Emission Measurements Research Articles

Quantitative analysis of optical emission spectroscopy for plasma process monitoring

In the field of plasma materials processing, various plasma parameters should be evaluated quantitatively and precisely to control the plasma process adequately, particularly with non-invasive methods, one of which is optical emission spectroscopy (OES) measurement. It has sufficient scientific feasibility to derive the electron density N e, electron temperature T e, and the electron energy distribution function (EEDF) even for various processing plasmas in a state of non-equilibrium. In this review, previous studies are reviewed to measure the N e, T e, and EEDF values of argon plasma with low-electron temperature (T e ≃ 1–10 eV) under not only low-pressure conditions but also atmospheric-pressure discharge using the OES measurement. First, to diagnose low-pressure discharge argon plasmas, we explain the basics and applications of the “collisional radiative model”, which models the population kinetics of the excited states in plasma at the elementary process level in non-equilibrium plasma. Methods for analyzing the plasma parameters are shown from the actual measurement results of emission spectra, including machine learning analysis of the excited-state populations. Next, the research results of the method to measure N e, T e, and EEDF are introduced for the measurement of atmospheric-pressure non-equilibrium plasmas using OES measurement of continuum emission, which also includes methods based on machine learning and data-scientific methods for the analysis of the OES data observed as bremsstrahlung of free electrons scattered against neutral molecules.

EIGER. V. Characterizing the Host Galaxies of Luminous Quasars at z ≳ 6

Abstract We report JWST/NIRCam measurements of quasar host galaxy emissions and supermassive black hole (SMBH) masses for six quasars at 5.9 < z < 7.1 in the Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization (EIGER) project. We obtain deep NIRCam imaging in the F115W, F200W, and F356W bands, as well as F356W grism spectroscopy of the quasars. We use bright unsaturated stars to construct models of the point-spread functions (PSFs) and estimate the errors of these PSFs. We then measure or constrain the fluxes and morphology of the quasar host galaxies by fitting the quasar images as a point source plus an exponential disk. We successfully detect the host galaxies of three quasars, which have host-to-quasar-flux ratios of ∼1%–5%. Spectral energy distribution fitting suggests that these quasar host galaxies have stellar masses of M * ≳ 1010 M ⊙. For quasars with host galaxy nondetections, we estimate the upper limits of their stellar masses. We use the grism spectra to measure the Hβ line profile and the continuum luminosity, then estimate the SMBH masses for the quasars. Our results indicate that the positive relation between SMBH masses and host galaxy stellar masses already exists at redshift z ≳ 6. The quasars in our sample show a high BH-to-stellar-mass ratio of M BH/M * ∼ 0.15, which is about ∼2 dex higher than local relations. We find that selection effects only contribute partially to the high M BH/M * ratios of high-redshift quasars. This result hints at a possible redshift evolution of the M BH–M * relation.

Selective detection of azelnidipine in pharmaceuticals via carbon dot mediated spectrofluorimetric method: A green approach.

A spectrofluorimetric method using fluorescent carbon dots (CDs) was developed for the selective detection of azelnidipine (AZEL) pharmaceutical in the presence of other drugs. In this study, N-doped CDs (N-CDs) were synthesized through a single-step hydrothermal process, using citric acid and urea as precursor materials. The prepared N-CDs showed a highly intense blue fluorescence emission at 447 nm, with a photoluminescence quantum yield of ~21.15% and a fluorescence lifetime of 0.47 ns. The N-CDs showed selective fluorescence quenching in the presence of all three antihypertensive drugs, which was used as a successful detection platform for the analysis of AZEL. The photophysical properties, UV-vis light absorbance, fluorescence emission, and lifetime measurements support the interaction between N-CDs and AZEL, leading to fluorescence quenching of N-CDs as a result of ground-state complex formation followed by a static fluorescence quenching phenomenon. The detection platform showed linearity in the range 10-200 μg/ml (R2 = 0.9837). The developed method was effectively utilized for the quantitative analysis of AZEL in commercially available pharmaceutical tablets, yielding results that closely align with those obtained from the standard method (UV spectroscopy). With a score of 0.76 on the 'Analytical GREEnness (AGREE)' scale, the developed analytical method, incorporating 12 distinct green analytical chemistry components, stands out as an important technique for estimating AZEL.

