Action Of Ponderomotive Force Research Articles

Experimental study of cavitation development in liquid in pulsed non-uniform electric field under the action of ponderomotive forces

In this paper, the Rayleigh scattering method is used to study the formation of cavitation in water in a pulsed inhomogeneous electric field when a nanosecond high voltage pulse is applied to a needlelike electrode. The observational results confirm the theoretical picture of cavitation development under the action of electrostrictive ponderomotive forces. The values of the negative pressure, the average size of the cavitation nanovoids, and their concentration were obtained from these measurements, which are in agreement with theoretical estimates.

FEATURES OF THE FILM FLOW OF A LIQUID OVER A VERTICAL SURFACE IN A TRANSVERSE MAGNETIC FIELD

One of the actual problems of magnetohydrodynamics is the problem of the flow of electrically conductive liquids in thin liquid layers in the presence of a transverse magnetic field. Unfortunately, studies of these problems have not been sufficient so far. The influence of a transverse magnetic field can affect a number of factors: the change in the viscosity of the flow due to the magnetic field on the physico-chemical characteristics of the medium; manifestation of the effect of flow deceleration, which can have a significant effect on the hydrodynamic characteristics of the film flow in the processes of heat and mass transfer. In this regard, in this work was made an attempt to consider the influence of a constant magnetic field on the formation of a thin liquid layer on a vertical surface under the action of ponderomotive forces. As known, ponderomotive forces in the case under consideration can lead to a number of effects associated with a change in viscosity and flow deceleration. To a greater extent, this can manifest itself in thin liquid layers, depending on the ratio of gravitational forces, inertia forces and forces of a magnetic nature. An analysis of the influence of this phenomenon in the considered case of thin liquid layers, as shown in the work, significantly affects the length of the hydrodynamic initial section, the thickness of the liquid layer, and the damping of wave motion in the zone of stabilized flow. Recommendations for calculating these characteristics are presented in this article, in which much attention is paid to the definition of the liquid layer, depending on the ratio between the forces of inertia and the forces of a magnetic nature. An expression was also obtained for determining the distribution of velocities in the zone of a stabilized film flow in a transverse magnetic field. Thus, by comparing the expression for determining the distribution of velocities in a film without the influence of a magnetic field with the expression in the presence of a magnetic field, one can estimate the effect of ponderomotive forces on the flow of a liquid film.

Analysis of the forces acting from the side of the magneto-abrasive tool on parts being machined during magneto-abrasive machining in conditions of the annular bath with large working gaps

Background. For effective magneto-abrasive machining (MAM) of complex-shaped parts, comprehensive information is needed on the processes that occur when the magneto-abrasive tool (MAT) contacts with the surfaces being machined. Effective magneto-abrasive machining occurs in the presence of sufficient values of the normal and tangential components of the interaction forces between the MAT and the machined surfaces and the powder mixing during machining. Previously carried out analytical studies of dynamic parameters did not take into account the real conditions of the interaction of grains and their groups with machined surfaces. Objective. Complex analysis of the processes that occur during magneto-abrasive machining of parts made from different types of materials, based on the results of the study of the friction forces between the magneto-abrasive tool and the surface being machined and the drag forces during the movement of parts in the working zone of the machine. Methods. To achieve the set goal, the forces acting on the samples during their magneto-abrasive machining were measured with subsequent analytical analysis. Results. The complex analysis of the processes occurring during MAM in conditions of the annular working zone with large working gaps of parts made of various materials was carried out based on the results of the study of the friction and drag forces that occur when the part moves relative to the magneto-abrasive tool. Conclusions. It has been determined that when machining non-magnetic samples at the constant value of the magnetic field in the working zone, the specific drag forces are practically independent of the shape of the used powder. According to the analytical representation of the friction and drag forces, their ratio between their specific values was calculated. By the nature of the change in this ratio, it was found that it decreases with an increase in the velocity of samples movement along the working zone, and with an increase in the angular velocity of rotation of the samples around its axis, this value increases in the studied velocity range. It has been determined that at the velocity of movement along the working zone of 2.2 m/s, there is a slight increase in the ratio between the specific forces of friction and drag, which is associated with the action of ponderomotive forces that appear near the surface of the machined parts and lead to an increase in local magnetic forces in these zones.

