The circularly symmetric grille spectrometer.
Grille spectrometer, noting greater signal to noise ratio than that of scanning Fabry-Perot spectrometer for airglow observations
FABRY-PEROT SPECTROMETER↗
SEARCH · Engineering Papers
Results for “spectrometer”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Tracking Elevated Pollution Layers with a Newly Developed Hyperspectral Sun/Sky Spectrometer (4STAR): Results from the TCAP 2012 and 2013 Campaigns
Total columnar amounts of water vapor, nitrogen dioxide (NO2) and ozone (O3) are derived from a newly developed, hyperspectral airborne sun-sky spectrometer (4STAR) for the first time during the two intensive phases of the Two Column Aerosol Project (TCAP) in summer 2012 and winter 2013 aboard the DOE G-1 aircraft. We compare results with coincident measurements. We find 0.045 g/cm2 (4.2%) negative bias and 0.28 g/cm2 (26.3%) root-mean-square (RMS) difference in water vapor layer comparison with in-situ hygrometer, and an overall RMS difference of 1.28 g/m3 (38%) water vapor amount in profile by profile comparisons, with differences distributed evenly around zero in most cases. The RMS differences for O3 values average to 3%, with a 1% negative bias for 4STAR compared with the spaceborne Ozone Measuring Instrument (OMI) along the aircraft flight-track for 14 flights during both TCAP phases. Ground-based comparisons with the Pandora spectrometer system at the Goddard Space Flight Center (GSFC), Greenbelt, Maryland showed excellent agreement between the instruments for both O3 and NO2, further emphasizing 4STAR’s new capabilities. During the summer phase, we have succeeded in identifying variations in elevated pollution layers corresponding to urban pollution outflow and transported biomass burning. This was done using clustering analysis of the retrieved products (e.g. Ångstrom exponent, NO2 and columnar water vapor), and was confirmed by aerosol type identification by HSRL2 aboard the NASA B-200 aircraft. These newly demonstrated 4STAR capabilities are expected to be instrumental in improving our understanding of atmospheric composition variability and aerosol-trace-gas interactions; they open new horizons and opportunities in airborne sunphotometry.
4STAR↗
Airborne Single Particle Mass Spectrometers (SPLAT II & miniSPLAT) and New Software for Data Visualization and Analysis in a Geo-Spatial Context
Understanding the effect of aerosols on climate requires knowledge of the size and chemical composition of individual aerosol particles - two fundamental properties that determine an aerosol’s optical properties and ability to serve as cloud condensation or ice nuclei. Here we present miniSPLAT, our new aircraft compatible single particle mass spectrometer, that measures in-situ and in real-time size and chemical composition of individual aerosol particles with extremely high sensitivity, temporal resolution, and sizing precision on the order of a monolayer. miniSPLAT operates in dual data acquisition mode to measure, in addition to single particle size and composition, particle number concentrations, size distributions, density, and asphericity with high temporal resolution. When compared to our previous instrument, SPLAT II, miniSPLAT has been significantly reduced in size, weight, and power consumption without loss in performance. We also present ND-Scope, our newly developed interactive visual analytics software package. ND-Scope is designed to explore and visualize the vast amount of complex, multidimensional data acquired by our single particle mass spectrometers, along with other aerosol and cloud characterization instruments on-board aircraft. We demonstrate that ND-Scope makes it possible to visualize the relationships between different observables and to view the data in a geo-spatial context, using the interactive and fully coupled Google Earth and Parallel Coordinates displays. Here we illustrate the utility of ND-Scope to visualize the spatial distribution of atmospheric particles of different compositions, and explore the relationship between individual particle composition and their activity as cloud condensation nuclei.
