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Title: XUV interaction with warm dense matter
Author: Kettle, Brendan
ISNI:       0000 0004 6424 6253
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2017
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The absorption of extreme ultraviolet light (XUV) in warm dense matter (WDM), specifically aluminium, has been investigated. The weak scattering model of Vinko et al. (HEDP, 5, 2009) and the corrected classical model of Iglesias (HEDP, 6, 2010), show distinctly different absorption behaviours with electron temperature. Upon heating to a temperature of approximately Te« 1 eV, the Vinko et al. model predicts an increase in absorption (from cold material) of 40-70 % for 20-30 eV photons, whereas the Iglesias model predicts little or no change. Understanding which model is more accurate helps uncover the underlying physical properties of WDM, for example the electron-ion collision rate. Two preliminary experimental campaigns to investigate the production of a suitable XUV probe (through laser-driven high harmonic generation in a gas jet) and an x-ray radiative heating source (from laser-irradiated palladium foils) are described in detail. A third experiment combined these techniques to measure the XUV absorption of radiatively heat warm dense, aluminium samples. There is strong evidence of a number of points. The measured room temperature (“cold”) absorption coefficient of aluminium, is closest to the datasets of Henke et al. (At. Data and Nuc. Data Tables, 54,1993) and compares well to the predictions of both the Vinko et al. and Iglesias theoretical models. This is an important result as many experimentalists rely on the absorption coefficients of Gullikson et al. (Phys. Rev. B, 49,1994), which differ to our results by a factor of nearly 2. Furthermore, upon x-ray heating, the measured absorption of Te« 1 eV solid density aluminium remains very similar to its absorption under cold ambient conditions, for photons of 21.2 eV and 25.9 eV. This is a significant result, as it indicates that the Iglesias model better describes the absorption behaviour of the warm dense aluminium.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available