Графен/нанотрубные квази-1D-структуры в сильных электрических полях

In silico studies of the behavior of graphene/nanotube quasi-one-dimensional (1D) structures with covalent bonded graphene and nanotube in strong electric fields with a strength of 10^7–10^8 V/cm have been carried out. The atomic structure, band structure, electron transmission function, electrical conductivity, and regularity of the electronic structure changes in strong fields have been studied. It is found that the electron transmission function of quasi-1D structures has an intensity peak at the Fermi level in contrast to nanotubes and graphene. As a result of quantum molecular dynamics modeling, the regularities of deformation of the atomic framework and its destruction under the action of ponderomotive force have been established. We have found a critical value of the strength at which the electric field detaches the graphene from the tube. It is ~ 2 ∙ 10^8 V/cm. A further increase leads to the detachment of graphene from the tube with its simultaneous destruction.

Graphene/nanotube quasi-1D structures in strong electric fields

In silico studies of the behavior of graphene/nanotube quasi-one-dimensional (1D) structures with covalent bonded graphene and nanotube in strong electric fields with a strength of 10^7-108 V/cm have been carried out. The atomic structure, band structure, electron transmission function, electrical conductivity, and regularity of the electronic structure changes in strong fields have been studied. It is found that the electron transmission function of quasi-1D structures has an intensity peak at the Fermi level in contrast to nanotubes and graphene. As a result of quantum molecular dynamics modeling, the regularities of deformation of the atomic framework and its destruction under the action of ponderomotive force have been established. We have found a critical value of the strength at which the electric field detaches the graphene from the tube. It is ~2·108 V/cm. A further increase leads to the detachment of graphene from the tube with its simultaneous destruction. Keywords: graphene/nanotube structures, electrical conductivity, ponderomotive force, strong electric fields.

Propagation of Waves and Particles Through Porous Structures (I)

The processes of the propagation of quantum and classical charged particles through porous films are studied. The propagation of quantum particles is analyzed by numerically calculating the Schrodinger equation. The polarization force acting on the charge is calculated within the framework of classical electrodynamics. The possibility of pore formation in the films is analyzed in the problem of the propagation of ions with large charges through ultrathin carbon films. Mathematical modeling of the film accompanied by elucidation of the most important polarization properties is carried out to understand the process more clearly. The calculations show the possibility of film perforation because of the action of ponderomotive forces generated by the strong polarization field of the wave packet of the passing ion.

Formation of Negative Ions on the Surface of a Solid Body and Their Influence on the Thermoelectronic and Autoelectronic Emission of Free Electrons

On the surface of the main crystal, positive ions interact with a negative cloud of free electrons and turn into neutral atoms. Neutral atoms having affinity to the electron other than zero additionally capture the electron and become negative ions. It is shown that under the action of ponderomotive forces the crystal surface is noticeably deformed, and it is experimentally confirmed. Besides, it is experimentally proved that three-atomic molecules possess allotropy in distribution of the built-in electric moments. The analysis of different physical models, which describe the thermo-and auto-electric emission of free electrons, is carried out and their inconsistency is shown. Thermal electron and field emission arise due to the temperature population of negative ions on the crystal surface and cluster vibrations in the near-surface layer. Field emission is thermal electron emission from negative ions and the Fermi level, which is transformed due to the action of the external electric field on the work of the surface by ponderomotive forces.

О пондеромоторных силах, действующих на погруженное в слабопроводящую жидкость тело в электрическом поле

The possible model of the mechanism of action of ponderomotive forces acting on immersed in the low conductive liquid body in an electric field, based on formal analogies between the equations for field strength in an electrostatic field and in a conducting medium under the conditions of flow of direct current. Experimental results are presented, from which it follows that this model inadequately describes the real mechanism of action of ponderomotive forces in weakly conducting liquid.

Spreading of melts over solid surfaces under the action of electric and magnetic fields

The interaction of electric and magnetic fields with melted metals increases the area of spreading of the melt over the surfaces of the conducting bodies and the melt’s penetration ability into capillary slits in the connections due to the action of ponderomotive forces. This facilitates the increasing of the mechanical durability of the soldered connections.

Angular distributions of ions emitted from laser plasma produced at various irradiation angles and laser intensities

AbstractAngular distributions of currents and velocities (energies) of ions produced at various target irradiation angles and laser intensities ranged from 1010 W/cm2 to 1017 W/cm2 were analyzed. It was confirmed that for low laser intensities the ion current distributions are always peaked along the target normal. However, at laser intensities comparable to or higher than 1014 W/cm2, the preferred direction of ion emission strongly depends on the irradiation geometry (laser focus setting, the irradiation angle), and can be off the target normal. This is very likely caused by the non-linear interaction of the laser beam with produced plasma, in particular, by the action of ponderomotive forces and the laser beam self-focusing.

