Differential Absorption Method Research Articles

Preliminary analysis of global column-averaged CO2 concentration data from the spaceborne aerosol and carbon dioxide detection lidar onboard AEMS

In contrast to the passive remote sensing of global CO2 column concentrations (XCO2), active remote sensing with a lidar enables continuous XCO2 measurements throughout the entire atmosphere in daytime and nighttime. The lidar could penetrate most cirrus and is almost unaffected by aerosols. Atmospheric environment monitoring satellite (AEMS, also named DQ-1) aerosol and carbon dioxide detection Lidar (ACDL) is a novel spaceborne lidar that implements a 1572 nm integrated path differential absorption (IPDA) method to measure the global XCO2 for the first time. In this study, special methods have been developed for ACDL data processing and XCO2 retrieval. The CO2 measurement data products of ACDL, including the differential absorption optical depth between the online and offline wavelengths, the integral weighting function, and XCO2, are presented. The results of XCO2 measurements over the period from 1st June 2022 to 30th June 2022 (first month data of ACDL) are analyzed to demonstrate the measurement capabilities of the spaceborne ACDL system.

Application and Research of Microseismic Monitoring System and Hydraulic Fracturing Technology in Coal Mines

In order to improve the effectiveness of coal mine gas control and enhance the level of coal mine safety production, the application of a microseismic monitoring system and hydraulic fracturing technology in coal mines was studied. Applying hydraulic fracturing technology to coal mine gas treatment, firstly, the geological structure and gas concentration in the mining area are detected using the radio tunnel perspective method and infrared differential absorption method. Then, the relevant parameters of hydraulic fracturing are determined, and finally, hydraulic fracturing technology is implemented. Microseismic monitoring technology is used to monitor the cracks formed during hydraulic fracturing construction and evaluate the fracturing effect. The instantaneous energy envelope is obtained from the microseismic data of each detection channel after stacking and Hilbert transform static correction. A microseismic in-phase inversion positioning objective function based on travel time residuals is constructed, and under the constraints of polarization analysis, the optimal solution is obtained through search iteration to complete microseismic in-phase inversion positioning. Experimental results have shown that after applying this method to coal mine gas control, the gas concentration decreases below the execution standard, achieving good control effects. Under microseismic monitoring in coal mines, the hydraulic fracturing effect can be effectively and reasonably evaluated, and the safety production level of coal mines can be improved.

Characterization of bright betatron radiation generated by direct laser acceleration of electrons in plasma of near critical density

Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativistic laser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In an experiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 1019 W/cm2 laser intensity. The spectrum of directed x-rays in the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0° and 10° to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 1013 photons/sr with energies >5 keV measured at 0° to the laser axis and a brilliance of 1021 photons s−1 mm−2 mrad−2 (0.1%BW)−1. The angular distribution of the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emission time, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laser facilities.

Broadband continuous-wave differential absorption lidar for atmospheric remote sensing of water vapor.

What we believe to be a novel low-cost broadband continuous-wave water vapor differential absorption lidar (CW-DIAL) technique has been proposed and implemented by combing the Scheimpflug principle and the differential absorption method. The broadband CW-DIAL technique utilizes an 830-nm high-power multimode laser diode with 3-W output power as a tunable light source and a CMOS image sensor tilted at 45° as the detector. A retrieval algorithm dedicated for the broadband CW-DIAL technique has been developed to obtain range-resolved water vapor concentration from the DIAL signal. Atmospheric remote sensing of water vapor has been carried out on a near-horizontal water vapor path to validate the performance of the broadband CW-DIAL system. The retrieved water vapor concentration showed a good consistency with those measured by an air quality monitoring station, with a correlation coefficient of 0.9669. The fitting error of the water vapor concentration is found to be less than 10%. Numerical simulation studies have revealed that the aerosol-induced error on the water vapor concentration is below 5% with a background water vapor concentration of 5 g/m3 for most atmospheric conditions. The experimental results have successfully demonstrated the feasibility of the present broadband CW-DIAL technique for range-resolved water vapor remote sensing.

