Recombination Of Charged Particles Research Articles

Planetary nurseries: vortices formed at smooth viscosity transition

ABSTRACT Excitation of Rossby wave instability and development of a large-scale vortex at the outer dead zone edge of protoplanetary discs is one of the leading theories that explains horseshoe-like brightness distribution in transition discs. Formation of such vortices requires a relatively sharp viscosity transition. Detailed modelling, however, indicates that viscosity transitions at the outer edge of the dead zone is relatively smooth. In this study, we present 2D global, non-isothermal, gas–dust coupled hydrodynamic simulations to investigate the possibility of vortex excitation at smooth viscosity transitions. Our models are based on a recently postulated scenario, wherein the recombination of charged particles on the surface of dust grains results in reduced ionization fraction and, in turn, the turbulence due to magnetorotational instability. Thus, the α-parameter for the disc viscosity depends on the local dust-to-gas mass ratio. We found that the smooth viscosity transitions at the outer edge of the dead zone can become Rossby unstable and form vortices. A single large-scale vortex develops if the dust content of the disc is well coupled to the gas; however, multiple small-scale vortices ensue for the case of less coupled dust. As both type of vortices are trapped at the dead zone outer edge, they provide sufficient time for dust growth. The solid content collected by the vortices can exceed several hundred Earth masses, while the dust-to-gas density ratio within often exceeds unity. Thus, such vortices function as planetary nurseries within the disc, providing ideal sites for formation of planetesimals and eventually planetary systems.

Simulation of High-Voltage Ion Diode with Wire Cathode at Atmospheric Pressure of Nitrogen

Physic-topological simulation of a high-voltage coaxial ion diode with a wire metal cathode at atmospheric nitrogen pressure in the hydrodynamic drift-diffusion approximation is performed. The reactions of nitrogen ionization by electrons, attachment of electrons to nitrogen molecules with the formation of negative ions, recombination of charged particles with opposite signs of charge, secondary ion-electron emission of the cathode were taken into account. The distribution of potential and density (concentration) of charged particles in the interelectrode gap, the density of ionic and electron currents at the electrodes were calculated within the self-consistent problem with the following parameters: diameter of wire metal cathode 0.01-0.16 mm, diameter of tubular anode 6 or 20 cm, voltage 20-40 kV, gas temperature 300 or 600K. The influence of geometry, voltage and gas temperature on the discharge parameters has been determined. The obtained calculated data on the discharge current are consistent with the experiment. It is shown that two zones are formed in the discharge between the electrode gap – one is with a width of about 1 mm with a strong and rapidly changing electric field near the cathode and the second long zone with the drift of charged particles towards the anode with a smaller but constant field strength. This is a characteristic feature of negative corona discharges. In the cathode zone there is an intensive ionization of nitrogen with the generation of positive ions and electrons. In the second zone, the density of positive ions decreases sharply due to recombination and weak ionization. The reaction of attachment of electrons to nitrogen molecules begins almost near the cathode surface and continues throughout the cathode zone, in the drift zone the concentration of negative ions gradually decreases. Moreover, the role of electronic conductivity is greatly reduced as we approach the anode. Due to the low mobility of negative ions and, accordingly, the high electrical resistance of the drift zone, the voltage drop on this space part represents a significant portion of the discharge voltage (~1.5 kV on the cathode zone and 18.5 kV on the drift space, at the total voltage of 20 kV). The fact that the highest concentration of positive ions is formed near the cathode, and negative – along the entire interelectrode gap, it can be used, respectively, in the processes of ionic nitriding of wire cathode metal materials and for processing materials and biological substances (bacteria, viruses, fungi), sensitive to negative ions, at the location of the carriers of these substances near the anode. To implement the latter, it is advisable to modify the design of the external anode for efficient extraction of nitrogen ions into the environment. It is also advisable to continue research in the direction of increasing the energy efficiency of ion generation by determining the method of the maximum allowable reduction of the voltage drop on the space of drift of charged particles.

Variations in Ionospheric Parameters during the Formation of a Polarization Jet

The calculation results and experimental data on the formation and development of a polarization jet in subauroral latitudes are compared. It is shown that the alternation of vertical and horizontal components of the ionospheric plasma–drift velocity leads to different variations in the main parameters of the F2 layer. An increase in the critical frequency of the F2 layer is revealed in certain cases before the formation of a polarization jet. This behavior of the F2 layer may be caused by a decrease in the rate of the recombination of charged particles due to an increase in the altitude of the layer maximum, which results in particle accumulation at these altitudes. An increase in the critical frequency of the F2 layer can be an additional indicator of the development of a polarization jet over an observation station.

