The interaction between charged dust particles in a plasma

A solution to the Poisson-Boltzmann equation for a cloud of charges surrounding two charged dust particles, considered as Debye atoms forming a Debye molecule, is studied by numerical methods. It is demonstrated that attractive forces between the particles arise when two conditions are satisfied. First, the Debye screening radius, corresponding to the electron density at a half average spacing between particles, must be equal to approximately half of this distance. In this case, the attraction arises at a distance equal approximately to the average spacing between particles. Second, charges of one sign must be concentrated predominantly on the particles. Should the particles possess only a small fraction of charges of one sign, they will repulse at any distance. Estimates of the electrostatic pressure and surface tension in a gas of dust particles are obtained.     

Unstable oscillations of charged particles at the electric field node of a standing electromagnetic wave

Unstable motion of charged particles at the electric field node of a standing electromagnetic wave is described. The analysis is based on the homogeneous and inhomogeneous Mathieu equations derived from the equations of motion with allowance for nonlinearity. A solution is constructed in the domains of stability adjacent to the boundaries of the first interval of instability.     

Interaction of charged dust particles. Debye quasimolecule

An analysis is made of an electrically neutral system of two small positive charges surrounded by a common cloud of Boltzmann-distributed electrons. This system, which simulates macroparticle interaction in a dusty plasma, is called a Debye quasimolecule. Calculations are made of the force and potential interaction energy of shielded dust particles as a function of the distance between them. It is shown that the electron shells are polarized so that the forces of attraction of the dust particles in a Debye quasimolecule predominate over the forces of repulsion of their like charges. This may occur up to distances equal to the size of the dust particles. It is concluded that metastable dusty liquids and crystals cannot exist when the electron clouds of the charged particles obey a Boltzmann distribution. Pis’ma Zh. Tekh. Fiz. 25, 83–89 (August 26, 1999)     

Stable oscillations and effective acceleration of charged particles at the electric field antinode of a standing electromagnetic wave

The phenomenon of the stable motion of charged particles at the electric field antinode of a standing electromagnetic wave is analyzed using the Hill equation derived from the equations of motion. The domains of parameters characterizing the field and charges are determined for the regime of stable oscillations. It is shown that the charged particles remaining at the electric field antinode can be accelerated to relativistic velocities.     

The interaction between charged dust particles calculated in Cassini coordinates

The Poisson-Boltzmann equation for two charged dust particles surrounded by a cloud of charged plasma was numerically solved using the Cassini coordinates. The force of the electric field acting on each particle was determined by integrating the field pressure over the particle surface. It is shown that the dust particles can exhibit attraction at distances on the order of the Debye screening radius and the average spacing between particles. The attraction drops sharply if the particle charge is significantly smaller than the charge of surrounding plasma species.     

Reflection of an electromagnetic wave by a layered superconductor-dielectric structure

An analysis is made of the propagation of an electromagnetic wave through an infinite periodic superconductor-dielectric structure consisting of alternating layers of dielectric and thin layers of type II superconductor. The presence of thin layers of superconductor is taken into account by introducing a suitable boundary condition. It is observed that the reflection coefficient depends abruptly on the angle of incidence of the wave, the thickness of the superconducting film, and the external magnetic field. Pis’ma Zh. Tekh. Fiz. 24, 9–12 (January 12, 1998)     

Longitudinal dynamics of a nonrelativistic bunch of charged particles in a traveling wave field

The longitudinal dynamics of a nonrelativistic bunch of charged particles in a traveling wave field has been studied. A Lagrange function for this motion is constructed and the Lagrange equation describing longitudinal envelopes of the bunch is derived.     

Inversion of the theory for electromagnetic radiation from charged particles

The problem whether it is possible to calculate from a given radiation field, i.e. with an electric field vector in the wave zone in a given direction and a certain time dependence, the trajectory of a charged particle emitting this field is discussed and solved.     