Mid-infrared Fine Structure Lines from the Galactic Warm Ionized Medium

The Warm Ionized Medium (WIM) hosts most of the ionized gas in the Galaxy and occupies perhaps a quarter of the volume of the Galactic disk. Decoding the spectrum of the Galactic diffuse ionizing field is of fundamental interest. This can be done via direct measurements of ionization fractions of various elements. Based on current physical models for the WIM we predicted that mid-IR fine structure lines of Ne, Ar and S would be within the grasp of the Mid-Infrared Imager-Medium Resolution Spectrometer (MIRI-MRS), an Integral Field Unit (IFU) spectrograph, aboard the James Webb Space Telescope (JWST). Motivated thus we analyzed a pair of commissioning data sets and detected [Ne ii] 12.81 μm, [S iii] 18.71 μm and possibly [S iv] 10.51 μm. The inferred emission measure for these detections is about 10 cm−6 pc, typical of the WIM. These detections are broadly consistent with expectations of physical models for the WIM. The current detections are limited by uncorrected fringing (and to a lesser extent by baseline variations). In due course, we expect, as with other IFUs, the calibration pipeline to deliver photon-noise-limited spectra. The detections reported here bode well for the study of the WIM. Along most lines-of-sight hour-long MIRI-MRS observations should detect line emission from the WIM. When combined with optical observations by modern IFUs with high spectral resolution on large ground-based telescopes, the ionization fraction and temperature of neon and sulfur can be robustly inferred. Separately, the ionization of helium in the WIM can be probed by NIRspec. Finally, joint JWST and optical IFU studies will open up a new cottage industry of studying the WIM on arcsecond scales.

Angle-Resolved Direct Emissivity Measurements on Unencapsulated Solar Cells for Passive Thermal Control

Angle-Resolved Direct Emissivity Measurements on Unencapsulated Solar Cells for Passive Thermal Control

Thermal Evolution of an Active Region Through Quiet and Flaring Phases as Observed by NuSTAR, XRT, and AIA

Solar active regions (ARs) contain a broad range of temperatures, with the thermal plasma distribution often observed to peak in the few millions of kelvin. Differential emission measure (DEM) analysis can allow instruments with diverse temperature responses to be used in concert to estimate this distribution. Nuclear Spectroscopic Telescope ARray (NuSTAR) hard X-ray (HXR) observations are uniquely sensitive to the highest-temperature components of the corona, and thus extremely powerful for examining signatures of reconnection-driven heating. Here, we use NuSTAR diagnostics in combination with extreme-ultraviolet and soft X-ray observations (from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and Hinode/X-Ray Telescope) to construct DEMs over 170 distinct time intervals during a 5 hr observation of an alternately flaring and quiet active region (NOAA designation AR 12712). This represents the first HXR study to examine the time evolution of the distribution of thermal plasma in an AR. During microflares, we find that the initial microflare-associated plasma heating is predominantly heating of material that is already relatively hot, followed later on by broader heating of initially cooler material. During quiescent times, we show that the amount of extremely hot (>10 MK) material in this region is significantly (∼2–4 orders of magnitude) less than that found in the quiescent AR observed in HXRs by FOXSI-2. This result implies there can be radically different high-temperature thermal distributions in different ARs, and strongly motivates future HXR DEM studies covering a large number of these regions.

