Charge Distribution In Dielectrics Research Articles

Analysis of uncertainties in the measurement of the space charge distribution in dielectrics

The results obtained from the commonly used space charge distribution measurement methods are frequently apparent and one-dimensional results of a localized area; moreover, random errors can be caused by various factors. In this work, three factors—sample thickness uniformity, pressure wave intensity uniformity, and space charge distribution uniformity—that may cause measurement uncertainties are examined. The analysis and evaluation of the experimental data are affected by the measurement uncertainties, which are particularly noticeable in experiments on semiconductive electrode-flat polyethylene samples that use the laser-induced pressure propagation method. These factors are investigated separately using several auxiliary experiments, including laser beam spot energy distribution measurements and space charge distribution measurements, at different measurement positions on the same uniform sample. A clear and intelligible model is developed to discuss the influence of these factors on the uncertainties in the space charge distribution measurement in dielectrics.

Epoxy-hBN nanocomposites: A study on space charge behavior and effects upon material

The emergence of nano dielectrics for specialized high voltage applications sparked off a variety of research activities, which proved that nano-fillers are capable of improving the electrical, thermal and mechanical properties of polymers. This paper primarily investigates the effect of addition of hBN (hexagonal boron nitride) nanoparticles into an epoxy polymer base by increasing fill-grade, from 0.2 to 5 % by volume, from two different standpoints: (a) characterizing the electrical space charge (S.C.) accumulation threshold under DC electrical fields, and, (b) demonstrating the alterations in material properties of the modified polymeric materials, from the unfilled polymer. Objective (a) is experimentally investigated by the pulsed electro-acoustic (PEA) technique, well known for determining spatial charge distribution in dielectrics. Objective (b) is investigated by determining the ultrasonic velocity response of the modified composites and unfilled polymer. The obtained results suggest a relation between electrical threshold fields for S.C. accumulation & fill-grades, as well as the fact that incorporating stiff filler materials into brittle polymer bases leads to a tougher composite (capable of withstanding greater breaking stress levels), but with reduced ductility.

Measurement of internal charge distribution in dielectrics using the pulsed electro-acoustic method in non contact mode

We introduce a pulsed electro acoustic (PEA) device enabling space charge measurement inside dielectric films without the need of sample to excitation unit contact. The new device -called open PEA because one face of the film is at a floating potential- has been used to investigate the internal charge of electron beam irradiated dielectrics. Details are given on the system and its calibration for performing quantitative charge measurements. Charge distributions in electron beam irradiated polytetrafluoroethylene (PTFE) films are compared using the classical and the open PEA. Due to the short-circuit condition in the classical PEA, the implanted charges measured using the two systems are drastically different. Surface potential and current measurements performed during irradiation have been used to validate the measurement in the open configuration which is well suited to investigate the behaviour of dielectrics in space environment.

Pulse Acoustic Technology for Measurement of Charge Distribution in Dielectric Materials for Spacecraft

Recently, some accidents in spacecraft due to charging up by irradiation of charged particles have been reported. Some of them are caused by a surface discharge, which normally takes place in a plasma environment in space. Some others seem to be caused by a discharge due to an accumulation of charge in the bulk of materials in a relatively high-altitude environment. To investigate the charge accumulation in the bulk of materials, the authors have been developing an internal charge measurement system. The internal charge accumulation in dielectric materials under irradiation of artificial radioactive rays is observed using the developed system, which employs the so-called pulsed electroacoustic method and pressure wave propagation method based on pulse acoustic measurement techniques. The developed system is applicable to the measurement of the charge distribution in dielectrics in air atmosphere or vacuum environments under electron beam, proton beam, and gamma ray irradiations. Using the system, we measured bulk charge distributions in polymeric films and glass materials. In this paper, summaries of some typical measurement results are presented following a brief explanation of measurement principles

Modeling of optical waveguide poling and thermally stimulated discharge (TSD) charge and current densities for guest/host electro-optic polymers

A charge density and current density model of a waveguide system has been developed to explore the effects of electric field electrode poling. An optical waveguide is modeled during poling by considering the dielectric charge distribution, polarization charge distribution, and conduction charge generated by the poling field. The charge distributions are the source of poling current densities. The model shows that boundary charge current density and polarization current density are the major source of currents measured during poling and thermally stimulated discharge measurements. Charge distributions provide insight into the poling mechanisms and are directly related to E/sub A/ and /spl alpha//sub r/. Initial comparisons with experimental data show excellent correlation to the model results.