Erratum to “Ion Confinement in Electron Cyclotron Resonance Ion Sources (ECRIS): Importance of Nonlinear Plasma–Wave Interaction”

In electron cyclotron resonance ion sources (ECRIS), ions are produced in a highly ionized microwave heated plasma contained in a minimum-B magnetic trap. Recent experiments have revealed that the absorption of electromagnetic wave energy is accompanied by a weak ion sound turbulence, a signature of a decay instability of the electromagnetic plasma wave excited by the admitted microwave. Ions are heated by the ion sound waves more effectively than by electron ion collisions. In case of gas mixtures (gas-mixing), it is possible to heat preferentially the lighter species under appropriate conditions. As confinement of ions is best at low ion temperatures, selective ion heating enhances losses of the preferentially heated ion component, reducing at the same time losses of the less effectively heated ions. Experimental results are compared with a theory of the sketched processes. We further (qualitatively) discuss open questions like plasma transport in highly ionized multi-component plasma contained by conducting walls, direct influence of the weak ion sound turbulence on plasma transport, and the action of ponderomotive forces in the so-called resonance zones.

Ion confinement in electron cyclotron resonance ion sources (ECRIS): importance of nonlinear plasma-wave interaction

In electron cyclotron resonance ion sources (ECRIS), ions are produced in a highly ionized microwave heated plasma contained in a minimum-B magnetic trap. Recent experiments have revealed that the absorption of electromagnetic wave energy is accompanied by a weak ion sound turbulence, a signature of a decay instability of the electromagnetic plasma wave excited by the admitted microwave. Ions are heated by the ion sound waves more effectively than by electron ion collisions. In case of gas mixtures ("gas-mixing"), it is possible to heat preferentially the lighter species under appropriate conditions. As confinement of ions is best at low ion temperatures, selective ion heating enhances losses of the preferentially heated ion component, reducing at the same time losses of the less effectively heated ions. Experimental results are compared with a theory of the sketched processes. We further (qualitatively) discuss open questions like plasma transport in highly ionized multi-component plasma contained by conducting walls, direct influence of the weak ion sound turbulence on plasma transport, and the action of ponderomotive forces in the so-called resonance zones.

Effect of secondary electron emission on surface wave propagation

This study aims to contribute to the analysis of the mechanisms of surface-wave-energy absorption. The discussion is based on a consideration of emissive processes from dielectric surface, which is in contact with collisional nonisothermal plasma, and on an analysis of secondary electron motion in the wave-fields. Through electron acceleration due to the action of ponderomotive force, the secondary emission affects the wave behavior. The conditions of the existence of secondary-emission-induced absorption of the wave are analyzed and its role in maintenance of wave-produced gas discharges, as one of its applications, is discussed as well.

Ponderomotive nongradient force acting on a relativistic particle crossing an inhomogeneous electromagnetic wave

The ponderomotive force acting on a relativistic charged particle crossing an inhomogeneous electromagnetic wave is investigated numerically and analytically. The initial velocity of the particle is perpendicular to the electric field vector of the wave and to the direction of its propagation. The wave has zero gradient in the direction of propagation and is inhomogeneous in both transverse directions. It is shown that the ponderomotive force acting on the particle is parallel to the wave vector. The magnitude of the force is determined not only by the extent of wave inhomogeneity in the direction of the translational motion of particle, but also by its inhomogeneity in the transverse direction. It is found that the trajectory of a particle is determined by the action of ponderomotive forces as well as by its drift in a nonuniform field.

Ponderomotive impacts of ion cyclotron waves on the ions in the equatorial zone of the magnetosphere

The ponderomotive influence of ion cyclotron waves on the field-aligned distribution and motion of ions in the equatorial zone of the magnetosphere is examined. The hydrodynamic, quasi-hydrodynamic and “test-particle” approaches are used for the study of ponderomotive wave-particle interaction. Particular attention has been given to the challenging questions encountered in applying the general theory to the magnetospheric physics. The closed system of quasi-linear equations describing the ponderomotive effects is derived. Analytical investigation of the basic equations has demonstrated the diverse manifestations of the ponderomotive impact of ion cyclotron waves on the ion population in the magnetosphere. It is found that the redistribution of ion density under the action of ponderomotive force with increase in the wave amplitude follows the pattern of phase transition of the second kind. The density distribution changes qualitatively as the point in plane of the governing parameters of system crosses a demarcation line. It has been found that the magnetic equator is an attractor for heavy ion. The period of the finite (oscillatory) motion of a heavy ion, which is trapped in the potential trough in the vicinity of magnetic equator, depends on the wave frequency, wave amplitude, together with the energy of motion. In addition, the diffusion equilibrium of ions in a multicomponent plasma is considered, and the ponderomotive separation of ions in a binary mixture is demonstrated. It is shown that the heavy ions collect near the magnetic equator provided the waves are comparatively strong. It suggests that the ponderomotive effects play a part in formation of structure and dynamics of the magnetosphere.

