Conductor Radius Research Articles

Density profiles of corona discharge plasmas

Corona discharge properties in the reactor chamber are investigated, assuming that a specified voltage profile V( t) is fed through the inner conductor. The analytical description is based on the electron moment equation. Defining the plasma breakdown parameter u = V R c p , plasma is generated for a high voltage pulse satisfying u > u c, where u c is the critical breakdown parameter defined by the geometrical configuration. Here, u is in units of a million volts per m per atm, and R c is the outer conductor radius. It is found that the plasma density profile generated inside the reactor chamber depends very sensitively on the system parameters. A small change of a physical parameter can easily lead to a density change of one order of magnitude.

An analytical theory of corona discharge plasmas

In this paper we describe an analytical investigation of corona discharge systems. Electrical charge and the energy transfer mechanism are investigated based on the circuit analysis. Efficient delivery of electrical energy from the external circuit to the reactor chamber is a major issue in design studies. The optimum condition obtained in this paper ensures 100% energy transfer. Second-order coupled differential equations are numerically solved. All the analytical results agree remarkably well with numerical data. The reactor capacitor plays a pivotal role in circuit performance. The voltage profile is dominated by the reactor capacitor. Corona discharge properties in the reactor chamber are also investigated, assuming that a specified voltage profile V(t) is fed through the inner conductor. The analytical description is based on the electron moment equation. Defining the plasma breakdown parameter u=V/Rcp, plasma is generated for a high-voltage pulse satisfying u>uc, where uc is the critical breakdown parameter defined by geometrical configuration. Here, u is in units of a million volts per m per atm, and Rc is the outer conductor radius. It is found that the plasma density profile generated inside the reactor chamber depends very sensitively on the system parameters. A small change of a physical parameter can easily lead to a density change in one order of magnitude.

A Special-Case Surface Voltage Gradient Formula

In the electrical design of a high-voltage substation, the designer needs a simple and reliable tool, preferably a closed-form formula, when calculating the surface voltage gradient of line segments within the substation since the surface voltage gradient is the governing parameter of the corona performance. This paper presents a derivation of a closed-form formula for calculation of the maximum surface voltage gradient of a special line configuration, namely a horizontal AC three-phase line configuration with bundle conductors consisting of three sub-conductors in a horizontal arrangement. The formula has been verified against exact calculations and was found to have an error less than 5% for all practical combinations of the conductor radius, the sub-conductor spacing, the phase distance, and the height above earth.

Coaxial cavities with corrugated inner conductor for gyrotrons

This paper investigates coaxial gyrotron cavities with longitudinal slots on the inner conductor as a means to reduce the number of possible competing modes. In the analytic theory the corrugated surface is treated as a homogeneous impedance surface ("impedance corrugation") to obtain simple formulas for the characteristic equation of the eigenmodes, for the electromagnetic fields and the wall losses. The developed model applies if the number of slots is sufficiently high (cutoff wavelength much larger than the corruption period). The characteristic equation in terms of the ratio C of the outer wall radius to the inner conductor radius is solved numerically to determine a range of eigenvalues and C where the eigenvalue curves are monotonically decreasing. In such a region a cavity having its inner conductor downtapered (radius decreasing toward the cavity output) can be used to reduce the diffractive quality factors of several modes, leaving the working mode undisturbed and without favoring other modes. In addition the electromagnetic field profiles are investigated, and in particular it is shown that for certain cavity parameters a mode could have its energy concentrated close to the inner conductor. As a check on the validity of the theoretical approximations, simulations with the MAFIA code are carried out. These give good agreement with the results of the analytic equations.

A special-case surface voltage gradient formula [for substation design

In the electrical design of a high-voltage substation, the designer needs a simple and reliable tool, preferably a closed-form formula, when calculating the surface voltage gradient of line segments within the substation since the surface voltage gradient is the governing parameter of the corona performance. This paper presents a derivation of a closed-form formula for calculation of the maximum surface voltage gradient of a special line configuration, namely a horizontal AC three-phase line configuration with bundle conductors consisting of three sub-conductors in a horizontal arrangement. The formula has been verified against exact calculations and was found to have an error less than 5% for all practical combinations of the conductor radius, the sub-conductor spacing, the phase distance, and the height above earth.

Geometry effects on the dispersion in chiral coaxial lines

AbstractIn comparison to some other chirowaveguides the geometry of the chiral coaxial line offers an additional degree of freedom, namely, the ratio of inner to outer conductor radius. The influence of this parameter on the dispersion characteristics, in particular also of the dominant mode, is investigated in this report. © 1995 John Wiley & Sons, Inc.