Evolution mechanism of ultraviolet and electrical phenomena induced by protrusion discharge in GIS

Abstract To improve the sensitive and reliability of condition monitoring in gas insulated switchgear (GIS), discharge perception system applied to GIS insulators protrusion discharge based on single ultraviolet photon is built. Step method is used to inspire the discharges of different severity, based on which, the regression relationship of ultraviolet (UV) signal and electrical signal are studied, and the perception mechanism of UV signal in different severity of discharges is analyzed. The study indicates that, the development of protrusion discharge in GIS can be divided into four stages, and there is no positive correlation between the number of ultraviolet photons caused by discharge radiation and insulation deterioration level, but related to the diffusion, migration and recombination of charged particles, then UV optical method for quantitative monitoring of discharge in each stage is provided, which provide a new method for quantitative measurement of GIS insulator discharge.

Ionization yield measurement using metal electrodes with a static electric field in ambient air

The amount of ionization produced in a laser-matter interaction provides critical information in studying strong field physics and attosecond science. The amount of ionization can be accurately measured in vacuum using a photoelectron/ion spectrometer by counting the number of charged particles. However, an ionization yield measurement in ambient air requires the considerations of post processes such as drift and recombination of charged particles, which may add an unwanted nonlinearity to the measurement. Here we investigate the kinetics of the charged particles after optical field ionization in ambient air under a static bias field. A simple kinetic model is used in which coupled rate equations are numerically solved. The kinetic model explains the recombination loss of the charged particles observed in ionization yield measurements. A condition for the static bias field is derived for an accurate ionization yield measurement.

The Omori Law: The 150-Year Birthday Jubilee of Fusakichi Omori

The outstanding Japanese seismologist Fusakichi Omori was born 150 years ago, on October 30, 1868. He discovered his first law in earthquake physics that now bears his name when he was 26. Essentially, Omori’s law tells us that the decay of aftershock rate follows a hyperbolic law. This paper provides a brief account of how that discovery was made. Attention is focused on two approaches in an attempt at generalizing Omori’s law. One of these has been known for many years and to many researchers. It is based on the concept that the aftershock rate depends on time as a power law. The other approach was discovered recently by using a formal analogy between the decay of aftershock activity in the lithosphere and the recombination of charged particles in the ionosphere. A differential equation for aftershocks has been proposed. The general solution to the equation retains the hyperbolic structure of Omori’s law, but also enables a flexible simulation of rock instability at the earthquake source that is “cooling down” after the main shock. The general solution also incorporates the non-monotonic function that describes the time-dependent decay of aftershock rate, which occurs when an earthquake source is acted on by endogenous and exogenous triggers. The aftershock equation is used to formulate the inverse problem in earthquake source physics.

Structure formation of atmospheric pressure discharge

In this paper it is shown, by analyzing the results of experimental studies, that the outer boundary of the atmospheric pressure discharge pinch is determined by the condition of equality of plasma flows based on the thermal and electric field energy. In most cases, the number of charged particles coming from near-electrode zones is sufficient to compensate for losses in the discharge bulk. At large currents and enhanced heating, plasma is in the diffusion mode of losses, with recombination of charged particles at the pinch boundary.

Plasma deionization features in gas discharge device

Results of plasma excess conductivity investigations of gas discharge device under conditions of plasma decay have been presented. This case involves the need of taking into account the recombination of charged particles both on the device electrodes and in its volume. It was established that the volume recombination of charged particles at the stage of plasma excess conductivity materially affects the duration of plasma excess conductivity and modifies the pattern of its decay.

MODELING OF DIELECTRIC BARRIER DISCHARGE ACTUATORS AT VARIOUS GAS PRESSURES AND ESTIMATION OF THEIR INFLUENCE ON SHEAR FLOWS

Numerical research of the gas pressure influence on a conduction current in a dielectric barrier discharge (DBD), the average volumetric force acting on gas from the discharge, and the power of heat release in the discharge is carried out for aerodynamic applications. The calculations are implemented with use of the earlier proposed boundary problem about the DBD generation near a flat dielectric plate. This problem statement takes into account such factors as the finite thickness of the exposed electrode, finite rates of desorption and the recombination of charged particles on the dielectric surface, and the electric field induced by a superficial charge. Represented are the results of numerical modeling of the incompressible Poiseuille and Couette flows under the time-averaged transverse force impact of DBD actuators placed along the main flow. The possibility of significant influence of an additional transfer of the main flow momentum due to the cross-flow (induced by actuators) on the structure and the characteristics of the considered shear flows is demonstrated.

Characteristic of a Spherical Probe in a Stationary Gas during Ionization of Alkaline Metals

This paper considers a spherical Langmuir probe in a stationary weakly ionized collisional plasma consisting of neutral molecules, positive ions, and the electrons resulting from ionization of additive atoms. The effect of the ionization of the additive and recombination of charged particles on the current-voltage characteristics of the probe was studied numerically under the assumption that the plasma is isothermal. Probe characteristics are presented in the form of plots over a wide range of the ratio of the Debye radius to the radius of the probe for various types of particle-surface interactions.

