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Case Studies of the Impact of Orbital Sampling on Stratospheric Trend Detection and Derivation of Tropical Vertical Velocities: Solar Occultation versus Limb Emission Sounding
摘要： This study investigates the representativeness of two types of orbital sampling applied to stratospheric temperature and trace gas fields. Model fields are sampled using real sampling patterns from the Aura Microwave Limb Sounder (MLS), the HALogen Occultation Experiment (HALOE) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The MLS sampling acts as a proxy for a dense uniform sampling pattern typical of limb emission sounders, while HALOE and ACE-FTS represent coarse non-uniform sampling patterns characteristic of solar occultation instruments. First, this study revisits the impact of sampling patterns in terms of the sampling bias, as previous studies have done. Then, it quantifies the impact of different sampling patterns on the estimation of trends and their associated detectability. In general, we find that coarse non-uniform sampling patterns may introduce non-negligible errors in the inferred magnitude of temperature and trace gas trends and necessitate considerably longer records for their definitive detection. Lastly, we explore the impact of these sampling patterns on tropical vertical velocities derived from stratospheric water vapor measurements. We find that coarse non-uniform sampling may lead to a biased depiction of the tropical vertical velocities and, hence, to a biased estimation of the impact of the mechanisms that modulate these velocities. These case studies suggest that dense uniform sampling such as that available from limb emission sounders provides much greater fidelity in detecting signals of stratospheric change (for example, fingerprints of greenhouse gas warming and stratospheric ozone recovery) than coarse non-uniform sampling such as that of solar occultation instruments.
关键词： Atmospheric Chemistry Experiment Fourier Transform Spectrometer,trace gas fields,HALogen Occultation Experiment,Aura Microwave Limb Sounder,orbital sampling,stratospheric temperature,tropical vertical velocities,trend detection
更新于2025-09-09 09:28:46
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Fourier transform spectrometer measurements of column CO<sub>2</sub> at Sodankyl?, Finland
摘要： Fourier transform spectrometer (FTS) observations at Sodankyl?, Finland (67.4? N, 26.6? E) have been performed since early 2009. The FTS instrument is participating in the Total Carbon Column Observing Network (TCCON) and has been optimized to measure abundances of the key greenhouse gases in the atmosphere. Sodankyl? is the only TCCON station in the Fennoscandia region. Here we report the measured CO2 time series over a 7-year period (2009–2015) and provide a description of the FTS system and data processing at Sodankyl?. We ?nd the lowest monthly column CO2 values in August and the highest monthly values during the February–May season. Inter-annual variability is the highest in the June–September period, which correlates with the growing season. During the time period of FTS measurements from 2009 to 2015, we have observed a 2.2 ± 0.2 ppm increase per year in column CO2. The monthly mean column CO2 values have exceeded 400 ppm level for the ?rst time in February 2014.
关键词： CO2,Sodankyl?,TCCON,Fourier transform spectrometer,greenhouse gases
更新于2025-09-09 09:28:46
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Binary Zone Plate Infrared Spectrometer for Dissolved Gas Analysis in High Voltage Equipment
摘要： An IR spectrometer based on a Binary Zone Plate (BZP) is presented for dissolved gas analysis. The wavelength selective focal length of the BZP can effectively discriminate between wavelengths ranging from 800 nm to 8 μm, by adjusting the focus distance onto an aperture in the image plane from 19 mm to 200 mm. The aperture serves to pass focused radiation onto the detector. The BZP has a focal length of 50 mm for a design wavelength of 3 μm, with 400 zones. This design enables discrimination between all key fault gases present in oil impregnated high voltage equipment.
