We investigate the existence of the electric field reversal in the negative glow of a dc discharg... more We investigate the existence of the electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time, and as well the trapping time. Based on a stress-energy tensor analysis we show the inherent instability of the well. We suggest that the Fermi mechanism is a possible process for pumping out electrons from the through, and linking this phenomena with electrostatic plasma instabilities. A power law distribution function for trapped electrons is also obtained. Analytical expressions are derived which can be used to calculate these characteristics from geometrical dimensions and the operational parameters of the discharge.
We present a comparison between the solutions of Boltzmann equation obtained from four different ... more We present a comparison between the solutions of Boltzmann equation obtained from four different representations of the evdf and a Monte Carlo particle model and applied to the description of a pulsed Townsend discharge in the hydrodynamic regime. The comparison is made in neon at a constant and homogeneous electric field bellow 500 Td. The importance of non-conservative processes; of taking into account the electron density gradients and the order of the spherical harmonics expansion of the evdf on several transport parameters is analysed. For the isotropic component of the evdf we obtain an excellent agreement between the Boltzmann results from a density gradients expansion representation, a 8-term Legendre expansion, an elliptic representation and the Monte Carlo results. However the results show that to obtain a correct description of the electron swarm and correct results for the drift velocity and diffusion tensor we need to take into account the non-conservative processes and the e-density gradients. In the conditions studied, it is found that although the two-term velocity expansion is less accurate than the other representations, the relative errors in the corresponding rate coefficients are bellow the typical experimental error.
The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimen... more The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimensional fluid model at atmospheric pressure. The computational model assumes the drift-diffusion approximation and uses a simple plasma kinetic model. It investigated the electrical and kinetic properties of the plasma, calculated the charged species concentrations, surface charge density, electrohydrodynamic forces, and gas speed. The present computational model contributes to understand the main physical mechanisms, and suggests ways to improve its performance.
The phenomena of electric field reversal in glow discharges is discussed. Several models are desc... more The phenomena of electric field reversal in glow discharges is discussed. Several models are described and the link between the electric field reversal, electron's trapping and the discharge structure is analyzed.
The present work intends to compare the propulsion force developed in an asymmetric capacitor, ac... more The present work intends to compare the propulsion force developed in an asymmetric capacitor, according to the number of positive ion sources used. The ion source is a corona wire, which generates a positive corona discharge in nitrogen gas directed towards the ground electrode. We are going to apply the known theory of electrohydrodynamics (EHD) and electrostatics in order to compute all hydrodynamic and electrostatic forces that act on the considered geometry in an attempt to provide a physical insight on the force mechanism that acts on each asymmetrical capacitor, and also to compare propulsion efficiencies.
The presence of small amounts of gas impurities in argon glow discharges used for optical emissio... more The presence of small amounts of gas impurities in argon glow discharges used for optical emission spectrometry (GDOES) has strong implications on the accurate calibration of GDOES. To circumvent these difficulties, the intentional admixture of controlled amounts of H2 or N2 to argon has been practiced [1]. The understanding of the electron kinetics in these mixtures is valuable for the characterization and calibration of the cell. In this work the electron velocity distribution function, rate coefficients and transport parameters are computed in Ar + xH2 and Ar + xN2 mixtures, with 0% <= x <= 10%, for pulsed Townsend discharge conditions. Different computational techniques are used: a classical two-term expansion, a modified finite elements method applied to the density gradients representation, and a Monte Carlo simulation at the same discharge conditions. Two different set of cross sections for H2 are used [2,3], allowing a comparison between them. [1] Hodoroaba et al. J. Anal. At. Spectrom. 18, 521 (2003) [2] [http://jilawww.colorado.edu/˜avp] [3] Loureiro et al. J. Phys. D: Appl. Phys. 22 1680 (1989)
We comment about the general argument given to obtain the rocket equation as it is exposed in sta... more We comment about the general argument given to obtain the rocket equation as it is exposed in standard textbooks. In our opinion, it can induce students to a wrong answer when solving variable mass problems.
