Showing papers on "Electric current published in 1969"

High-energy electroproduction and the constitution of the electric current

Abstract: The asymptotic behavior of electroproduction cross sections is shown to contain information about the constitution of the electric current.

Surface Waves in Piezoelectrics

Abstract: The effect of various electromagnetic boundary conditions on the propagation of surface waves in piezo‐electrics is considered. Basic for the analysis is the introduction of an electric ``surface impedance'' which relates the electric potential to the normal component of electric displacement in the surface. An analytic expression for this impedance is found in the case of weak piezoelectric coupling which permits the calculation of the phase velocity for arbitrary values of the impedance. It is also shown that within the weak coupling approximation the surface impedance contains the information on material parameters necessary for calculating the power transferred to surface waves from an impressed electric current.

Electric fields in the vicinity of auroral forms from motions of barium vapor releases.

Abstract: Electric field variations in vicinity of auroral forms from motions of Ba vapor clouds released from Nike-Tomahawk rockets

A relaxation method of calculating arc temperature profiles applied to discharges in sodium vapor

Abstract: A relaxation method based on the time dependent energy balance equation is used to derive steady state characteristics of arcs taking account of energy transfer due to thermal conduction, emission and absorption of radiation. The method involves calculating the radiation flux density as a function of radius for a given temperature profile using an integral solution of the radiation transport equation. An alternative but slightly less efficient form of the relaxation method uses a similar integration procedure but calculates the average radiation intensity. The methods have been applied to calculate the characteristics of discharges in sodium vapor where radiation other than from the D lines has been neglected. Results are presented for a pressure of 250 torr giving (1) temperature profiles and radiation efficiency as a function of electric current, tube radius and wall temperature, (2) characteristic line profiles of the radiation, and (3) the E-I characteristics of the discharge for the tube radii of 3·5 and 5 mm for currents ranging from 2 to 10 amps.

Area averaging of atmospheric electric currents.

Abstract: The global atmospheric electric current flow may be determined, if local influences can be eliminated, by measuring the total Maxwell current flowing to the surface of all fairweather areas. A new method to reduce the effect of locally produced disturbances on surface measurements of the atmospheric electric current density is described. Experiments indicate that in the time domain from a few seconds to a few hours the standard deviation of the total current density decreases approximately with the square root of the sensor size. Locally generated currents may therefore be effectively suppressed by area averaging.

Electric field sensor

Abstract: The invention is a method and means for sensing and measuring an electric field within sea water or any other environmental medium. It contains three pairs of diametrically opposed electric current sensing electrodes that are combined and configured in such manner as to form opposite faces of a cube. Each electrode is segmented to effect a predetermined mosaic pattern; and between each pair thereof, a differential amplifier, having an input impedance that is substantially equal to the operational environmental medium, is connected. A signal-processing system, including a telemetering link, a computer, and/or a readout, is connected to the outputs of the differential amplifiers.

Paraconductivity in type-II superconductors

Abstract: The additional conductivity due to the fluctuation of the order parameter in dirty type-II superconductors is reconsidered It is shown that in a magnetic fieldH slightly above the upper critical field the electric conductivity is strongly anisotropic depending on the relative direction of the magnetic field and the electric current In the parallel case (ie,H ∥J) the conductivity diverges like(H−H c2)−3/2, while in the perpendicular case (H ⊥J) it diverges like(H−H c2)−1/2

Direct current transformer employing magnetoresistance diodes for use in current measurement

Abstract: This is a direct current transformer wherein there is inserted through the interior space of a C-shaped core a primary conductor through which there flows a direct current; there is disposed a magnetosensitive semiconductor device in a space defined between both ends of said core; a difference between the value of voltages obtained in proportion to the magnetic fluxes generated by the direct current travelling across both terminals of the magnetosensitive semiconductor device and the value of output voltages obtained from a constant voltage element serially connected to the magnetosensitive semiconductor device without being affected by the magnetic fluxes, is amplified by a differential amplifier; a current determined by said voltage difference is impressed, after being amplified, on a coil wound around part of the C-shaped core to generate such magnetic fluxes as offsetting the magnetic fluxes produced in the core by an electric current introduced through the primary conductor thereby always to maintain the magnetic fluxes prevailing in the core substantially at zero and current outputs from the differential amplifier are measured to find the value of the direct current passing through the primary conductor.

