Behavior Of Charged Particles Research Articles

General classification of charged test particle circular orbits in Reissner\u2013Nordstr\xf6m spacetime

We investigate charged particles’ circular motion in the gravitational field of a charged mass distribution described by the Reissner–Nordström spacetime. We introduce a set of independent parameters completely characterizing the different spatial regions in which circular motion is allowed. We provide a most complete classification of circular orbits for different sets of particle and source charge-to-mass ratios. We study both black holes and naked singularities and show that the behavior of charged particles depend drastically on the type of source. Our analysis shows in an alternative manner that the behavior of circular orbits can in principle be used to distinguish between black holes and naked singularities. From this analysis, special limiting values for the dimensionless charge of black hole and naked singularity emerge, namely, Q/M = 1/2, Q/M=sqrt{13}/5 and Q/M=sqrt{2/3} for the black hole case and Q/M = 1, Q/M=5/ (2 sqrt{6}), Q/M=3 sqrt{6}/7, and finally Q/M= sqrt{9/8} for the naked singularity case. Similarly and surprisingly, analogous limits emerge for the orbiting particles charge-to-mass ratio epsilon , for positive charges epsilon =1, epsilon =2 and epsilon =M/Q. These limits play an important role in the study of the coupled electromagnetic and gravitational interactions, and the investigation of the role of the charge in the gravitational collapse of compact objects.

Simulation of Re-Entrainment in the Annular Channel of an Electrostatic Cyclone

The behavior of charged particles in a curved electrostatic-cyclone channel model is described. The model is built using a finite-element method. The electric field is calculated for a corona discharge electrode voltage of 15 kV. The flow field is calculated for gas velocities of 1, 3, and 5 m/sec. Trajectories for particle sizes of 1, 10, 50, and 100 μm are obtained. Re-entrainment is demonstrated to exist within the annular channel.

In-Line Hologram for Plasma Diagnostics

Diagnostic sensors are demanded during plasma processes. Holograms of plasma taken with laser light without a reference beam were used to monitor behaviors of charged particles produced in nitrogen plasma as a function of electrode temperature ranging between 50 and 300℃. Holograms were characterized as a function of the pixel sum and grayscale value. Pixel sum calculated in identified grayscale ranges strongly correlated with ion density and emitted light intensity measured with a langmuir probe and optical emission spectroscopy, respectively. The performance was further evaluated with data acquired as a function of N2 and NH3 flow rates and improved correlations were observed in the new grayscale range. The confirmed correlations indicate that a hologram is a viable means to diagnose behaviors of plasma particles such as ions. Underlying principles are discussed in view of particle and charge composing vacuum and light.

Energy loss of tens keV charged particles traveling in the hot dense carbon plasma

The energy loss of charged particles, including electrons, protons, and α-particles with tens keV initial energy E0, traveling in the hot dense carbon (C) plasma for densities from 2.281 to 22.81 g/cm3 and temperatures from 400 to 1500 eV is systematically and quantitatively studied by using the dimensional continuation method. The behaviors of different charged particles are readily distinguishable from each other. Firstly, because an ion is thousands times heavier than an electron, the penetration distance of the electron is much longer than that of proton and α-particle traveling in the plasma. Secondly, most energy of electron projectile with E0 < 100 keV deposits into the electron species of C plasma, while for the cases of proton and α-particle with E0 < 100 keV, about more than half energy transfers into the ion species of C plasma. A simple decreasing law of the penetration distance as a function of the plasma density is fitted, and different behaviors of each projectile particle can be clearly found from the fitted data. We believe that with the advanced progress of the present experimental technology, the findings shown here could be confirmed in ion-stopping experiments in the near future.

