Author: Pablo Jose Barriga Campino
Publisher:
Published: 2009
Total Pages: 324
ISBN-13:
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The research described in this thesis investigates some of the key technologies required to improve the sensitivity of the next generation of interferometric gravitational wave detectors. A complete optical design of a high optical power, suspended mode-cleaner was undertaken in order to reduce any spatial or frequency instability of the input laser beam. This includes a study of thermal effects due to high circulating power, and a separate study of a vibration isolation system. In the last few years the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) has developed an advanced vibration isolation system, which is planned for use in the Australian International Gravitational Observatory (AIGO). A local control system originally developed for the mode-cleaner vibration isolator has evolved for application to the main vibration isolation system. Two vibration isolator systems have been assembled and installed at the Gingin Test Facility ( 80km north of Perth in Western Australia) for performance testing, requiring installation of a Nd:YAG laser to measure the cavity longitudinal residual motion. Results demonstrate residual motion at nanometre level at 1 Hz. Increasing the circulating power in the main arm cavities of the interferometer can amplify the photon-phonon interaction between the test mass and the circulating beam, enhancing the three-mode parametric interaction and creating an optical spring effect. As part of a broader study of parametric instabilities, in collaboration with the California Institute of Technology, a simulation of the circulating beam in the main arms of Advanced LIGO was completed to determine the characteristics of the higher order optical modes. The simulation encompassed di raction losses, optical gain, optical mode Q-factor and mode frequency separation. The results are presented for varying mode orders as a function of mirror diameter. The effect of test mass tilt on diffraction losses, and different coatings conffgurations are also presented. These simulations led to a study of the effect of power recycling cavities in higher order mode suppression. Current interferometric gravitational wave detectors in operation have marginally stable recycling cavities, where higher order modes are enhanced by the power recycling cavity, effectively increasing the parametric gain. A study of stable recycling cavities was undertaken in collaboration with the University of Florida, which has evolved into a proposed design for a 5 kilometre AIGO interferometer. This thesis concludes with an analysis of the work here presented and an outline of future work that will help to improve the design of advanced interferometric gravitational wave detectors.