Some personal reflections are made about the philosophical posture of Erwin Schrodinger, as expos... more Some personal reflections are made about the philosophical posture of Erwin Schrodinger, as exposed in one of his book "Ma Conception du Monde". It is argued that the Taoist view of the world, as pursued by Schrodinger, although characterized by the dialectical struggle between opposite truths does not contain the temporal dimension, the unique which allows an evolving understanding of phenomena and objects that compose this world in constant evolution. In our point of view, only a genetic view - which is missing in the actual scientific paradigm - will bring a more deep explanation and understanding of Reality.
A theoretical analysis of the anomalous diffusion transport mechanism suggests a possible connect... more A theoretical analysis of the anomalous diffusion transport mechanism suggests a possible connection between wall current drain and magnetic flux through the orbital trajectories of charged particles in a plasma submitted to a strong magnetic field. Then Bohm diffusion coefficient is straightforwardly obtained.
From this ground we offer a fluidic approach to different kind of issues with interest in propuls... more From this ground we offer a fluidic approach to different kind of issues with interest in propulsion, e.g., the force exerted by a charged particle on a body carrying current; the magnetic force between two parallel currents; the Magnus's force. It is shown how the intermingle between the fluid vectors fields and electromagnetic fields lead to new insights on their dynamics. The new concepts introduced in this work suggest possible applications to electromagnetic (EM) propulsion devices and the mastery of the principles of producing electric fields of required configuration in plasma medium.
A non-markovian stochastic model is shown to lead to a universal relationship between particle's ... more A non-markovian stochastic model is shown to lead to a universal relationship between particle's energy, driven frequency and a frequency of interaction with the medium. It is briefly discussed the possible relevance of this general structure to various phenomena in the context of the formation of patterns in granular media, computation in a Brownian-type computer and the Haisch-Rueda-Puthoff inertial mass theory.
From the equilibrium condition δS = 0 applied to an isolated thermodynamic system of electrically... more From the equilibrium condition δS = 0 applied to an isolated thermodynamic system of electrically charged particles and the fundamental equation of thermodynamics (dU = TdS - (f · dr)) subject to a new procedure, it is obtained the Lorentz's force together with non-inertial terms of mechanical nature. Other well known ponderomotive forces, like the Stern Gerlach's force and a force term related to the Einstein de Haas's effect are also obtained. In addition, a new force term appears, possibly related to a change in weight when a system of charged particles is accelerated.
Small admixtures of molecular gases are known to influence significantly the characteristics of n... more Small admixtures of molecular gases are known to influence significantly the characteristics of noble gas glow discharges. The rotational and vibrational levels of the molecules having much lower excitation thresholds, compared to those of the electronic transitions of the noble gases, may drain the energy of electrons, especially at low reduced electric fields where the mean electron en-ergy is low. As a practical example where such effects become important, Glow Discharge Optical Emission Spectroscopy (GDOES) may be mentioned. GDOES is a widely used technique for quantitative analysis of the composition of materials. Molecular gases present in the discharge (e.g. as impurities) can modify the emission spectra of the investigated samples thereby making impos-sible an accurate quantitative analysis. Thus, in order to avoid the effect of uncontrolled trace amounts of these gases on the observed spectra, mixing of small amounts of molecular gases (N2, H2) to Ar has become a widely use...
We report a 1-D (along Pedersen axis) test particle Monte Carlo (TPMC) simulation of electrons be... more We report a 1-D (along Pedersen axis) test particle Monte Carlo (TPMC) simulation of electrons behaviour in a parallel plate magnetron discharge, considering a complet set of electronic processes in Ar. The Lorentz's force system of equations is solved yielding the 3 components of the electron velocity for various electric (E) and crossed magnetic field (B) configurations. The main advantage is simplicity albeit phenomena related to the Hall current are not described. Simulation results are presented for various E and B profiles and strength. For a given ExB profile, it is shown that when B increases also increases the electronic density due to a higher confinement but decreases the electronic temperature. At least below 0.1 Torr, the value of pressure (p) at which occurs a maximization of ionizing and elastic collisions increases when B decreases. It is shown that the direct current grows with p but can decrease with B, depending on the plasma sheath thickness near the cathode....
