Showing papers on "Electric potential published in 1977"

A mathematical model for calculating electrical conditions in wire‐duct electrostatic precipitation devices

Abstract: A new method is developed which can be used to calculate electrical conditions in wire‐duct electrostatic precipitation devices. The method, based upon a numerical solution to the governing differential equations under a suitable choice of boundary conditions, accounts for the effect of space charge and is applicable over the entire range of current and voltage before sparkover. The procedure yields voltage‐current characteristics and determines the electric potential and electric field strength as functions of position for each current and applied voltage. Predictions of the theory are compared with existing experimental data and the agreement is excellent.

A simple two-dimensional model for IGFET operation in the saturation region

Abstract: A model is developed for an IGFET operating in saturation and accounting for the two-dimensional potential distribution in the section of the surface space-charge region adjacent to the drain. This section is treated as a volume obeying Gauss's law, thereby enabling the charge contained in it to be related to the integral of the electric displacement density normal to its surface without the need to consider the detailed distribution of charge inside. The resulting model shows, explicitly, the dependence of device output characteristics on applied potentials, geometric and processing parameters. It is also shown that by making adequate approximations, simple yet accurate forms of the model are obtained. The accuracy of the model is demonstrated by comparisons between calculated and measured device output characteristics.

The signature of parallel electric fields in a collisionless plasma

Abstract: The presence of a parallel electric field in the magnetosphere should be apparent through its effect on particles. An analysis is made of particle trajectories in phase space for a steady state collisionless plasma. The analysis utilizes the concepts of distribution function, total energy, and magnetic moment because all three quantities are conserved in a steady state situation in the absence of collisions. Two methods are presented for using particle data to gain information on the potential distribution. The first method involves the use of measurements of both ion and electron distribution functions and invokes the principle of quasi-neutrality. The second method involves the observation of discontinuities in velocity space which can be interpreted in terms of the effect of the electric field on the apparent loss or source cone.

Localized induced electric field within the magnetotail

Abstract: The conversion of magnetic energy, stored within the magnetotail during the growth phase, into particle kinetic energy is studied by taking induced electric fields, due to explicit time dependence of magnetic fields, into consideration The polarization of a plasma in the presence of such a field is discussed, and the topological difference between a polarized and an induced electric field, namely that one is irrotational and the other is not, is pointed out A localized perturbation in neutral sheet current is also discussed

Thermoelectric power in inhomogeneous materials

Abstract: The thermal conductivity and thermoelectric power of an inhomogeneous material subjected simultaneously to gradients of temperature and electric potential are accounted for in terms of an effective-medium theory as well as by numerical simulations in cubic networks with correlated bonds.

Creation of Soliton Pairs by Electric Fields in Charge-Density—Wave Condensates

Abstract: The creation probability of soliton-antisoliton pairs due to quantum-mechanical tunneling in the presence of an electric field in charge-density---wave condensates is calculated. This process gives rise to an additional electric conductivity strongly nonlinear in the electric field, which may account in part for the anomalous conductivity observed in Nb${\mathrm{Se}}_{3}$.

Finite element solution of complex potential electric fields

Abstract: A computer program is described, which calculates electric fields in configurations with both capacitive and resistive distribution of potentials. Resistive coating on the surface of the insulation as well as conductivity in the insulation itself can be handled.

Field-aligned currents and ionospheric electric fields

Abstract: It is shown that the observed distribution of the ionospheric electric field can be deduced from an equation combining Ohm's law with the current continuity equation by using the 'observed' distribution of field-aligned currents as the boundary condition for two models of the ionosphere. The first model has one conductive annular ring representing the quiet-time auroral precipitation belt; the second has two conductive annular rings that simulate the discrete and diffuse auroral regions. An analysis is performed to determine how well the electric-field distribution can be reproduced. The results indicate that the first model reproduces the Sq(p)-type distribution, the second model reproduces reasonably well a substorm-type potential and ionospheric current patterns together with the Harang discontinuity, and that the distribution of field-aligned currents is the same for both models.

