Behavior Of Charged Particles Research Articles

CHARGED SPINNING PARTICLES ON CIRCULAR ORBITS IN THE REISSNER–NORDSTRÖM SPACE–TIME

The behavior of charged spinning test particles moving along circular orbits in the equatorial plane of the Reissner–Nordström space–time is studied in the framework of the Dixon–Souriau model completed with standard choices of supplementary conditions. The gravitomagnetic "clock effect," i.e. the delay in the arrival times of two oppositely circulating particles as measured by a static observer, is derived and discussed in the cases in which the particles have equal/opposite charge and spin, the latter being directed along the z-axis.

Chapman Conference on Magnetospheric ULF Waves

Waves in the ultra‐low‐frequency (ULF) band (periods of 1 to 1000 s) are a permanent feature in the region called the magnetosphere, where the behavior of charged particles is influenced by the Earth's intrinsic magnetic field. These waves transport momentum and energy from the solar wind to the magnetosphere and farther down to the ionosphere. In addition, the waves interact with charged particles in the magnetosphere and modify their energy and direction of motion with important consequences for dynamic processes such as geomagnetic storms and the formation of auroral arcs.The physics of magnetospheric ULF waves is far from being completely understood primarily because many ULF waves have a wavelength comparable to the size of the magnetosphere, which is of the order of 10 Earth radii (RE). Just establishing the structure of such waves from observations is a daunting task. The source mechanisms for the waves are also often difficult to determine.

Do phase portraits resist current sheet bifurcation?

We investigate the non-linear dynamics of charged particles in the double-humped current sheets that develop in the Earth’s magnetotail. Using Poincaré surfaces of section, we examine the various dynamical regimes that occur in a sharp field reversal and compare them to those obtained in single-humped current sheets. We demonstrate that bifurcation of the magnetotail current sheet does not alter the overall phase portrait structure which is characterized by three distinct regimes, viz., trapped, quasi-trapped, and transient. The phase portraits in single- and double-humped current sheets are not strictly identical though. A greater abundance of trapped particles and a distortion of the transient orbit domain are obtained in the latter case. In contrast, numerical simulations performed with an asymmetrical double-humped current distribution reveal considerable modification of the phase portrait with an expansion of the stochastic regime and a drastic reduction of the transient one. The degree of asymmetry in double-humped current sheets accordingly appears as a primary parameter to characterize the nonadiabatic behavior of charged particles.

Coagulation of bipolarly charged ultrafine aerosol particles

Particle charging during coagulational growth is widely used in material synthesis processes as well as with industrial particle removal equipment. Coagulation behavior of charged particles is significantly different from that of neutral particles. To calculate the change in size/charge distribution of particles undergoing bipolar coagulation, a two-dimensional sectional model has been usually used. This method, however, needs considerable computation time although it gives very accurate prediction. In this study, the moment model, to solve the bipolar coagulation problem in the free-molecule regime, was developed to provide a time-efficient tool. Simultaneous particle charging by bipolar ions was also considered in this study. The developed model is based on the assumption that particles cannot have more than one unit charge and the particle size distribution remains log normal. The developed model was compared to the two-dimensional sectional model, with good agreement being shown. Some characteristics of bipolar coagulation were investigated using the developed model. The bipolar coagulation with simultaneous bipolar diffusion charging was shown to significantly increase the coagulation rate compared to the neutral Brownian coagulation. It was also shown from the simulation results that if one needs a higher coagulation rate in the initial stage, bipolar coagulation without ions is recommended, while bipolar coagulation with simultaneous charging by bipolar ions should be used if one wants a high coagulation rate for a long time.

Electrodiffusion near an ion channel and the effect of mobile buffer

A numerical method was set up to calculate the dynamic concentration behavior of charged particles in the vicinity of an ion channel. It takes into account the electric potential due to the charge of the transported ions. Additionally, the finite on- and off-kinetics of mobile ion-buffers such as EGTA can be added to the simulations. The calculations were carried out using a modified Crank–Nicolson algorithm to solve the partial differential equations describing the problem. It was found that the electrostatic effect on the concentration of permeating ions is negligible in the presence of physiological salt concentrations. Nevertheless, there are electrostatic effects on other ion species near the channel mouth. Studies on the effect of a Ba 2+-current through a Ca 2+-channel onto the Ca 2+-concentration in the bath, and on the amplification of the Ca 2+-effect on the BK-channel due to the K +-flux are presented. Additionally, the effect of mobile buffers was simulated and the numerical results are compared with some common analytical approximations.