We report a 1-D (along Peterson axis) direct simulation Monte Carlo of the behaviour of electrons... more We report a 1-D (along Peterson axis) direct simulation Monte Carlo of the behaviour of electrons in a parallel plate magnetron discharge, considering a complet set of electronic processes in Ar. The Lorentz's force system of equations is solved yielding the 3 components of the electron velocity for various electric (E) and crossed magnetic field (B) configurations. The main advantage is simplicity albeit phenomena related to the Hall current are not described. Simulation results are presented for various E and B profiles and strength. For a given ExB profile, it is shown that when B increases also increases the electronic density due to a higher confinement but decreases the electronic temperature. At least below 0.1 Torr, the value of pressure (p) at which occurs a maximization of ionizing and elastic collisions increases when B decreases. It is shown that the direct current grows with p but can decrease with B, depending on the plasma sheath thickness near the cathode. It is ...
We investigate the existence of the electric field reversal in the negative glow of a dc discharg... more We investigate the existence of the electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time as well the fraction of ions build up in the glow and returning to cathode. A simple analytical model is presented which includes a Boltzmann transport equations for electrons submitted to an external electric field E along x, the ions conservation equation in a diffusion-dominated plasma and the Poisson equation. The position of the field reversal is found to be at x = d fracbeta - R2 alpha, where d is the distance between electrodes, beta ≡ frac&surd;2DK &surd;fracE_0Ec with D=(fracdr_D)^2 (rD is the Debye radius), K = fracld (l=frac1&surd;2n0 sigma^*_ion is the electrons effective mean free path) is the Knudsen number and E0 and Ec are, resp., the non-dimensional electric field (defined by frace d Em v_0^2)at the cathode (v0 represents the initial velocity of electrons emitted from the ca...
The law of action-reaction is thoroughly used in textbooks to derive the conservation laws of lin... more The law of action-reaction is thoroughly used in textbooks to derive the conservation laws of linear and angular momentum, and it was considered by Ernst Mach the the cornerstone of physics. We give here a background survey of several questions raised by the action-reaction law, and in particular, the role of the physical vacuum is shown to provide an appropriate framework to clarify the occurrence of possible violations of the action-reaction law. It is also obtained an expression for the general linear momentum of a body-particle in the context of statistical mechanics. It is shown that Newton's third law is not verified in systems out of equilibrium due to an additional entropic gradient term present in the particle's momentum.
We investigate the existence of the electric field reversal in the negative glow of a dc discharg... more We investigate the existence of the electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time, and as well the trapping time. Based on a stress-energy tensor analysis we show the inherent instability of the well. We suggest that the Fermi mechanism is a possible process for pumping out electrons from the through, and linking this phenomena with electrostatic plasma instabilities. A power law distribution function for trapped electrons is also obtained. Analytical expressions are derived which can be used to calculate these characteristics from geometrical dimensions and the operational parameters of the discharge.
We present a comparison between the solutions of Boltzmann equation obtained from four different ... more We present a comparison between the solutions of Boltzmann equation obtained from four different representations of the evdf and a Monte Carlo particle model and applied to the description of a pulsed Townsend discharge in the hydrodynamic regime. The comparison is made in neon at a constant and homogeneous electric field bellow 500 Td. The importance of non-conservative processes; of taking into account the electron density gradients and the order of the spherical harmonics expansion of the evdf on several transport parameters is analysed. For the isotropic component of the evdf we obtain an excellent agreement between the Boltzmann results from a density gradients expansion representation, a 8-term Legendre expansion, an elliptic representation and the Monte Carlo results. However the results show that to obtain a correct description of the electron swarm and correct results for the drift velocity and diffusion tensor we need to take into account the non-conservative processes and the e-density gradients. In the conditions studied, it is found that although the two-term velocity expansion is less accurate than the other representations, the relative errors in the corresponding rate coefficients are bellow the typical experimental error.
The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimen... more The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimensional fluid model at atmospheric pressure. The computational model assumes the drift-diffusion approximation and uses a simple plasma kinetic model. It investigated the electrical and kinetic properties of the plasma, calculated the charged species concentrations, surface charge density, electrohydrodynamic forces, and gas speed. The present computational model contributes to understand the main physical mechanisms, and suggests ways to improve its performance.
The phenomena of electric field reversal in glow discharges is discussed. Several models are desc... more The phenomena of electric field reversal in glow discharges is discussed. Several models are described and the link between the electric field reversal, electron's trapping and the discharge structure is analyzed.