Thermophoresis of charged colloidal particles in aqueous media – Effect of particle size

We investigated the particle size effect on the thermophoresis of colloidal particles in an aqueous medium via a microfluidic approach. A microfluidic device was used to directly observe and quantitatively characterize the thermophoretic behaviors of charged hydrophobic polystyrene particles within a wide diameter range from 100nm to 5μm dispersed in deionized water. Our experimental findings showed an interesting particle size effect – a sign switch of the thermodiffusion coefficient from positive to negative with increasing particle size from submicron to micron. Moreover, a linear size-dependence of the thermodiffusion coefficient for micron-sized particles was obtained. Through comparing our experimental results with Duhr–Dhont’s analytical model that includes effects of the electric double layer ionic shielding and the hydration entropy, we found that both the sign switch and the particle size linear dependence can be explained by this model. In addition, a separation of submicron particles from micron-sized particles was demonstrated experimentally via the particle size-dependent sign switch of thermophoresis.

Charged particle behavior in the growth and damping stages of ultralow frequency waves: Theory and Van Allen Probes observations

AbstractUltralow frequency (ULF) electromagnetic waves in Earth's magnetosphere can accelerate charged particles via a process called drift resonance. In the conventional drift resonance theory, a default assumption is that the wave growth rate is time independent, positive, and extremely small. However, this is not the case for ULF waves in the real magnetosphere. The ULF waves must have experienced an earlier growth stage when their energy was taken from external and/or internal sources, and as time proceeds the waves have to be damped with a negative growth rate. Therefore, a more generalized theory on particle behavior during different stages of ULF wave evolution is required. In this paper, we introduce a time‐dependent imaginary wave frequency to accommodate the growth and damping of the waves in the drift resonance theory, so that the wave‐particle interactions during the entire wave lifespan can be studied. We then predict from the generalized theory particle signatures during different stages of the wave evolution, which are consistent with observations from Van Allen Probes. The more generalized theory, therefore, provides new insights into ULF wave evolution and wave‐particle interactions in the magnetosphere.

Approximants to the Tonks-Langmuir theory for a collisionless annular plasma.

Maclaurin series approximant and Padé rational approximant are used to solve the Tonks-Langmuir theory for an annular plasma and investigate the radial transport behavior of charged particles. Coefficients of the well-known Maclaurin approximant are given in a novel form of recurrence relations which are convenient for computation and present a lower limit for the annular ratio of inner radius to outer radius (i.e., this approximant is not applicable to annular geometries with small inner radii). The newly introduced Padé approximant extrapolates the annular ratio limit determined by the Maclaurin approximant to a lower value and hence is applicable to most annular geometries. General radial profiles of the normalized plasma density and mean drift velocity of ions are given across the annulus and they are independent of the gas type and the Paschen number of the discharge. The annular modeling is applied to an argon plasma and obtains the electron temperature as a function of the Paschen number for different annular geometries.

The role of electrostatic charge in the adhesion of spherical particles onto planar surfaces in atmospheric systems

• Surface charge and humidity play strong roles in the adhesion of two surfaces. • Changes in adhesive force are greater for surfaces with higher charge densities. • The role of capillary force in surface adhesion is stronger for larger particles. • Humidity effects on the electrostatic force depend on surface hydrophobicity. The influence of electrostatic charge on the adhesive force between spherical particles and planar surfaces in atmospheric systems was studied using atomic force microscopy. Electrical bias was applied to modify the surface charge, and it was found that application of a stronger positive bias to a particle induces a stronger total adhesive force. The sensitivity of the system to changes in the bias depended on the surface charge density. For larger-size particles, the contribution of the electrostatic force decreased, and the capillary force became the major contributor to the total adhesive force. The influence of water adsorption on the total adhesive force and, specifically, on the contribution of the electrostatic force depended on the hydrophobicity of interacting surfaces. For a hydrophilic surface, water adsorption either attenuated the surface charge or screened the effect of surface potential. An excessive amount of adsorbed water provided a path to surface charge leakage, which might cancel out the electrostatic force, leading to a reduction in the adhesive force. Theoretically calculated forces were comparable with measured adhesive forces except for mica which has a highly localized surface potential. The results of this study provide information on the behavior of charged colloidal particles in atmospheric systems.

