Searches for gravitational and electro-magnetic waves from extra-terrestrial sources
Başlık:
Searches for gravitational and electro-magnetic waves from extra-terrestrial sources
Yazar:
McCourt, James, author.
ISBN:
9780438057012
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (103 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: R. W.P Drever.
Özet:
Since there is a chapter-by-chapter breakdown of this thesis in the Preface which follows, this summary will contain only a general description of the various topics covered. The thesis is in two parts. In the first, a complete account is given of a radio search of the Galactic Centre at a frequency of 408 MHz, performed in Glasgow in the summer of 1975. The search is related to its inspiration - a positive result by Hughes and Retallack, who surveyed the galactic nucleus at 858 MHz in 1971; and who were in turn activated by the claims of Weber that he had recorded gravitational radiation from this region. The possible generators of the Hughes//Retallack result - short time-constant radio pulses - are surveyed, and the other radio searches of the Galactic Centre in recent times are noted and briefly discussed. The Glasgow search is then described in detail: choice of observing frequency, site, components, and mode of operation are justified. The search was a coincidence one, the Glasgow unit running concurrently with two stations in Italy. The advantages of this scheme are listed. The writer's main responsibility in all this lay in the mechanical aspects of the new radiometer required for the search. These are described and illustrated. The sensitivity of the 408 MHz system is calculated and also found by drift scans. An account of the results of the search, correlated from the three stations is given. Conclusions, discussion of the experiment and a statement of an upper limit in flux density of radio pulses at 408 MHz follow, and the first part of the thesis ends with an attempt to relate the result to that of Hughes and Retallack. part 2 of the thesis deals with a number of topics. These, are linked by the objective which subtends them: an attempt to increase the sensitivity of the next generation of Gravitational wave detectors resident at Glasgow University. The writer was occupied with this project for two years. The nature of gravitational radiation as predicted by Einstein is described and related(by reference to texts and papers), to electro-magnetic radiation. The difficulties that attend attempts to detect gravitational waves and the form of gravitational wave detectors are delineated, Brief accounts are given of experiments performed with the Glasgow detectors. Theory is used to isolate those factors in the design of the detector which by enhancement, would result in greater sensitivity. The strategy of investigation - miniature model building and testing - is justified, and a number of avenues are then investigated: 1) the possibility of using solder to bond aluminium bars to ceramic transducers; the effect of heat and soldering on these transducers; 2) the improvement in performance by employing a new transducer material; 3) the possibility of improvement by using an alloy of aluminium rather than the metal itself for detector bars; 4) methods of improving the response of a given specimen of bar material; 5) investigation of glues, and the relevance of the thickness of glue layers in detectors; attempts to achieve optimally thin uniform glue layers. Finally, these investigations and the results obtained from them are viewed in the context of the new gravitational wave detector bar presently under construction at Glasgow. was to develop the mechanical side of the construction. Dr. Meikle took upon himself the radio/electronic end of the operation. The search performed was a coincidence one. Italian groups based in Florence and Bologna were our collaborators. Sensitivity calculations and calibrations performed by Dr. Meikle with the aid of the writer are detailed in Chapter 5. The final chapter of Part 1 is concerned with an account of the results of the radio searches of Summer 1975, conclusions that can be drawn, and the deficiencies in the experimental programme which has made the repetition of the search in 1976 a worthwhile investment of time and material. Scanning of data and correlation with Italian results was done by the writer. Part 2 is more diffuse than Part 1. Its subject matter is an account of efforts of the writer and others to discover methods by which the sensitivity of the next generation of gravitational wave detectors at Glasgow University might be increased.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684560.1) | 684560-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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