The present work intends to compare the propulsion force developed in an asymmetric capacitor, ac... more The present work intends to compare the propulsion force developed in an asymmetric capacitor, according to the number of positive ion sources used. The ion source is a corona wire, which generates a positive corona discharge in nitrogen gas directed towards the ground electrode. We are going to apply the known theory of electrohydrodynamics (EHD) and electrostatics in order to compute all hydrodynamic and electrostatic forces that act on the considered geometry in an attempt to provide a physical insight on the force mechanism that acts on each asymmetrical capacitor, and also to compare propulsion efficiencies.
The presence of small amounts of gas impurities in argon glow discharges used for optical emissio... more The presence of small amounts of gas impurities in argon glow discharges used for optical emission spectrometry (GDOES) has strong implications on the accurate calibration of GDOES. To circumvent these difficulties, the intentional admixture of controlled amounts of H2 or N2 to argon has been practiced [1]. The understanding of the electron kinetics in these mixtures is valuable for the characterization and calibration of the cell. In this work the electron velocity distribution function, rate coefficients and transport parameters are computed in Ar + xH2 and Ar + xN2 mixtures, with 0% <= x <= 10%, for pulsed Townsend discharge conditions. Different computational techniques are used: a classical two-term expansion, a modified finite elements method applied to the density gradients representation, and a Monte Carlo simulation at the same discharge conditions. Two different set of cross sections for H2 are used [2,3], allowing a comparison between them. [1] Hodoroaba et al. J. Anal. At. Spectrom. 18, 521 (2003) [2] [http://jilawww.colorado.edu/˜avp] [3] Loureiro et al. J. Phys. D: Appl. Phys. 22 1680 (1989)
We comment about the general argument given to obtain the rocket equation as it is exposed in sta... more We comment about the general argument given to obtain the rocket equation as it is exposed in standard textbooks. In our opinion, it can induce students to a wrong answer when solving variable mass problems.
Some personal reflections are made about the philosophical posture of Erwin Schrodinger, as expos... more Some personal reflections are made about the philosophical posture of Erwin Schrodinger, as exposed in one of his book "Ma Conception du Monde". It is argued that the Taoist view of the world, as pursued by Schrodinger, although characterized by the dialectical struggle between opposite truths does not contain the temporal dimension, the unique which allows an evolving understanding of phenomena and objects that compose this world in constant evolution. In our point of view, only a genetic view - which is missing in the actual scientific paradigm - will bring a more deep explanation and understanding of Reality.
A theoretical analysis of the anomalous diffusion transport mechanism suggests a possible connect... more A theoretical analysis of the anomalous diffusion transport mechanism suggests a possible connection between wall current drain and magnetic flux through the orbital trajectories of charged particles in a plasma submitted to a strong magnetic field. Then Bohm diffusion coefficient is straightforwardly obtained.
From this ground we offer a fluidic approach to different kind of issues with interest in propuls... more From this ground we offer a fluidic approach to different kind of issues with interest in propulsion, e.g., the force exerted by a charged particle on a body carrying current; the magnetic force between two parallel currents; the Magnus's force. It is shown how the intermingle between the fluid vectors fields and electromagnetic fields lead to new insights on their dynamics. The new concepts introduced in this work suggest possible applications to electromagnetic (EM) propulsion devices and the mastery of the principles of producing electric fields of required configuration in plasma medium.
A non-markovian stochastic model is shown to lead to a universal relationship between particle's ... more A non-markovian stochastic model is shown to lead to a universal relationship between particle's energy, driven frequency and a frequency of interaction with the medium. It is briefly discussed the possible relevance of this general structure to various phenomena in the context of the formation of patterns in granular media, computation in a Brownian-type computer and the Haisch-Rueda-Puthoff inertial mass theory.
From the equilibrium condition δS = 0 applied to an isolated thermodynamic system of electrically... more From the equilibrium condition δS = 0 applied to an isolated thermodynamic system of electrically charged particles and the fundamental equation of thermodynamics (dU = TdS - (f · dr)) subject to a new procedure, it is obtained the Lorentz's force together with non-inertial terms of mechanical nature. Other well known ponderomotive forces, like the Stern Gerlach's force and a force term related to the Einstein de Haas's effect are also obtained. In addition, a new force term appears, possibly related to a change in weight when a system of charged particles is accelerated.