54 ENVIRONMENTAL SCIENCES↗
Isobar Separation in a Multiple-Reflection Time-of-Flight Mass Spectrometer by Mass-Selective Re-Trapping
A novel method for (ultra-)high-resolution spatial mass separation in time-of-flight mass spectrometers is presented. Ions are injected into a time-of-flight analyzer from a radio frequency (rf) trap, dispersed in time-of-flight according to their mass-to-charge ratios and then re-trapped dynamically in the same rf trap. This re-trapping technique is highly mass-selective and after sufficiently long flight times can provide even isobaric separation. A theoretical treatment of the method is presented and the conditions for optimum performance of the method are derived. The method has been implemented in a multiple-reflection time-of-flight mass spectrometer and mass separation powers (FWHM) in excess of 70,000, and re-trapping efficiencies of up to 35% have been obtained for the protonated molecular ion of caffeine. The isobars glutamine and lysine (relative mass difference of 1/4000) have been separated after a flight time of 0.2 ms only. Higher mass separation powers can be achieved using longer flight times. The method will have important applications, including isobar separation in nuclear physics and (ultra-)high-resolution precursor ion selection in multiple-stage tandem mass spectrometry. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Mobility Peak Tailing Reduction in a Differential Mobility Analyzer (DMA) Coupled with a Mass Spectrometer and Several Ionization Sources
The differential mobility analyzer (DMA) is a narrow-band linear ion mobility filter operating at atmospheric pressure. It combines in series with a quadrupole mass spectrometer (Q-MS) for mobility/mass analysis, greatly reducing chemical noise in selected ion monitoring. However, the large flow rate of drift gas (~1000 L/min) required by DMAs complicates the achievement of high gas purity. Additionally, the symmetry of the drying counterflow gas at the interface of many commercial MS instruments, is degraded by the lateral motion of the drift gas at the DMA entrance slit. As a result, DMA mobility peaks often exhibit tails due to the attachment of impurity vapors, either (1) to the reagent ion within the separation cell, or (2) to the analyte of interest in the ionization region. In order to greatly increase the noise-suppression capacity of the DMA, we describe various vapor-removal schemes and measure the resulting increase in the tailing ratio, (TR = signal at the peak maximum over signal two half-widths away from this maximum). Here we develop a low-outgassing DMA circuit connected to a mass spectrometer, and test it with three ionization sources (APCI, Desolvating-nano ESI, and Desolvating low flow SESI). While prior TR values were in the range 100–1000, the three new sources achieve TR ~ 10{sup 5}. The SESI source has been optimized for maximum sensitivity, delivering an unprecedented gain for TNT of 190 counts/fg, equivalent to an ionization efficiency of one out of 140 neutral molecules. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Direct Analysis of Organic Compounds in Liquid Using a Miniature Photoionization Ion Trap Mass Spectrometer with Pulsed Carrier-Gas Capillary Inlet
A miniature ion trap mass spectrometer with capillary direct sampling and vacuum ultraviolet photoionization source was developed to conduct trace analysis of organic compounds in liquids. Self-aspiration sampling is available where the samples are drawn into the vacuum chamber through a capillary with an extremely low flow rate (less than 1 μL/min), which minimizes sample consumption in each analysis to tens of micrograms. A pulsed gas-assisted inlet was designed and optimized to promote sample transmission in the tube and facilitate the cooling of ions, thereby improving instrument sensitivity. A limit of detection of 2 ppb could be achieved for 2,4-dimethylaniline in a methanol solution. The sampling system described in the present study is specifically suitable for a miniature photoionization ion trap mass spectrometer that can perform rapid and online analysis for liquid samples. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
On the Nature of Mass Spectrometer Analyzer Contamination
Sample throughput in electrospray ionization mass spectrometry (ESI-MS) is limited by the need for frequent ion path cleaning to remove accumulated debris that can lead to charging and general performance degradation. Contamination of ion optics within the vacuum system is particularly problematic as routine cleaning requires additional time for cycling the vacuum pumps. Differential mobility spectrometry (DMS) can select targeted ion species for transmission, thereby reducing the total number of charged particles entering the vacuum system. In this work, we characterize the nature of instrument contamination, describe efforts to improve mass spectrometer robustness by applying DMS prefiltering to reduce contamination of the vacuum ion optics, and demonstrate the capability of DMS to extend the interval between mass spectrometer cleaning. In addition, we introduce a new approach to effectively detect large charged particles formed during the electrospray ionization (ESI) process. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
MONSTER: a TOF Spectrometer for β-delayed Neutron Spectroscopy
β-delayed neutron (DN) data, including emission probabilities, Pn, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Development of position-sensitive time-of-flight spectrometer for fission fragment research
A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEtermination in fission Research (SPIDER) is a 2E–2v spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with α-particles from 229Th and its decay chain and α-particles and spontaneous fission fragments from 252Cf. Each detector module is comprised of thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700 mm are determined accurately to within 0.7 mm. Flight times were measured with 250 ps resolution FWHM. Computed particle velocities are accurate to within 0.06 mm/ns corresponding to a precision of 0.5%. As a result, an ionization chamber capable of 400 keV energy resolution coupled with the velocity measurements described here will pave the way for modestly efficient measurements of light fission fragments with unit mass resolution.