Real-world black carbon emissions of gasoline vehicles at urban intersections

To gain insight into the real-world black carbon (BC) emission patterns at urban intersections, we employed a portable emission measurement system (PEMS) to assess the BC emissions from three light-duty gasoline vehicles along a designated urban route. The BC emission factors were evaluated, and the contributions of vehicle operating conditions at the intersections to the total BC emissions were quantified. The results show that the BC emission factors in an intersection area range from 0.045 to 0.291 mg/km, higher than those at an intersection's connecting sections. The average BC emission factor at signalized intersections is 17.07% higher than at roundabouts. Emission contribution analysis of driving conditions showed that in a state of non-free traffic flow, acceleration and deceleration conditions are responsible for 39% ∼ 56% and 24% ∼ 33% of BC emissions at intersections, respectively. We also found that vehicle specific power (VSP) and delay time are almost equally crucial for BC emissions from vehicles at intersections in the multiple linear regression. Our research reveals the significant impact of vehicle delay time and acceleration conditions on black carbon emissions at urban intersections, further emphasizing the importance of smooth (congestion-free) intersection operation and steady driving in reducing urban black carbon emissions.

Latest Evolution of the X-Ray Remnant of SN 1987A: Beyond the Inner Ring

Based on our Chandra imaging-spectroscopic observations, we present the latest evolution of the X-ray remnant of SN 1987A. Recent changes in the electron temperatures and volume emission measures suggest that the blast wave in SN 1987A is moving out of the dense inner ring structure, also called the equatorial ring (ER). The 0.5–2.0 keV X-ray light curve shows a linearly declining trend (by ∼4.5% yr−1) between 2016 and 2020 as the blast wave heats the hitherto unknown circumstellar medium (CSM) outside the ER. While the peak X-ray emission in the latest 0.3–8.0 keV image is still within the ER, the radial expansion rate in the 3.0–8.0 keV images suggests an increasing contribution of the X-ray emission from less dense CSM since 2012, at least partly from beyond the ER. It is remarkable that, since 2020, the declining soft X-ray flux has stabilized around ∼7 × 10−12 erg s−1 cm−2, which may signal a contribution from the reverse-shocked outer layers of ejecta as predicted by the three-dimensional magnetohydrodynamic models. In the latest ACIS spectrum of supernova remnant 1987A in 2022 we report a significant detection of the Fe K line at ∼6.7 keV, which may be due to changing thermal conditions of the X-ray emitting CSM and/or the onset of reverse shock interactions with the Fe ejecta.

Vacuum-Ultraviolet spectrometer system for impurity emission measurement on a Compact Torus Injection System of EAST

Recently, a compact torus injection (CTI) system was developed for central fueling on experimental advanced superconducting tokamak (EAST). As impurity generated by the interaction between CTI plasma and the electrode material can dilute the fuel particle, it is important to measure impurity content in CTI and evaluate the effect of impurity on the plasma before the application of CTI to EAST. A vacuum-ultraviolet (VUV) spectrometer that utilizes a concave holographic grating with 1200 groove mm-1 was developed and installed on EAST-CTI for impurity emission measurement and transport study. The mainly parts of the spectrometer are an entrance slit, a concave holographic grating with 1200 groove mm-1 and a charge coupled device (CCD). The spectrometer is designed to image the spectra of 50–460 nm by turning the grating. Preliminary experimental results were obtained from the recent EAST-CTI campaign. Impurity line spectra from 50 to 460 nm wavelength range were measured and identified for several impurity species, such as iron, copper, chromium, oxygen, carbon and fluorine. For example, spectra in the intervals of 150 nm to 300 nm contained strong Fe lines. Helium spectra are also measured in the form of He I and He II spectral lines as helium is the main component of the plasma. The results show that the VUV spectrometer is capable of measuring impurity radiations on EAST-CTI and will be a useful tool for impurity behavior study.

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study.

