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Title: Remote analysis of materials using the technique of laser induced breakdown spectroscopy
Author: Davies, C. M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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This thesis is concerned with the development and application of the technique of Laser Induced Breakdown Spectroscopy (LIBS) for remote materials analysis. Much of the study was carried out with a specific practical application in mind, namely the analysis of ferrous samples in the hostile environment within the area of nuclear reactors. Thus simplicity, manoeuvrability, and ease of use were important considerations in the research. For these reasons, an investigation into the use of a fibre optic as a compact, easy to handle means of laser delivery was undertaken, and all spectroscopic measurements were made with samples in air at normal atmospheric pressure. The investigation into the use of a fibre optic for laser beam delivery involved the design, building and assessment of two laser beam delivery systems. The first system, which utilised a Galilean telescope to produce a divergent beam for coupling to the fibre, was found to be unsuitable for transmitting the laser pulse energies required to produce plasmas suitable for LIBS. The second system, which was successfully used as part of a remote LIBS system, provided a divergent beam for coupling to the fibre. The proposed use of this system in hostile environments within nuclear reactor buildings, restricted the choice of fibre used to those which possess a good degree of radiation resistance. A similar fibre optic system was utilised for collecting and delivering a portion of the laser produced plasma emission to the spectrometer for analysis. In recent years there has been a considerable amount of research into the application of LIBS to the analysis of materials in buffer gas environments. Our research, however, assesses the potential of the remote LIBS technique for the analysis of materials under normal atmospheric conditions, since the application of a low pressure buffer gas environment is often impracticable for the in situ analysis of materials. One of the main aims of the LIBS experiments was the production of calibration curves, utilising spectroscopic standard steel and iron samples, for trace elements commonly found in ferrous materials. Measurements were made to gain an insight into the temporal evolution of the spectroscopic emission from plasmas, produced by ablating ferrous materials with laser radiation, to determine suitable 'time windows' for recording spectra to be used in the production of calibration curves. Calibration curves were produced for chromium, manganese, molybdenum, nickel, vanadium, and silicon, utilising iron as the reference element in relative intensity and concentration ratios, and also for manganese, nickel, vanadium and silicon, utilising chromium as the reference element. Estimates were made of the detection limits for each of these elements.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available