Calculation of sheath and wake structure about a pillbox-shaped spacecraft in a flowing plasma

Abstract: A computer program was used for studies of the disturbed zones around bodies in flowing plasmas, particularly spacecraft and their associated sheaths and wakes. The program solved a coupled Poisson-Vlasov system of nonlinear partial differential integral equations to obtain distributions of electric potential and ion and electron density about a finite length cylinder in a plasma flow at arbitrary ion Mach numbers. The approach was applicable to a larger range of parameters than other available approaches. In sample calculations, bodies up to 100 Debye lengths in radius were treated, that is, larger than any previously treated realistically. Applications were made to in-situ satellite experiments.

Method and means for dynamic correction of electrostatic deflector for electron beam tube

Abstract: An electron beam tube electrostatic deflection system and method of operation is described. The electron beam tube includes an eight-fold deflector and means are provided for applying two different quadrupole correction electric potentials to selected ones of the eight-fold deflector members and for applying an octupole correction electrical potential to all eight deflector members. In the preferred embodiment, the quadrupole and octupole correction potentials applied to one set of four deflector members are represented by the respective values (V 2c - V), (-V 2c - V), (V 2c - V) and (-V 2c - V), and the quadrupole and octupole correction potentials applied to the second set of four deflector members are represented respectively by the values (V 2s + V), (-V 2s + V), (V 2s + V) and (-V 2s + V) where the quadrupole correction electric potential V.sub.2c = [A.sub.2c (V.sub.x.sup.2 - V.sub.y.sup.2)]/V.sub.c, (1) the quadrupole correction electric potential V.sub.2s = (2A.sub.2s V.sub.x V.sub.y)/V.sub.c, (2) and the octupole correction potential V applied to all eight of the eight-fold deflector members is given by the expression V = [A.sub.4 (V.sub.x.sup.4 - 6V.sub.x.sup.2 V.sub.y.sup.2 + V y 4 )]/4V c 3 (3) where A 2c , A 2s and A 4 are constants, V x and V y are the x and y deflection electric potentials, and -V c is the cathode voltage of the electron gun used in the electron beam tube apparatus. In preferred arrangements, the electrostatic deflection system further includes means for applying a dynamic focusing electric potential to the objective lens assembly of the electron beam tube apparatus in conjunction with both the correction and deflection electric potentials described above. The dynamic focusing electric potential is V.sub.OBJ(DF) = V.sub.OBJ(0) + [(A.sub.DF (V.sub.x.sup.2 + V y 2 ))/V c ] (4) where A DF is a constant and V OBJ (O) is the uncorrected value of the direct current objective lens supply voltage. Both deflection and correction electric potentials are developed by an eight-fold deflector voltage generator which includes as its heart a novel octupole-quadrupole generator.

Measurement of magnetic field aligned potential differences using high resolution conjugate photoelectron energy spectra

Abstract: Simultaneous high-resolution observations of a distinctive feature in the energy spectrum of conjugate photoelectrons and spacecraft potential relative to the local ionosphere have allowed the net potential difference between magnetic conjugate points at latitudes below the region of low-energy (i.e., lower than 100 eV) auroral electron precipitation to be determined. Measurements made at 300 km from Atmosphere Explorer C show that there is normally no net potential difference between hemispheres in this region, which extended up to invariant latitudes as high as 74 deg. Two types of apparently related anomalous behavior were infrequently observed at high latitudes. During these periods the incident flux of conjugate photoelectrons was either decelerated by about 3 eV or was not detected.

Avoided crossings of resonance energy curves of one-electron atoms in an external electric field

Abstract: A rule is developed which predicts avoided crossings of resonance energy curves of long-lived states of one-electron atoms in an external electric field.

On the polarity effect of the breakdown voltage for dielectric liquids in an inhomogeneous field

Abstract: The polarity difference of the breakdown voltage of some pure dielectric liquids and transformer oil is qualitatively explained by analysing the electric field distribution of a point-plane test cell under the condition of unipolar injection of charge carriers. Although the space charge reduces the electric field at the point, it leads to an increase in the stressed volume thus increasing the probability of breakdown. The magnitude of the space-charge contribution is inversely proportional to the mobility of the injected charge carriers. Since in some of these liquids electrons exhibit a much higher mobility than positive ions, the influence of the space charge is reduced for the point negative compared with the point positive.

