Experimental developments towards a long-baseline laser interferometric gravitational radiation detector

Astrophysics, Theoretical physics

Kerr, Graham Alexander

University:University of Glasgow

关键词: Astrophysics, Theoretical physics;   

Others  :  http://theses.gla.ac.uk/76597/1/10907195.pdf

来源: University of Glasgow

【 摘 要 】

Gravitational radiation (a wave-like disturbance in space-time, propagating with the speed of light) is predicted as a consequence of Einstein's General theory of Relativity. Indirectly verified by observations of the binary pulsar PSR1913+16, gravitational waves have still to be observed directly. Direct observation and study of these waves could provide detailed information on astrophysical events, unobtainable by the observation of any other form of radiation. Currently one of the most promising techniques is the use of laser interferometry to sense the motions of suspended test masses. This type of detector is broad-band in nature and, as such, is particularly attractive. Of the two possible types of interferometer in use, some aspects of the development of one of these (an optical cavity interferometer) are extensively investigated. Following a brief introduction to the theory of gravitational radiation and a review of gravitational wave sources and detection techniques, a detailed description of the design and operation of the Glasgow prototype detector is given. The sensitivity of the interferometric detector can be impaired by many noise sources, and the thesis describes how progress in the reduction of two of these noise sources improves the sensitivity. Firstly, a report is given on how progress in test mass design and the isolation of mechanical noise have improved sensitivity. The second noise source considered is the effect of fluctuations in the frequency of the illuminating laser light, and consideration of the influence of this noise source forms a large part of the thesis. An argon laser was rebuilt, with a separate cavity resonator, to reduce the level of intrinsic frequency noise, along with other noise sources, and a new technique of stabilising the laser frequency was developed. This method, which uses the reflection locking r. f. sideband technique, does not require the use of an intra-cavity modulator, and thus enables the laser to operate with a higher power output. The effects of residual laser frequency noise in the interferometer can be reduced by optical interference or by a technique which measures, and electronically subtracts, the frequency fluctuations. Both of these techniques are studied and their contributions to the improvement of detector sensitivity are reported. With a view to the future, some techniques applicable to a longer detector (>1km) are discussed and, finally, an experiment with a split-bar detector, which places an upper limit on gravitational radiation from the millisecond pulsar PSR1937+214, is described.