Studying the response of a Coulomb ball of charged dust particles to external pulsed loads

The behavior of Coulomb balls of charged spherical dust particles under conditions of pulsed uniform loading of their outermost shells at various intensities has been studied by molecular dynamics modeling. If the intensity of the external load is below a certain threshold, the shell structure of the Coulomb ball is retained and the oscillations of outer shells are characterized by gradually decaying beats. As the intensity of the uniform loading increases, the shell structure exhibits smearing and, under the action of a threshold load, the system passes to a fluid-like state. The oscillation frequency of the outermost shell is independent of the intensity of uniform loading. Calculations show that, as the number of dust particles in a Coulomb ball increases, this frequency tends to a certain limiting value.     

High-frequency diffraction of a electromagnetic plane wave by an imperfectly conducting rectangular cylinder

We shall consider the problem of determining the scattered far-wave field produced when a plane E-polarized wave is incident on an imperfectly conducting rectangular cylinder. On the basis of the uniform asymptotic solution for the problem of the diffraction of a plane wave by a right-angled impedance wedge, in conjunction with Keller’s method and multiple diffraction, a high-frequency far-field solution to the problem is given for two edge diffractions.     

Collisionality in an ensemble of identical charged particles in a closed magnetic trap

A strict proof of the theorem of infinite collisionality in an ensemble of identical charged particles in a closed magnetic trap is presented.     

Thermoluminescence induced by heavy charged particles

Thermoluminescent materials display complex features when exposed to heavy charged particles: the TL response shows a linear-supralinear saturation dependence on the fluence and the efficiency is a strong function of the particle's velocity. Results are presented from measurements performed with low energy ions incident on TLD-100. The measured supralinearity can be reproduced by a Monte Carlo track interaction model which incorporates saturation effects; however, the model parameters which describe the ion's radii do not display the expected dependence on incident energy. The efficiency data support the choice of reference radiation having a secondary electron spectrum 'matched' to that of the heavy charged particles. The systematics of the measured glow curve shapes and maximum supralinearity unifies results from light ions and photons based on characteristics of the secondary electron spectra.     

Millimeter wave electromagnetic interference shielding by coating expanded polystyrene particles with a copper film using magnetron sputtering

Expanded polystyrene (EPS) particles were coated with copper by magnetron sputtering in order to produce a material suitable for electromagnetic interference (EMI) shielding. Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDS) results demonstrated the effectiveness of successful copper deposition. The EMI shielding effectiveness (SE) of the Cu-coated EPS particles was measured to be 14–39 dB over a frequency range of 80–110 GHz, suggesting that Cu-coated EPS particles can be used as an effective lightweight millimeter wave EMI shielding material.     

Non-linear electromagnetic wave propagation in an isotropic material

It is shown that small departures from the classical linear constitutive relations can have significant cumulative effects on the propagation of electromagnetic waves. A non-linear far field theory is developed for holohedral isotropic materials. It is found that the amplitude of the signal propagates independently of the direction, although the local direction field depends strongly on this amplitude. The evolution of weak electromagnetic shocks is also discussed.     

磁控溅射中电磁场分布及带电粒子运动的模拟与计算

电磁场分布及其对各种带电粒子的约束情况对磁控溅射过程有着决定性的影响。本文首先利用物理场耦合分析软件Comsol 3．2a分析了直流磁控溅射电磁场的分布，并且计算分析了单个带电粒子的运动情况。在此基础上，计算分析了带电粒子束流在电磁场中的运动情况、空间分布，得到了磁控溅射电磁场区域分布、单个电子的运动轨迹及带电粒子在空间区域中位置分布。     

Near field zone of an integrated circuit exposed to an electromagnetic wave in a waveguide

The electromagnetic field distribution in the vicinity of an integrated circuit was calculated based on a numerical solution of the problem of electromagnetic wave diffraction on a model metal-dielectric structure in a waveguide tract. Using the obtained field distributions, it is possible to calculate currents in the microstructural elements of integrated circuits and develop a thermoelectric model of degradation processes in such circuits under the action of pulsed electromagnetic fields.     