Anomalous currents to a spherical electrostatic probe in a flame plasma

Abstract: By following the same line of reasoning which the authors used in a previous paper, concerned with cylindrical probes, the ion current Ii to a spherical probe (radius rp, bias voltage V) immersed in a collision-dominated flowing plasma of subsonic velocity vf has been calculated to be IMG1 where ne is the electron density, μi the ion mobility, e the electronic charge and 0 the permittivity of free space. This theory is only valid for conditions where the plasma sheath diameter r0>>rp. A propane-air flame with a moving probe was used to investigate the above relationship. Reasonable agreement (considering the approximations made in deriving the theoretical relationship) was obtained between measured and theoretical ion currents.

The electric polarization induced by temperature gradient and associated thermoelectric effects

Abstract: It is shown that the possible existence of a direct effect, which consists in the production of electric polarization in a temperature gradient, is connected with the existence of effects that are analogous to the known thermoelectric effects. The thermoelectric effects under study play a role in a periodic regime of temperature and electric current.

Electric current control apparatus

Abstract: A current control system particularly useful but not limited to high voltage non-linear load devices wherein a vacuum tube, connected in series relationship with the load device and a DC power source, is operated in a controlled electron emission mode. The current through the load may thus be controlled by controlling the current flowing from the anode to the cathode of the vacuum tube.

Superconducting Critical Fields and Currents of Nb–Ti–N Thin Films in Continuous Magnetic Fields to 175 kG

Abstract: Superconducting critical current‐field measurements were made on a series of Nb–Ti–N thin film alloys (1000–8000 A) prepared by reactive sputtering. Samples were measured in dc transverse and parallel fields. A pronounced maximum in the critical field occurs at approximately 20 mole % TiN. The extrapolated zero current value of Hc2 for this composition at 4.2°K was greater than 180 kG. Critical current densities in parallel fields are comparable to those of other high‐field bulk superconductors (104 A/cm2 at 150 kG). Films 2000 A thick and 0.1 in. wide carried a few tenths of an ampere in fields as high as 120 kG in the transverse fields and as high as 140 kG in parallel fields. In the transverse orientation the critical current density appears to be independent of thickness. Possible application of these materials to miniature thin‐film solenoids is discussed.

Power semiconductor device with negative thermal feedback

Abstract: A composite power semiconductor is disclosed which is adapted to avoid second breakdown and therefore provide stable operation. The composite semiconductor consists of an array of parallel-connected integrated circuits constructed in a single chip, each circuit comprising an output power device, for connection between an electric power source and a load, and one or more associated low-level control amplifiers. The effect of the thermal instability called second breakdown in such an array is to channel a disproportionate amount of electric current through the output device undergoing second breakdown, thereby increasing the temperature of the affected output device, thereby increasing the current, etc. until failure occurs. In the power semiconductor disclosed, the output power device and associated low-level amplifier are thermally closely coupled so that each is at all times substantially at the temperature of the other or bears a predetermined temperature relationship therewith, and the two are interconnected in a fashion that will produce high electrical gain. There is negative thermal feedback so that a change in power dissipation with resulting temperature change in the output device causes the low-level amplifier to alter the electric current carried by the output device. For example, an increase in temperature which will tend to cause the output device to conduct a larger amount of electric current and which will also tend to cause the low-level amplifier to conduct a larger amount of current, can have the result, because of the close thermal coupling and interconnection, of maintaining the output current substantially constant.

The CW gain characteristics of several gas mixtures at 337 microns.

Abstract: Gas mixtures CW gain characteristics at 337 mu as function of pressure, current, mixture and flow rate, considering HCN laser systems

Source of electrical energy

Abstract: A compact portable source of electrical energy for electric razors comprising: A. at least one electric cell having a gastight enclosure, which is rapidly chargeable at high amperages and safe from overcharging, B. a charging device adapted to receive power from an external source and adjusted to deliver a high amperage charging current to the cell, preferably by means of a thyristor circuit, and C. a temperature sensor in thermal proximity with said cell adapted to produce a signal when the temperature of the cell reaches a predetermined level, thereby indicating the degree of charge of the cell. The power sources of the present invention are especially useful to supply electrical energy to electric razors.

Electric Current in a Semiconductor Space‐Charge Region

Abstract: An equation for the electric current in a semiconductor space‐charge region such as a p‐n junction is derived. At low currents the equation has the usual form i=neμ*E−(q/e) μ*kTL∂n/∂x but the effective mobility μ* is shown to have a strong dependence on position and may be infinite or negative. This spatial dependence arises because the deviation of the average carrier energy from its equilibrium value has a first‐order dependence on the current.

