Measurement Of Charge Distribution Research Articles

パルス静電応力法によるケーブル絶縁体中の空間電荷分布測定

パルス静電応力法によるケーブル絶縁体中の空間電荷分布測定

High-resolution surface charge measurements on an organic photoconductor

A technique for making direct, quantitative measurements of surface charge distributions on photoconductors has been developed. The spatial resolution is better than 10 μm and the measurements take place under conditions closely approximating those in printers or copiers. Measurements of edge broadening in layered photoconductor arising from space-charge effects during image formation are presented. Edge broadening due to surface conduction has also been observed and data linking this to contamination of the surface by the charging corona is shown.

Application of ultrasonic techniques to the measurement of spatial charge and electric field distributions in solid dielectric materials

Application of ultrasonic techniques to the measurement of spatial charge and electric field distributions in solid dielectric materials

The mechanism of layer formation from charged powder particles

Theoretical as well as practical analyses of powder charging and deposition in an electric field were carried out. A working procedure was established enabling the measurement of charge distribution and of electric adhesive forces in the layer due to the potential measured at the layer surface. On the basis of determination of centrifugal acceleration necessary for powder layer detachment it is possible to compare the electric forces with the actual adhesive ones. There is a linear dependence between the two types of forces. An initial electric field strength in the powder layer was determined.

Electrical properties of electrode/polyethylene/electrode structures

The pressure-wave propagation (PWP) method allows for the nondestructive measurement of charge distributions in dielectric materials. This method has been used to study the electrical properties of electrode/polyethylene/electrode structures such as those involved in high-voltage cables. The influence of the composition of the insulating resin itself and that of the electrodes are analyzed in polyethylene samples. According to the chosen combination, charge transfer at the interfaces, migration of ionizable impurities, or a strong decrease of both is observed. This application of the PWP method is of particular interest, since it allows for a suitable choice of the materials and structures involved in insulator/conductor interfaces. >

Charge phenomena on technical boundary surfaces in air by D.C.-stress

The presented paper deals with the investigation of test samples in air with nonuniform potential distribution along the insulating boundary surface. The applied D.C. test voltage, the stressing time and the polarity have been varied as well as the relative air humidity (20% – 80%) for different insulator materials (epoxy resin, PMMA, PVC, kraftboard). The surface charge distribution was recorded by means of a computer controlled measuring system using an electrostatic probe. Increasing the voltage and stressing time as well as the surface resistivity of the insulator material increases the measured charge density, as expected. In contrast, especially two phenomena are observed as being considerable: 1. 1. An increase in humidity causes a partly enormous rise of the charge density. In case of a relatively high humidity, the measured charge distribution is always reproducible. In dry conditions the charge density is lower and the charge distribution is indeterminate. 2. 2. Charges may accumulate on the surface in the case of nearly uniform electrode configurations, i.e. without measurable partial discharges. Above a humidity of 30% the polarity of the charges always corresponds to the polarity of the D.C. voltage. Based on the assumption that the charge accumulation is attributed to ionization processes in air a model conception is derived. In spite of a larger attachment coefficient the influence of the humidity is traced back to a rise in the frequency of ionization events in air.

固体中の電荷および電界分布測定への超音波の利用

固体中の電荷および電界分布測定への超音波の利用

Automated system for measurement of the effective surface-charge decay rate of unshielded electrets

A rotating probe assembly suitable for effective surface-charge decay-rate measurements is described. Utilizing computer acquistion of data, low resolution charge distribution measurements can be made.

Consideration on the measurement of current distribution on bent wire antennas

As part of the measurement of the current distribution on a bent wire antenna with a shielded loop, the electromotive force (EMF) induced on the loop is theoretically formulated, and the relation between the current distribution and the measured values is investigated. The EMF is expressed as a summation of terms involving the current and the derivative of the current with coefficients depending on the measurement point. The calculated EMF agrees well with the measured value. At points away from the antenna ends and bend, the EMF is proportional to the current, but near the ends and bend the difference between EMF and current increases. It is shown that the current distribution is easily estimated from the measured data. The authors also present the measurement of charge distribution using a small dipole. The expression for the open-circuit voltage of the dipole is formulated and compared with measured values.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of spatial charge distribution in thick dielectrics using the pulsed electroacoustic method

Measurement techniques of volume charge distribution within insulating materials are developed using a pulsed electroacoustic method. The fundamental equation of the relation between the charge distribution in the insulating material and the signal voltage from the electroacoustic transducer is presented along with the typical measured charge profiles in polymethylmethacrylate (PMMA) during and after electron-beam irradiation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ChemInform Abstract: Determination of the Electric Field in Zeolites NaA, NaCaA and Ca6A. Calculation from the Ionic Charge Distribution and IR Measurements of the Induced Band of N2.

