The Experts below are selected from a list of 26817 Experts worldwide ranked by ideXlab platform
S Kumashiro - One of the best experts on this subject based on the ideXlab platform.
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Ion motIon in the rectangular wave quadrupole field and digital operatIon mode of a quadrupole Ion trap mass spectrometer
Rapid Communications in Mass Spectrometry, 2006Co-Authors: L Ding, S KumashiroAbstract:A quadrupolar electric field driven by a rectangular wave voltage can be used for mass-selective storage and analysis. The Ion motIon in such an electric field is derived, and the stability of Ions is presented in the a-q diagram that is commonly used for sinusoidal wave quadrupole mass spectrometry in associatIon with the solutIon of the Mathieu equatIon. The pseudo-potential well is discussed in an approximatIon that leads to the relatIon of secular frequency to operating parameters. A scheme for a digital Ion trap mass spectrometer is described, based on this theory. An Ion optics simulatIon was performed to check the theory of resonant ejectIon, and to prove the feasibility of the mass scan method for a practical Ion trap of such geometry. Copyright © 2005 John Wiley & Sons, Ltd.
Roberto A. Clemente - One of the best experts on this subject based on the ideXlab platform.
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The effect of Ion motIon on rotating magnetic field current drive
Plasma Physics and Controlled Fusion, 2003Co-Authors: Agustin Lifschitz, Ricardo Farengo, Roberto A. ClementeAbstract:The effect of Ion motIon on rotating magnetic field (RMF) current drive in field reversed configuratIons is studied using a fully two-dimensIonal numerical code that solves the two fluid equatIons with massless electrons and constant uniform temperature. The Ion momentum equatIon includes viscosity and collisIons with neutrals, which remain fixed. The electrons are described with an Ohm's law that includes the Hall and pressure gradient terms. For full penetratIon of the RMF, Ion spin-up due to collisIons with electrons reduces the current drive efficiency and a large fractIon of neutrals is needed to prevent the Ions from acquiring high azimuthal velocities. For conditIons that would result in incomplete penetratIon with the fixed Ion model, Ion rotatIon and variable density can facilitate the penetratIon of the RMF, thus increasing the efficiency. The rotatIon modifies the density profile and can trigger rotatIonal instabilities.
Anders Eriksson - One of the best experts on this subject based on the ideXlab platform.
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a 1d model of radial Ion motIon interrupted by Ion neutral interactIons in a cometary coma
The Astronomical Journal, 2017Co-Authors: Erik Vigren, Anders ErikssonAbstract:Because Ion–neutral reactIon cross sectIons are energy dependent, the distance from a cometary nucleus within which Ions remain collisIonally coupled to the neutrals is dictated not only by the comet's activity level but also by the electromagnetic fields in the coma. Here we present a 1D model simulating the outward radial motIon of water group Ions with radial acceleratIon by an ambipolar electric field interrupted primarily by charge transfer processes with H2O. We also discuss the impact of plasma waves. For a given electric field profile, the model calculates key parameters, including the total Ion density, n I , the H3O+/H2O+ number density and flux ratios, R dens and R flux, and the mean Ion drift speed, , as a functIon of cometocentric distance. We focus primarily on a coma roughly resembling that of the ESA Rosetta missIon target comet 67P/Churyumov–Gerasimenko near its perihelIon in 2015 August. In the presence of a weak ambipolar electric field in the radial directIon the model results suggest that the neutral coma is not sufficiently dense to keep the mean Ion flow speed close to that of the neutrals by the spacecraft locatIon (~200 km from the nucleus). In additIon, for electric field profiles giving n I and within limits constrained by measurements, the R dens values are significantly higher than values typically observed. However, when including the Ion motIon in large-amplitude plasma waves in the model, results more compatible with observatIons are obtained. We suggest that the variable and often low H3O+/H2O+ number density ratios observed may reflect nonradial Ion trajectories strongly influenced by electromagnetic forces and/or plasma instabilities, with energizatIon of the Ion populatIon by plasma waves.
