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Title: Optical diagnostics of laser plasmas
Author: Delserieys, A.
ISNI:       0000 0001 3421 7679
Awarding Body: Queen's University of Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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An optical Thomson scattering diagnostic has been implemented on low temperature laser-produced plasmas. This is a novel diagnostic for these types of plasmas which provides a reliable non-intrusi~e means of determining absolute values for electron number density and temperature, with a minimal number of assumptions required compared to most diagnostics used so far. A frequency doubled Nd:YAG laser was used as a source of scattered light, then detected with a gated ICCD detector after being spectrally resolved by a 1 meter grating spectrometer. The density and temperature of an expanding KrF laser-ablated magnesium plume have been obtained. The e.lectron temperature was found to decay with the expected Te oc C1 dependence. However, it was found that the electron density has a time dependence ne oc t-4 . 95 which can be explained by strong recombination processes. Atomic Raman satellites were also observed; they were identified as originating from transitions between the different angular momentum levels of the metastable 3pO term in Mgl. Comparison with preliminary calculations of Rayleigh and Raman cross-sections of Mgl ground state and first excited state showed variations in the population of metastables relative to atoms and ions. The study was then extended further by adapting the system to an optical emission spectroscopy diagnostic. Up to - 40% discrepancy was found between the results given by each diagnostics, questioning the assumption of local thermodynamic equilibrium in the plasma, assumed to analyse the emission spectra. Supplied by The British Librawe world's knowledge'
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available