We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < XIL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

Neutron detection in mixed short-pulsed fields with intense photon flashes for LINAC-based active interrogation applications

High-energy photon interrogation has established itself as a valuable tool for detecting special nuclear materials and characterizing nuclear waste. Previous research predominantly uses around 9-MV linear electron accelerators (LINACs) as photon sources and limited exploration has been conducted on the use of organic scintillators to determine the energy deposited in the detector and to separate photon and neutron radiation, crucial when the photon interrogation is based on the measurement of the neutron emission. The challenge arises from the intense photon flux typically produced by electron accelerators, resulting in issues such as pulse pile-up, detector saturation, and a suboptimal signal-to-background ratio. This study aims to extend the applicability of the conventional Active Photon Interrogation (API) techniques by introducing a novel method enabling the detection, in addition to nuclear materials, of light elements—specifically nitrogen, oxygen, and carbon—known to be present in conventional explosives, narcotics, and chemical weapons. The approach relies on active photon interrogation at high energies above 12 MeV, coupled with photoneutron spectrometry. Using a 22-MV electron LINAC, pulse shape discrimination with an organic liquid scintillator demonstrated promising performance. Our results highlight that the conventional pulse shape discrimination capabilities and rapid time-scale operation of organic scintillators enable the detection of fast neutrons from (γ,Xn) reactions, even in a mixed short-pulsed field of photon and neutron radiation with intense photon flashes. This exploration of the initial experimental aspects of photoneutron detection induced by high-energy photons establishes a foundation for a promising new method for the detection of illicit materials.

Effect of cementation on the mechanical response of sands using acoustic emission technique

This study investigates the impact of cementation on the mechanical behavior of sands with various cement content (CSR) in drained triaxial compression, employing both Acoustic Emission (AE) and Environmental Scanning Electron Microscopy (ESEM) measurements. The experimental findings, encompassing quantitative statistics of stress-strain relations, microstructure variations, and AE characteristics, demonstrate that: the addition of CSR from 1% to 20% leads to an exponential rise in peak strength and stiffness, marking a transition from ductile to brittle mechanical failure, which is pinpointed between CSR levels of 5% to 10%. AE characteristics unveil an upward-opening parabola of normalized AE hits with CSR, a clear transition zone identification, and three distinct types of AE rate evolutions corresponding to failure patterns of ductile bulging, shear banding, and brittle fracturing, respectively. It suggests an intimate correlation with the intrinsic differences in micro-mechanical behaviors and AE propagation properties of cemented sands with varying CSRs. Notably, the bulging and shear banding processes are divided by AE into three stages, whereas fracturing is characterized into five stages. Two precursory AE anomalies associated with incipient failure and complex failure modes are observed, emphasizing the advantage of using AE to reflect the internal micro-mechanical behavior of cemented sands over conventional stress-strain manifestations.

Acoustic emission measurement during the proof loading of the new bridge over Odra river in Wrocław

The acoustic emission method is applied for damage monitoring through the analysis of internal events within the material. Sensors were placed at the cantilever joint during the proof loading. Signal analysis revealed potential damages. Signal values were compared against criteria for assessing the condition of reinforced concrete structures. Regular measurements detect potential damages, and combining this technique with other methods enhances its efficiency

An Investigation of the Loop Oscillations after a Solar Flare

We study the loop oscillations after a solar flare on 19 January 2023, in the active region N11E40 3196, which is well observed by the SDO/AIA. After tracing the loop position and fitting, we find that the loop oscillations have a period between 3 and 9 min at various locations, such as from the leg to the top or from the inner to the outer loop. Their oscillating amplitudes decrease with time. Two loops display the position oscillation simultaneously with their brightness oscillation. After the analysis of the differential emission measure (DEM), we find that two of their loop position oscillations resulted from the plasma density fluctuation. Meanwhile, it is interesting that the brightness of these two position oscillations displays a typical period of about 4 min, similar to that of the position oscillation. This is possible due to both the plasma density and temperature fluctuation there. Our findings provide the physical clues for studying and understanding the mechanism of the loop position and brightness oscillations.

