Development and characterisation of a pulling machine to produce small diameter silica fibres for use in prototype advanced gravitational wave detectors

Toland, Karl William (2015) Development and characterisation of a pulling machine to produce small diameter silica fibres for use in prototype advanced gravitational wave detectors. MSc(R) thesis, University of Glasgow.

Abstract

This thesis will give an overview of gravitational waves and the history behind attempts to directly observe them using laser based interferometers and the detectors current configuration. The noise sources associated with the interferometers such as gravity gradient, seismic and quantum noise will also be discussed. Thermal noise will be discussed in depth.
The main body of this thesis focused on developing and characterising a pulling machine capable of producing small diameter silica fibres for use in prototype advanced gravitational wave detectors. An initial diameter target was to pull repeatable sets of fibres with a minimum diameter ≤ 20 µm. The pulling machine worked by heating a silica stock, with one end clamped down and the other clamped to a high velocity pulling stage, with a CO2 laser until the stock was sufficiently hot enough and producing a fibre by moving the pulling stage. The CO2 beam was directed to and focused down onto the stock using a series of mirrors and two lenses to a beam width of 105 ± 7 µm. Three different methods were used to create fibres: one stage absolute position pull, one stage velocity profile pull and two stage velocity profile pulls.
The one stage absolute position pull produced fibres that would taper down to a minimum diameter ranging between 20 to 48 µm.
The one stage velocity profile pulls produced fibres ranging between 7.4 ± 0.4 µm and 18.3 ± 0.6 µm. These fibres then ranged in breaking stress values of 2.26 ± 0.26 ×10^8 Pa and 6.05 ± 0.39 ×10^9 Pa and a Young’s modulus value between 14.4 ± 1.7 ×10^9 Pa and 106.0 ± 6.8 ×10^9 Pa.
The two stage velocity profile pulls produced fibres ranging between 8.72 ± 0.61 µm and 14.83 ± 0.57 µm. These fibres then ranged in breaking stress values of 2.14 ± 0.3 ×10^9 Pa and 4.82 ± 0.36 ×10^9 Pa and a Young’s modulus value between 54.0 ± 7.5 ×10^9 Pa and 87.0 ± 14.3 ×10^9 Pa.
The thinnest set of fibres were produced with two stage pulls and were found to have a higher Young’s modulus value than the literature value for bulk fused silica, indicating a possible change in properties when the diameter is ≤ 10 µm. Further investigation will need to be carried out to find out if this is the case.
The target of producing repeatable silica fibres with a minimum diameter ≤ 20 µm was met. There is still a lot of work to be completed with regards to perfecting the fibre’s shape, improving the strength and investigating the loss associated with the fibre. This will be carried out in the future.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Gravitational waves, silica fibres, small diameter, pulling machine, prototype advanced gravitational wave detectors,
• Subjects: Q Science > QB Astronomy; Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Hammond, Dr. Giles and Rowan, Prof. Sheila
• Date of Award: 2015
• Depositing User: Mr Karl Toland
• Unique ID: glathesis:2015-6997
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Dec 2015 14:19
• Last Modified: 13 Jan 2016 09:55
• URI: https://theses.gla.ac.uk/id/eprint/6997