Backscattering enhancement of an electromagnetic wave scattered by two-dimensional rough layers.

The problem of an electromagnetic wave scattered by a slab with two rough boundaries is solved by the small-perturbation method under the Rayleigh hypothesis. To obtain the perturbative development, we use a systematic procedure that involves integral equations called the reduced Rayleigh equations. Then we show for a dielectric slab deposited on a silver film that the backscattering enhancement can be produced by guided waves that interact with the two rough surfaces.     

Motions of charged particles in plasmas

The motion of a single charged particle in magnetic and electric fields B and E is described by the basic non-relativistic equation of motion in which radiation damping is neglected.

With emphasis on vector methods, data are obtained for the drift-free reference case of motion in a circular helix, and then the drift velocity perpendicular to B due to electric field perturbation of the circular case is used to obtain the familiar gravitational and curved magnetic line drifts. Application of the gravitational drift to the plasma physics Rayleigh-Taylor instability is examined critically in the light of information which can be obtained from the macroscopic equation of motion for a plasma in a magnetic field.

For a spatially perturbed magnetic field a guiding centre treatment using the standard orthogonal curvilinear co-ordinate system of differential geometry yields, after time averaging, the first-order Alfvén and curvature drifts, the latter being in agreement with the result obtained less rigorously from the electric drift velocity. The magnetic field geometry is described in terms of an extended set of Frenet-Serret partial derivatives which involve six scalar quantities, five of which are independent when a scalar magnetic potential exists. After time averaging there also exists a first order velocity component of unusual form parallel to B. For the usually encountered case of B irrotational, this component vanishes.

The three equations of motion for the components of the particle velocity are also obtained in terms of this curvilinear co-ordinate system, and when time averaged the equation of motion for the particle velocity component parallel to B enables the spatial adiabatic invariance of a spiralling particle's magnetic moment to be rapidly established.

The case of B dependent on the time, which can lead to radial compression of a plasma, is discussed from drift and non-drift view points, and the difference between Larmor's frequency and the gyrofrequency is emphasized. A simple microscopic treatment of the polarization drift is also included.

Finally the historical and mathematical significance of adiabatic invariance is discussed, with particular reference to the magnetic moment in plasma physics.     

An advanced BEM for electromagnetic wave scattering problems with axisymmetric dielectric particles

An advanced boundary element/fast Fourier transform (FFT) methodology for solving axisymmetric electromagnetic wave scattering problems with general, non-axisymmetric boundary conditions is presented. The incident field as well as the boundary quantities of the problem are expanded in complex Fourier series with respect to the circumferential direction. Each of the expanding coefficients satisfies a surface integral equation which, due to axisymmetry, is reduced to a line integral along the surface generator of the body and an integral over the angle of revolution. The first integral is evaluated by discretizing the meridional line of the body into isoparametric elements and employing Gauss quadrature. The integration over the angle of revolution is performed simultaneously for all the expanding coefficients through the FFT. The singular integrals are computed directly with high accuracy. Representative numerical examples demonstrate the accuracy of the proposed boundary element formulation.     

Thin electromagnetic wave absorber for quasi-microwave bandcontaining aligned thin magnetic metal particles

Soft magnetic material has been produced in which flaky thin amorphous metal particles, about 2 μm thick, are aligned in polymer in the direction perpendicular to electromagnetic wave propagation. This material yields a permeability two to three times higher than the spinel-type ferrite system in the quasi-microwave band. We have designed a thin wave absorber composed of the present material by introducing a low-permittivity area such as a free space into the present metal-containing material. This decreases the average permittivity, striking a balance between complex permeability and permittivity values, and thus reducing the reflection coefficient of the absorber. A thin (about 3-mm thick) wave absorber with a reflection loss of over 30 dB in the quasi-microwave band was successfully obtained when the free space region was 5% of the total volume