ChemInform Abstract: Determination of the Electric Field in Zeolites NaA, NaCaA and Ca6A. Calculation from the Ionic Charge Distribution and IR Measurements of the Induced Band of N2.

Sorption of sodium benzenesulfonate by charged cellulosic membranes.

Equilibrium sorption of sodium benzenesulfonate (NaSO3Ph) by charged cellulosic membranes was determined by measuring both of the cation and anion concentrations at 25°C. The membranes used were carboxyethyl cellulose (CEC), sulphoethyl cellulose (SEC), and phosphorylated cellulose (PC).The results were analyzed by the simple Donnan model in which a homogeneous charge distribution is assumed. In the range of C (aqueous salt concentration) >Cx (effective fixed charge density), the Donnan approach reproduced the experimental results quite well. In the range of C<Cx, however, the deviation was clearly observed, especially for SEC and PC membranes which have high Cx.The results were further interpreted by Petropoulos's theory, which is based on the nonhomogeneous charge distribution. By this method the sorption data could be explained well over all range of salt concentrations (1×10-3_??_4×10-1 mol/l). The Z-factors as the measure of the non-homogeneous charge distribution were estimated as 0.72_??_0.81 for NaCl and 0.82_??_0.85 for NaSO3Ph.The partition coefficients of NaSO3Ph were lower than NaCl. The effects of ionic size on these values were suggested.

Aiming technique for the distal interlocking of intramedullary nails

The characterization of dielectric materials in space environment requires to understand and predict their electric behaviour, taking into account ionisation, and ageing effect (through electron or UV radiation, thermal cycling, …)For this purpose, new methods have been developed for the characterisation and qualification of space materials and satellite structure. These studies led initially to the development of dedicated facilities for the simulation of representative irradiation conditions. This work is focused on a new non-disturbing technique for the measurement of charge distribution within space irradiated polymers. This technique named PEA (Pulsed Electro-Acoustic) has been implemented in the irradiation facility for in-situ and real time measurement during irradiation and relaxation of polymer materials. Implementation and validation of this technique are presented and discussed in this paper.

Central depression of the nuclear charge distribution

As a systematic feature of all measured charge distributions we find a shift in the form-factor zeroes as compared to a simple folding model. To first order, this shift can be interpreted as resulting from the central depression w, caused by the Coulomb repulsion. Accounting for it leads to an increase in the surface width of nuclear charge distributions by 0.105 fm. This interpretation of the experimental findings is compared with the droplet model, which relates w with the compression modulus K and the asymmetry energy J. Accounting for w leads to an increase in the extrapolated nuclear matter density by 7.5%. However, this macroscopic model is not able to describe the experimental results in detail since w is also influenced by shell effects. HF + BCS calculations with effective Skyrme-type interactions reproduce part of the data, revealing the influence of shells on w. Here, too, there remain discrepancies in details. A level of accuracy is reached at which most probably also the skewness of the charge distribution must be taken into account.

Evolution of Experimental Techniques for the Study of the Electrical Properties of Insulating Materials

When an electric field is applied to an insulating material three basic processes can take place: the dipoles tend to rotate, ions migrate and space charge can be injected at the interfaces, depending on such parameters as temperature or applied electric field. For many years, a direct analysis was impossible since the experimentally observable variables gave only an average of what was taking place in the samples under study. Many methods were developed over the years combining available measuring techniques with theoretical hypotheses. They led to phenomenological descriptions but it appeared that a direct measurement of space charge or polarization distributions in the materials would be a way for understanding the physical processes involved. In this paper we will present the evolution of these methods and will describe on which at present seems the most promising. It uses the propagation in the sample of a pressure wave which acts as a virtual probe sensitive to charge, field or potential. A very elegant technique to generate this pressure wave involves the use of a short-duration laser pulse. It will be shown how this can find applications in a very large number of areas. Examples will be given in such different fields as electrets, HV insulation, and transducer materials.

