Showing papers on "Electromagnetic field published in 1988"

Fundamentals of the Theory of Metals

Abstract: Preface. Part I. Normal Metals. 1. An electron in a periodic crystal lattice. 2. The electron Fermi liquid. 3. Electrical and thermal conductivity. 4. Scattering processes. 5. Galvanomagnetic properties of metals. 6. Thermoelectric and thermomagnetic phenomena. 7. Metals in a high-frequency electromagnetic field. Cyclotron resonance. 8. Size effects. 9. Propagation of electromagnetic waves in the presence of a magnetic field. 10. Magnetic susceptibility and the de Haas-van Alphen effect. 11. Quantum effects in conductivity. 12. Absorption of sound in metals. 13. Fermi-liquid effects. 14. Methods of calculating the electronic spectra of metals. Part II. Superconducting Metals. 15. Macroscopic theory of superconductivity. 16. Basic ideas of the BCS theory. 17. The Ginzburg-Landau theory. 18. Type II superconductivity. 19. Kinetics of superconductors. 20. The superconductor-normal metal interface. 21. Superconductivity and magnetism. 22. Tunnel junctions. The Josephson effect. Appendices. References. Suggested reading. Author index. Subject index.

Inflation-Produced, Large-Scale Magnetic Fields

Abstract: We study the production of large-scale (∼ Mpc) magnetic fields in inflationary Universe models. In the usual electromagnetic gauge theory, the photon field is conformally invariant and the magnetic fields that are produced during an inflationary epoch are uninterestingly small. We have considered four models in which the conformal invariance of electromagnetism is broken. The primeval magnetic fields which result can have astrophysically interesting strengths, but are very model-dependent.

Water as a Free Electric Dipole Laser

Abstract: We show that the usually neglected interaction between the electric dipole of the water molecule and the quantized electromagnetic radiation field can be treated in the context of a recent quantum field theoretical formulation of collective dynamics. We find the emergence of collective modes and the appearance of permanent electric polarization around any electrically polarized impurity.

Internal and near‐surface electromagnetic fields for a spherical particle irradiated by a focused laser beam

Abstract: Theoretical expressions for the internal and external electromagnetic fields for an arbitrary electromagnetic beam incident upon a homogeneous spherical particle are derived, and numerical calculations based upon this theoretical development are presented. In particular, spatial distributions of the internal and near‐surface electric field magnitude (source function) for a focused fundamental (TEM00 mode) Gaussian beam of 1.06 μm wavelength and 4 μm beam waist diameter incident upon a 5‐μm‐diam water droplet in air are presented as a function of the location of the beam focal point relative to the sphere center. The calculations indicate that the internal and near‐surface electric field magnitude distribution can be strongly dependent upon relative focal point positioning and may differ significantly from the corresponding electric field magnitude distribution expected from plane‐wave irradiation.

A 3-D impedance method to calculate power deposition in biological bodies subjected to time varying magnetic fields

Abstract: A previously described two-dimensional impedance method (ibid., vol.31, p.644-51, 1984) for modeling the response of biological bodies exposed to time-varying electromagnetic fields has been extended to three dimensions. This method is useful at those frequencies where the quasistatic approximation is valid and calculates the fields, current densities, and power depositions in the bodies. Solutions using this method for homogeneous spheres in plane waves are presented and compared to the analytic solutions for the same configuration. Solutions for a man exposed to a uniform radio-frequency magnetic field at 30 MHz, are presented, as well as for a man exposed to either circularly or linearly polarized magnetic fields at 63 MHz, uniform within a portion of his body and linearly decreasing outside of that portion, which approximates the exposure in some nuclear-magnetic-resonance imaging devices. >

Dielectric resonator apparatus

Abstract: The dielectric resonator apparatus is characterized in that electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in the using mode of a dielectric resonator, a dielectric resonator with either of dielectrics between the electric wall being removed in shape is provided by plurality, an equivalent axis is common to the central axis of each of the dielectric resonators, with the dielectric resonators being inductively coupled in the axial direction. A dielectric resonator which prevents the current from being concentrated on the central axis of the electromagnetic field distribution, is collectively smaller in the Joule loss and is higher in Q. The dielectric resonator of the present invention is characterized in that the dielectric close to the central axis is removed, wherein electric walls exist on one plane or two including the central axis of the electromagnetic field distribution in a dielectric resonator using, for instance, a TE01δ mode, with either of dielectrics between the electric wall being removed in shape.