Experiments and Numerical Analyses of Charged Particle's Behavior in a Plasma Display Panel

Experimental and numerical studies of erosion process of an MgO layer were performed in order to obtain a fundamental guideline for lifetime evaluation of a plasma display panel (PDP). From the experimental results of an over-voltage accelerated discharge test and surface analysis of the MgO layer, it was found that the erosion and deterioration progressed due to the bombarding ions and adsorbed impurities, respectively, in the MgO surface during the accelerated discharge. The numerical analysis of the plasma behavior and its structure in PDP discharge was performed to explain these experimental results. The localized erosion on the MgO surface was due to the discontinuity of the ion bombardment, which was further expedited by the charge accumulated in dielectric (wall charge) behavior. The combination of these behaviors of charge particle was found to explain the localized erosion process in the MgO layer in the accelerated PDP discharge.

Experimental Simulation on Discrimination of Charged Particles in a Cusp Direct Energy Converter for D-3He Fusion

A direct energy conversion system designed for D-3He fusion reactor consists of a CUSP direct energy converter (DEC) and a Traveling Wave DEC, where, respectively, electrons and thermal ions are separated from fusion protons and decelerated via Venetian blind type electrodes to produce DC power, and protons are velocity-modulated, bunched, and then decelerated by RF traveling waves to produce RF power. For the basic investigation of the CUSPDEC, a small scale experiment is conducted using a device consisting of a single cusp and low-energy plasma and ion sources. Performed are the measurements of basic characteristics of the behavior of charged particles in various conditions including magnetic field gradients, spatial locations of incidence, ion masses, and ion energies.

Electron-stimulated desorption of cations from dielectric matters: NaCl andH2Onanoclusters adsorbed on a solid Ar substrate

In order to gain insight into the behavior of charged particles in dielectric matters, electron-stimulated desorption of cations from NaCl and ${\mathrm{H}}_{2}\mathrm{O}$ nanoclusters adsorbed on a solid Ar substrate has been investigated. It is found that hydrated protons, ${\mathrm{H}}^{+}({\mathrm{H}}_{2}\mathrm{O}{)}_{n},$ and ${\mathrm{Na}}^{+}$ and ${\mathrm{Na}}^{+}(\mathrm{NaCl}{)}_{n}$ ions, respectively, are emitted from ${\mathrm{H}}_{2}\mathrm{O}$ and NaCl nanoclusters, suggesting that most of the excess protons formed in water are hydrated, whereas bare ${\mathrm{Na}}^{+}$ ions can exist in NaCl. The ion emission is induced by Coulombic repulsion of valence holes confined in the adsorbed nanoclusters. The ion yields decay almost exponentially with increasing coverage due to the delocalization of valence holes in the overlayer. No indication of the Coulombic ejection of ${\mathrm{Cl}}^{+}$ ions based on two Cl $3p$ holes is obtained from NaCl nanoclusters. The ${\mathrm{Cl}}^{+}$ ion is more likely to be emitted with a localized Cl $3s$ hole state.

On the behavior of charged particles in the near wall region of a channel flow

Direct Numerical Simulation (DNS) is used to compute a horizontal gas channel flow at Re b=2800 (based on bulk velocity and half channel width), and to investigate the motion and dispersion of solid particles under external influences such as gravity and/or electrostatic field. Other forces such as non-linear drag corrected for wall proximity and shear-induced lift are also implemented. Emphasis is put on the time correlations of the fluid velocity along the discrete particle path in order to investigate the integral time scales of the fluid seen by the particles in the near wall region. The effect of parameters such as wall distance or external field intensity is highlighted.

Sedimentation in dilute suspensions of charged particles

Sedimentation in dilute suspensions of charged particles with thin double layers was investigated. The study covered two different cases: sedimentation in polydisperse systems at a large Péclet number and sedimentation in polydisperse systems at a moderate Péclet number. For the first problem, the pair-distribution equation was solved by a regular perturbation method, and it was found that generally speaking the sedimentation coefficient deviates slightly from that at the infinite large Péclet number except the double layer was very thin. For the second problem, a flux-conservation discretization method was utilized in deriving an equivalent difference equation of the pair-distribution equation, which could be solved numerically. We found that the pair-distribution function showed a notable anisotropy in this case. Combing the results of the two problems, we, for the first time, presented an overall picture of the settling behavior of charged particles in which the Péclet number varied from a very small one up to a very large one. The results were found to possess much more diversities than the case of hard spheres.