Small admixtures of molecular gases are known to influence significantly the characteristics of n... more Small admixtures of molecular gases are known to influence significantly the characteristics of noble gas glow discharges. The rotational and vibrational levels of the molecules having much lower excitation thresholds, compared to those of the electronic transitions of the noble gases, may drain the energy of electrons, especially at low reduced electric fields where the mean electron en-ergy is low. As a practical example where such effects become important, Glow Discharge Optical Emission Spectroscopy (GDOES) may be mentioned. GDOES is a widely used technique for quantitative analysis of the composition of materials. Molecular gases present in the discharge (e.g. as impurities) can modify the emission spectra of the investigated samples thereby making impos-sible an accurate quantitative analysis. Thus, in order to avoid the effect of uncontrolled trace amounts of these gases on the observed spectra, mixing of small amounts of molecular gases (N2, H2) to Ar has become a widely use...
We report a 1-D (along Pedersen axis) test particle Monte Carlo (TPMC) simulation of electrons be... more We report a 1-D (along Pedersen axis) test particle Monte Carlo (TPMC) simulation of electrons behaviour in a parallel plate magnetron discharge, considering a complet set of electronic processes in Ar. The Lorentz's force system of equations is solved yielding the 3 components of the electron velocity for various electric (E) and crossed magnetic field (B) configurations. The main advantage is simplicity albeit phenomena related to the Hall current are not described. Simulation results are presented for various E and B profiles and strength. For a given ExB profile, it is shown that when B increases also increases the electronic density due to a higher confinement but decreases the electronic temperature. At least below 0.1 Torr, the value of pressure (p) at which occurs a maximization of ionizing and elastic collisions increases when B decreases. It is shown that the direct current grows with p but can decrease with B, depending on the plasma sheath thickness near the cathode....
We report a 1-D (along Peterson axis) direct simulation Monte Carlo of the behaviour of electrons... more We report a 1-D (along Peterson axis) direct simulation Monte Carlo of the behaviour of electrons in a parallel plate magnetron discharge, considering a complet set of electronic processes in Ar. The Lorentz's force system of equations is solved yielding the 3 components of the electron velocity for various electric (E) and crossed magnetic field (B) configurations. The main advantage is simplicity albeit phenomena related to the Hall current are not described. Simulation results are presented for various E and B profiles and strength. For a given ExB profile, it is shown that when B increases also increases the electronic density due to a higher confinement but decreases the electronic temperature. At least below 0.1 Torr, the value of pressure (p) at which occurs a maximization of ionizing and elastic collisions increases when B decreases. It is shown that the direct current grows with p but can decrease with B, depending on the plasma sheath thickness near the cathode. It is ...
We investigate the existence of the electric field reversal in the negative glow of a dc discharg... more We investigate the existence of the electric field reversal in the negative glow of a dc discharge, its location, the width of the well trapping the electrons, the slow electrons scattering time as well the fraction of ions build up in the glow and returning to cathode. A simple analytical model is presented which includes a Boltzmann transport equations for electrons submitted to an external electric field E along x, the ions conservation equation in a diffusion-dominated plasma and the Poisson equation. The position of the field reversal is found to be at x = d fracbeta - R2 alpha, where d is the distance between electrodes, beta ≡ frac&surd;2DK &surd;fracE_0Ec with D=(fracdr_D)^2 (rD is the Debye radius), K = fracld (l=frac1&surd;2n0 sigma^*_ion is the electrons effective mean free path) is the Knudsen number and E0 and Ec are, resp., the non-dimensional electric field (defined by frace d Em v_0^2)at the cathode (v0 represents the initial velocity of electrons emitted from the ca...
The law of action-reaction is thoroughly used in textbooks to derive the conservation laws of lin... more The law of action-reaction is thoroughly used in textbooks to derive the conservation laws of linear and angular momentum, and it was considered by Ernst Mach the the cornerstone of physics. We give here a background survey of several questions raised by the action-reaction law, and in particular, the role of the physical vacuum is shown to provide an appropriate framework to clarify the occurrence of possible violations of the action-reaction law. It is also obtained an expression for the general linear momentum of a body-particle in the context of statistical mechanics. It is shown that Newton's third law is not verified in systems out of equilibrium due to an additional entropic gradient term present in the particle's momentum.
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