Vorrichtung und Verfahren zur berührunglosen Detektion eines nicht infrarotaktiven Zielgases

The invention relates to a device and a method for remotely detecting a non-infrared active target gas at a target location where the target gas can be found, comprising an excitation laser 4 for emitting an excitation laser beam 5 which can be deflected towards at least two target locations Oi, Oi+1, comprising a detector 6 for detecting a radiation 16 originating from the respective target location Oi, Oi+1, comprising a control device for controlling the excitation laser 4, and comprising an analyzing device for analyzing output signals of the detector 6 dependent on the respective target location Oi, Oi+1 and in correlation with the excitation laser beam 5 emitted from the excitation laser 4. A reliable and safe detection of the target gas 1 is achieved in that the excitation laser 4 is designed to emit an infrared excitation laser beam 5, the wavelength of which can be matched to the wavelength of an infrared-active background gas 3 absorption line in the infrared region, said background gas being located in the surroundings of the respective target location Oi, Oi+1; a radiation which can be influenced on the basis of the excitation of the background gas 3 can be measured using the detector 6; and values can be displayed by the analyzing device using the output signals of the detector 6, wherein the values correlate to the concentration of the background gas at the respective target location Oi, Oi+1, and properties of a target gas 1 present at the respective target location Oi, Oi+1 can be ascertained from the values

Mid-infrared gas-sensing systems and applications

Due to technological advances, mid-infrared (MIR) gas sensors have gained importance in the last decade. Light sources and detectors for the MIR range have become available at acceptable quality and price levels to a greater extent, and advances in electronics design and packaging allow for sensing systems that are now more reliable, rugged, sensitive, and selective than ever. This certainly opens up new application fields for such gas sensors. This chapter comprises a description of the sensor technologies, both relying on coherent and incoherent MIR sources, and possible application scenarios. The first section gives an insight in the growing market with its high demands, waiting for novel gas sensor devices

Vorrichtung und Verfahren zum Messen eines Zielgases

Die Erfindung betrifft eine Vorrichtung und ein Verfahren zum Messen eines Zielgases, mit einem Anregungslaser 1 zur Emission eines infraroten Laserstrahls 2, der auf einen Zielort lenkbar ist, an dem sich das Zielgas 3 befinden kann, und dessen Wellenlänge auf eine Anregungswellenlänge einer Absorptionslinie des Zielgases 3 abstimmbar ist, die durch Anregung eines Zustandes des Rotationsschwingungsspektrums des Zielgases zustande kommt, mit einer Detektionsanordnung mit einem Messdetektor 5 zur Detektion einer von dem Zielort ausgehenden, durch das Zielgas 3 beeinflussbaren Strahlung, und mit einer Analyseeinrichtung 6 zur Analyse eines Ausgangssignals des Messdetektors 5 in Abhängigkeit von dem von dem Anregungslaser 1 emittierten Laserstrahl 2.; Ein einfacherer Aufbau und eine gute Messempfindlichkeit werden dadurch erzielt, dass der Anregungslaser 1 so ausgebildet ist, dass mit dem infraroten Laserstrahl 2 eine Absorptionslinie des Zielgases 3 derart anregbar ist, dass die Anregung zu einer Temperaturerhöhung des Zielgases 3 führt, und dass die Detektionsanordnung zum Messen einer durch die Temperaturerhöhung beeinflussbare Eigenschaft des Zielgases 3 ausgestattet ist

Molecular Beam Epitaxy of IV-VI Compounds

Binary lead chalcogenides PbS, PbSe, and PbTe, frequently called ‘lead salts,' are the major IV–VI MBE materials. These narrow gap semiconductors are used for infrared detectors, lasers, and thermoelectric devices. Ternary and quaternary materials include chalcogenides, for example cadmium, europium, strontium, and tin. By substitution of lead the band gap energy can be varied from zero to 0.65 eV. Growth on (100)-oriented IV–VI-substrates and heteroepitaxial growth on (111) oriented substrates like BaF2, Si, and on V–IV materials is performed for quantum well, quantum dot, and superlattice structures. Infrared buried heterostructure lasers, photodiode arrays, VCSEL and LEDs are fabricated

Noninvasive Magnetic-Marking-Based Flow Metering with Optically Pumped Magnetometers

We present a noninvasive procedure that measures the flow velocity of a fluid by using polarized hydrogen nuclei in the fluid. The measurement procedure is based on a time-of-flight method where magnetic information is applied on the fluid with a permanent magnet and an RF-pulse. In contrast to other methods, this magnetic-marking method works without tracers. The read-out of the magnetic information is performed by optically pumped magnetometers downstream. In order to function, the magnetometers have to be operated in a magnetic shield with magnetic field strengths lower than 100 nT, i.e., in the zero-to-ultra-low-field regime. In this regime, the magnetometers are capable of detecting induced magnetic signals of 10 pT or less with an inline-flow setup. The results presented in this paper demonstrate the viability of optically pumped magnetometers for flow metering. The first metering results yielded an average accuracy of 3% at flow velocities between 13 cm/s and 22.4 cm/s

Rapid Quantitative Analysis of IR Absorption Spectra for Trace Gas Detection by Artificial Neural Networks Trained with Synthetic Data