Scanning electric potential microscopy imaging of polymers: electrical charge distribution in dielectrics

Scanning electric potential images of polymer surfaces are presented and compared to standard non-contact AFM images. Samples used were a latex film with a well-known distribution of chemical constituents and thus of ionic electrical charges, as well as finished industrial products. Topography and electric potential images show a variable degree of correlation, thus evidencing the independence of topographic and electrical features of the samples, in the micro- and nanoscopic scales. Domains with non-zero negative or positive electric potentials are observed, extending for a few tenths of a micron and creating an electric mosaic in the otherwise neutral polymers. Large electric potential gradients are observed, e.g. in a HDPE film.

人工衛星の誘電体材料内部帯電計測装置の開発

Spacecraft charging occurs in space environment. There are two types of spacecraft charging. “Surface Charging” and “Internal Charging.” The former has been investigated for about 30 years. Until now, however, the latter has not been studied deeply enough and, as far as we know, measurement of internal charging in the spacecraft has not been made yet. Under these circumstances, we tried to develop equipment for measurement of internal charging in space environment, applying PIPWP (Piezo-electric Induced Pressure Wave Propagation) method, which enables us to measure electric charge distribution in dielectrics. The equipment was designed smaller and lighter in order to be able to be installed into spacecraft. The specific feature of this equipment is that it is capable of measuring charge distribution continuously in real-time. Using the equipment, we succeeded in measuring charge distribution in PMMA (Poly Methyl Methacrylate) film during and after electron beam irradiation and, we could obtain basis data to proceed to spacecraft borne equipment.

Si/SiO2Structures with Quantum Size Effects: The Construction of a Low-Dimensional Nanoscale Electronic System in the Interface Layer of Si by Incorporating a Regularly Distributed Charge into SiO2

A novel approach to producing long-lived, reconfigurable, self-organized nanoscale electronic systems of a low dimension (quantum wells, wires, dots, superlattices, etc.) in a semiconductor is discussed. This approach consists of creating a regular charge distribution in an adjacent dielectric, so that a two-dimensional potential distribution is induced in the interface layer of the semiconductor. Advanced methods to generate a desired charge distribution in dielectrics are reviewed. They use (1) the local injection of electrons or ions into a thin dielectric layer by a precisely focused beam, (2) the local electronic or ionic polarization of dielectrics with a scanning tunneling microscope, or (3) nanoscale charge patterns that can be spontaneously formed by electrons or ions in dielectrics. The possible applications of the approach are considered in the context of the Si/SiO2system.

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Much progress had been made during the last two decades in acoustic and optical methods for measuring charge distributions in dielectrics. A review on this topic is given, which mainly covers the past research activities associated with that at our laboratory. For acoustic methods, we will discuss andoompare the pulsed electroacoustic (PEA) and pressure wave propagation (pwP) methods and present some of the results that enabled us to gain physical insights into the charge dynamics within solid plate samples and coaxial cables. For optical methods, we will discuss the Pockels effect technique that is used for the dynamic measurement of surface charge distributions, and the Kerr effect technique that is developed for measuring electric field distributions within liquid dielectrics.

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Review of space charge measurements in dielectrics

In the last two decades, a significant effort has been directed to understand the internal charge distributions in dielectrics. This has resulted in the development of a number of methods which give detailed information about space charge distributions. This review presents the evolution of several experimental approaches for the determination of spatial charge and field distributions in dielectrics, including the nondestructive methods of direct probing such as the thermal-pulse methods and the methods using pressure waves that propagate through the charged sample. Detailed information is also provided on the principles used in each technique, typical resolution, limitations and advantages associated with each method. The applications of the methods to several insulating materials charged with various mechanisms are described. The paper concludes with a discussion on a number of quite interesting techniques which seem most promising.

Analysis of laser induced acoustic pulse probing of charge distributions in dielectrics

Some features of the laser induced acoustic pulse method for the determination of electric field or charge distributions in dielectrics are analysed. Three aspects of this method are described. 1) The electric field can be derived by a numerical method whose resolution depends essentially on the rise time of the pressure wave. Measurements are described which support this analysis. 2) The mechanisms of generation of the pressure wave are studied; a method is described which allows the production of hundreds of pulses without noticeable alteration, with a good energy conversion efficiency. 3) The influence of the elastic properties of the material on the attenuation and dispersion of the wave is considered. Measurements performed on Polyfluoroethylenepropylene (FEP) samples show that one has to take these parameters into account if the rise time of the pressure is much shorter than the transit time.