The Experts below are selected from a list of 12885 Experts worldwide ranked by ideXlab platform
Mark A Cappelli - One of the best experts on this subject based on the ideXlab platform.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical ~collision-driven! Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electrontransport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (v cet) eff’16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies ~elastic collision induced plus fluctuation induced!, as proposed by Boeuf and Garrigues @J. Appl. Phys. 84, 3541 ~1998!#. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of $({\ensuremath{\omega}}_{\mathrm{ce}}\ensuremath{\tau}{)}_{\mathrm{eff}}\ensuremath{\approx}16.$ These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.
N B Meezan - One of the best experts on this subject based on the ideXlab platform.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical ~collision-driven! Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electrontransport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (v cet) eff’16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies ~elastic collision induced plus fluctuation induced!, as proposed by Boeuf and Garrigues @J. Appl. Phys. 84, 3541 ~1998!#. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of $({\ensuremath{\omega}}_{\mathrm{ce}}\ensuremath{\tau}{)}_{\mathrm{eff}}\ensuremath{\approx}16.$ These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.
John R. Grace - One of the best experts on this subject based on the ideXlab platform.
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simultaneous measurements of particle charge density and bubble properties in gas solid fluidized beds by dual tip Electrostatic Probes
Chemical Engineering Science, 2015Co-Authors: Chuan He, Xiaotao Bi, John R. GraceAbstract:Abstract The aim of this work was to develop a new dual-tip Electrostatic Probe for in-situ measurements of particle charge density and bubble properties in bubbling fluidized beds. Probes containing two retractable, vertically-aligned tips were tested in a lab-scale two-dimensional fluidized bed operated in both single bubble injection and freely bubbling modes, with glass beads and polyethylene particles of narrow size distributions as bed materials. Different decoupling methods were proposed and employed to analyze the Electrostatic signals from the Probes. The estimated particle charge density and bubble rise velocity were found to follow the same trends as those measured by a Faraday cup sampling system and obtained from video images respectively, with relative errors depending on the decoupling methods and Probe configurations, especially for polyethylene particles.
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contact electrification of a novel dual material Probe with charged particulate flow
Powder Technology, 2014Co-Authors: John R. GraceAbstract:Abstract A novel dual-material collision Electrostatic Probe was developed and calibrated in an ejector-funnel setup, which produced charged particulate flow with different magnitudes and polarities of charge density on the particles. The charged particles then collided with the dual-material Probe tip, with the transferred charges/currents recorded by electrometers. Experiments were conducted to examine the effects of particle charge density, solid flux, particle collision velocity and angle during the charge transfer process between particles and the Probe tip surfaces. A semi-empirical transferred current model which quantifies the effect of the above parameters is proposed, building on the linkage of transferred current measured by the Probe and the charge density on the particles.
Trevor Lafleur - One of the best experts on this subject based on the ideXlab platform.
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secondary electron emission due to multi species iodine ion bombardment of different target materials
Journal of Applied Physics, 2021Co-Authors: L Habl, Dmytro Rafalskyi, Trevor LafleurAbstract:Ion-induced secondary electron emission (SEE) is a fundamental surface interaction that strongly influences many plasma discharges. Recently, interest in iodine plasmas is growing due to new material processing and space propulsion applications, but data for SEE yields due to iodine ion bombardment remain scarce. Additionally, due to the formation of multiple ion species in typical iodine plasmas and surface chemical reactions leading to iodide layer formation, the effective SEE yield is expected to differ from that for individual ion species on clean surfaces. In this work, we measure the SEE yield of multi-species iodine ion beams bombarding different target materials (Mo, W, Al, Ti, Cu, carbon-carbon, and steel) in the energy range of 0.6–1.4 keV. An ion beam is produced by extracting and accelerating ions from a gridded ion source based on an inductively coupled plasma (ICP). SEE yields of downstream targets are measured using a conventional Electrostatic Probe technique, and the ion beam composition is determined using time-of-flight spectrometry. The beam is composed predominately of atomic ( I +) and molecular ( I 2 +) ions whose ratio changes depending on the ICP power. Yields depend strongly on the target material and beam composition and vary between 0.05 and 0.4 depending on whether potential or kinetic emission processes dominate.
W Hargus - One of the best experts on this subject based on the ideXlab platform.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical ~collision-driven! Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electrontransport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of (v cet) eff’16. These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies ~elastic collision induced plus fluctuation induced!, as proposed by Boeuf and Garrigues @J. Appl. Phys. 84, 3541 ~1998!#. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.
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anomalous electron mobility in a coaxial hall discharge plasma
Physical Review E, 2001Co-Authors: N B Meezan, W Hargus, Mark A CappelliAbstract:A comprehensive analysis of measurements supporting the presence of anomalous cross-field electron mobility in Hall plasma accelerators is presented. Nonintrusive laser-induced fluorescence measurements of neutral xenon and ionized xenon velocities, and various Electrostatic Probe diagnostic measurements are used to locally determine the effective electron Hall parameter inside the accelerator channel. These values are then compared to the classical (collision-driven) Hall parameters expected for a quiescent magnetized plasma. The results indicate that in the vicinity of the anode, where there are fewer plasma instabilities, the electron-transport mechanism is likely elastic collisions with the background neutral xenon. However, we find that in the vicinity of the discharge channel exit, where the magnetic field is the strongest and where there are intense fluctuations in the plasma properties, the inferred Hall parameter departs from the classical value, and is close to the Bohm value of $({\ensuremath{\omega}}_{\mathrm{ce}}\ensuremath{\tau}{)}_{\mathrm{eff}}\ensuremath{\approx}16.$ These results are used to support a simple model for the Hall parameter that is based on the scalar addition of the electron collision frequencies (elastic collision induced plus fluctuation induced), as proposed by Boeuf and Garrigues [J. Appl. Phys. 84, 3541 (1998)]. The results also draw attention to the possible role of fluctuations in enhancing electron transport in regions where the electrons are highly magnetized.