Three-dimensional finite, boundary, and hybrid element solutions of the Maxwell equations for lossy dielectric media

Abstract: Finite, boundary, and hybrid element approaches are presented as numerical methods for computing electromagnetic (EM) fields inside lossy dielectric objects. These techniques are implemented as computer algorithms for solving the Maxwell equations in heterogeneous media in three dimensions. Algorithm verification takes the form of comparisons of test cases with analytic solutions. Computed results for each technique are in good agreement with exact solutions, especially in light of the coarse computational grid resolutions used. Implementation was in FORTRAN on a moderate-sized computer (MicroVax II). The basic problem formulation is quite general; however, it has direct application in hyperthermia as a cancer therapy where the EM fields produced inside the patient by external sources are of interest. An example of the application of these numerical methods in a three-dimensional clinical setting is shown. >

Bridged loop–gap resonator: A resonant structure for pulsed ESR transparent to high‐frequency radiation

Abstract: A new and inexpensive X‐band resonator structure for pulsed electron‐spin resonance and electron‐nuclear‐double‐resonance applications is introduced The resonator consists of a bridged loop structure and is distinguished by a good reproducibility and reliability It has a high filling factor and an adjustable Q value and is transparent to radio frequency fields with an upper limit >100 MHz The inner diameter of 5 mm allows convenient sample access of standard 4‐mm quartz tubes in the temperature range between 4 and 300 K Numerical computations of the resonant frequencies, the Q values, and the three‐dimensional distributions of the electromagnetic fields are presented They are based on a discretization method for the solution of Maxwell’s equations and include all dielectric elements of the resonator structure The field homogeneity in the sample area and the influence of the dimensions and the thickness of the metallic layers on field intensity, quality factor, and resonant frequency are determined e

Shielded electromagnetic transducer

Abstract: An electrical to electromagnetic transducer for applying electromagnetic energy to damaged potions of the living body, which provides high efficiency generation of electromagnetic fields for electromagnetic therapy by directing electromagnetic radiation to the damaged body part. Electromagnetic radiation is initially generated by a dipole consisting of a bar of high permeability material wrapped with an electrically conductive coil. The dipole is placed between a conductive shield and the damaged body part. An electrical signal passes through the coil which causes a magnetic field to be generated through and around the high permeability material. The field radiation pattern of the dipole is directed toward the damaged body part by a conductive shield. Magnetic fields which are generated away from the damaged body part intersect the conductive shield and establish eddy currents. These eddy currents in turn generate magnetic fields opposite and nearly equal to the magnetic fields generated by the electromagnetic source. These resultant redirected electromagnetic fields then reinforce the electromagnetic field directed towards the damaged body part and diminish the electromagnetic field directed away from the damaged body part.

Electromagnetic scattering and radiation by arbitrary conducting wire/surface configurations

Abstract: The electric field integral equation is used with the moment method to develop an efficient numerical procedure for treating problems of arbitrary conducting wire/surface configurations. Three triangular-type basis functions are used to represent the currents on the bodies, wires, and wire/surface junctions. A junction basis function is developed which is applicable to any junction configuration. >

Thin‐skin electromagnetic fields around surface‐breaking cracks in metals

Abstract: In situations where the electrical skin depth δ is small compared with a typical crack dimension l, substantial progress has been achieved in recent years in modeling surface electromagnetic fields and the perturbations that are produced in them by surface-breaking flaws [1,2,3]. The development of an unfolding theory at UCL for thin-skin surface fields was based on the approximation that the electric and magnetic field vectors E and H are essentially tangential to the surface of the material in the surface skin. It was motivated by the desire to measure fatigue cracks in ferrous materials used in large-scale steel structures such as offshore oil rigs [2], and the method to which it was applied was the a.c. field measurement technique. Auld et al [4,5] later adapted the unfolding approach in considering thin-skin field models for the eddy current method, and their major concern was with applications to non-ferrous materials used in airframe and aero-engine manufacture. For acfm work, the unfolding theory leads to a surface Laplacian field on both the metal surface and the crack face and information on the crack presence is deduced by measuring perturbations in the surface field. Auld’s model for eddy currents also has a plane Laplacian field on the crack face, but it is assumed that the crack produces no change in the field on the metal surface. Field lines in the unfolded plane for both models are shown schematically in Figure 1(b,c) for the case when the interrogating field is uniform and the crack is semi-circular. Auld’s model has been described as a Born type of approximation from an analogy with wave scattering theory which ignores the scattered field when calculating scattering cross-sections.

