Search

The effect of bromine (Br 2) doping on the hole transfer properties in amorphous polyethylene (PE) oligomer is studied by utilizing a multi-scale computational approach without adopting any empirical models. The computational method comprises molecular dynamics simulations, quantum chemical calculations, and kinetic Monte Carlo simulations. The electronic structure of the Br 2 /PE oligomer cluster and the ionization energies of Br 2 and PE oligomer showed that no impurity states are introduced in the HOMO-LUMO gap of PE oligomers upon Br 2 doping, i.e., holes tend to hop between PE oligomers instead of residing in Br 2. Nevertheless, owing to the increase of electronic couplings between PE oligomers due to the occupied states of Br 2 , the hole mobility is increased by an order of magnitude with Br 2 doping. In addition, the hole mobility activation energy was decreased upon Br 2 doping, even though the activation energies of hole hopping rates remain the same. The computational results are consistent with experimental observations in literature and imply that the hole mobility in PE is increased by the bridge mediated hole transfer. [ABSTRACT FROM AUTHOR]

When an electrostatic probe is used for surface charge measurement on an insulating plate with constant thickness or a long insulating pipe, the configuration of the measuring system is regarded as shift-invariant and the relation between the surface charge density and the probe output can be treated in the spatial frequency domain through Fourier analysis. In the inverse calculation from the probe output to the charge distribution, a Wiener-filter technique is effectively used to suppress the excessive amplification of the noise. Influences of the probe geometry and experimental errors on the spatial resolution of the total measuring system, including the restoration process with the Wiener filter, are quantitatively discussed through the analysis of transfer characteristics in the spatial frequency domain. Index Terms--Charge accumulation, electrostatic probe, spatial resolution, Fourier transformation, Wiener filter, regularization.

When an electrostatic probe is used to measure the surface charge on an insulating plate of constant thickness, the measuring system is regarded a shift-invariant system and the relation between the surface charge density and the probe output can be treated in the spatial frequency domain. The distribution of the surface charge density on an insulating plate just after occurrence of a surface discharge is measured by a Pockels probe, which is regarded as a kind of electrostatic probe without the guard electrode, and restored by Wiener inverse filter. The performance of a Pockels probe and a conventional electrostatic probe are compared quantitatively in terms of the spatial resolution. In the case that the measured object is 3 mm thickness PMMA plate and is charged up to 10 nC/c[m.sub.2] in atmospheric air, it is estimated that the spatial resolution of the Pockels probe with 0.2 mm gap is 1.5 mm and that of the conventional electrostatic probe with the grounded guard electrode with 3 mm gap is 2.2 mm. Index Terms--Accumulated charge, electrostatic probe, resolution, Pockels, Fourier transformation, point spread function, Wiener inverse filter.

In designing superconducting electrical power apparatus, the knowledge of cryogenic gas and liquid insulation characteristics is essential. The authors have studied the discharge characteristics of relatively long-gap configurations in air and nitrogen at a cryogenic temperature. A sphere-to-sphere electrode with a gap length of 20 to 150 mm is used for measurements in uniform electric field. The breakdown voltage characteristics basically obey Paschen's law at cryogenic temperature for 50 Hz, ac, dc and lightning impulse voltage applications. A rod-to-plane electrode with a gap length of 20 to 330 mm is used for measurements in non-uniform electric field. In air at cryogenic temperature and nitrogen gas at both room and cryogenic temperature, streamer-like corona discharge appears near the tip of the rod electrode before the breakdown, and the breakdown voltage increases linearly with gap length. In air at room temperature thin film-like corona discharge, however, appears near the tip of the rod electrode before breakdown, and the breakdown voltage becomes higher than the other case. In order to examine the variation of corona discharge characteristics, some additional experiments are conducted. As a result, it becomes clear that thin film-like glow corona discharge appears when electronegative gas is contained and sufficient electrons are supplied from the cathode. Index Terms--Cryogenic temperature, electrical discharge, air, nitrogen, uniform field, non-uniform field, ac, dc, lightning impulse.

A noncontact measurement of electric field is proposed on the basis of Kerr effect in gases. It is a measurement system using optical phase modulation.

A positive surface discharge on a solid insulator in air consists of many branched streamers. The length of the streamers is controlled by the applied voltage at the instant when the streamers occur. The relationship between the inception voltage and the streamer length depends on the thickness of the solid insulator and the number of streamer branches. At a low voltage, the length of a streamer decreases with increasing the thickness of the insulator, but at a high voltage, it increases with thickness. The length of a streamer with a large number of branches is shorter than that with a few branches. This phenomenon can be explained as follows: the electrons generated in each branch flow into a positive high-potential electrode through the stem of the streamer, and the potential drop in the stem is enhanced due to this electron flow.