Theory of X-ray Thomson scattering in warm dense matter
Wünsch, Kathrin (2011) Theory of X-ray Thomson scattering in warm dense matter. PhD thesis, University of Warwick.Full text not available from this repository.
Official URL: http://webcat.warwick.ac.uk/record=b2565771~S1
This thesis presents the theoretical framework required to apply spectrally
resolved x-ray Thomson scattering (XRTS) as a diagnostic method for warm dense
matter. In particular, the theory is generalised to allow for the description of systems
with multiple ion species where all mutual correlations are taken into account
within the new approach. Supplemented with the theory presented, XRTS is now
a promising diagnostics for high-energy-density matter containing different chemical
elements or mixtures of different materials.
The signal measured at XRTS contains the unshifted Rayleigh peak and
frequency-shifted features. The first is related to elastic scattering from electrons
co-moving with the ions whilst the second occurs due to scattering from free electrons
and excitation/ionisation events. The focus of this thesis lies on the elastic
scattering feature which requires the ion structure and the electron density around
the ion as input for the theoretical modelling. The ion structure is obtained from
quantum simulations (DFT-MD) and classical hypernetted-chain (HNC) equations.
The analysis of the DTF-MD simulation data reveals that partial ionisation yields
strong modifications of the ion-ion interactions. Similar effects are found for the
form of the electron screening cloud around an ion.
On the basis of the newly developed theory and structural models, multicomponent
effects on the XRTS signal are studied. It is shown that the Rayleigh
feature is very sensitive to the ratio of the elements in the scattering volume and
their mutual correlations. These results indicate that XRTS is well-suited to probe
the properties of complex materials and the process of mixing in the WDM regime.
The advanced theories are finally applied to experimental spectra. The procedure
allows for both extracting the basic plasma parameters and assessing the
quality of the theoretical models applied. Comparisons with several experiments
demonstrated that the non-collective regime (large scattering angle) is reasonably
well understood whereas the collective regime (small scattering angle/long wavelength
limit) still holds challenges. The collective regime is problematic as here
strong correlations and screening are highly relevant and, thus, a yet unknown description
for fully coupled quantum systems needs to be applied.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QC Physics|
|Library of Congress Subject Headings (LCSH):||Thomson scattering, Matter -- Properties|
|Official Date:||September 2011|
|Institution:||University of Warwick|
|Theses Department:||Department of Physics|
|Supervisor(s)/Advisor:||Gericke, Dirk O.|
|Sponsors:||Engineering and Physical Sciences Research Council (EPSRC)|
|Extent:||xiii, 180 leaves : ill., charts|
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