Duct propagation of hydromagnetic waves in the upper ionosphere, 1, Electromagnetic field disturbances in high latitudes associated with localized incidence of a shear Alfvén wave

Abstract: Mode conversion to the fast magnetosonic wave by anisotropic ionospheric currents from a localized incident shear Alfven wave is studied in detail, based on a simple layered model inclusive of an anisotropic conducting sheet (the ionospheric E layer) and an upper ionospheric ducting layer under vertical, uniform ambient magnetic field lines. A horizontal profile of electromagnetic field intensity at the E layer shows a wider spread than that of the incident wave due to trapping of the fast magnetosonic wave in the ducting layer. Since electrostatic electric field intensity of the incident Alfven wave is dominant in the central region, the eddy Hall current associated with the Alfven wave generates the ground magnetic field variations. On the other hand, since electromagnetic electric field intensity of the trapped fast magnetosonic wave exceeds to that of the incident Alfven wave in the region surrounding the central region, both the magnetic field of the fast magnetosonic wave and the secondary field due to the eddy Pedersen current contribute to the ground magnetic field variations.

An error‐based approach to complementary formulations of static field solutions

Abstract: The constitutive relationship between fields in electromagnetic media is cast in error form. For well-posed static problems, the error splits systematically into complementary functionals. Error minimization provides a universal variational principle that generates complementary and dual solution formulations. The error, which is wholly attributed to the numerical constraints in approximate solutions, is always defined and computable locally and globally.

Calculation of self and mutual impedances for coils on ferromagnetic cores

Abstract: By means of integral transform techniques, the paper establishes a new set of self- and mutual-impedance formulas relating to coils on ferromagnetic cores of circular cross-section. If the core is straight and infinitely long, the formulas are expressed in terms of convergent integrals that may be evaluated numerically. In the case of closed cores, e.g. toroidal cores, the formulas formally reduce to convergent series that may be truncated according to the degree of accuracy required. The formulas follow directly from the solution of Maxwell's equations and therefore offer the ultimate in accuracy.

Derivation of a matrix describing a rugate dielectric thin film

Abstract: In optical coating calculations, a 2 × 2 matrix formalism is generally used to describe the effect of each layer on the electromagnetic field. In current applications, the layers are considered homogeneous, and, therefore, the matrix used is restricted to this particular case. In this paper, a 2 × 2 matrix describing an inhomogeneous dielectric thin film is derived from Maxwell’s equations. The inhomogeneity is assumed to vary along the direction perpendicular to the film plane. No restriction is made on the amplitude of its variation. The matrix is illustrated in the case of a rugate filter designed according to Sossi’s Fourier transform technique. An improved approximation for the Fourier transform technique is then introduced.

The magnicon — An advanced version of the gyrocon

Abstract: A new VHF generator with circular deflection of a high power relativistic electron beam is described as an outgrowing of the gyrocon proposed by Budker in 1967. The output resonator of the device is placed in a static magnetic field providing synchronous interaction of electrons with the electromagnetic field. An accompanying magnetic field and prolonged time of interaction enable one to achieve higher power within the decimeter and centimeter wave range compared to that of the gyrocon and klystron due to the higher electrical strength of the output resonator, a decreased heat generation and an easier beam guidance. In order to get higher gain and efficiency the magnicon deflection resonator is also placed in a magnetic field (of double magnitude). Test results for a magnicon of 30 cm wave range built at the INP are given. The power obtained is 2.6 MW for a pulse duration of 30 μs with a repetition rate of 1 Hz and an electron efficiency of 85%.

Blood flow detection device

Abstract: A blood flow monitoring system employing a disposable sensor for directing a flow of blood through an electromagnetic field to generate a voltage proportional to the flow of blood through the electromagnetic field. The flow detection system employs a disposable sensor having a lumen with a constricted cross-sectional area adapted to interact with an electromagnetic field to detect blood flow and in an enhanced variation includes an electromagnetic field focusing device for enhancing the electromagnetic field to focus the electromagnetic field across the path of blood flow through the constricted section of the lumen to intensify the voltage generated by the blood flow through the intensified electromagnetic field.

Scattering by a lossy dielectric cylinder in a rectangular waveguide

Abstract: Electromagnetic fields in a rectangular waveguide containing a lossy dielectric cylinder are investigated by means of the orthogonal expansion method. The calculated results are provided by measurement. Resonance effects become visible through the frequency responses of the scattering parameters and understandable by patterns due to magnetic fields and Poynting vectors. The lowest resonance is nonsymmetric and can be used to realize tunable bandstop filters with a relative 3-dB bandwidth of about 0.04 and an attenuation of more than 40 dB. >

Coupling of saturated electromagnetic systems to non-linear power electronic devices

Abstract: 2-D saturated electromagnetic systems associated with nonlinear electric circuits are analyzed. The nonlinear electromagnetic equations are modeled with the help of finite elements. The nonlinear electric equations are directly coupled with the electromagnetic ones, and the Newton-Raphson method is used to solve the resulting matrix system. Numerical results for a saturated magnetic core coil fed by an electric source through a diode are reported. The results illustrate the importance of coupling the two systems of equations. >

