The problem of compensation of the initial energy spread of ions by multigap reflectors of time-of-flight mass spectrometers with grids has been considered. Cases of catastrophes A.sub.4, A.sub.5, ...A.sub.6, and A.sub.7 for the simplest variant of potential distribution are considered. It is shown that multigap reflectors, the time-of-flight function of which is described by the catastrophes A.sub.4, A.sub.5, A.sub.6, and A.sub.7, compensate for much larger energy spreads of ions in comparison with the catastrophes A.sub.2 and A.sub.3. The results obtained can be used to design gridless mass spectrometers that compensate for large initial energy spreads of ions.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared ...spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm
−1
. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, we study the detection of acetylene (C2H2), carbon dioxide (CO2) and water vapor (H2O) gases in the near-infrared (NIR) range using an on-chip silicon micro-electro-mechanical system ...(MEMS) Fourier transform infrared (FT-IR) spectrometer in the wavelength range 1300–2500 nm (4000–7692 cm−1). The spectrometer core engine is a scanning Michelson interferometer micro-fabricated using a deep-etching technology producing self-aligned components. The light is free-space propagating in-plane with respect to the silicon chip substrate. The moving mirror of the interferometer is driven by a relatively large stroke electrostatic comb-drive actuator corresponding to about 30 cm−1 resolution. Multi-mode optical fibers are used to connect light between the wideband light source, the interferometer, the 10 cm gas cell, and the optical detector. A wide dynamic range of gas concentration down to 2000 parts per million (ppm) in only 10 cm length gas cell is demonstrated. Extending the wavelength range to the mid-infrared (MIR) range up to 4200 nm (2380 cm−1) is also experimentally demonstrated, for the first time, using a bulk micro-machined on-chip MEMS FT-IR spectrometer. The obtained results open the door for an on-chip optical gas sensor for many applications including environmental sensing and industrial process control in the NIR/MIR spectral ranges.
Full text
Available for:
NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with ...unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr-field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eVq to 30000 eVq. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory's Instrument Suite Central Instrument Data processor. This paper described the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Motivated by applications in mobile optical sensing, ultracompact high‐resolution integrated spectrometers have attracted much interest. Here, a high‐resolution integrated speckle spectrometer, ...comprising a linear coherent network formed by mutually coupled Mach–Zehnder interferometers and nonidentical microring resonators, is proposed and demonstrated. Deep‐etched grating lines used as mirrors on the edges of the coherent network increase the effective optical path lengths. The speckle spectrometer is realized on a silicon nitride platform, operating at 776 nm central wavelength. The eight‐in−eight‐out linear coherent network provides 64 physical channels. Fine spectral lines separated by 20 pm are experimentally resolved within a device footprint of 520 µm × 220 µm. Compressive sensing is achieved for sparse spectra over a wide optical bandwidth. Up to 600 distinctive wavelength channels can be reconstructed from the 64 physical channels, giving 12 nm operating bandwidth. Both sparse spectra and continuous spectra are well reconstructed experimentally. The integrated speckle spectrometer has great potential for use in future biosensing and bioimaging applications where high spectral resolution is desired.
An integrated speckle spectrometer is proposed by using an integrated linear coherent network formed by mutually coupled Mach–Zehnder interferometers and microring resonators. On‐chip mirrors and nonidentical rings are used to create a rapid decorrelation of the speckle pattern and thus provide high spectral resolution.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
With the recent progress regarding the development of x‐ray instrumentation, compact x‐ray spectrometers are becoming more and more popular as they allow x‐ray absorption spectroscopy (XAS) and x‐ray ...emission spectroscopy (XES) studies at the research institutes laboratories. Such setups provide a cost‐effective tool for routine sample characterization with unlimited access and are of great utility in feasibility studies preceding the experiments at synchrotrons and x‐ray free‐electron lasers (XFELs). Herein, we present the operation and capabilities of the von Hámos type x‐ray spectrometer in x‐ray absorption spectra measurement for various 3d metal elements. Results allowed us to establish the photon counting performance of the setup, demonstrating a possible range of applications of the in‐house x‐ray spectroscopy apparatus.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
7.
How to Design a Spectrometer Scheeline, Alexander
Applied Spectroscopy,
10/2017, Volume:
71, Issue:
10
Book Review, Journal Article
Peer reviewed
Open access
Designing a spectrometer requires knowledge of the problem to be solved, the molecules whose properties will contribute to a solution of that problem and skill in many subfields of science and ...engineering. A seemingly simple problem, design of an ultraviolet, visible, and near-infrared spectrometer, is used to show the reasoning behind the trade-offs in instrument design. Rather than reporting a fully optimized instrument, the Yin and Yang of design choices, leading to decisions about financial cost, materials choice, resolution, throughput, aperture, and layout are described. To limit scope, aspects such as grating blaze, electronics design, and light sources are not presented. The review illustrates the mixture of mathematical rigor, rule of thumb, esthetics, and availability of components that contribute to the art of spectrometer design.
