The use of radiometric partial discharge location equipment in distribution substations

his paper describes a vehicle mounted radiometric system consisting of an array of four antennas connected to broadband, high-speed recording hardware capable of locating the source of partial discharges (PD). The significant advantages of the system lie in its ease of application, not requiring any electrical plant interface, and its ability to monitor emissions from several items of plant simultaneously. The system has been widely used at transmission level

Pump-probe measurement of lifetime engineering in far-infrared SiGe quantum wells

No abstract available

Pump-probe measurement of lifetime engineering in far-infrared SiGe quantum wells

No abstract available

Degenerate four wave mixing spectroscopy of oxygen vibrations in amorphous silicon

We report on DFWM spectroscopy on the asymmetric stretching mode in a-SiOx with x from 0.1 to 1.11. For a-SiO0.1, a 10 K lifetime of 2.8 ps is obtained using laser-induced transient grating spectroscopy. Two-pulse photon echo measurements reveal phase dynamics having a temperature dependent component due to elastic phonon scattering and an excitation dependent component suggesting the presence of non-equilibrium Si-Si modes. At high excitation densities, the DFWM signal is dominated by a quasi-thermal grating whose population decay is extremely long lived (much greater than 1 ns). This effect is enhanced as the oxygen concentration is increased. (C) 2004 Elsevier B.V. All rights reserved

Ultrafast spectroscopy of localised vibrational modes in amorphous silicon using a free electron laser

Ultrafast vibrational relaxation of localised modes associated with hydrogen, deuterium and oxygen in amorphous silicon based alloys are discussed. The availability of internal defect vibrations to act as accepting modes is discovered to be a crucial factor in the population decay dynamics. Phase relaxation is shown to have both a temperature dependent component due to elastic phonon scattering as well as an excitation dependence contributed by non-equilibrium phonons. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim