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Title: Experiments on, and relating to, the detection of gravitational radiation
Author: Pugh, John R.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1976
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The fact that an accelerating mass can radiate energy in the form of gravitational waves was predicted by Einstein in 1918, as a result of his general Theory of relativity. Recently much interest has been shown in the possible detection of this radiation, due to the reported detection of gravitational wave pulses in 1969 by J. Weber. Work was started at Glasgow in 1970 and by 1973 a search had been made for pulses of radiation expected from stellar collapse. The author joined the group in 1973 and it was clear then that improvements had to be made in the detector sensitivity, if gravitational wave pulses were to be observable at an acceptable rate. This thesis therefore is an account of research aimed to improve the sensitivity of searches for gravitational radiation. After a brief historical note various sources of gravitational radiation are considered. Estimates of the expected effects, as measured at the earth, are presented; these illustrate the need for improving detector sensitivity. One of the first fields considered is the low noise amplification of signals from gravitational wave detectors. The experimental work done on this problem includes investigations into the possible improvements by cooling field effect transistors, and the use of a superconducting quantum interference device as a low noise amplifier. Using the results of these investigations the sensitivities of two proposed types of gravitational wave detector are then calculated. As a detector is very sensitive to applied forces the effect of noise in the sensing circuit producing a feedback force is considered. This effect has not been taken account of in the majority of previous calculations performed by others, and indeed it is found to be an important factor. As well as an investigation into possible improvements, a search which sets a more sensitive upper limit to gravitational radiation of a continuous nature is described. This experiment has also proved worthwhile in relation to conclusions about the reported detection of gravitational wave pulses by Weber in 1970. This work led to a more general consideration of possible methods for the extraction of continuous gravitational wave signals from detector noise, and a discussion of the implementation (by use of an on-line computer) of some of these techniques is presented. A power spectrum analysis programme developed for the purpose of gravitational wave experiments was also used in a different experiment to search for extra-terrestrial X-rays, and this work is presented in Appendix A.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available