Performance of a plasma opening switch in positive polarity on Gamble I using flashboard plasma sources

The successful development of the Plasma Opening Switch (POS) for inductive storage applications has been largely confined to negative polarity operation. Some models of POS behavior suggest that this is because in a positive polarity coaxial configuration, the weaker magnetic field at the cathode position retards the switch opening process. This article describes experiments in which both conductor radii in the POS region were significantly reduced. Anode- and cathode-side current monitors indicate that voltages greater than open-circuit are generated at the POS position, but there is a significant amount of electron flow out of the POS, depending upon load impedance. Flow impedance analysis indicates that a relatively small gap appears in the POS plasma after switch opening. Switch performance is also compared between flashboard and carbon gun plasma sources, with the latter operated both in positive and negative polarity.

Magnetic Field Effects in High‐Power Batteries: II . Time Constant of a Radial Circuit Terminated by a Cylindrical Cell with Inductance

The time constant to steady state of an electric signal applied to the outer boundary of a radial circuit that propagates to a centrally located cylindrical conductor is determined rigorously by a transmission‐line analysis. Two cases are reported: the perfect radial conductor and a radial conductor with a finite resistance. The time constant is featured as a function of the ratio of the radius of the radial conductive leads to the radius of the inner conductor. As the ratio is increased, the time constant departs from that of an electric field penetrating a cylindrical conductor and approaches the inductive time constant of the leads. An analytic approximation of the time constant of the system also is provided. This analysis should assist in the development of high‐power circuitry design when the discharge time is on the order of the inductive time constant.

Critical switching impulse strength of phase-to-phase air insulation

A new physical approach is presented to modeling of positive leader inception and breakdown of phase-to-phase insulation in air, exposed to critical switching impulses of synchronized peaks and opposite polarity. This is a generalization of a recently published model dealing with phase-to-ground insulation. Both conductor-conductor and horizontal rod-rod configurations are discussed. The influence of interphase separation, conductor height above ground, conductor radius and relative amplitude of the negative impulse on critical insulation strength is systematically investigated. An application of the model, is a physically based prediction of air density effects on phase-to-phase leader inception and breakdown, is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Short-circuit electromagnetic forces in three phase gas insulated systems with steel enclosure

In this paper, the short-circuit forces acting on the phase-conductors of arrangements with 3-phase steel enclosure, are examined. In the case of tubular conductors the forces result from the vector potentials calculated in the different arrangement areas. The potentials result as Fourier series ofn terms; their coefficients are determined from the numerical solution of a 10×n algebraic equations system. But in the case of filamentary conductors the corresponding system of equations consists of two independent systems, 4×n equations each, that can be analytically solved and lead to simpler relations for the forces. Parametric investigations showed that, for the praxis arrangements, the influence of the conductor radius on forces is very small and consequently the conductors may be considered as filamentary. The influence of the relative permeability, the conductivity and the thickness of the shell on the electromagnetic forces has also been examined.

Electrical behavior of a skeletal muscle fiber in a volume conductor of finite extent

A model study of the spatial distribution of the extracellular potentials and current densities arising from an active single skeletal muscle fiber in a cylindrical volume conductor of finite radial extent is presented. The paper examines the influence of the radius of the volume conductor,b, on the extracellular potentials and currents at different field points. The equivalent sources with respect to the extracellular potential are investigated as well. The axial source density associated with the primary and secondary sources is calculated using the expressions for the intracellular and extracellular potentials. The density of the secondary sources is a decreasing function of the radius of the conducting medium and approaches zero whenb becomes infinitely big.

Helicity injection and diagnostics for orbitron millimeter wave source

Conventional orbitrons utilize the radially injected electrons for production of electromagnetic waves. In such a scheme, however, more than half of the electrons would not participate in the orbital motion around the anode due to the lack of acceleration. Only the electrons who did not suffer collisions till the radius 2/3 of the outer conductor (cathode) radius are possible to acquire the azimuthal velocity, via collisions, as large as the critical velocity with which the electrons can undergo circular equilibrium orbits. The axisymmetric injection is also a problem; 50% of electrons would be lost directly to the anode by the head-on collisions. This paper discusses various ways to enhance the efficiency and absolute power of an orbitron millimeterwave source. Experimental results are described on employment of a tapered metal-end, tangential injection of a thin electron beam, axial injection of rotating annular electron beams, and application of external magnetic fields. Further problem of conventional orbitrons is in its construction in which the potential-well is prematurely destroyed due to the shortening discharge current. Its diagnostics and consequence are discussed together with a new scheme leading towards the goal, an efficient injection of helicity (or helical electron-beam) into the potential-well conserved orbitron interation region.

Characteristic impedance and loss data for a common stripline pickup geometry

Most particle accelerators routinely employ some type of stripline pickups and/or kickers. In this paper, characteristic impedance and resistance per unit length are calculated for a strip transmission line geometry consisting of a circular outer conductor and an infinitely thin concentric inner conductor which subtends an angle φ 0 in azimuth (see fig. 1). Useful design plots for these parameters as functions of φ 0 and inner to outer conductor radius ratio, b/ a, are given.