Infrared absorption spectroscopy is a widely used tool to quantify and monitor compositions of gases. The concentration information is often retrieved by fitting absorption profiles to the acquired spectra, utilizing spectroscopic databases. In complex gas matrices an expanded parameter space leads to long computation times of the fitting routines due to the increased number of spectral features that need to be computed for each iteration during the fit. This hinders the capability of real-time analysis of the gas matrix. Here, an artificial neural network (ANN) is employed for rapid prediction of gas concentrations in complex infrared absorption spectra composed of mixtures of CO and N2O. Experimental data is acquired with a mid-infrared dual frequency comb spectrometer. To circumvent the experimental collection of huge amounts of training data, the network is trained on synthetically generated spectra. The spectra are based on simulated absorption profiles making use of the HITRAN database. In addition, the spectrometer’s influence on the measured spectra is characterized and included in the synthetic training data generation. The ANN was tested on measured spectra and compared to a non-linear least squares fitting algorithm. An average evaluation time of 303 µs for a single measured spectrum was achieved. Coefficients of determination were 0.99997 for the predictions of N2O concentrations and 0.99987 for the predictions of CO concentrations, with uncertainties on the predicted concentrations between 0.04 and 0.18 ppm for 0 to 100 ppm N2O and between 0.05 and 0.18 ppm for 0 to 60 ppm CO

Remote detection of leakages of non-IR-active gases by laser spectroscopy

Remote leak detection of gases such as the homonuclear molecules (N2, H2, etc.) and noble gases (He, Ar etc.) is still an issue for tunable laser spectroscopy (TLS) because these gases do not have infrared absorption bands. In order to detect a leak in air, the gas displacement of the ambient air is used as an indirect indication of the leak. So, the unique idea is to measure the reduced oxygen concentration by a standoff laser spectrometer at an emission wavelength of 761 nm. The advantage of oxygen as indicator gas is the stable concentration level with respect to low spatial and temporal fluctuations. The challenge of the standoff detection is to analyze the small relative transmission change for weak light intensity scattered by the background. Furthermore, a remote measurement technique for high-level oxygen concentration on ppm level resolution is demonstrated. Here the combination of a high performance distributed feedback laser at 761 nm and high end sophisticated electronics for driver and data acquisition is required and designed. With the direct absorption spectroscopy, the concentration change of 2000 ppm within a 1 cm plume size (10 ml/min flow, ambient room conditions) corresponds to a transmission change in order of 2E-4 has been resolved on a low absolute power level of few micro watts in 1m distance. The detection limit corresponds to a nitrogen leakage rate of 0.1mbar·l/s which is comparable to ordinary remote detection systems for methane leakages

Diamond-Coated Silicon ATR Elements for Process Analytics

Infrared attenuated total reflection (ATR) spectroscopy is a common laboratory technique for the analysis of highly absorbing liquids or solid samples. However, ATR spectroscopy is rarely found in industrial processes, where inline measurement, continuous operation, and minimal maintenance are important issues. Most materials for mid-infrared (MIR) spectroscopy and specifically for ATR elements do not have either high enough infrared transmission or sufficient mechanical and chemical stability to be exposed to process fluids, abrasive components, and aggressive cleaning agents. Sapphire is the usual choice for infrared wavelengths below 5 µm, and beyond that, only diamond is an established material. The use of diamond coatings on other ATR materials such as silicon will increase the stability of the sensor and will enable the use of larger ATR elements with increased sensitivity at lower cost for wavelengths above 5 µm. Theoretical and experimental investigations of the dependence of ATR absorbances on the incidence angle and thickness of nanocrystalline diamond (NCD) coatings on silicon were performed. By optimizing the coating thickness, a substantial amplification of the ATR absorbance can be achieved compared to an uncoated silicon element. Using a compact FTIR instrument, ATR spectra of water, acetonitrile, and propylene carbonate were measured with planar ATR elements made of coated and uncoated silicon. Compared to sapphire, the long wavelength extreme of the spectral range is extended to approximately 8 μm. With effectively nine ATR reflections, the sensitivity is expected to exceed the performance of typical diamond tip probes

Gas leak detection by dilution of atmospheric oxygen

Gas leak detection is an important issue in infrastructure monitoring and industrial production. In this context, infrared (IR) absorption spectroscopy is a major measurement method. It can be applied in an extractive or remote detection scheme. Tunable laser spectroscopy (TLS) instruments are able to detect CH4 leaks with column densities below 10 ppm·m from a distance of 30 m in less than a second. However, leak detection of non-IR absorbing gases such as N2 is not possible in this manner. Due to the fact that any leaking gas displaces or dilutes the surrounding background gas, an indirect detection is still possible. It is shown by sensitive TLS measurements of the ambient background concentration of O2 that N2 leaks can be localized with extractive and standoff methods for distances below 1 m. Minimum leak rates of 0.1 mbar·L/s were determined. Flow simulations confirm that the leakage gas typically effuses in a narrow jet. The sensitivity is mainly determined by ambient flow conditions. Compared to TLS detection of CH4 at 1651 nm, the indirect method using O2 at 761 nm is experimentally found to be less sensitive by a factor of 100. However, the well-established TLS of O2 may become a universal tool for rapid leakage screening of vessels that contain unknown or inexpensive gases, such as N2