Particle Segregation at Contact Lines of Evaporating Colloidal Drops: Influence of the Substrate Wettability and Particle Charge-Mass Ratio.

Segregation of particles during capillary/convective self-assembly is interesting for self-stratification in colloidal deposits. In evaporating drops containing colloidal particles, the wettability properties of substrate and the sedimentation of particles can affect their accumulation at contact lines. In this work we studied the size segregation and discrimination of charged particles with different densities. We performed in-plane particle counting at evaporating triple lines by using fluorescence confocal microscopy. We studied separately substrates with very different wettability properties and particles with different charge-mass ratios at low ionic strength. We used binary colloidal suspensions to compare simultaneously the deposition of two different particles. The particle deposition rate strongly depends on the receding contact angle of the substrate. We further observed a singular behavior of charged polystyrene particles in binary mixtures under "salt-free" conditions explained by the "colloidal Brazil nut" effect.

Transport Characteristics of Secondary Charged Particles Resulting from High Energy Neutron in Silicon

Silicon is always the dominant semiconductor material of the modern semiconductor industry. This is as silicon can retain its semiconductor characteristics even at a higher temperature while the other semiconductor materials can't. However, when a silicon device is exposed to a flux of energetic radiation or particles, the effects from the radiation and the induced secondary particles can cause several degradation of the device performance. For the purpose of investigate the resultant effects from the bombardment of neutrons and the behavior of secondary charged particles in the silicon model, the neutron displacement defect was measured in situ and then followed by the simulation based on Monte Carlo method. The bombardment of neutron in the silicon model produce at least three secondary particles, which are alpha ˸α˹ particles, proton (p) particles and silicon recoil atoms, through the reactions of ˸̾˼α˹˼˰˸̾˼̀˹˰and neutron scattering respectively. The kinetic energy and range of these charged particles are different among themselves, and thus the probability of hitting and degradation effects in the silicon materials are varies. The simulation calculation showed that ˸̾˼α˹˰reaction induced soft error cross section of about 8.7 x 10-14 cm2 and for recoil atoms, it is about 2.9 x 10-15 cm2. There was no error of the silicon device configuration induced by proton particles until 1010 n/cm2.neutron fluence. It can be concluded that the largest portion of error in the silicon model is induced by the secondary alpha ˸α˹ particles.

Analysis on the effects of optics thermal deformation on the ion thruster operation

Optics thermal deformation is an important factor that impacts the performance and lifetime of ion thrusters. Although some theoretical reflearch concerned with this problem was reported, its mechanism has not been fully understood. In this study, numerical investigations are performed to explain the effect of thermal deformation on the performance and lifetime of ion thrusters. The transient behavior of charged particles is calculated using a particle-in-cell simulation, while the momentum transfer collision and the charge exchange collision are calculated by means of the Monte Carlo method. Electron backstreaming restriction, perveance restriction, ions through rate, and divergence angle losses are compared and analyzed for optics deformed and undeformed. And the influence of these factors on thruster’s performance and lifetime is discussed. Results show that the ion through rate of the screen grid increases when optics begin deformed, and the thrust is slightly higher than the theoretical values predicted; the perveance threshold of the accelerator grid increases with optics haveing thermal deformation, while the crossover limit threshold is little changed, namely the thruster can be operated in conditions of a larger beam current; the electron backstreaming restriction threshold is significantly lower under a high beam current condition with optics deformed, which means that a lower accelerating gate bias is necessary to ensure thruster work. For the less obvious change of acceleratng grid current when the beam is focused, there is no moreflerosion and change of lifetime. Results provide a reflerence for the optimization design of optics and evaluation of thruster performance and lifetime.

