Impressed Electric Field Research Articles

Reformulation of the Roy–Shafai Generalization of the Ludwig-3 Co-/Cross-Polarization Definition

The Roy-Shafai generalization of the Ludwig-3 polarization pattern definition is well-suited to the representation of the far electromagnetic field of a flanged aperture, either a perfect electric conductor (PEC)-flanged aperture with an impressed electric field as was shown by Roy and Shafai or a perfect magnetic conductor (PMC)-flanged aperture with an impressed magnetic field which can be similarly derived. We show that the Roy-Shafai generalization of the Ludwig-3 polarization definition is in fact equivalent to the transformed Ludwig-2 definition. The Ludwig-3 polarization is that of a Huygens source, while the Ludwig-2 polarization definition corresponds to either an electric or, with transformation, a magnetic dipole. That the Roy-Shafai polarization definition is equivalent to a transformed Ludwig-2 definition is reasonable as the rectangular PEC-flanged aperture with an impressed electric field behaves as a magnetic dipole in the low frequency limit and, subject to some restrictions, maintains the same polarization pattern for all frequency assuming the aperture field remains uniform. Likewise, the rectangular PMC-flanged aperture with an impressed magnetic field behaves like an electric dipole in the low-frequency limit and maintains the same polarization pattern for all frequency again, assuming that the aperture field remains uniform and, thus, exhibits a Ludwig-2 polarization pattern.

Modified axion electrodynamics as impressed electromagnetic sources through oscillating background polarization and magnetization

A reformulation of axion modified electrodynamics is presented where the equations maintain a similar form to the unmodified Maxwell’s equations, with all modifications redefined within the constitutive relations between the D→, H→, B→ and E→ fields. This allows the interpretation of the axion induced background bound charge, polarization current and bound current along with the axion induced polarization and magnetization with the former satisfying the charge–current continuity equation. This representation is of similar form to odd-parity Lorentz invariance violating background fields in the photon sector of the Standard Model Extension. We show that when a DC B→-field is applied an oscillating background polarization is induced at a frequency equivalent to the axion mass. In contrast, when a large DC E→-field is applied, an oscillating background magnetization is induced at a frequency equivalent to the axion mass. It is evident that these terms are equivalent to impressed source terms, analogous to the way that voltage and current sources are impressed into Maxwell’s equations in circuit and antenna theory. The impressed source terms represent the conversion of external energy into electromagnetic energy due to the inverse Primakoff effect converting energy from axions into oscillating electromagnetic fields. It is shown that the impressed electrical DC current that drives a DC magnetic field of an electromagnet, induces an impressed effective magnetic current (or voltage source) parallel to the DC electrical current oscillating at the Compton frequency of the axion. The effective magnetic current drives a voltage source through an electric vector potential and also defines the boundary condition of the oscillating axion induced polarization (or impressed axion induced electric field) inside and outside the electromagnet. This impressed electric field, like in any voltage source, represents an extra force per unit charge supplied to the system, which also adds to the Lorentz force.

Statistical mechanics model for orientational motion of two-dimensional rigid rotator

A comparison of thermodynamics properties of two-dimensional linear rigid rotator is presented in the absence, and presence of an impressed weak electric field at low and high temperatures. It is shown that specific heat and entropy fall off rapidly at low temperatures. At ultra low temperatures, the entire normal entropy is lost and we have complete ordering by the impressed field. In the classical limit it is shown that there is a temperature dependent polarizability

An RGF Delta-Gap Source for Thin-Wire EFIE

The derivation of a novel delta source based on a reduced Green's function (RGF) is presented for thin-wire scattering problems. The impressed electric field, typically represented by a delta source, is generated by a current defined at the source location. By using electrically small assumptions at the source location, the electric field integral equations (EFIEs) representing the impressed field created by the defined current can be evaluated analytically with an RGF. This impressed field is denoted here as the RGF delta source, or simply, the RGF source. The RGF source is in the range of the EFIE operator and does not contain the dipole that is present in the traditional delta source. The numerical results show the improved convergence of the new RGF source while maintaining accuracy comparable to that of existing delta source models used in other thin-wire models, such as the numerical electromagnetics code.