Full text
Available for:
NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
A major goal of remote sensing is the development of generalizable algorithms to repeatedly and accurately map ecosystem properties across space and time. Imaging spectroscopy has great potential to ...map vegetation traits that cannot be retrieved from broadband spectral data, but rarely have such methods been tested across broad regions. Here we illustrate a general approach for estimating key foliar chemical and morphological traits through space and time using NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-Classic). We apply partial least squares regression (PLSR) to data from 237 field plots within 51 images acquired between 2008 and 2011. Using a series of 500 randomized 50/50 subsets of the original data, we generated spatially explicit maps of seven traits (leaf mass per area (
M
area
), percentage nitrogen, carbon, fiber, lignin, and cellulose, and isotopic nitrogen concentration, δ
15
N) as well as pixel-wise uncertainties in their estimates based on error propagation in the analytical methods. Both
M
area
and %N PLSR models had a
R
2
> 0.85. Root mean square errors (RMSEs) for both variables were less than 9% of the range of data. Fiber and lignin were predicted with
R
2
> 0.65 and carbon and cellulose with
R
2
> 0.45. Although
R
2
of %C and cellulose were lower than
M
area
and %N, the measured variability of these constituents (especially %C) was also lower, and their RMSE values were beneath 12% of the range in overall variability. Model performance for δ
15
N was the lowest (
R
2
= 0.48, RMSE = 0.95‰), but within 15% of the observed range. The resulting maps of chemical and morphological traits, together with their overall uncertainties, represent a first-of-its-kind approach for examining the spatiotemporal patterns of forest functioning and nutrient cycling across a broad range of temperate and sub-boreal ecosystems. These results offer an alternative to categorical maps of functional or physiognomic types by providing non-discrete maps (i.e., on a continuum) of traits that define those functional types. A key contribution of this work is the ability to assign retrieval uncertainties by pixel, a requirement to enable assimilation of these data products into ecosystem modeling frameworks to constrain carbon and nutrient cycling projections.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
The CLAS12 Spectrometer at Jefferson Laboratory Adhikari, S.; Amaryan, M.J.; Angelini, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Volume:
959, Issue:
C
Journal Article
Peer reviewed
Open access
The CEBAF Large Acceptance Spectrometer for operation at 12 GeV beam energy (CLAS12) in Hall B at Jefferson Laboratory is used to study electro-induced nuclear and hadronic reactions. This ...spectrometer provides efficient detection of charged and neutral particles over a large fraction of the full solid angle. CLAS12 has been part of the energy-doubling project of Jefferson Lab’s Continuous Electron Beam Accelerator Facility, funded by the United States Department of Energy. An international collaboration of 48 institutions contributed to the design and construction of detector hardware, developed the software packages for the simulation of complex event patterns, and commissioned the detector systems. CLAS12 is based on a dual-magnet system with a superconducting torus magnet that provides a largely azimuthal field distribution that covers the forward polar angle range up to 35∘, and a solenoid magnet and detector covering the polar angles from 35° to 125° with full azimuthal coverage. Trajectory reconstruction in the forward direction using drift chambers and in the central direction using a vertex tracker results in momentum resolutions of <1% and <3%, respectively. Cherenkov counters, time-of-flight scintillators, and electromagnetic calorimeters provide good particle identification. Fast triggering and high data-acquisition rates allow operation at a luminosity of 1035 cm−2s−1. These capabilities are being used in a broad program to study the structure and interactions of nucleons, nuclei, and mesons, using polarized and unpolarized electron beams and targets for beam energies up to 11 GeV. This paper gives a general description of the design, construction, and performance of CLAS12.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Gaia Data Release 2 Katz, D.; Sartoretti, P.; Cropper, M. ...
Astronomy and astrophysics (Berlin),
02/2019, Volume:
622
Journal Article, Web Resource
Peer reviewed
Open access
Context.
For
Gaia
DR2, 280 million spectra collected by the Radial Velocity Spectrometer instrument on board
Gaia
were processed, and median radial velocities were derived for 9.8 million sources ...brighter than
G
RVS
= 12 mag.
Aims.
This paper describes the validation and properties of the median radial velocities published in
Gaia
DR2.
Methods.
Quality tests and filters were applied to select those of the 9.8 million radial velocities that have the quality to be published in
Gaia
DR2. The accuracy of the selected sample was assessed with respect to ground-based catalogues. Its precision was estimated using both ground-based catalogues and the distribution of the
Gaia
radial velocity uncertainties.
Results. Gaia
DR2 contains median radial velocities for 7 224 631 stars, with
T
eff
in the range 3550, 6900 K, which successfully passed the quality tests. The published median radial velocities provide a full-sky coverage and are complete with respect to the astrometric data to within 77.2% (for
G
≤ 12.5 mag). The median radial velocity residuals with respect to the ground-based surveys vary from one catalogue to another, but do not exceed a few 100 m s
−1
. In addition, the
Gaia
radial velocities show a positive trend as a function of magnitude, which starts around
G
RVS
~ 9 mag and reaches about + 500 m s
−1
at
G
RVS
= 11.75 mag. The origin of the trend is under investigation, with the aim to correct for it in
Gaia
DR3. The overall precision, estimated from the median of the
Gaia
radial velocity uncertainties, is 1.05 km s
−1
. The radial velocity precision is a function of many parameters, in particular, the magnitude and effective temperature. For bright stars,
G
RVS
∈ 4, 8 mag, the precision, estimated using the full dataset, is in the range 220–350 m s
−1
, which is about three to five times more precise than the pre-launch specification of 1 km s
−1
. At the faint end,
G
RVS
= 11.75 mag, the precisions for
T
eff
= 5000 and 6500 K are 1.4 and 3.7 km s
−1
, respectively.
Full text
Available for:
FMFMET, NUK, UL, UM, UPUK
PDF