Calibration and field test of mobile lidar for remote sensing of atmospheric methane

Subject of study. Methane concentration in near-the-surface tropospheric sensing paths was investigated under background conditions using a mobile differential absorption lidar. Aim of study. A mobile differential absorption lidar for remote sensing of atmospheric methane in the mid-infrared spectral range was designed, calibrated, and tested in natural field experiments. Method. The designed lidar enables investigation in the atmosphere using the differential absorption method. This method is based on the effect of resonant absorption of laser emission by gases. The emission source of the lidar has two operating wavelengths, one (on-line) in the center of the methane absorption line and the other (off-line) on the wing of the absorption line. The lidar signals obtained at on- and off-line wavelengths enable retrieval of the methane concentration under background conditions. Main results. The designed mobile IR differential absorption lidar for investigation of atmospheric methane is described. The mobile IR emission source of the differential absorption lidar was calibrated in the informative range of methane sensing near 3400 nm. The results of a natural field test of the mobile IR lidar for detection of atmospheric response at the calibrated sensing wavelengths and retrieval of methane background concentrations of approximately 2.0 ppm in horizontal surface atmospheric sensing paths are presented. Practical significance. The technical solutions for the design of the mobile lidar for remote methane sensing proposed in this paper enable formulation of the requirements on its further improvement aiming to increase the measurement range, design a vertical configuration for remote sensing from an aircraft, and use it at arctic latitudes.

A general formalism to include inelastic scatterings in the differential absorption method for hard x-ray spectroscopy

A complete formulation of the differential absorption method that includes inelastic scatterings inside the filters, is presented. Such scatterings produce secondary photons that can reach the detector system modifying the registered spectrum as compared with that emitted by the source under study. Erroneous results can be obtained as a consequence. It is shown that, for instance, as much as 22% of photons belonging to the 200 keV region that incide on 3 mm thick Cu filters can reach the detector with an energy that differs from that they had when emitted from the source. A total of 12 materials of different thicknesses commonly used as filters together with incident photon energies covering the 20–600 keV range is reported. The formalism is detailed, discussed and applied to a real case.

METHOD FOR REMOTE DETECTION OF HAZARDOUS SUBSTANCES IN THE NEAR AND MIDDLE IR RANGE

A scheme of a lidar complex for remote identification of explosives by the method of differential absorption and scattering is proposed. Calculation studies on remote sensing of spectroscopic parameters of some hazardous chemicals have been carried out.

Analysis of the Possibility of Remote Laser Detection of Propane Leaks

Propane is one of the main components of the wide fraction of light hydrocarbons (WLHF). A large volume of WLHF is transported to petrochemical plants via pipelines. Control of pipelines is carried out by means of in-line pressure sensors. However, they are ineffective for detecting low-intensity leaks.To detect low-intensity propane leaks from pipelines, it is promising to use a remote laser gas analyzer installed on an aircraft.The article is devoted to the analysis of the possibilities of remote laser detection of propane leaks.Based on the data on the absorption of propane and atmospheric gases, the wavelengths of 3370 nm (in the maximum absorption of propane) and 3550 nm (in the spectral region where there is no absorption of propane) were chosen as the sounding wavelengths.It was believed that the monitoring of propane leaks is carried out by a lidar installed on the aircraft in a monostatic sensing scheme. The method of differential absorption with scattering from the earth's surface is used.To detect propane leaks, an information parameter was used, which is equal to the ratio of the power recorded by the receiver at wavelengths of 3370 nm and 3550 nm. The value of the information parameter was calculated for different heights of the propane layer on the earth's surface and different concentrations of propane in the layer.Statistical modeling was performed to quantify the effectiveness of remote detection of propane leaks.In the work, the probability of correct detection of a propane leak (detection of a leak when it is in reality) and the probability of false alarms (detection of a leak when it is not in reality) were calculated.The decision to detect propane leaks was made when the value of the information parameter was less than the threshold.The results of mathematical modeling show that for a propane content in the leak of at least 0.17 % (an order of magnitude less than the concentration limit of flame propagation), the problem of remote detection of propane leaks from the pipeline can be solved with a probability of correct detection of more than 0.999 and a probability of false alarms of less than 0.001 with a thickness of the propane layer on the earth's surface of at least 20 cm.

Technologies for remote lidar sensing of the surface to detect low concentrations of hydrocarbons in Siberia and the far north

The results of research in the field of remote sensing using the technologies of radar and laser detection of hydrocarbons raw materials aimed at the search, localization and topographic location of discovered oil and gas field, the determination of leaks and atmospheric pollution by hydrocarbon gases (e.g. methane) are presented. The main problems with sounding are revealed. To determine the extremely low concentrations of methane in the atmosphere, the main constraining factors were determined and the need to suppress side interference arising on the probing path of the laser beam was shown. To formulate requirements for the sensitivity of equipment and the accuracy of software calculations, the choice of a mathematical model of the path of the laser beam is justified. A modification of the known model is proposed to represent the lidar path based on the differential absorption method taking into account correction coefficients of molecular and aerosol absorption and scattering. Thus, the presented model is a set of methods for providing more accurate and localized data for the implementation of a hardware-software complex.