Parallel, series, and intermediate interconnections of optical nanocircuit elements 2 Nanocircuit and physical interpretation

Applying the analytical closed-form solutions of the quasi-static potential distribution around two conjoined resonant half-cylinders with different permittivities, reported in the first part of this manuscript, here we interpret these results in terms of our nanocircuit paradigm applicable to nanoparticles at infrared and optical frequencies [Phys. Rev. Lett.95, 095504 (2005)]. We investigate the possibility of connecting in series and parallel configurations plasmonic and/or dielectric nanoparticles acting as nanocircuit elements, with a goal for the design of a more-complex nanocircuit system with the desired response. The present analysis fully validates the heuristic predictions regarding the parallel and series combination of a pair of nanocircuit elements depending on their relative orientation with respect to the field polarization. Moreover, the geometries under analysis present interesting peculiar features in their wave interaction, such as an intermediate stage between the parallel and series configurations, which may be of interest for certain applications. In particular, the resonant nanocircuit configuration analyzed here may dramatically change, in a continuous way, its effective total impedance by simply rotating its orientation with respect to the polarization of the impressed optical electric field, providing a novel optical nanodevice that may alter its function by rotation with respect to the impressed optical local field.

Experimental investigation of the matching and impressed electric field of a multipolar electron cyclotron resonance discharge

The experimental performance of an end excited, internally tuned, multipolar electron cyclotron resonance plasma source is investigated versus several independent input variables: (1) incident power (185–350 W), (2) discharge pressure (1–7 mTorr), and (3) microwave matching (applicator length, Ls, varies from 65–170 mm). Plasma source performance in argon gas is determined from measurements of (1) absorbed microwave power, (2) the magnitude, and (3) the spatial variation of the impressed electric field, and the output (4) plasma density and (5) electron temperature. The nonlinear experimental relationships between variations in the input variables and performance variables are established. Two well-matched stable discharge operational regions or modes are identified as Ls is varied. Using the measured impressed electric field patterns, these two modes are identified as TM, Φ symmetric, λg, and λg/2 standing wave modes. As Ls, pressure and power vary, considerable hysteresis in absorbed power and density is observed. However, it is shown that this complex input/output discharge behavior can be approximately explained using simple global plasma models. Despite the multiple steady states and hystereses, it is shown that the discharge can be easily maintained in well-matched, high density (ne>3×1011/cm3) stable operating conditions. The impressed electric field varies between 3 and 4.5 kV/m. An equivalent circuit of the plasma loaded cavity applicator is developed and provides important insights for the plasma matching process. The microwave coupling efficiencies are greater than 98% and the ion production costs vary between 300 and 450 eV/ion versus the experimental inputs. The data presented is useful for plasma source optimization and in developing intelligent plasma processing control strategies.

Measurements of the impressed electric field inside a coaxial electron cyclotron resonance plasma source

The magnitude and spatial variation of the impressed electric-field patterns inside a compact electron cyclotron resonance ion/plasma source are experimentally measured for argon and nitrogen feed gases. This ECR plasma source consists of several components: a resonant coaxial coupling section, an evanescent circular waveguide section, coupling loop, and the ECR discharge load itself. The electric fields inside the coaxial and circular waveguide sections are measured as the operating pressure and input power and are varied from 0.2 to 2.0 mTorr and 100 to 170 W, respectively. The measured fields verify that a standing wave with a maximum of 20–40 kV/m exists inside the coaxial section of length l. For matched conditions the length of this section varies only slightly between 0.6 and 0.7λ as pressure, power, and gas type vary. However, the evanescent impedance-matching circular waveguide section of length d changes from 2.5 for argon to 3.2 cm for nitrogen, indicating that the gas type influences the plasma impedance. Field pattern measurements in the ECR section of the source demonstrate the presence of nonevanescent fields in the discharge region. Measured plasma loaded and unloaded quality factors varied from 220 to 1800, respectively, indicating that 87% of the net input power is coupled into the discharge load. Additional calculations of conductive wall losses show that about 6% of the input power is lost in the cavity walls, and the remaining 7% is lost in the coupling loop.

