Murray, Peter G.
Measurement of the mechanical loss of test mass materials for advanced gravitational wave detectors.
PhD thesis, University of Glasgow.
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Einstein's General Theory of Relativity (1916) predicted the existence of gravitational waves. These waves can be considered as fluctuations, or ripples, in the curvature of space-time. Until now there has been only indirect evidence, produced by Hulse and Taylor, of their existence. However, for many years various groups of scientists around the world have been developing ultra-sensitive instruments and techniques which are expected to be capable of detecting gravitational wave signals. The direct detection of these waves will provide new information about the astrophysical processes and sources which produce them.
Gravitational radiation is quadropole in nature, producing orthogonal stretching and squeezing of space. The resulting fluctuations in distance are, however, very small, with gravitational waves emmitted from violent astrophysical phenomena expected to produce strains in space of the order ~10 [superscript -22] over relevant timescales.
One technique for detecting such strains is based on a Michelson Interferometer. The Institute for Gravitational Research at the University of Glasgow under the leadership of Professor James Hough, has been an active contributor of research targeted towards the detection of gravitational waves for over 35 years. A strong collaboration exists with the Albert-Einstein-Institut in Hanover and Golm, the University of Hanover and the University of Cardiff. This collaboration has developed and constructed a laser interferometer, with arms of 600 m length, in Germany named GEO600. The research presented in this thesis details experiments undertaken on materials and techniques used in current interferometric detectors and for proposed future detectors. The aim of this research is to investigate methods of reducing the levels of mechanical loss associated with the detector optics and thereby minimise the impact of thermal noise on the overall sensitivity of detectors.
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