Evaluation of the rate constants of dissociative and ternary recombination reactions of argon ions on the basis of the results of ballistic experiments

AbstractExperimental data on the change in the electron density in the wake of a ballistic object traveling at velocities V ∞=3.4–4.9 km/s in argon at pressures p ∞=30–100 Torr are processed and analyzed. A reaction scheme is proposed which takes into account the recombination of charged particles, processes of ionic conversion, and the excited states of the atom. The solution of the equations of a nonequilibrium boundary layer for flow in the wake is used to formulate the inverse problem of determining the rate constants for dissociative recombination Ar 2 + +e→Ar+Ar and ternary recombination Ar++e+Ar→Ar+Ar. The “nearest-neighbor” approximation is used to obtain theoretically an expression for the ternary recombination coefficient as a function of temperature and pressure. Numerous solutions of inverse problems and a comparison with experiments demonstrates the validity of the expression obtained for the ternary recombination coefficient. It is shown that this expression is valid for moderate pressures and complements the Pitaevskii result for low pressures and the Langevin result for high pressures.

Recombination processes in disordered media with external field

A recombination of charged particles in disordered media in the presence of a strong external field, which causes the non-classical drift of particles, is considered. It is shown that the particles spend most of the time in randomly distributed regimes, impenetrable for diffusing particles, stretched along the field. Positively and negatively charged particles are hidden in different cavities and this causes a reduction of the recombination rate.

The Effects of Gas Composition and Pressure on RF Plasma Sintering of MgO

ABSTRACTRapid densification of MgO in an rf plasma without sintering aids is demonstrated. The sintered densities of MgO are sensitive to the plasma composition and gas pressure. In general, specimens are sintered to higher densities in Ar/O2 and Ar/H2O plasmas than in pure Ar plasmas. This may be explained by the effects of plasma enthalpy and surface recombination of charged particles and of atomic species. Analyses show that the evolution of the microstructures of the sintered specimens remains similar, regardless of the plasma conditions. No substantial grain growth is observed.

Gas-discharge plasma initiated in air by a radiation pulse

Formation of a nonequilibriuin gas-discharge plasma in air under the action of radiation at a wavelength of 10.6 μ with a duration of 10−6 sec is considered. It is shown that the air discharge occurs under nonequilibrium conditions by formation of an autoionization complex with subsequent oscillatory excitation of molecules. The molecular distribution function over oscillatory degrees of freedom is found in the diffusion approximation. The electron temperature and concentration in the breakdown plasma are calculated with consideration of multistep ionization of molecules and dissociative recombination of charged particles. Results are compared with experiment.

Der aerosol-ionisationsdetektor —ein neuartiger detektor für die gas-chromatographie

The aerosol ionization detector —a new detector for gas chromatography A new, selective and sensitive ionisation detector for gas chromatography is described. The mode of operation is based on the recombination of charged particles in presence of aerosols. A general kinetic model of the reactions is developed analogous to the performances of Wentworth and coworkers for electron capture detectors. An expression for the functional relationship between response of the aerosol ionisation detector and concentration has been derived. The response was estimated to be linear over a range of about 5 · 10 2. Lower detection limits for a number of substances (halogenated hydrocarbons, NO 2, Cl 2, HCl, HF, NH 3) are given.

Measurement of the rate constants for recombination of charged particles in flames

Measurement of the rate constants for recombination of charged particles in flames

Intensity of recombination of charged particles on some borides of refractory metals in a weakly ionized hydrogen plasma

Intensity of recombination of charged particles on some borides of refractory metals in a weakly ionized hydrogen plasma

501. Elastic interactions and recombination of charged particles in potassium discharge plasma: D Ya Dudko et al, Zh Tekh Fiz, 41 (6), 1971, 1164–1169 ( in Russian)

501. Elastic interactions and recombination of charged particles in potassium discharge plasma: D Ya Dudko et al, Zh Tekh Fiz, 41 (6), 1971, 1164–1169 ( in Russian)

Rankine–Hugoniot-Berechnungen für Nichtgleichgewichts-Plasmen

In optically thin plasmas produced by strong shock waves the SAHA equation is no longer valid to describe the conditions directly behind the shock wave. Photoionisation may be neglected in the balance of production and recombination of charged particles. For the case of nonequilibrium a calculation assuming various ratios of electron to ion temperature (ϑ= TeT) shows that the shock wave parameters are described sufficiently well by the Korona-equation. Temperature, density ratio and electron density are increased with increasing ϑ whereas the pressure ratio is independent of the kind of equilibrium and ϑ.