New high dielectric constant materials: Micro/nanocomposites of suspended Au clusters in SiO 2/SiO 2Al 2O 3Li 2O gels and relevant theory for high capacitance applications

We have materials-designed, synthesized, processed, tested, and interpreted a micro/nanocomposite material consisting of a suspension of gold clusters in an insulating matrix, aimed at producing a high-dielectric constant (>200) high-breakdown-voltage capacitor. The resulting suspension utilizes SiO 2 or a reacted form of SiO 2Al 2O 3Li 2O as the insulating matrix, and was prepared by the sol-gel technique. The scientific approach employs the percolation theory expectation that at a critical topology of small metal elongated clusters amidst a ceramic or other insulating matrix, the dielectric constant of the resulting materials will reach a peak value as a function of spatial geometric loci. Our theoretical work indicates that the metal clusters should be optimally of atomic dimensions and approximately 100–300 A apart. The metal islands must be ellipsoidal-like (or elongated globules or flocculates) to establish a dipole moment (that will be summed over the sample volume). High resolution microscope studies reveal that the gold clusters are observed to take on the general shape of truncated octahedra, which indeed are appropriate for having a polarization vector (charge separation) due to an impressed electric field. From electron spectroscopy chemical analysis there exists indication that some of the clusters appear to be in a charged state. Dielectric constant measurements from 1 to 10 kHz have shown an average dielectric constant of 5000 in the AuSiO 2 gel sample over a wide temperature range of −100 to +100 °C, and a dielectric constant of 364–986 (with consideration for porosity) in the AuSiO 2/Al 2O 3/Li 2O produced from Eucryptite (LiAlSiO 4).

Sign discriminating field mill

The construction and analysis of a symmetric rotating field mill is described. Theoretical modelling of the mill's operation successfully predicts the experimentally observed features of the mill output. A pick-up phase signal generated by the mill rotor blades cutting field lines of a permanent magnet was used as a sampling pulse in a sample-and-hold electronic arrangement to determine both magnitude and direction of an impressed electric field. The mill's output voltage regressed on the electric field gave a correlation coefficient of 0.998. The sensitivity of the mill could be set arbitrarily and field changes of 0.5 V/m could be measured routinely. The time constant of 0.3 s makes the mill ideal for studies of the fair-weather field as well as of other phenomena with relatively long time constants. Special steps were incorporated in the mill construction to reduce effectively the damaging effects of water condensation on the performance of the mill.

A Multifilament Method-of-Moments Solution for the Input Impedance of a Probe-Excited Semi-Infinite Waveguide

The input impedance and surface currents of a probe-excited, short-circuited semi-infinite waveguide are determined by the method of moments. Expressions are given for the impressed electric field used to excite the probe from the coaxial source input using a semi-infinite-waveguide Green's function, and expressions are given for a free-space approximate impressed electric field which arises from the coaxial source input. The method-of-moments formulation used is based on a multifilament current approximation and solves for the surface currents of the probe as a function of probe angle around the probe. Comparison of theory and experiment is made.

Millstone Hill studies of the trough: Boundary between the plasmapause and magnetosphere or not?