Electrodynamic Behavior of a Charged Particle among Two-Dimensional Quadrupole Electrodes

An inhomogeneous hyperbolic electric field is established among two-dimensional quadrupole electrodes to which an ac voltage is applied. Conditions under which charged particles are focused into a narrow axis region of the plug laminar flow are discussed. The aerodynamic forces influence the behavior of the charged particles in the quadrupole electric field. We derived the dimensionless equations of motion of a charged particle in the alternating quadrupole electric field, and discussed particle trajectories and focusing performance in terms of two dimensionless parameters, which are functions of particle size, operating pressure, and the amplitude and frequency of applied AC voltage, with the results of numerical simulations and experiments.

Distribution of electric field strength around a large-scale charged particle cloud

To investigate an electrical discharge occurring from or in a space-charge cloud, a large-scale charged particle cloud was formed by using a cloud generator consisting of a blower and corona charger. The distribution of the electric field strength around a charged particle cloud has been investigated to determine the behavior of charged particles. The soil-conditioning particles were charged by corona charging and blown by high-speed air flow in a test room, 5 m wide, 10 m long, and 3 m high. The average charge-to-mass ratio of the particles blown by this method was 170 /spl mu/C/kg. The space-charge density of the cloud was calculated at the order of 10 /spl mu/C/m/sup 3/ from the electric field strength outside of the cloud. While the electric field strength at the outside of the cloud increased up to 52 kV/m within 2 m downstream from the cloud generator, it decreased below 25 kV/m farther than 2 m away from the cloud generator due to dispersion of charged particles. The change in the electric field strength due to dispersion of charged particles can be qualitatively explained by a simple cloud model. The velocity of charged particles transported by air flow and mobility of charged particles are found to be effective factors increasing the electric field strength around the large-scale charged particle cloud.

Modelling of conducting particle behaviour in plate-type electrostatic separators

The charging of conductive particles in contact with an electrode affected by a non-uniform electric field is a physical mechanism of paramount importance for various electrostatic technologies, including the separation of particulate mixtures. The aim of this paper is to model the behaviour of such charged particles in plate-type electrostatic separators. A computer program based on the boundary element method enabled the evaluation of the electric field strength at the surface of the plate electrode of these installations. The results of field computation were then employed for estimating the charge of perfectly-conducting spherical particles, as well as their position on the plate electrode, at the moment of detachment under the action of the electric force acting on them. The data reported in the paper point out the following factors which affect particle detachment and hence the efficiency of the electrostatic separation: the size and specific mass of the particles; the slope of the plate electrode; the dimensions and relative position of the high-voltage electrode; and the level of the high voltage applied to the electrode system. Experiments carried out with two kinds of particles (silver-plated polyamide spheres of radius 1.5 mm and mass 0.0192 g; and steel balls of radius 0.2-0.25 mm and average mass 0.000 45 g) confirmed the conclusions of numerical simulations. The modelling of particle behaviour in contact with plate electrodes facilitates the feasibility studies and can guide the experimental tests, which are needed for the development of any new application of the electrostatic separation method.

Parallelization of semi-Lagrangian Vlasov codes

We describe the parallel implementation of semi-Lagrangian Vlasov solvers, which are an alternative to particle-in-cell (PIC) simulations for the numerical investigation of the behaviour of charged particles in their self-consistent electromagnetic fields. The semi-Lagrangian method, which couples the Lagrangian and Eulerian points of view, is particularly interesting on parallel computers, since the solution is computed on grid points, the number of which remains constant in time on each processor, unlike the number of particles in PIC simulations, and thus greatly simplifies the parallelization process.

Turbulent particle dispersion in an electrostatic precipitator

The behaviour of charged particles in turbulent gas flow in electrostatic precipitators (ESPs) is crucial information to optimise precipitator efficiency. This paper describes a strongly coupled calculation procedure for the rigorous computation of particle dynamics during ESP taking into account the statistical particle size distribution. The turbulent gas flow and the particle motion under electrostatic forces are calculated by using the commercial computational fluid dynamics (CFD) package FLUENT linked to a finite volume solver for the electric field and ion charge. Particle charge is determined from both local electrical conditions and the cell residence time which the particle has experienced through its path. Particle charge density and the particle velocity are averaged in a control volume to use Lagrangian information of the particle motion in calculating the gas and electric fields. The turbulent particulate transport and the effects of particulate space charge on the electrical current flow are investigated. The calculated results for poly-dispersed particles are compared with those for mono-dispersed particles, and significant differences are demonstrated.

