Some Techniques Relevant to the Development of a Long Baseline Gravitational Wave Detector Using Laser Interferometry

Mangan, John B (1987) Some Techniques Relevant to the Development of a Long Baseline Gravitational Wave Detector Using Laser Interferometry. PhD thesis, University of Glasgow.

Abstract

Gravitational radiation is a travelling distortion in foar-dimensional space-time which is predicted by most relativistic theories. This distortion may be detected by monitoring the changes in the separation of test masses. Since the gravitational interaction is so weak appreciable levels of gravitational radiation are only produced by violent astrophysical phenomena in which large masses are accelerated coherently to velocities approaching the speed of light. However, due to the conservation of momentum the lowest order of gravitational radiation is quadrupole and so the source must contain some asymmetry in its dynamics. Chapter 1 is intended to introduce the reader to the concept of gravitational radiation by outlining its properties, describing some of the possible sources and indicating the levels which might be observed by a terrestrial detector. Chapter 1 also includes a brief overview of main detection schemes currently being pursued. Chapter 2 includes a brief overview of the current status of the prototype detector at Glasgow, which uses laser interferometry to monitor the relative lengths of two orthogonal optical cavities, before describing, briefly, the sources of noise which are most likely to limit the sensitivity of this type of system and the levels at which they become important. Theoretical work suggests that to see several gravitational wave events per year a sensitivity to strain, h ~ 10-22 is required and so the levels have been scaled to the proposed 1km long observatory which should have this potential. The following chapters are concerned with experiments related to reducing the effects of some of these possibly limiting sources of noise, in particular fluctuations in the quality of the laser light used to illuminate the optical cavities of the detector. Chapter 3 is concerned with the development of a laser intensity stabilisation system and investigations into limits to its observed performance which included geometry and frequency fluctuations in the laser light. Chapter 4 covers the development of the feedback circuit for the intensity stabilisation system in more depth and describes another circuit designed for the fast frequency stabilisation of an Argon Ion laser. The possible use of optical fibres to reduce the effects of geometry fluctuations in laser light is investigated in Chapter 5. This chapter describes the investigation of the suppression available from a sample fibre and calculates the efficiency with which a fundamental Gaussian beam may be transmitted through a mono-mode fibre. Chapter 6 describes the construction of a data collection system designed to capture pulses in the output of an interferometric gravitational wave detector. Although the prototype detector is probably not sufficiently sensitive to detect likely levels of gravitational radiation the system was tested by sampling data from the prototype system. These data were then used to study the noise statistics of the detector to search for any non-random effects. Chapter 7 briefly describes the state of the gravitational radiation detection effort world-wide and the prospects for future development.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Astronomy
• Date of Award: 1987
• Depositing User: Enlighten Team
• Unique ID: glathesis:1987-77655
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 11:53
• Last Modified: 14 Jan 2020 11:53
• URI: https://theses.gla.ac.uk/id/eprint/77655