Stochastic optics: A reaffirmation of the wave nature of light

Abstract: Quantum optics does not give a local explanation of the coincidence counts in spatially separated photodetectors. This is the case for a wide variety of phenomena, including the anticorrelated counting rates in the two channels of a beam splitter, the coincident counting rates of the two “photons” in an atomic cascade, and the “antibunching” observed in resonance fluorescence. We propose a local realist theory that explains all of these data in a consistent manner. The theory uses a completely classical description of the electromagnetic field, but with boundary conditions of the far field that are equivalent to assuming a real fluctuating, zero-point field. It is related to stochastic electrodynamics similarly to the way classical optics is related to classical electromagnetic theory. The quantitative aspects of the theory are developed sufficiently to show that there is agreement with all experiments performed till now.

Conservation laws and transverse motion of energy on reflection and transmission of electromagnetic waves

Abstract: The conservation laws for the process of reflection and transmission of electromagnetic waves on a plane interface of isotropic transparent media are determined Using these laws, relations have been established between the transverse shift (TS) of a centre of gravity of reflected and transmitted wavepackets, the change of the normal component of the intrinsic Minkowski angular momentum of the electromagnetic field and the Abraham transverse momentum (or the transverse electromagnetic power flow (TPF)) The previous investigations of the TS and TPF phenomena are discussed from the point of view of conservation laws

The effect of coil design on materials synthesis in an inductively coupled plasma torch

Abstract: A mathematical model for the analysis and design of inductively coupled plasma torches is presented. The model is based upon a solution of the electromagnetic vector potential equation and is capable of predicting the two‐dimensional velocity, temperature, and electromagnetic fields as well as the reaction kinetics inside the torch for any axisymmetric coil configuration. The model is used to study the effect of coil design on the thermal decomposition of silicon tetrachloride to silicon. The coil design is found to affect both the temperature field and the flow field and to have a significant effect on the reaction kinetics in the torch. It is demonstrated that through fundamental changes in the coil design it is possible to control the location of the reaction zone and to reduce silicon deposition on the wall of the reactor.

Nonlinear optics and transport in laser-excited semiconductors.

Abstract: The theory of the spectral and kinetic properties of the excited electron-hole plasma and of the electromagnetic field is developed in the framework of a nonequilibrium many-body theory. Particular emphasis is given to the effect of the laser-induced energy branches on the transport (intraband kinetics) and nonlinear-optical properties (interband kinetics) of the system.

Magnetic fields and time dependent effects on development.

Abstract: Pulsed, extremely-low-frequency electromagnetic fields caused a significant increase in abnormalities in the developing chick embryo. The effect was observed when the field was presented during the first 24 h of incubation; no significant effect was observed with exposure from 24 to 48 h of incubation.

Dynamical screening at a metal surface probed by second-harmonic generation.

Abstract: Mesure de la variation spatiale et en frequence du champ local genere a la surface d'un metal a electrons quasi libres par un champ electromagnetique externe

Electromagnetic Penetration into a Conducting Circular Cylinder through a Narrow Slot, TM Case

Abstract: A procedure is presented for calculating the electromagnetic field in the vicinity of an infinitesimally thin conducting circular cylindrical shell with an infinitely long slot illuminated by a TE plane wave. This field is the short-circuit field plus the field due to the slot. The short-circuit field is the field that would exist if there were no slot. The field due to the slot stems from the Φ -component of the electric field in the slot. Approximated by a linear combination of expansion functions that satisfy the edge conditions, this field component is determined by testing the equation of continuity of the axial magnetic field in the slot with non-negative powers of Φ where |Φ| is the angular distance from the center of the slot. Alternative expansion functions are introduced to preserve the accuracy of the solution in the vicinity of an internal resonance. Containing the resonant electric field, the first alternative expansion function is normalized so that its axial magnetic field remains finite as...

Quantum electrodynamical approach to multiphoton ionisation in the high-intensity H field

Abstract: The authors solve the Dirac equation for an electron interacting with a quantised and elliptically polarised electromagnetic field. They use the solution to obtain a relativistic S-matrix amplitude for multiphoton ionisation in the high-intensity limit. Its nonrelativistic limit is also derived and is used to construct a multiphoton transition-rate formula which is compared with previous results.

The behavior of the electromagnetic field near the edge of a resistive half-plane

Abstract: The authors define the behavior of the electromagnetic field near the edge of a resistive half-plane, taken separately, as well as in conjunction with a perfectly conducting halfplane. The efficiency of accounting for the established field behavior while finding the solution of boundary problems of electrodynamics is illustrated by computational results. >