Non-Ohmic Conduction in Germanium under a Strong Magnetic Field

Abstract: A distinct non-ohmic current-voltage characteristics in n -type germanium containing 10 20 to 10 22 impurity atoms/m 3 under a strong impulsive magnetic field was found at liquid hydrogen temperatures. The effect was also observed in p -type germanium with appropriate impurity concentrations for the transverse magnetic field stronger than 1 Wb/m 2 . Essential mechanism underlying this effect would be a “transverse breakdown” introduced by M. Toda et al. In the present case, however, “transverse impact ionization” should be more appropriate than “transverse breakdown”. Necessary conditions for the occurrence of this non-ohmic effect are (1) the existence of the strong Hall field and (2) neutralized donors or acceptors in germanium crystals. Some peculiar phenomena associated with this effect i.e. , a kind of instability in electric current, negative differential drift mobility and the anomalous electric field dependence of the Hall angle were also observed.

Electrical processes in heavy rain in the tropics

Abstract: The thesis is based on research carried out in Sierra Leone over a period of several years. An asymmetric field mill and a 'wide-angle' shielded receiver have been developed for the measurement of electric field and precipitation current in tropical thunderstorms. A detailed field-mill theory is presented which analyses the effects of leakage currents, inadequate grounding, contact potentials, conduction current, 'pick-up' of fluctuating electric fields and noise in the amplifier. Principles are deduced for the optimum design of a precision field mill using either a phase sensitive detector or an asymmetric signal. Measurements of precipitation current and its response to step changes in the field show that turbulent diffusion of splash droplets probably constitutes an important, even dominant, electrical process in heavy rain. The response of precipitation current to a lightning flash, averaged over many flashes, is large and has a delay of a few seconds. From the analysis of various models considered as a mechanism to explain the results it is deduced that charge carried on splash droplets is being diffused upwards by turbulence, transported by wind and is itself precipitating into the rain receiver. An experiment was performed to measure the electric current due to evaporation. The results show that the current due to evaporation in the presence of an electric field is much smaller than that due to conduction in air. The observation of a 'warm' thunderstorm cloud is reported. A project was developed to make visual and electrical measurements simultaneously on the same cloud. A time lapse film of tropical clouds, together with some electric field measurements beneath them, are used to discuss the flow pattern associated with a tropical thunderstorm and the mechanism by which it becomes charged. Appendices include an analysis of the shielding effect of a vertical rod at ground potential, the description of some further instrumentation, including a data processing system designed by the author which uses a novel but effective method of detecting the occurrence of the peak of a signal, more detailed mathematical derivations of equations used in the main text and a filming schedule for the time-lapse photography.

Plasma thermal emission energy conversion

Abstract: : The problem of obtaining electrical energy directly, without use of machines with moving parts, has now obtained practical value. The development of direct conversion will essentially influence power engineering in the near future. Atomic power engineering assumes the creation of reactors-generators in which electric energy is produced in the actual reactor, without turbines and generators of electric current. The offered monograph is dedicated to physics of low-temperature plasma utilized in plasma thermoemission energy converters. A classification of various operating conditions of a converter and transport theory for a 3-component plasma (electrons, ions, atoms) are given. Volt-ampere characteristics and distribution of density, temperature and the electrical field between electrodes are investigated in different conditions. A method of experimental investigations is expounded. Results of calculation are compared with experiments. The influence of different impurities on work of a cesium thermoemission converter is investigated. (Author)

Theory of Electrical and Thermal Stability of a Superconductor in the Resistive State

Abstract: The problem of electrical and thermal stability of a superconductor when carrying a steady‐state transport current beyond the critical current has been analyzed for a bare superconductor. The following relation is derived ν = I(I−1)/1−θI2, where ν is the nondimensional voltage, I is the current in units of the critical current, Ic, of the superconductor, and θ is a parameter involving only the constants of the superconductor, and the heat transfer coefficient of the cooling medium. To have a reversible voltage current characteristic beyond the critical current, the parameter θ should be «1. Factors affecting this parameter are analyzed. The influence of this parameter on the propagation of a resistive front is discussed. Furthermore, the influence of a normal metal in good electrical and thermal contact with the superconductor is also included.

Effects of Field-Aligned Currents on the Structure of the Ionosphere

Abstract: The influence of electric currents along the magnetic field lines on the high-latitude F-layer ionosphere is investigated theoretically. It is shown that a current of either sign leads to a reduction of the total electron content and the maximum density, if the charge carriers have to be produced in the ionosphere. Low-energy precipitation leads to a corresponding increase. Extremely low densities in the topside ionosphere may be reached for ion currents of the order of 10-6 amp/m2 or electron currents of 10-3 amp/m2. Observational evidence exists for currents at least of the order of 10-6 amp/m2. It is suggested that the ionospheric trough, the F-layer storm, and other similar effects may be explained by field-aligned currents or plasma diffusion, which is also quantitatively accounted for by the present theory.