Numerical simulation of temperature effect on particles behavior via electrostatic precipitators

A comprehensive numerical model is developed and applied to study the effect of temperature on the behavior of charged particles in a wire-plate electrostatic precipitator (ESP). In this model, the complex interactions in different temperature conditions between the electric field, fluid dynamics and the particulate flow are taken into account. The finite volume method is used to solve the electric field and Euler-Lagrange model is used to describe particle-laden flows. From the present simulation, the effect of temperature on electro-hydrodynamics (EHD) characteristics and particle charging and tracing are investigated. The numerical results show that high temperature thickens the boundary layer along the plate and strengthens turbulence. The corona onset electric field intensity and mean field intensity both decrease as temperature increases. Considering space charging and diffusion charging, high temperature weakens the particle charging. With the increase of temperature, the Coulomb, Saffman lift and Brownian forces go down while the drag force goes up. The Coulomb force and the drag force are the key forces acting on particles in the ESP for 10 μm particle. The variation of the two forces along with particles trajectories indicates that high temperature enhances the interaction between particles and fluid. Finally, it becomes more difficult to collect particles when temperature increases.

Dynamic Characteristics of SF6-N2-CO2 Gas Mixtures in DC Discharge Process

Dynamic characteristics of discharge particles are described within the framework of a two-dimensional photoionization-hydrodynamic numerical model for the discharge process of SF6-N2-CO2 gas mixtures at atmospheric pressure, under a uniform DC applied field. The finite difference—flux corrected transport (FD-FCT) algorithm is used in the numerical implementation for improving the accuracy and efficiency. Then the tempo-spatial distributions of the gap—space electric field and electron velocity are calculated from the microscopic mechanism, and the dynamic behaviors of charged particles are obtained in detail. Meanwhile, the tempo—spatial critical point of the avalanche-to-streamer in this model is discovered, and several microscopic parameters are also investigated. The results showed that the entire gap discharge process can be divided into two phases of avalanche and streamer according to Raether-Meek criterion; the electron density within the discharge channel is lower compared to that of positive and negative ions; space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster; photoionization provides seed electrons for a secondary electron avalanche, promoting the formation and development speed of the streamer.

Area-selective deposition of charged particles derived from colloidal aerosol droplets on a surface with different hydrophilic levels

The effect of chemical treatment of a metallic substrate on the deposition behavior of charged aerosol particles derived from spraying droplets was investigated. A single substrate with areas having different hydrophilic levels was prepared as target surface. The treated (i.e., higher hydrophilic level) area, measured using a surface potential meter, showed a higher negative potential. A numerical simulation predicted that positively charged aerosol particles tended to approach and were subsequently immobilized on the high hydrophilic area. The area with higher hydrophilicity could collect particles with higher number concentration (density) than the other areas. The relationships were demonstrated in (i) the electrostatic surface potential, (ii) the hydrophilicity of surface, and (iii) the enhancement of adhesive force between the deposited particles and the surface.

Electro-optical properties of porous zeolite cathode in the gas discharge electronic devices for plasma light source applications

The stable dc air cold plasma is investigated experimentally functions of pressure p (8–760 Torr), electrode gaps d (50–250 µm), and diameters (9–22 mm) of the cathode areas in the gas discharge electronic devices (GDED) with nanoporous zeolite cathode (ZC). It is found that the current density and plasma emission (PE) intensity increase if the amplitude of the applied voltage reaches given threshold. Moreover, uniform PE inside the ZCs develops from the surface and can be generated in air up to atmospheric pressure (AP). The effect of various diameter of the ZC area on the gas breakdown is also considered. It is shown that breakdown voltage UB is reduced significantly for the larger diameters of the ZC area. Because of the very small d in our GDED, the behavior of charged particles in the electric field is described with the dc Townsend breakdown theory, depending upon the pressure range.

Understanding the behavior of charged particles in the magnetotail

When the Sun spews charged particles toward Earth, they can enter the magnetosphere and become energized as they move closer to the Earth's surface. These energetic particles can induce the bright colors of auroras, disrupt navigational satellites, and even distort terrestrial telecommunications.