Development of a laser complex for ecological monitoring of the atmosphere of urban and industrial areas

The object of research is methods of remote ecological monitoring of the surface layer of the atmosphere within residential areas and industrial zones of big cities. For the remote determination of the quantitative characteristics of gas and aerosol air pollution with high accuracy and spatial resolution, a mobile laser complex has been proposed. Determination of the composition and concentration of gas pollutants is carried out using two methods – the differential absorption method and the spontaneous Raman scattering (SRS) method. The differential absorption method is used to detect low concentrations of polluting gases along a stationary sounding path. The spontaneous Raman scattering method is used for remote detection of harmful gaseous substances at their concentrations exceeding the maximum permissible standards. SRS method used in the developed gas aerosol lidar allows one to obtain three-dimensional distributions of the concentrations of the gases being determined with a resolution of the order of one meter. This makes it possible to quickly and accurately identify environmentally hazardous sources of air pollution and reasonably apply penalties to violators of environmental standards. Remote analysis of the aerosol composition of the surface layer of the atmosphere is carried out using lidar holography methods, which were developed in the laboratory of radio and optical holography of V.N. Karazin Kharkiv National University (Ukraine). The difference in reflection from liquid and solid aerosol particles makes it possible to form polarization holograms and consider them separately for liquid and solid aerosols. Quantitative analysis of the composition and concentration of particles observed from their holographic images is characterized by a high level of sensitivity, since, unlike other known methods, it does not require a priori assumptions about the qualitative composition of the determined aerosol. Thus, due to the use of various physical principles of the interaction of laser radiation with gaseous and aerosol components of the air, the developed laser complex for environmental monitoring of the atmosphere is an effective means of monitoring the state of the air in the conditions of modern megacities.

Remote detection of heterogeneously spread alcohol vapors in the cabins of moving vehicles

This study concerns remote detection of alcohol vapors in cabins of moving vehicles. By means of a simplified description of propagation of two combined laser beams differently absorbed in alcohol vapors and in vehicle windowpanes, difficulties in detecting alcohol vapors in vehicle cabins using classical differential absorption method are demonstrated. Unreported in the literature, this method of remote detection of alcohol vapors in the air exhaled by a driver or a passenger in moving vehicles is proposed. The method uses two combined laser beams that illuminate different zones in the car cabin through the same windowpane. Based on the correlation between the spread of the transmission of these zones and the alcohol concentration in the air exhaled by a drunken person, it is possible to determine if the alcohol exists in the exhaled air. The effectiveness of the presented method is confirmed experimentally.

ЛАЗЕРНОЕ ЗОНДИРОВАНИЕ ВЗРЫВЧАТЫХ ВЕЩЕСТВ МЕТОДОМ ДИФФЕРЕНЦИАЛЬНОГО ПОГЛОЩЕНИЯ И РАССЕЯНИЯ

A scheme of a lidar complex for remote identification of explosives by the method of differential absorption and scattering is proposed. Computational studies on the remote study of the spectroscopic parameters of some explosives (TNT, TATR, DNT) were carried out.

Software system for numerical simulation of broadband laser gas analysis of the atmosphere

Introduction: Successful monitoring of environmental parameters requires the development of flexible software complexes with evolvable calculation functionality. Purpose: Developing a modular system for numerical simulation of atmospheric laser gas analysis. Results: Based on differential absorption method, a software system has been developed which provides the calculation of molecular absorption cross-sections, molecular absorption coefficients, atmospheric transmission spectra, and lidar signals. Absorption line contours are calculated using the Voigt profile. The prior information sources are HITRAN spectroscopic databases and statistical models of the distribution of temperature, pressure and gas components in the atmosphere. For modeling lidar signals, software blocks of calculating the molecular scattering coefficient and aerosol absorption/scattering coefficients were developed. For testing the applicability of various laser sources in the problems of environmental monitoring of the atmosphere, a concentration reconstruction error calculation block was developed for the atmospheric gas components, ignoring the interfering absorption of laser radiation by foreign gases. To verify the correct functioning of the software, a program block was developed for comparing the results of the modeling of atmospheric absorption and transmission spectra by using the standard SPECTRA information system. The discrepancy between the calculation of the atmospheric transmission spectra obtained using the developed system as compared to the SPECTRA results is less than 1%. Thus, a set of the presented program blocks allows you to carry out complex modeling of remote atmospheric gas analysis. Practical relevance: The software complex allows you to rapidly assess the possibilities of using a wide range of laser radiation sources for the problems of remote gas analysis.

