb-level mid-infrared ethane (C2H6) sensor was developed using a continuous-wave, thermoelectrically cooled, distributed feedback interband cascade laser emitting at 3.34 μm and a miniature dense patterned multipass gas cell with a 54.6-m optical path length. The performance of the sensor was investigated using two different techniques based on the tunable interband cascade laser: direct absorption spectroscopy (DAS) and second-harmonic wavelength modulation spectroscopy (2f-WMS). Three measurement schemes, DAS, WMS and quasi-simultaneous DAS and WMS, were realized based on the same optical sensor core. A detection limit of ~7.92 ppbv with a precision of ±30 ppbv for the separate DAS scheme with an averaging time of 1 s and a detection limit of ~1.19 ppbv with a precision of about ±4 ppbv for the separate WMS scheme with a 4-s averaging time were achieved. An Allan–Werle variance analysis indicated that the precisions can be further improved to 777 pptv @ 166 s for the separate DAS scheme and 269 pptv @ 108 s for the WMS scheme, respectively. For the quasi-simultaneous DAS and WMS scheme, both the 2f signal and the direct absorption signal were simultaneously extracted using a LabVIEW platform, and four C2H6 samples (0, 30, 60 and 90 ppbv with nitrogen as the balance gas) were used as the target gases to assess the sensor performance. A detailed comparison of the three measurement schemes is reported. Atmospheric C2H6 measurements on the Rice University campus and a field test at a compressed natural gas station in Houston, TX, were conducted to evaluate the performance of the sensor system as a robust and reliable field-deployable sensor system.

Compact TDLAS based optical sensor for ppb-level ethane detection by use of a 3.34 μm room-temperature CW interband cascade laser

A mid-infrared ethane (C2H6) sensor based on a wavelength modulation spectroscopy (WMS) technique was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) interband cascade laser (ICL) emitting at 3.34μm and a dense multi-pass gas cell (MPGC, 17×6.5×5.5cm3) with a 54.6m optical path length. A compact optical sensor system with a physical size of 35.5×18×12.5cm3 was designed and constructed. An ICL was employed for targeting a strong C2H6 line at 2996.88cm−1 at <100Torr gas pressure in the fundamental absorption band of C2H6. The sensor performance, including the minimum detection limit (MDL) and the stability were improved by reducing the effect of laser power drift by means of the 2f/1f-WMS technique. A MDL of ∼1.2 parts per billion (ppbv) for 2f-WMS and ∼1.0ppbv for 2f/1f-WMS were achieved, respectively, with a measurement time of 4s. The MDL was further improved from 299pptv (@108s for 2f-WMS) to 239pptv (@208s for 2f/1f-WMS), based on an Allan deviation analysis. The rise time (@0→100ppbv) and fall time (@100→0ppbv) were determined to be ∼64s and ∼48s, respectively, at a gas pressure of <100Torr for the C2H6 sensor operation.

Suppressing the influence of optical fringes in dispersion spectroscopy

In this letter we show that in chirped laser dispersion spectroscopy (CLaDS) a significant reduction of parasitic optical fringes can be achieved. Good agreement between theoretical model and experimental data is demonstrated. Such a fringe reduction capability makes CLaDS technique a good candidate for field applications in which long-term accuracy is critical. Full Text: PDF References A. Cygan et al., High-signal-to-noise-ratio laser technique for accurate measurements of spectral line parameters, Phys. Rev. A 85, 022508 (2012) CrossRef B. Tuzson et al., Continuous isotopic composition measurements of tropospheric CO2 at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events, Atmos. Chem. Phys. 11 1685 (2011) CrossRef M. Nikodem, G. Wysocki, Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing, Sensors 12, 16466 (2012) CrossRef B. Brumfield, et al., Direct In Situ Quantification of HO2 from a Flow Reactor, J. Phys. Chem. Lett. 4, 872 (2013) CrossRef P. Kluczynski et al., Detection of acetylene impurities in ethylene and polyethylene manufacturing processes using tunable diode laser spectroscopy in the 3-?m range, Appl. Phys. B 105, 427 (2011) CrossRef M. R. McCurdy et al., Recent advances of laser-spectroscopy-based techniques for applications in breath analysis, J. Breath Res. 1, 014001 (2007) CrossRef K. Krzempek et al., CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell, Appl. Phys. B 112, 461 (2013) CrossRef R. W. Wood, The Anomalous Dispersion of Sodium Vapour, Proc. of the Royal Society of London 69, 157 (1902) CrossRef G. C. Bjorklund, Frequency-modulation spectroscopy: a new method for measuring weak absorptions and dispersions, Opt. Lett. 5, 15 (1980) CrossRef S. Marchett, R. Simili, Measurement of the refractive index dispersion around an absorbing line, Opt. Comm. 249, 37 (2005) CrossRef R. Lewicki et al., Ultrasensitive detection of nitric oxide at 5.33 ?m by using external cavity quantum cascade laser-based Faraday rotation spectroscopy, Proc. Natl. Acad. Sci. U. S. A. 106, 12587 (2009) CrossRef P. Ehlers et al., Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrumentation for Doppler-broadened detection in the 10?12??cm?1?Hz?1/2 region, J. Opt. Soc. Am. B 29, 1305 (2012) CrossRef G. Wysocki, D. Weidmann, Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser, Opt. Exp. 18, 26123 (2010) CrossRef M. Nikodem, G. Wysocki, Molecular dispersion spectroscopy ? new capabilities in laser chemical sensing, Ann. NY Acad.Sci. 1260, 101 (2012) CrossRef M. Nikodem, G. Wysocki, Measuring optically thick molecular samples using chirped laser dispersion spectroscopy, Opt. Lett. 38, 3834 (2013) CrossRef N.-Y. Chou et al., Optical fringe reduction technique for FM laser spectroscopy, Appl. Opt. 28, 4973 (1989) CrossRef M. Nikodem et al., Signal-to-noise ratio in chirped laser dispersion spectroscopy, Opt. Expr. 20, 644 (2012) CrossRef A. Fried et al., Reduction of interference fringes in small multipass absorption cells by pressure modulation, Appl. Opt. 29, 900 (1990) CrossRef

CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell

The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5–4 μm range TEC mercury–cadmium–telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm−1, a 1σ minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

Continuous wave, distributed feedback diode laser based sensor for trace-gas detection of ethane

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) based on a 2f wavelength modulation (WM) detection technique. TDLAS was performed with a 100 m optical path length astigmatic Herriott cell. For an interference free C2H6 absorption line located at 2976.8 cm−1 a 1σ minimum detection limit of 240 pptv (part per trillion by volume) with a 1 second lock-in amplifier time constant was achieved. In addition, reliable and long-term sensor performance was obtained when operating the sensor in an absorption line locked mode.