Search results for "Spectrometer"
showing 10 items of 751 documents
Imaging spin filter for electrons based on specular reflection from iridium (001)
2013
Abstract As Stern–Gerlach type spin filters do not work with electrons, spin analysis of electron beams is accomplished by spin-dependent scattering processes based on spin–orbit or exchange interaction. Existing polarimeters are single-channel devices characterized by an inherently low figure of merit (FoM) of typically 10 −4 –10 −3 . This single-channel approach is not compatible with parallel imaging microscopes and also not with modern electron spectrometers that acquire a certain energy and angular interval simultaneously. We present a novel type of polarimeter that can transport a full image by making use of k -parallel conservation in low-energy electron diffraction. We studied specul…
Analysis of hazardous chemicals by “stand alone” drift tube ion mobility spectrometry: a review
2020
Ion mobility spectrometry (IMS) is a widely used technique based on gas phase ion separation under an electric field by differences in ion mobilities. In the last decade, IMS techniques have received increased attention due to their high operational speed and sensitivity. Currently, there are different IMS devices focused on solving different analytical performances, mainly based on linear drift tube (DT IMS), traveling wave, and field asymmetric waveform ion mobility spectrometers. In this review we summarize the main applications of DT-IMS devices for the determination of semi-volatile hazardous chemicals such as: illegal drugs, pesticides, explosives, chemical warfare agents, and others,…
The B 1Pi state of NaCs: high resolution laser induced fluorescence spectroscopy and potential construction.
2007
The lowest (1)Pi state of the NaCs molecule, the B(1)(1)Pi state, was studied using a dye laser for inducing fluorescence that was resolved by a high resolution Fourier-transform spectrometer. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the B(1)(1)Pi state, to obtain Lambda-splittings and to reveal numerous local perturbations. 543 weakly perturbed energy levels for rotational quantum numbers from J(')=5 to 168 and vibrational quantum numbers from v(')=0 to 25, which cover about 87% of the potential well depth, were used for a direct pointwise fit of the potential energy curve applying the inverted perturbation approach me…
Laser resonant ionization of plutonium
1985
Resonance ionization mass spectrometry (RIMS) has been tested for the isotope-selective determination of trace amounts of plutonium. An atomic beam is formed by evaporating plutonium atoms from a rhenium-filament heated to 1800 °C. The radiation of a pulsed dye laser excites the atoms in a two-photon process (λ=595.2 nm) followed by photoionization of the excited atoms. Mass selectivity is obtained by use of a time-of-flight spectrometer. A resonant signal of239Pu was measured with 1013 atoms deposited on the filament.
Determination of trace elements by resonant ionization mass spectrometry (RIMS)
1988
A resonant ionization mass spectrometer has been developed as an analytical tool for the detection of trace elements, especially of plutonium and other radionuclides. The sample, deposited on a rhenium filament, is evaporated by electrical heating and the atoms of the element under investigation are selectively ionized by laser light delivered from three dye lasers pumped by a copper vapour laser. The resulting photoions are detected in a time-of-flight spectrometer with a channelplate detector. For plutonium a mass resolution of M/δM=1500 was obtained and an overall detection efficiency of 4×10−6 was determined for stepwise excitation and ionization via autoionizing states. With a laser li…
First results from the PROBA/CHRIS hyperspectral/multiangular satellite system over land and water targets
2005
The Project for On-Board Autonomy (PROBA) platform developed by the European Space Agency was launched on October 22, 2001. The instrument payload includes the Compact High Resolution Imaging Spectrometer (CHRIS). The coupled system provides high spatial resolution hyperspectral/multi-angular data, which represents a new-generation source of information for Earth observation purposes. The first results obtained from the preprocessing (noise removal and geometric/atmospheric correction) of two different datasets, collected over agricultural crops and inland waters, are presented in this letter. In situ measurements are used to assess the quality of the data and to validate the processing alg…
On the demands on imaging spectrometry for the monitoring of global vegetation fluorescence from space
2013
Vegetation fluorescence when measured from space contributes only a tiny fraction of the signal coming on top of the reflected radiance by the Earth surface and the atmosphere. As a consequence, imaging spectrometers have to provide sufficient throughput and radiometric accuracy to enable accurate global monitoring of the daily to seasonal variations of the Earth's vegetation breath, which is particularly challenging if ground resolutions of a few hundred meters are targeted. Since fluorescence retrieval algorithms have to make corrections for atmospheric effects, it is necessary to provide sufficient spectral resolution, so that signal alterations due to the main parameters such as surface…
A Geant4 simulation package for the sage spectrometer
2012
International audience; A comprehensive Geant4 simulation was built for the SAGE spectrometer. The simulation package includes the silicon and germanium detectors, the mechanical structure and the electromagnetic fields present in SAGE. This simulation can be used for making predictions through simulating experiments and for comparing simulated and experimental data to better understand the underlying physics.
New constraints on Lorentz invariance violation from the neutron electric dipole moment
2010
We propose an original test of Lorentz invariance in the interaction between a particle spin and an electromagnetic field and report on a first measurement using ultracold neutrons. We used a high sensitivity neutron electric dipole moment (nEDM) spectrometer and searched for a direction dependence of a nEDM signal leading to a modulation of its magnitude at periods of 12 and 24 hours. We constrain such a modulation to $d_{12} < 15 \times 10^{-25} \ e\,{\rm cm}$ and $d_{24} < 10 \times 10^{-25} \ e\,{\rm cm}$ at 95~\% C.L. The result translates into a limit on the energy scale for this type of Lorentz violation effect at the level of ${\cal E}_{LV} > 10^{10}$~GeV.
Lessons learned with the SAGE spectrometer
2012
The SAGE spectrometer combines a high-efficiency γ-ray detection system with an electron spectrometer. Some of the design features have been known to be problematic and surprises have come up during the early implementation of the spectrometer. Tests related to bismuth germanate Compton-suppression shields, electron detection efficiency and an improved cooling system are discussed in the paper.