Required accuracy in manufacturing process of three‐wire transmission line used in inductive radio system for detecting linear motor vehicle position

AbstractThe three‐wire transmission lines consisting of square‐wave‐formed line conductors has a structure in which any two of the three line conductors iterate narrow and wide sections at a specified interval along the longitudinal direction. Among those sections, the narrow section has the following problem. If line conductors deviate even a little from their normal positions due to the inaccuracies in the manufacturing process, relatively large unbalances will be produced in the mutual impedances and admittances between them. This leads to the crosstalk between the positive and negative phase sequence components of the signal and consequently to the detection error in the position of the vehicle. We considered the case where the manufacturing inaccuracies distribute at random or uniformly along the longitudinal direction. A quantitative analysis is made for the problem arriving at a guide for the manufacturing accuracy of the transmission line, which is required to ensure the desired accuracy of position detection. It is desirable in the narrow section that the two conductors maintain a distance above a certain value. It is also desirable that the radius of the line conductor be as small as possible, as long as the transmission loss of the line is within the tolerable value. Compared with the transmission line consisting of helically wound conductors, which we have already reported, there will still be a more strict requirement on the manufacturing accuracy on the transmission line consisting of square‐wave‐formed conductors.

TE&amp;lt;inf&amp;gt;11&amp;lt;/inf&amp;gt;mode excitation of flanged circular coaxial waveguides with an extended center conductor

Properties of circular coaxial Waveguide antennas terminated in a plane conductor are analyzed where in the most general case the center conductor is of infinite extent. Solutions for mutual admittance and radiated fields are detailed for all asymmetric modes. An asymptotic solution is also derived for the far-zone fields. We describe results for TE_{11} mode excitation of coaxial waveguides where 1) outside the aperture the conductor is absent, and 2) the center conductor extends to infinity. These antennas are of practical interest as feeds for reflectors. Experimental results are described for several examples and excellent agreement with theory is shown. Comparison of the two cases shows that in 1) there is always an optimum frequency for good pattern symmetry and low cross polarization. The mismatch in case 2) is less than in 1) but pattern symmetry is poor if the ratio of inner to outer conductor radius is greater than about 0.2. Further, in 2) mutual coupling to adjacent annular rings is stronger and the principal plane radiation patterns has widely spaced phase centers.

Nonlinear theory of the orbitron maser in three dimensions.

Abstract : The nonlinear analysis of the Orbitron Maser is studied numerically for an amplifier configuration in which an electron beam propagates through a coaxial waveguide with a voltage applied between the inner and out conductors. A set of coupled nonlinear differential equations is derived in three dimensions which governs the self consistent evolution of either the TE, TM, or TEM modes in a loss-free coaxial waveguide as well as the trajectories of an ensemble of electrons. The saturation efficiency as well as the linear growth rate are calculated and, although the linear growth rate for the orbitron amplifier is moderately high (about 1.0 dB/cm), the efficiency is low (somewhat 6.1%). Severe limitations arise in the high frequency operation of the orbitron amplifier in the fundamental mode due to the break-down electric field and extremely small radius of the inner conductor.

A Mathematical Analysis of the Glow and Dark Space Regions in Positive Corona

The authors present a mathematical analysis of the electric field, current density, and charge density in the entire airgap in positive dc corona in cylindrical geometry. The currents are found using the Townsend breakdown theory and the Sarma empirical equation for the ionization coefficient in air. Since the ionization coefficient is a function of the local field intensity and the electric field distribution depends on the ionization process, an iterative numerical method was used. White-head's empirical formula describing the conductor surface onset field intensity as a function of the conductor radius was used to establish the field intensity at the point in the gap where the ionization process begins. The results show good agreement with available experimental data on particle-charging.

Characteristic Impedance of the Slab Line with an Anisotropic Dielectric (Short Papers)

The characteristic impedance of the slab line with a circular conductor having an anisotropic dielectric is presented by rising the affine and conformal transformations. Moreover, a simpler approximate formula of the impedance expressed in term of epsilon /spl par/, epsilon /spl perp/, and r/h is also presented, where epsilon /spl par/, epsilon /spl perp/ r, and h, are the principal axes-relative dielectric constants of the anisotropic dielectric, the inner conductor radius, and the half Iength between ground planes, respectively.

A New Method of Calculating 3-Meter Site Attenuation

A new method of calculating 3-m site attenuation is described. To obtain an accurate site-attenuation curve, the problem of coupling between antennas is formulated in the form of coupled integral equations for the antenna currents, and solved by the method of moments (MOM). The site-attenuation curve thus obtained shows about 1.3-dB larger attenuation than that given in an IEC document. The deviations in the site-attenuation curve due to the impedance mismatch between the coaxial cable and the measuring equipment, and the influence of the antenna conductor radius on the attenuation curve are also considered. Finally, the calculated site attenuation is compared with the measured attenuation data available in the literature.

The Potential Field around Subsurface Electrically Excited Conductors

A simple mathematical model has been developed for determining the depth and radius of an excited electrical conductor (e.g., a grout ball) located underground. The method uses voltage profiles, measured on the ground surface or in boreholes, and it is expected to be more accurate than conventional four-probe resistivity surveys.