Charging of Insulators in a surface Discharge Switch

Surface discharge switches, which have exceptionally low inductance, are of interest for fast switching of electrical energy. This paper describes experimental data on the residual electric field and spatial charge distribution measurements on three insulators, namely, G-10, Delrin, and Lucite used in a surface discharge switch. The insulators were subjected to different numbers of shots in the switch and the measurements were carried out after the applied field was turned off. The G-10 samples exhibit positive charging with 1/e decay times ranging from 3.8 to 7.4 h, and show a great deal of structure in the charge distribution patterns. Delrin specimens exhibit negative charging with considerably longer decay times than those of G-10, and the charge patterns are not well defined. Lucite, on the other hand, shows quite different results, i. e. no detectable charge decay after fifteen hours and no definite charge patterns. The results are qualitatively discussed and are related to the resistivity of the dielectricts and the switch operating characteristics.

Ion—Aerosol Attachment Coefficients and the Steady-State Charge Distribution on Aerosols in a Bipolar Ion Environment

Calculations of the ion—aerosol attachment coefficients are carried out for Fuchs' theory (as corrected in this paper) and for a theory which includes three body trapping. The resulting charge distributions agree quite well for particles with radii greater than about 0.007 μm. For smaller particles three-body trapping becomes increasingly important. Comparison of theoretically predicted charge distributions with recently measured charge distributions at radii smaller than 0.02 μm show good agreement. Asymmetric charging due to differences in the physical properties of positive and negative ions can result in large differences in the number of positively and negatively charged particles, particularly at larger radii. The asymmetric charge distribution is also shown to depend on the ionization rate. For the case when aerosol concentrations are comparable to the ion concentrations the effect of polydispersity on the charge distribution is difficult to predict. It is shown that a dominant size particle can es...

Ion‐aerosol attachment coefficients, ion depletion, and the charge distribution on aerosols

Calculations of the ion‐aerosol attachment coefficients are carried out for particles with radii between 0.001 and 4 μm in a bipolar ion environment by using the theory (Hoppel, 1977) that includes both image capture and three‐body trapping of ions. These attachment coefficients are used to calculate the equilibrium charge distribution on aerosols. The results are compared to Fuchs' theory and to several recent measurements of the equilibrium charge distribution. The experimentally measured charge distributions agree quite well with theory. Recent measurements of aerosol size distributions made with the differential mobility size spectrometer in both continental and oceanic atmospheres are used together with the calculated attachment coefficients to study the sensitivity of the atmospheric ion concentration on the aerosol size distribution.

Nuclear deformations ofMg24,Si28, andS32from fast neutron scattering

Nuclear deformation of the $s\ensuremath{-}d$ shell nuclei $^{24}\mathrm{Mg}$, $^{28}\mathrm{Si}$, and $^{32}\mathrm{S}$ has been investigated by means of fast neutron scattering. Differential cross sections have been measured at the incident neutron energies of 9.76 and 14.83 MeV, over the angular range from 15\ifmmode^\circ\else\textdegree\fi{} to 160\ifmmode^\circ\else\textdegree\fi{}. Angular distributions have been obtained for the elastic scattering and the inelastic scattering to low lying collective states. The measurements have been compared to the predictions of collective models, and nuclear deformations have been determined for these nuclei. The coupled-channel and compound-nucleus formalisms were used in the calculations. The analysis shows that these nuclei exhibit quite different shapes, and confirms the oblate deformation of $^{28}\mathrm{Si}$ established in recent works. A detailed comparison of the deformations obtained in this study with those deduced from (p,p\ensuremath{'}), (d,d\ensuremath{'}), ($\ensuremath{\alpha}$,${\ensuremath{\alpha}}^{\ensuremath{'}}$), ($^{16}\mathrm{O}$, $^{16}\mathrm{O}\ensuremath{'}$), other (n,n\ensuremath{'}), and charge distribution measurements is presented and discussed. It is emphasized that for these $N=Z$ nuclei the quadrupole deformations and deformation lengths are in very good agreement when measured through neutron and proton scattering as well as electromagnetic excitations.

Direct determination of the ionic charge distribution of helium and iron in He-3-rich solar energetic particle events

The first direct measurement of the ionic charge distribution of the helium isotopes and of iron in (He-3)-Fe-rich solar energetic particle events is reported. No significant contribution of singly ionized helium to the events is found. The two-sigma upper limits for the He-3(+)/He-3(2+) and He-4(+)/He-4(2+) ratios are 0.02 and 0.03, respectively. The mean charge state of iron found by averaging five (He-3)-Fe-rich solar energetic particle events is 19 + or -2, significantly larger than the iron charge state for energetic solar particles in normal composition events. These results appear to favor the resonant heating model proposed by Fisk (1978). It is concluded that temperatures in the source region exceed 5 million K in the events under study.