The Field from an Isolated Nerve in a Volume Conductor

Abstract: Experimental recordings of electric field potentials from an active frog sciatic nerve in an "infinite" volume conductor were obtained. The dorsal and ventral roots supplying the isolated sciatic nerve were dissected and stimulated separately and in combination. The measured electric field potentials from dorsal/ventral root stimulation, as well as whole nerve stimulation, were recorded at the nerve surface and at several radii from the nerve. The field potentials, at these radius values, were predicted from a solution of Laplace's equation. The Fourier transform development of the solution of Laplace's equation, as presented by Clark and Plonsey [4], [5], allowed the determination of the field potentials to be viewed as a one-dimensional linear filtering procedure with the surface potential as an input and the field potential at a given radius as an output. Standard techniques in linear system theory were utilized to perform convolution via the discrete Fourier transform (DFT) and to perform inverse filtering via optimal filtering methods. With these techniques the surface potential could be predicted given a field potential measurement at a known radial distance from the nerve.

Plasma rotation by electric and magnetic fields in a discharge cylinder

Abstract: A theoretical model for an electric discharge consisting of a spatially diverging plasma sustained electrically between a small ring cathode and a larger ring anode in a cylindrical chamber with an axial magnetic field is developed to study the rotation of the discharge plasma in the crossed electric and magnetic fields. The associated boundary-value problem for the coupled partial differential equations which describe the electric potential and the plasma velocity fields is solved in closed form. The electric field, current density, and velocity distributions are discussed in terms of the Hartmann number and the Hall coefficient. As a result of Lorentz forces, the plasma rotates with speeds as high as 1 million cm/sec around its axis of symmetry at typical conditions. As an application, it is noted that rotating discharges of this type could be used to develop a high-density plasma-ultracentrifuge driven by j x B forces, in which the lighter (heavier) ion and atom components would be enriched in (off) the center of the discharge cylinder.

Multiple-scattering and ion effective charge deviation effect on the energy spectrum form of particles back-scattered from a thick target

Abstract: The multiple-scattering, straggling and the ion effective charge deviation effect on the energy spectrum form of back-scattered nitrogen ions having the initial energy E 0 = 7.4 MeV is described. The multiple-scattering effect depends on the geometrical conditions of the experiment and the atomic number of the target atoms. To describe adequately the multiple-scattering of multicharged ions it is necessary to fit screened Coulomb potential by introducing the effective charge of ions. The influence of the straggling in our case was found to be negligible.

Space charge limited current flow between coaxial cylinders at potentials up to 15 MV

Abstract: Poisson's equation in cylindrical symmetry is solved numerically with the assumptions of zero field and zero electron energy at the cathode surface. The computed current is expressed in terms of an analytical solution obtained for the extreme relativistic case. Internal and external anode configurations are treated, with ratio of electrode radii extending to 10000 and potential difference up to 15 MV. Application of this analysis to the high-power field-emission diode is considered, with particular reference to the radially pumped ultraviolet laser.

Surface Charge Buildup During Electrostatic Spraying

Abstract: In industrial electrostatic spray coating operations, liquid paint is applied to substrates of varying electrical characteristics. In many cases a metal substrate is chemically pretreated and/or primed prior to electrostatic spraying. A previously rejected part may have already received a number of thoroughly cured topcoats prior to the final spray application. Typical primers and topcoats have large surface resistivities (108 to 1010 ohm.cm-2) and exhibit slow surface potential decay rates. A surface potential measurement system has been developed to determine the time dependent electrical properties of various substrates when coated with commercial water base and organic paint systems. It has been observed that during some electrostatic recoat operations, the charged paint particles appear to be repelled from the surface to be coated. It is found that this phenomenon can be predicted when conditions are such that adequate charge leakage paths to ground are not available due to high surface and bulk resistivities of the film resulting in a repelling charge and potential buildup on the surface. It has been found that the charge removal process cannot be described as a simple exponential decay, but as a superposition of three exponential decay processes each with its own decay constant ?.