Beyond radial profiles: using log-normal distributions to model the multiphase circumgalactic medium

ABSTRACT Recent observations and simulations reveal that the circumgalactic medium (CGM) surrounding galaxies is multiphase, with the gas temperatures spanning a wide range at most radii, ∼104 K to the virial temperature (∼106 K for Milky Way). Traditional CGM models using simple density profiles are inadequate at reproducing observations that indicate a broad temperature range. Alternatively, a model based on probability distribution functions (PDFs) with parameters motivated by simulations can better match multiwavelength observations. In this work, we use log-normal distributions, commonly seen in the simulations of the multiphase interstellar and circumgalactic media, to model the multiphase CGM. We generalize the isothermal background model by Faerman et al. to include more general CGM profiles. We extend the existing probabilistic models from 1D-PDFs in temperature to 2D-PDFs in density–temperature phase space and constrain its parameters using a Milky Way-like Illustris TNG50-1 halo. We generate various synthetic observables such as column densities of different ions, UV/X-ray spectra, and dispersion and emission measures. X-ray and radio (Fast Radio Burst) observations mainly constrain the hot gas properties. However, interpreting cold/warm phase diagnostics is not straightforward since these phases are patchy, with inherent variability in intercepting these clouds along arbitrary lines of sight. We provide a tabulated comparison of model predictions with observations and plan to expand this into a comprehensive compilation of models and data. Our modelling provides a simple analytical framework that is useful for describing important aspects of the multiphase CGM.

Missing Measurements of Sesquiterpene Ozonolysis Rates and Composition Limit Understanding of Atmospheric Reactivity.

Emissions of biogenic reactive carbon significantly influence atmospheric chemistry, contributing to the formation and destruction of secondary pollutants, such as secondary organic aerosol and ozone. While isoprene and monoterpenes are a major fraction of emissions and have been extensively studied, substantially less is known about the atmospheric impacts of higher-molecular-weight terpenes such as sesquiterpenes. In particular, sesquiterpenes have been proposed to play a significant role in ozone chemical loss due to the very high ozone reaction rates of certain isomers. However, relatively little data are available on the isomer-resolved composition of this compound class or its role in ozone chemistry. This study examines the chemical diversity of sesquiterpenes and availability of ozone reaction rate constants to evaluate the current understanding of their ozone reactivity. Sesquiterpenes are found to be highly diverse, with 72 different isomers reported and relatively few isomers that contribute a large mass fraction across all studies. For the small number of isomers with known ozone reaction rates, estimated rates may be 25 times higher or lower than measurements, indicating that estimated reaction rates are highly uncertain. Isomers with known ozone reaction rates make up approximately half of the mass of sesquiterpenes in concentration and emission measurements. Consequently, the current state of the knowledge suggests that the total ozone reactivity of sesquiterpenes cannot be quantified without very high uncertainty, even if isomer-resolved composition is known. These results are in contrast to monoterpenes, which are less diverse and for which ozone reaction rates are well-known, and in contrast to hydroxyl reactivity of monoterpenes and sesquiterpenes, for which reaction rates can be reasonably well estimated. Improved measurements of a relatively small number of sesquiterpene isomers would reduce uncertainties and improve our understanding of their role in regional and global ozone chemistry.

Acoustic Emission in Ceramic Matrix Composites

Abstract The integration of ceramic matrix composites (CMCs) into safety-critical applications, such as turbine engines and aerospace structures, necessitates a sound understanding of their expected damage evolution under in-service conditions and real-time health-monitoring methods to assess their damage state. The measurement of acoustic emissions (AEs), the transient elastic waves emitted during damage formation, offers an enhanced capability for evaluating damage evolution and structural health in CMCs due to its high sensitivity, accurate temporal resolution, and relative ease of use compared to other nondestructive evaluation (NDE) techniques. Recent advances in numerical simulation methods and data-driven model development, in combination with improved multimodal experimental characterization methods and sensor hardware, are rapidly advancing AE to a mature technique for damage quantification. This review discusses the fundamental principles of acoustic emissions, provides practical guidelines on their experimental characterization and analysis, and offers perspectives on the current state-of-the-art.