Simulation of Second Harmonic Based on Optical Fiber Sensor

This paper is based on the Lambert-Beer law and the differential optical absorption method is used to measure the concentration of methane gas. Simulation of the whole experiment is carried out by using MATLAB. Sine waves with periodic changes are simultaneously superimposed on triangular waves are simulating the light source in the experiment. Adding harmonic modulation to eliminate the interference of noise and fundamental components obtain the second harmonic components which carrying the concentration information. Finally, different concentration will bring the second harmonic voltage value. Records are corresponding with concentration of the second harmonic voltage value. Experiments show that the resulting second harmonic signal can meet the gas detection requirements.

Laser detection of explosives based on differential absorption and scattering

A multifunctional Infrared (IR) parametric laser system for standoff detection and identification of trace atmospheric gases, including explosives and chemically aggressive substances has been developed and tested. The method can detect vapors of condensed explosives. Computational and experimental studies on the standoff determination of spectroscopic parameters of known explosives such as TNT, RDX, and PETN have been performed. It has been shown that the multifunctional IR optical parametric oscillator is suitable for high-sensitivity detection (∼1 ppm) of these substances using the method of differential absorption and scattering.

国外差分吸收激光雷达探测大气CO 2 研究综述

Differential absorption lidar is an indispensable tool to measure atmospheric CO2 for temporal and spatial distribution. The 2.0 μm wavelength Ho:Tm:YLF/Ho:Tm:LuLiF lidar were used for remote sensing atmospheric CO2 with heterodyne receiver. The KTP parametric oscillator was injected into the seeds, and a differential absorption lidar (DIAL) system of 1.6 μm by using the photon counting technique to profile the atmospheric CO2 in the troposphere under 7 km. Modulation continuous wave seed laser intensity and the integral path differential absorption lidar, common 1.6 μm optical fiber amplifier, and the use of correlation detection technique, have unique advantages and characteristics in the detection of atmospheric CO2 column concentrations. The space program for detecting atmospheric CO2 column concentrations is NASA's ASENDS (active sensing of CO2 emission over nights, days, and seasons) mission which adopts the method of pulse and integral path differential absorption. The absorption of CO2 gas cell as a reference to stabilize seed light frequency and the precise control of cavity length lock the on-line wavelength of transmitter, is the key technique for DIAL to measure atmospheric CO2.

Laser-Based Remote Sensing of Explosives by a Differential Absorption and Scattering Method

A multifunctional IR parametric laser system is developed and tested for remote detection and identification of atmospheric gases, including explosive and chemically aggressive substances. Calculations and experimental studies of remote determination of the spectroscopic parameters of the best known explosive substances TNT, RDX, and PETN are carried out. The feasibility of high sensitivity detection (~1 ppm) of these substances with the aid of a multifunctional IR parametric light source by differential absorption and scattering is demonstrated.

Lidar investigations of ozone in the upper troposphere – lower stratosphere: technique and results of measurements

The main aim of the research is to develop the technique for laser remote ozone sensing in the upper troposphere – lower stratosphere by differential absorption method for temperature and aerosol correction and analysis of measurement results. The authors have determined wavelengths, promising to measure ozone profiles in the upper troposphere – lower stratosphere. We present the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station in Tomsk. The recovered ozone profiles were compared with IASI satellite data and Kruger model.

Study of the possibility of using a parametric-light-generator-based laser system for lidar probing of the composition of the atmosphere

This paper discusses the possibility of using a laser system with parametric light generation based on a nonlinear KTiOAsO4 crystal for lidar probing of the atmosphere in the 3–4 μm range. A combined technique has been developed for lidar measurements of the gaseous components of the atmosphere, using the differential-absorption method (DAM) and differential optical absorption spectroscopy (DOAS). The DAM–DOAS technique has been tested in a numerical experiment to estimate the possibilities of lidar probing of minor gaseous components of the atmosphere.

Reconstruction of N2O and CH4Content by Dial Measurements at Wavelengths of Overtone CO Laser

The paper presents the results of laboratory experiments on measurement of absorption and extinction of radiation of the overtone СО laser at wavelengths used for sensing of methane and N2 O in the mid-IR spectral range with the differential absorption (DIAL) method, as well as the concentrations of the studied gases reconstructed from the analysis of experimentally obtained absorption coefficients.