Central Electricity Research Laboratories

Leatherhead, United Kingdom

Central Electricity Research Laboratories

Leatherhead, United Kingdom
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Robertson J.,Central Electricity Research Laboratories
Advances in Physics | Year: 2011

The properties of various types of amorphous carbon and hydrogenated amorphous carbon are reviewed with particular emphasis on the effect of atomic structure on the electronic structure. It is shown how the proportion of sp3 and sp2 sites not only defines the short-range order but also a substantial medium-range order. Medium-range order is particularly important in amorphous carbon because it is the source of its optical gap, whereas short-range order is usually sufficient to guarantee a gap in other amorphous semiconductors. The review discusses the following properties: short-range order and the radial distribution function, the infrared and Raman spectra, mechanical strength, the electronic structure, photoemission spectra, optical properties, electron energy-loss spectra, core-level excitation spectra, electrical conductivity, electronic defects and the electronic doping of hydrogenated amorphous carbon. © 2011 Taylor & Francis.


PubMed | Central Electricity Research Laboratories
Type: Journal Article | Journal: Applied optics | Year: 2010

An all-dielectric, electrically passive, optical temperature sensor for use in high voltage environments has been constructed and tested. It is based on the temperature dependence of the optical activity in crystalline quartz. The sensor showed excellent linearity over the 20-180 degrees C temperature range, providing temperature measurements within this range to an accuracy of +/-2 degrees C. The output indication was not affected by external magnetic or electric fields. The materials used in the construction of the device are expected to possess long-term chemical compatibility with harsh environments, including transformer insulating oil at temperatures up to 180 degrees C.


PubMed | Central Electricity Research Laboratories
Type: Journal Article | Journal: Applied optics | Year: 2010

The technique of polarization-optical time-domain reflectometry is analyzed to see how the polarization properties of an optical fiber may be deduced from the backscattered light. It is shown that, subject to certain assumptions, the polarization is modified as it would be by a linear retarder. The results of measurements on a fiber showing both linear and circular retardation are given and compared with a theoretical model. The experiments show that the accuracy of measurement is limited by changes in the polarization, due to the scattering process, which vary randomly along the fiber.

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