关键词： spectrometer,fourier optics,IR spectroscopy,dissolved gas analysis,binary zone plate,gas detection
更新于2025-09-09 09:28:46
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Experimental determination of reference pulses for highly segmented HPGe detectors and application to Pulse Shape Analysis used in $\gamma$γ-ray tracking arrays
摘要： For the first time, bases of signals delivered by highly segmented HPGe detectors, for identified hit locations, have been determined in situ, that is in the actual accelerator-target-detection system conditions corresponding to data acquisition during a physics experiment. As a consequence, these bases include all the genuine features and alterations of the signals induced by the experimental setup, e.g. diaphony, electronic response, specificity of individual crystals. The present pulse shape bases were constructed using calibration source data taken at the beginning of the AGATA campaign at GANIL. An experiment performed at GANIL using the AGATA γ-ray detector together with the VAMOS spectrometer was used to validate the bases. The performance of the bases when used for pulse-shape analysis has been compared to the performance of the standard bases, composed of pulse shapes generated by a computer simulation used for AGATA. This is done by comparing the Doppler correction capability. The so-called Jacobian method used to generate the in situ bases also produces correlations that can be applied to locate in a direct way (no search algorithm) the location where a γ-ray interacted given that only one segment is hit. As about 50% of all pulse-shape analysis is performed on crystals with only one segment hit this will allow for a large reduction in the needed computer power. Different ways to improve the results of this prospective work are discussed.
关键词： HPGe detectors,Doppler correction,γ-ray tracking arrays,VAMOS spectrometer,Pulse Shape Analysis,AGATA
更新于2025-09-09 09:28:46
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Design, development and use of the spectrometer for investigating coherent THz radiation produced by micro-bunching instabilities at Diamond Light Source
摘要： Schottky barrier diodes (SBDs) are known for their low noise, ultra-fast response and excellent sensitivity. They are often implemented as detectors in the millimetre wavelength regime. Micro-bunch instabilities (MBI) have been detected at many light sources around the world including the Diamond Light Source, UK. These MBI can result in bursts of coherent synchrotron radiation (CSR) with millimetre wavelengths. More research needs to be carried out with regards to the dynamics of MBI in order to con?rm the simulations and to eventually harness the power of the CSR bursts. A single shot spectrometer has been designed and is under operation at the Diamond Light Source (DLS). It is composed of eight SBDs ranging from 33-1000 GHz. Unlike previous measurements carried out, each of the SBDs has been individually characterised thus making the results obtained comparable to simulations. In this paper, we present the assessment of each SBD in the spectrometer and the ?rst results of the spectrometer’s use in the beam.
关键词： Schottky barrier diodes,micro-bunch instabilities,spectrometer,coherent synchrotron radiation,Diamond Light Source
更新于2025-09-09 09:28:46
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Recording Raman Spectra Using a Dynamic Fourier Transform Spectrometer
摘要： We have developed a dynamic Fourier transform spectrometer for recording Raman spectra in the near-IR range (800–1100 nm). Stability and reliability of operation of the spectrometer is achieved by using corner re? ectors in the design as mirrors in the main channel. In order to record a weak Raman signal, we set up a white light channel in the spectrometer which enables locking into the zero optical path difference when summing the interferograms over several scans. A reference channel with sampling frequency λ/4 lets us improve the sampling accuracy and the signal-to-noise ratio of the emission spectra. Using our spectrometer, we recorded the Raman spectra of test substances with known positions of the emission lines: 1,4-bis(5-phenyl-2-oxazolyl)benzene (POPOP, C24H16N2O2), stilbene (C14H12), acetylsalicylic acid (C9H8O4). Comparison of the POPOP Raman spectra obtained on the dynamic Fourier transform spectrometer and a diffraction spectrometer for the same experimental conditions showed that they qualitatively matched, and the time required to record the spectrum on the dynamic Fourier transform spectrometer was 4 times shorter.
关键词： Raman spectroscopy,dynamic Fourier transform spectrometer,white-light channel,Fourier transform spectrometer in the visible and near-IR ranges,corner re? ector
更新于2025-09-04 15:30:14
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Effect of Sputtering Technique and Properties of TiO2 Doped with SnO2 Thin Films
摘要： Doped oxide materials of 90% of TiO2 was doped with 10% of SnO2 that target has been deposited at a substrate temperature of 250°C for 1 hour by using DC Sputtering technique. The as synthesized target was TiO2-SnO2 was used to deposit on the glass substrates. The deposited oxide thin film was characterized for their structural, surface morphological, electrical and optical properties. X-ray diffraction is used for studying the nature and structure, scanning electron, atomic force microscopy and transmission electron microscopy are used to identify the surface morphology of the prepared films. The Van der Pauw technique is employed to measure electrical resistivity and Hall mobility of the film. Wide varieties of methods are available for measuring thin film thicknesses. Stylus profilometry will be helpful to find the thickness of the film, structural studies by X-ray, and micros structural analysis of the film.