How do oil price uncertainty and economic policy uncertainty influence achievement of net-zero emissions targets by 2050? A quantile-based analysis

ABSTRACT Governments globally have prioritized carbon neutrality and reduction as a response to the intensifying menace of climate change. These objectives align with the United Nations Sustainable Development Goals (UNSDG-13), stressing the imperative to take decisive action on climate change. Thus, this study aimed to assess the impact of oil price uncertainty, economic policy uncertainty, financial development, and renewable energy on ecological proxies (CO2 emissions, Ecological footprint, and Load capacity factor) using quarterly data spanning from 1990 to 2019. As far as the investigators are aware, this is the first empirical analysis examining the impact of oil price uncertainty on ecological quality. To achieve this, we employed advanced techniques, including quantile-on-quantile KRLS (QQKRLS) and quantile-on-quantile Granger causality (QQGC), to analyse the interconnections among these variables. The findings based on the load capacity factor exposed that renewable energy, economic policy uncertainty, financial development, and economic growth positively contribute to ecological quality, whereas oil price uncertainty has a detrimental effect. Additionally, as a measure of robustness, CO2 emissions and ecological footprint were included in the analysis, demonstrating comparable outcomes when assessed alongside the load capacity factor model. Furthermore, QQGC results demonstrated that all regressors significantly forecast ecological quality. Drawing from the findings, policy interventions ought to prioritize incentivizing the adoption of renewable energy, mitigating economic policy uncertainty, fostering financial development, and stimulating economic growth as pivotal strategies for augmenting ecological quality. Furthermore, integrating measures to alleviate oil price uncertainty stands as a crucial imperative for ensuring environmental sustainability.

Analysis of the Impact of Carbon Tariffs on China's Trade

As the impact of the financial crisis deepened, on March 17, 2009, US Energy Secretary Steven Chu prepared to impose carbon tariffs on imported goods to avoid unfair competition in the US manufacturing industry. Meanwhile, in recent years, some developed countries or regions, such as the United States and the European Union, have proposed punitive tariffs on imported products from developing countries such as China and India based on carbon content under the pretext of addressing climate change. This measure has sparked widespread international discussion. Therefore, this article takes carbon tariffs as the research object and analyzes the impact of China's carbon emissions on its export trade and the impact of international emission reduction regulations and measures on China's export trade through qualitative and quantitative analysis methods. The paper is divided into 7 chapters. Chapters 1, 2, and 3 provide explanations on the relevant concepts and development trends of carbon tariffs. Carbon tariffs are essentially border tax regulatory measures with trade protectionism attributes. Chapters 4 and 5 analyze the impact of carbon tariff policies. Chapters 6 and 7 propose corresponding strategies and suggestions based on the previous analysis.

Rapid carbon emission measurement during the building operation phase based on PSO–SVM: electric big data perspective

With the rapid development of urbanization in China, urban energy consumption increases rapidly, leading to energy shortages and environmental pollution, of which building operational energy consumption carbon emissions (BECCE) account for a large proportion. It has a vital impact on global warming and urban green and sustainable development. Chengdu city in Sichuan Province is taken as the research area in this paper. First, basic information and power data on four types of single buildings, including large-sized buildings, small- and medium-sized buildings, government agencies, and residential buildings, are collected. Second, the characteristics of the four types of buildings are extracted, and the calculation model of BECCE (“electricity-carbon” model) based on particle swarm optimization algorithm–support vector machine (PSO–SVM) is constructed, and the model is trained and verified using the method of five-fold cross-validation. Then, according to the mean absolute error (MAE), root mean square error (RMSE), and R2 evaluation indicators, the constructed “electricity-carbon” model is compared and evaluated. Finally, the generalization ability of the “electricity-carbon” model is verified. The research results show that (1) the “electricity-carbon” model constructed in this paper has a high accuracy rate, and the fitting ability of the PSO–SVM model is significantly better than that of the support vector regression (SVR) model; (2) in the testing stage, the fitting situation of large buildings is the best, and MAE, RMSE, and R2 are 858.7, 1108.6, and 0.91, respectively; and (3) the spatial distribution map of regional BECCE can be quickly obtained using the “electricity-carbon” model constructed in this paper. The “electricity-carbon” model constructed in this paper can provide a scientific reference for building emission reduction.