Kinetic theory of plasma adiabatic major radius compression in tokamaks

In order to understand the individual charged particle behavior as well as plasma macroparameters (temperature, density, etc.) during the adiabatic major radius compression (R-compression) in a tokamak, a kinetic approach is used. The perpendicular electric field from the Ohm’s law at zero resistivity is made use of in order to describe particle motion during the R-compression. Expressions for both passing and trapped particle energy and pitch angle change are derived for a plasma with high aspect ratio and circular magnetic surfaces. The particle behavior near the passing trapped boundary during the compression is studied to simulate the compression-induced collisional losses of alpha particles. Qualitative agreement is obtained with the alphas loss measurements in deuterium-tritium (D-T) experiments in the Tokamak Fusion Test Reactor (TFTR) [World Survey of Activities in Controlled Fusion Research [Nucl. Fusion special supplement (1991)] (International Atomic Energy Agency, Vienna, 1991)]. The plasma macroparameters evolution at the R-compression is calculated by solving the gyroaveraged drift kinetic equation.

Temporal Behavior of Charged Particles in a Radio Frequency Afterglow Plasma Containing Negative Ions

Temporal behavior of charged particles in pure He and He–SF6 radio frequency (rf) afterglow plasmas has been experimentally clarified for various SF6 gas concentrations (1, 25, 50%). The electron density in the pure He plasma increased just after the rf power was switched off, unlike in a pure Ar plasma, and then decreased slowly. The increase was probably due to collisional ionization of metastable He atoms. The electron density in the He–SF6 plasmas decreased exponentially. This was due to electron attachment to various molecules in the afterglow plasma.

Charged particles in random magnetic fields and the critical behavior in the fractional quantum Hall effect.

As a model for the transitions between plateaus in the fractional Quantum Hall effect we study the critical behavior of non-interacting charged particles in a static random magnetic field with finite mean value. We argue that this model belongs to the same universality class as the integer Quantum Hall effect. The universality is proved for the limiting cases of the lowest Landau level, and slowly fluctuating magnetic fields in arbitrary Landau levels. The conjecture that the universality holds in general is based on the study of the statistical properties of the corresponding random matrix model.

Certain theoretical aspects of ion trajectories in multipole systems

The motion of single ions through a perfect quadrupole is governed by linear differential equations in both static (d.c. only) and radio-frequency cases. However, motion in distorted quadrupole fields and higher multipoles (e.g. hexapoles, octapoles etc.) is determined by non-linear differential equations with coupled ( x,y) terms in Cartesian coordinates. In imperfect quadrupoles with electrodes of circular cross-section this non-linearity is “weak”. Motion in multipoles, in contrast, is entirely non-linear and it is to these multipoles that we turn our attention. We are aware that this work may also have significance for quadrupoles. Trajectory plotting can be successfully achieved by numerical methods, e.g. Runge—Kutta and the objective of any such studies is to discover the functional properties of the device apparent in the behaviour of charged particles during transit. In multipole and distorted systems the application of numerical methods is complicated by the substantially increased number of parameters involved. This mitigates against achieving the objective stated above. We have found that a simplification may be introduced which allows a semi-analytical treatment of the static cases and furthermore reduces the number of parameters required for the numerical analysis of the radio-frequency cases. Despite the simplification, the r.f. special case trajectories retain many of the features that occur in general cases. The simplification involves removing the ( x,y) product terms from the differential equations. This is not unreasonable as the equations then describe motion confined to the symmetry planes of the multipole. Results are shown that demonstrate, semi-analytically, the types of function encountered in the approximate solutions for the r.f. case over small increments of time. Trajectory plots are shown for the r.f. case, for which the simplification described above allows the production of phase-space diagrams.

Numerical studies on charged particle behavior in a cathode sheath of normal and abnormal glow dc discharge

The charged-particle energy distribution and scattering angular distribution for helium normal and abnormal dc glow discharge in the cathode sheath region are studied by Monte Carlo simulation (MCS). Some types of collisions (elastic, excitation, and ionization collision for electrons, elastic and charge-exchange collision for ions) are considered. The charged-particle free-flying time between collisions is determined by the charged-particle-neutral-gas collision frequency. The electron and ion energy distribution function, and the scattering angular distribution are calculated in this paper. The electron mean energy and mean drift velocity are also investigated. The results indicate that high-energy electrons exist in the cathode region, and the electron beam behavior is obtained for two kinds of discharges. Results are in good agreement with experiment.