Vlasov-Poisson Simulations of Strong Wave-Plasma Interaction in Conditions of Relevance for Radio Frequency Plasma Heating

The nonlinear aspects of the interaction between externally applied electrostatic oscillations and a one-dimensional electron-ion plasma is investigated by numerically integrating the Vlasov-Poisson system of equations. The forcing field is in the form of a broad symmetric $k$ spectrum which simulates that used in low-frequency wave-heating experiments in tokamak plasmas. It is shown that, for realistic values of the plasma and field parameters, numerous nonlinear effects accompany the wave-plasma interaction, as, for example, the formation of density cavities by the action of ponderomotive forces, the acceleration of charged particles, and the nonlinear plasma heating.

The non-linear suppression of ionisation waves by the high-frequency field of surface waves. II. Theory and comparison with the experiments

For pt.I see ibid., vol.21, p.1597 (1988). The authors have investigated theoretically the interaction of self-excited ionisation waves with high-frequency surface waves with a view to obtaining the dispersion of the ionisation waves at the present surface wave field. Mainly the action of ponderomotive force and additional electron heating due to excitation of the high-frequency wave are considered as non-linear mechanisms responsible for the changes of the dispersion characteristics of the ionisation waves. The theoretical results are in good agreement with the experimental data presented in part I for the suppression of ionisation waves by the field of the high-frequency surface waves and their frequency shift.

Stabilization of plasma flow in a transverse magnetic field

Results are given of a theoretical and experimental investigation of the intensive interaction between a plasma flow and a transverse magnetic field. The calculation is made for problems formulated so as to approximate the conditions realized experimentally. The experiment is carried out in a magneto-hydrodynamic (MHD) channel with segmented electrodes (altogether, a total of 10 pairs of electrodes). The electrode length in the direction of the flow is 1 cm, and the interelectrode gap is 0.5 cm. The leading edge of the first electrode pair is at x = 0. The region of interaction (the region of flow) for 10 pairs of electrodes is of length 14.5 cm. An intense shock wave S propagates through argon with an initial temperature To = 293 °K and pressure po = 10 mm Hg. The front S moves with constant velocity in the region x < 0 and at time t = 0 is at x = 0. The flow parameters behind the incident shock wave are determined from conservation laws at its front in terms of the gas parameters preceding the wave and the wave velocity WS. The parameters of the flow entering the interaction region are as follows: temperature T01 = 10,000 °K, pressure P01 = 1.5 atm, conduction σ01 = 3000 Ω−1·m−1, velocity of flow u01 = 3000 m·sec−1, velocity of sounda01 = 1600 m·sec−1, degree of ionization α = 2%, ∼ 0.4. The induction of the transverse magnetic field B = [0, By(x), 0] is determined only by the external source. Induced magnetic fields are neglected, since the magnetic Reynolds number Rem ∼ 0.1. It is assumed that the current j = (0, 0, jz) induced in the plasma is removed using the segmented-electrode system of resistance Re. The internal plasma resistance is Ri = h(σA)−1 (h = 7.2 cm is the channel height; A = 7 cm2 is the electrode surface area). From the investigation of the intensive interaction between the plasma flow and the transverse magnetic field in [1–6] it is possible to establish the place x* and time t* of formation of the shock discontinuity formed by the action of ponderomotive forces (the retardation wave RT), its velocity WT, and also the changes in its shape in the course of its formation. Two methods are used for the calculation. The characteristic method is used when there are no discontinuities in the flow. When a shock wave RT is formed, a system of nonsteady one-dimensional equations of magnetohydrodynamics describing the interaction between the ionized gas and the magnetic field is solved numerically using an implicit homogeneous conservative difference scheme for the continuous calculation of shock waves with artificial viscosity [2].

PONDEROMOTIVE FORCES IN THE OPTICS OF NONLINEAR MEDIA

A theory of the electromagnetic field is developed for elastically deformable media. This theory can describe changes in the mechanical, electrical, and magnetic parameters of a medium under the action of ponderomotive forces. A simultaneous analysis of the field equations in a medium and of the equations of motion of the medium makes it possible to introduce thermodynamic functions relating these parameters to each other. Expressions are obtained for the law of conservation of energy, thermal and electron equilibrium, equilibrium density, and density of the ponderomotive forces. Two examples of media consisting of isotropically or anisotropically polarizable molecules in a strong electromagnetic field are discussed in detail.