2E-2v↗
Refining instrument response functions with 3-D Monte Carlo simulations of differential hard x-ray spectrometers
Three x-ray spectrometers – the hard x-ray detector (HXRD), the bremsstrahlung MeV x-ray spectrometer (BMXS), and the hard x-ray image plate (HXIP) – areused here to estimate hot-electron bremsstrahlung spectrum parameters for inertial confinement fusion experiments on OMEGA. Using 1-D deterministically calculated response functions, they show significantly different estimates of spectrum slope temperature. For all three detectors, 3-D Geant4 Monte Carlo simulations are developed and used to compute instrument response functions. Simulations explain features in raw image-plate data, but only significantly improve systematic errors in predicted detector channel signals for BMXS and do not entirely eliminate the discrepancy between estimates of slope temperature.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Time interval distributions of nuclear events in a digital spectrometer
This study compares the theoretical formula for time interval density distributions (TIDs) in counters with pileup rejection to TIDs measured using a digital spectrometer with trapezoid filtering. The TIDs were derived from successive time stamps of 60 Co and 133 Ba γ rays detected with a HPGe spectrometer. The results demonstrate that the theoretical formula is applicable up to 40% count loss and can be used to retrospectively deduce the incident event rate.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
C-III flow measurements with a coherence imaging spectrometer
This work describes a coherence imaging spectrometer capable of making spatially resolved CIII flow measurements in the DIII-D lower divertor. The spectrometer exploits a periscope view of the plasma to produce line-of-sight averaged velocity measurements of CIII. From these chord averaged flow measurements, a 2D poloidal cross section of the CIII flow is tomographically reconstructed. Details of the diagnostic setup, acquired data, and data analysis will be presented, along with prospects for future applications.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Bragg x-ray survey spectrometer for ITER
Several potential impurity ions in the ITER plasmas will lead to loss of confined energy through line and continuum emission. For real time monitoring of impurities, a seven channel Bragg x-ray spectrometer (XRCS survey) is considered. This paper presents design and analysis of the spectrometer, including x-ray tracing by the Shadow-XOP code, sensitivity calculations for reference H-mode plasma and neutronics assessment. The XRCS survey performance analysis shows that the ITER measurement requirements of impurity monitoring in 10 ms integration time at the minimum levels for low-Z to high-Z impurity ions can largely be met.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Light ion transfer reactions with the HELIOS spectrometer
Light-ion induced transfer and inelastic scattering reactions on stable or long-lived targets have been used extensively to study the structure of nuclei near the line of {beta}-stability, and much of the detailed information on the single-particle structure of nuclei has been derived from such studies. Recently, however, a substantial expansion of the range of isotopes, for which this nuclear structure information can be obtained, has presented itself by using radioactive beams in inverse kinematics reactions. Such beams are now available at a number of facilities around the world, including the in-flight production method and CARIBU facility at ATLAS. The HELIOS spectrometer, which has been used since August 2008 at ATLAS, circumvents many of the problems associated with inverse kinematics. In this talk I will discuss the principle of the spectrometer as well as some of main physics results that have been obtained to date in nuclei ranging from {sup 13}B to {sup 137}Xe using both stable and radioactive beams.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Sensitivity calibration of an imaging extreme ultraviolet spectrometer-detector system for determining the efficiency of broadband extreme ultraviolet sources
We report on the absolute sensitivity calibration of an extreme ultraviolet (XUV) spectrometer system that is frequently employed to study emission from short-pulse laser experiments. The XUV spectrometer, consisting of a toroidal mirror and a transmission grating, was characterized at a synchrotron source in respect of the ratio of the detected to the incident photon flux at photon energies ranging from 15.5 eV to 99 eV. The absolute calibration allows the determination of the XUV photon number emitted by laser-based XUV sources, e.g., high-harmonic generation from plasma surfaces or in gaseous media. We have demonstrated high-harmonic generation in gases and plasma surfaces providing 2.3 {mu}W and {mu}J per harmonic using the respective generation mechanisms.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
An energy-filtering device coupled to a quadrupole mass spectrometer for soft-landing molecular ions on surfaces with controlled energy
We have developed an energy-filtering device coupled to a quadrupole mass spectrometer to deposit ionized molecules on surfaces with controlled energy in ultra high vacuum environment. Extensive numerical simulations as well as direct measurements show that the ion beam flying out of a quadrupole exhibits a high-energy tail decreasing slowly up to several hundred eV. This energy distribution renders impossible any direct soft-landing deposition of molecular ions. To remove this high-energy tail by energy filtering, a 127° electrostatic sector and a specific triplet lenses were designed and added after the last quadrupole of a triple quadrupole mass spectrometer. The results obtained with this energy-filtering device show clearly the elimination of the high-energy tail. The ion beam that impinges on the sample surface satisfies now the soft-landing criterion for molecular ions, opening new research opportunities in the numerous scientific domains involving charges adsorbed on insulating surfaces.
43 PARTICLE ACCELERATORS↗
Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES
The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response
CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