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The TEA-CO2 laser as a means of generating ultrasound in solids
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Taylor, Gregory Stuart (1990) The TEA-CO2 laser as a means of generating ultrasound in solids. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3226690~S1
Abstract
The aim of this thesis is to characterise the interaction between pulsed, high power, 10.6 μm radiation and solids. The work is considered both in the general context of laser generation of ultrasound and specifically to gain a deeper understanding of the interaction between a laser supported plasma and a solid.
The predominant experimental tools used are the homodyne Michelson interferometer and a range of electromagnetic acoustic transducers. To complement the ultrasonic data, various plasma inspection techniques, such as high speed, streak camera photography and reflection photometry, have been used to correlate the plasma properties with those of the ultrasonic transients.
The work involving the characterisation of a laser supported plasma with a solid, which is based on previous experimental and theoretical analysis, gives an increased understanding of the plasma’s ultrasonic generation mechanism. The ability to record the entire plasma-sample interaction, time history yields information of the internal dynamics of the plasma growth and shock wave generation.
The interaction of the radiation with a solid is characterised in both the plasma breakdown and non-breakdown regimes by a wide ultrasonic source. The variation in source diameter enables the transition from a point to a near planar ultrasonic source to be studied. The resultant ultrasonic modifications are examined in terms of the wave structure and the directivity pattern. The wave structure is analysed in terms of existing wide source, bulk wave theories and extended to consider the effects on surface and Lamb waves. The directivity patterns of the longitudinal and shear waves are analysed in terms of top-hat and non-uniform source profiles, giving additional information into the radiation-solid interaction. The wide, one dimensional source analysis is continued to a two dimensional, extended ultrasonic source, generated on non-metals by the optical penetration of radiation within the target.
The generation of ultrasound in both metals and non-metals, using the CO2 laser, is shown to be an efficient process and may be employed almost totally non-destructively. Such a laser may therefore be used effectively on a greatly enhanced range of materials than those tested to-date via laser generation, resulting in the increased suitability of the laser technique within the field of Non Destructive Testing.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics | ||||
Library of Congress Subject Headings (LCSH): | Carbon dioxide lasers, Ultrasonic waves -- Industrial applications, Ultrasonic testing, Laser-plasma interactions, Nondestructive testing -- Technological innovations | ||||
Official Date: | December 1990 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Palmer, Stuart B. | ||||
Sponsors: | Science and Engineering Research Council (Great Britain) ; United Kingdom Atomic Energy Authority | ||||
Format of File: | |||||
Extent: | 169 leaves : illustrations, charts | ||||
Language: | eng |
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