Enhanced characteristics of fused silica fibers using laser polishing
The search for gravitational wave signals from astrophysical sources has led to the current work to upgrade the two largest of the long-baseline laser interferometers, the LIGO detectors. The first fused silica mirror suspensions for the Advanced LIGO gravitational wave detectors have been installed at the LIGO Hanford and Livingston sites. These quadruple pendulums use synthetic fused silica fibers produced using a CO_2 laser pulling machine to reduce thermal noise in the final suspension stage. The suspension thermal noise in Advanced LIGO is predicted to be limited by internal damping in the surface layer of the fibers, damping in the weld regions, and the strength of the fibers. We present here a new method for increasing the fracture strength of fused silica fibers by laser polishing of the stock material from which they are produced. We also show measurements of mechanical loss in laser polished fibers, showing a reduction of 30% in internal damping in the surface layer.
© 2014 Institute of Physics Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 22 January 2014. Accepted for publication 20 February 2014. Published 29 April 2014. We would like to thank our colleagues in the LIGO Scientific Collaboration, the GEO600 project, and the Scottish Universities Physics Alliance (SUPA) for their interest in this work. We also wish to thank the ILIAS Strega project and Leverhulme Trust for support. We are grateful for the financial support provided by the NSF in the USA and the STFC and the University of Glasgow in the UK. The LIGO Observatories were constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the NSF under cooperative agreement PHY-9210038. The LIGO Laboratory operates under cooperative agreement PHY-0107417. STFC funding is provided under grant ST/J000361/1.
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