Extensions to Study Electrochemical Interfaces - A Contribution to the Theory of Ions

In the present study an alternative model allows the extension of the Debye-Huckel Theory (DHT) considering time dependence explicitly. From the Electro-Quasistatic approach (EQS) done in earlier studies time dependent potentials are suitable to describe several phenomena especially conducting media as well as the behaviour of charged particles in arbitrary solutions acting as electrolytes. This leads to a new formulation of the meaning of the nonlinear Poisson-Boltzmann Equation (PBE). If a concentration and/or flux gradient of particles is considered the original structure of the mPBE will be modified leading to a new nonlinear partial differential equation (nPDE) of the third order. It is shown how one can derive classes of solutions for the potential function analytically by application of an algebraic method. The benefit of the mathematical tools used here is the fact that closed-form solutions can be calculated without any numerical approximations.

Numerical simulation of electric double layer in contact with dielectric barrier discharge: Effects of ion transport parameters in liquid

The spatiotemporal distribution of charged particles has been investigated through numerical simulation of charged particle behavior in gas and liquid phases in the dielectric barrier discharge of Ar gas in contact with a liquid. In the case of a liquid with a low ion concentration such as de-ionized water, the amount of liquid-phase ions generated by electron or ion irradiation from gas-phase plasma is higher by approximately one order of magnitude than that in the pure electric double layer formed only with the potential difference between the top and bottom of the liquid. When the molecular weight of the ions is larger, the residence time of the ions at the liquid surface becomes longer. If the molecular weight of positive and negative ions is different, heavier ions become dominant at the liquid surface. These characteristics are pronounced by employing a higher frequency voltage, which implies the possibility of preferential reactions at the plasma-liquid interface.

Influence of Ionization Degrees on the Evolutions of Charged Particles in Atmospheric Plasma at Low Altitude

A zero-dimensional model which includes 56 species of reactants and 427 reactions is used to study the behavior of charged particles in atmospheric plasmas with different ionization degrees at low altitude (near 0 km). The constant coefficient nonlinear equations are solved by using the Quasi-steady-state approximation method. The electron lifetimes are obtained for afterglow plasma with different initial values, and the temporal evolutions of the main charged species are presented, which are dominant in reaction processes. The results show that the electron number density decays quickly. The lifetimes of electrons are shortened by about two orders with increasing ionization degree. Electrons then attach to neutral particles and produce negative ions. When the initial electron densities are in the range of 1010 ∼ 1014 cm−3, the negative ions have sufficiently high densities and long lifetimes for air purification, disinfection and sterilization. Electrons, O2−, O4−, CO4− and CO3− are the dominant negative species when the initial electron density ne0 ≤ 1013 cm−3, and only electrons and CO3− are left when ne0 ≥ 1015 cm−3 · N+2, N+4 and O+2 are dominant in the positive charges for any ionization degree. Other positive species, such as O+4, N+3, NO+, NO+2, Ar+2 and H3O+·H2O, are dominant only for a certain ionization degree and in a certain period.

Web site lets solar scientists inform and inspire students

Where on the Web can a middle school girl ask a female solar scientist about solar storms, the course and behavior of charged solar particles, and the origin of the Sun's dynamo—and also find out what the scientist was like as a child, whether the scientist has tattoos or enjoys snowboarding, what she likes and dislikes about her career, and how she balances her energy for work and family life? These kinds of exchanges happen at Solar Week (http://www.solarweek.org; see Figure 1). Established in 2000, Solar Week is an online resource for middle and lower high school students about the science of the Sun, sponsored by the Center for Science Education at the Space Sciences Laboratory (CSE@SSL) at the University of California, Berkeley (UC Berkeley). The Web site's goals are to educate students about the Sun and solar physics and to encourage future careers in science—especially for girls. One way is by giving solar scientists the chance to be relatable role models, to answer students' questions, and to share their experiences in an online forum.