关键词： Scanning Electron microscopy (SEM),Stylus profilometry,TiO2-SnO2,X-ray diffraction (XRD),UV-Vis-NIR spectrometer
更新于2025-09-04 15:30:14
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Sulfur dioxide (SO<sub>2</sub>) vertical column density measurements by Pandora spectrometer over the Canadian oil sands
摘要： Vertical column densities (VCDs) of SO2 retrieved by a Pandora spectral sun photometer at Fort McKay, Alberta, Canada, from 2013 to 2015 were analysed. The Fort McKay site is located in the Canadian oil sands region, approximately 20 km north of two major SO2 sources (upgraders), with total emission of about 45 kt yr?1. Elevated SO2 VCD values were frequently recorded by the instrument, with the highest values of about 9 Dobson Units (DU; DU = 2.69 × 1016 molecules cm?2). Comparisons with co-located in situ measurements demonstrated that there was a very good correlation between VCDs and surface concentrations in some cases, while in other cases, elevated VCDs did not correspond to high surface concentrations, suggesting the plume was above the ground. Elevated VCDs and surface concentrations were observed when the wind direction was from south to southeast, i.e. from the direction of the two local SO2 sources. The precision of the SO2 measurements, estimated from parallel measurements by two Pandora instruments at Toronto, is 0.17 DU. The total uncertainty of Pandora SO2 VCD, estimated using measurements when the wind direction was away from the sources, is less than 0.26 DU (1σ ). Comparisons with integrated SO2 pro?les from concurrent aircraft measurements support these estimates.
关键词： Pandora spectrometer,vertical column density,Sulfur dioxide,oil sands,air quality
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Analysis of Over-the-Counter Drugs Using Raman Spectroscopy
摘要： Commercial over-the-counter drugs such as Advil?, Aleve?, Tylenol?, Mucinex?, Excedrin?, and aspirin were analyzed with a portable handheld Raman spectrometer. The peaks from their Raman spectra were determined, and common peaks were observed in all samples. Unique peaks were also noticed and used as identifying markers to identify a particular drug. Theoretical calculations of active ingredients present in drugs were also performed, compared with experimental Raman spectra, and used to assign the functional groups responsible for the peaks. In addition, Raman spectra obtained from a benchtop instrument were also compared with that from a portable Raman spectrometer. Different forms and brands of the drugs were also analyzed to determine the effect of other materials on the active ingredient. Results showed that the dosage of active ingredients has a direct impact on the signals exhibited in Raman spectra. Lastly, different degradation processes (exposure to microwaves, UV light, and high temperature) were tested on Tylenol? and results showed peak changes in certain regions and more fluorescence background.
关键词： active ingredients,Raman spectroscopy,over-the-counter drugs,degradation processes,portable handheld Raman spectrometer
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Quantitative Analysis of Xylene Mixtures Using a Handheld Raman Spectrometer
摘要： Xylene isomers (meta-xylene, ortho-xylene, and para-xylene) have been extensively analyzed by different instrumental methods. In this chapter, xylene isomers and their mixtures were analyzed qualitatively and quantitatively by Raman spectroscopy. First, we identified peaks that discriminated each isomer along with peaks that remain unchanged regardless of isomeric form. We used theoretical calculations to aid in the peak assignments. Then, we tested the efficacy of the technique in qualitatively and quantitatively apportioning isomeric mixtures of xylenes.
关键词： Xylene isomers,DFT calculations,Raman spectroscopy,quantitative analysis,handheld Raman spectrometer
更新于2025-09-04 15:30:14