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a 1d model of radial Ion motIon interrupted by Ion neutral interactIons in a cometary coma
The Astronomical Journal, 2017Co-Authors: Erik Vigren, Anders ErikssonAbstract:Because Ion–neutral reactIon cross sectIons are energy dependent, the distance from a cometary nucleus within which Ions remain collisIonally coupled to the neutrals is dictated not only by the comet's activity level but also by the electromagnetic fields in the coma. Here we present a 1D model simulating the outward radial motIon of water group Ions with radial acceleratIon by an ambipolar electric field interrupted primarily by charge transfer processes with H2O. We also discuss the impact of plasma waves. For a given electric field profile, the model calculates key parameters, including the total Ion density, n I , the H3O+/H2O+ number density and flux ratios, R dens and R flux, and the mean Ion drift speed, , as a functIon of cometocentric distance. We focus primarily on a coma roughly resembling that of the ESA Rosetta missIon target comet 67P/Churyumov–Gerasimenko near its perihelIon in 2015 August. In the presence of a weak ambipolar electric field in the radial directIon the model results suggest that the neutral coma is not sufficiently dense to keep the mean Ion flow speed close to that of the neutrals by the spacecraft locatIon (~200 km from the nucleus). In additIon, for electric field profiles giving n I and within limits constrained by measurements, the R dens values are significantly higher than values typically observed. However, when including the Ion motIon in large-amplitude plasma waves in the model, results more compatible with observatIons are obtained. We suggest that the variable and often low H3O+/H2O+ number density ratios observed may reflect nonradial Ion trajectories strongly influenced by electromagnetic forces and/or plasma instabilities, with energizatIon of the Ion populatIon by plasma waves.
L Ding - One of the best experts on this subject based on the ideXlab platform.
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Ion motIon in the rectangular wave quadrupole field and digital operatIon mode of a quadrupole Ion trap mass spectrometer
Rapid Communications in Mass Spectrometry, 2006Co-Authors: L Ding, S KumashiroAbstract:A quadrupolar electric field driven by a rectangular wave voltage can be used for mass-selective storage and analysis. The Ion motIon in such an electric field is derived, and the stability of Ions is presented in the a-q diagram that is commonly used for sinusoidal wave quadrupole mass spectrometry in associatIon with the solutIon of the Mathieu equatIon. The pseudo-potential well is discussed in an approximatIon that leads to the relatIon of secular frequency to operating parameters. A scheme for a digital Ion trap mass spectrometer is described, based on this theory. An Ion optics simulatIon was performed to check the theory of resonant ejectIon, and to prove the feasibility of the mass scan method for a practical Ion trap of such geometry. Copyright © 2005 John Wiley & Sons, Ltd.
Wei Xu - One of the best experts on this subject based on the ideXlab platform.
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the coupling effects of hexapole and octopole fields in quadrupole Ion traps a theoretical study
Journal of Mass Spectrometry, 2013Co-Authors: Yuzhuo Wang, Zejian Huang, You Jiang, Xingchuang Xiong, Yulin Deng, Xiang Fang, Wei XuAbstract:A theoretical method, the harmonic balance method, was introduced to study the coupling effects of hexapole and octopole fields on Ion motIon in a quadrupole Ion trap. Ion motIon characteristics, such as Ion motIon center displacement, Ion secular frequency shift, nonlinear resonance curve and buffer gas damping effects, have been studied with the presence of both hexapole and octopole fields. It is found that hexapole fields have bigger impacts on Ion motIon center displacement, while octopole fields dominate Ion secular frequency shift. Furthermore, the nonlinear features originated from hexapole and octopole fields could enhance or cancel each other, which provide us more space in a practical Ion trap design process. As an example, an Ion trap with improved performance was designed using a specific combinatIon of hexapole and octopole fields. In this Ion trap, a hexapole field was used to achieve efficient Ion directIonal ejectIon, while an octopole field was added to correct the chemical mass shift and resolutIon degradatIon introduced by the hexapole field. Copyright © 2013 John Wiley & Sons, Ltd.