Troughs in the auroral ionosphere have been observed in satellite and radar data since 1965. One explanation for the appearance of these troughs is the stagnation theory of trough formation. According to this model, magnetic flux tubes are convected from the dayside to the nightside across the polar cap as a result of the impressed magnetospheric electric field. These tubes return to the dayside by subsequently drifting westward or eastward. Tubes drifting westward must travel faster than earth rotation if they are to reemerge in sunlit regions, and some fail to do so, allowing the ionization in them to fall to very low levels as it recombines. The trough is the locus of flux tubes which spend a long time in darkness due to the competing effects of the convection electric field and earth rotation. Commencing in 1979, a new observing technique was implemented at Millstone Hill in which the 150‐ft antenna is moved slowly under computer control as data collection proceeds. The electron density results obtained with these experiments show that when a trough does form there is a great variation in when and where it is seen and how long it is present. On some nights the trough does not form at all. Furthermore, the appearance of the trough in the data often seems to occur in regions where the electric field is very large, with the ion drift velocity often far exceeding the speed of earth rotation. None of this behavior is entirely consistent with the stagnation theory of trough formation. An alternative explanation is to suppose that troughs are formed in regions of very strong convection (>1 km/s) as a result of the increase in the rate of charge transfer between O+ and O that occurs when the ions are driven through the neutral gas at high speed. According to such a view, “troughs” would be created in localized regions during substorms. The troughs might be created in regions of strong westward flow in the dusk sector. They then could migrate south and eastward depending upon the effects of convection and corotation. In an effort to test this picture we have begun conducting observations through 360° azimuth to see if the ionosphere to the northeast of the radar is the same as that seen later to the northwest. Results are presented for December 21–22, 1980. These do exhibit significant differences, tending to confirm that the trough is not a persistent extended E‐W feature.

Some Considerations on AC Water Trees in Crosslinked Polyethylene

This paper first confirms that moisture absorption of XLPE (crosslinked polyethylene) obeys Fick's law. The effects of moisture absorption and temperature on water treeing in XLPE are then discussed. The results of physical and chemical tests of the sites of water trees are presented. Infrared Fourier Transform Spectro-scopy (FT-IR) test results show the chemical aspects of the deterioration. Finally, the authors suggest that the water tree is due to a shift in chemical equilibrium (free energy) of the insulating materials due to the impressed electric field.

AlxGa1–xAs/GaAs thin window concentrator solar cells by LPE plus vapour phase diffusion

AbstractZinc diffusion from the vapour phase on a previously grown LPE nAlxGa1–xAs/nGaAs sample is discussed for thin window concentrator solar cell manufacture. A high cell shunt resistance and a low series resistance are achieved together with improved optical parameters via an impressed electric field in the emitter. Dark current components are rather low and 21.8% conversion efficiency is measured at AM 1.3. When the photogenerated short circuit current density is 8 A · cm−2, the fill factor is 0.77 and open circuit voltage is 1140 mv.

ELF electric field coupling to dielectric spheroidal models of biological objects.

The extremely low frequency (ELF) electric field coupling to dielectric spheroidal models of biological objects is studied. Simple expressions are obtained to determine the internal electric field strength induced inside two nonspherical spheroids; a prolate dielectric spheroid and an oblate dielectric spheroid. Certain numerical results are graphically presented for various geometric shapes of the spheroid. The results show that, unlike the symmetric dielectric sphere, the relative position of the spheroid with respect to the orientation of the impressed electric field is an extremely important parameter which considerably affects the electric field coupling.

Space dependent electron transport by an integral approach

The aim of the present paper is to study the diffusion of a rarefied electron gas in a random distribution of field particles, and in presence of an impressed external electric field. Electrons are emitted by a plane source, and undergo scattering or ionization collisions against field particles. The analysis is carried out resorting to the linear Boltzmann transport equation for the electron distribution function, and following a recently developed integral formulation. Several results of physical interest are presented and briefly discussed.

Velocity distribution symmetry of ions in a hollow-cathode discharge

The velocity distribution of radiating ions in a gaseous discharge under an impressed electric field is calculated, with both charge transfer (CT) and momentum transfer (MT) being considered. The present study was instituted in order to develop a distribution which is more symmetric than one based upon CT alone. Such a symmetric distribution was needed for interpretation of Ne II quartet interferograms from a hollow-cathode discharge which were found to be strongly symmetric. The MT collisions are introduced into the CT distribution in an approximate manner by utilising the equation of motion which holds for a plasma in an electric field containing a velocity-dependent damping term. From the values of the parameters which are calculated to fit the derived interferogram to an observed Ne II 3694 AA interferogram, values of the damping constant and the internal field are obtained. These values are in reasonable agreement with corresponding values obtained from independent atomic scattering data and electric probe measurements.

Transmission of polar electric fields to the Equator

SEVERAL kinds of geomagnetic variations are observed simultaneously at high latitudes and in the equatorial region. These are substorms or DP-1 variations, Spq or DP-2 variations, some kinds of pulsations, and the DS-part of SSC and SI. Araki1 analysed the relationship of the preliminary reverse impulse of SC* occurring in the high-latitude and the equatorial regions and found that their occurrence in both regions is well correlated, almost simultaneous, and that the waveforms are very similar. From the characteristics of these geomagnetic variations, it seems that a horizontal electric field impressed in the polar ionosphere from the magnetosphere greatly contributes to the equatorial part of these geomagnetic variations. This electric field is generated by large scale dynamic processes in the magnetosphere such as a sudden compression by an interplanetary shock wave or a change of the magnetospheric convection, and its direction will be approximately east–west (dawn–dusk)2. To clarify the mechanism of the instantaneous horizontal transmission of the polar electric field, we have analysed the response of the ionosphere to a suddenly impressed electric field.

Doubled-layered polycrystalline cadmium sulfide on lithium niobate

We have developed a technique for fabricating polycrystalline thin films of CdS on z-cut LiNbO3. A single film will show a light-to-dark–conductivity ratio of approximately unity with very high sheet resistance after curing. To make a good photoconductor, a second film is then deposited. This film is protected during the subsequent curing from out-diffusion from the LiNbO3 by the first film and develops a light-to-dark–conductivity ratio of 10 000 in room light with a sheet conductivity of 10−10 s/⧠ mcd. Films produced by this layered process also possess a remarkably large conductivity-modulation dependence (20%) on the square of an impressed electric field provided by a traveling surface acoustic wave in the LiNbO3 substrate.

Excitation of an infinite antenna above a dissipative earth

The antenna problem consisting of exciting an infinitely long horizontal thin wire with an arbitrary distribution of impressed electric field along the axis of the wire is discussed. The special case of excitation by a delta function voltage source is solved. The current on the antenna is found as a sum of two residue (discrete) contributions and two branch integration (continuous) contributions. The far field and orthogonality properties of both the discrete and continuous modes are discussed. Finally, expressions are given for the current on the antenna. From this current the input conductance of the antenna can be obtained.

Theory of an Electric-Current-Carrying Discontinuity Driven through Nonconducting Gas by a Lorentz Force

A physical model is presented for the structure of an electric‐current‐carrying discontinuity moving into nonconducting gas and leaving nonconducting gas behind. The model assumes a normal shock wave followed by a porous current sheet. A three‐fluid analysis (electrons, neutrals, and singly charged ions) is made for the case where the component of magnetic field normal to the plane of the discontinuity is zero. All the dependent variables can be computed as functions of displacement in the streamwise direction, as demonstrated in two specific examples. The model admits finite‐strength current sheets as solutions, with the electron and ion density diminishing to zero upstream and downstream of the sheet. As seen moving with the discontinuity, the impressed electric field and the induced electric field are additive on both sides of the discontinuity. This is in contrast to the case for magnetohydrodynamic shock waves, where these two fields cancel on both sides; and to gas‐ionizing shock waves, where the two fields cancel on the downstream side. In the frame of reference moving with the discontinuity, the discontinuity dissipates electrical energy and decelerates the gas. A new jump relation is found which may be described as a “sheet Ohm's law.” The fact that one and only one such relation exists, implies that a current‐carrying discontinuity moving through nonconducting gas is unstable and cannot be part of a unique flow solution unless the discontinuity moves supersonically with respect to the upstream gas and subsonically with respect to the downstream gas.