Diagnosing the temperatures and densities of plasmas is critical to the understanding of a wide variety of phenomena. Everything from equations of state for warm dense matter (WDM) found in Jovian planets and inertial confinement fusion (ICF) to turbulent and dissipative processes in laser-produced plasmas, rely on accurate and precise measurements of temperature and density. This work presents improvements on two distinct techniques for measuring temperatures and densities in plasmas: x-ray Thomson scattering (XRTS), and Langmuir probes (LPs). At the OMEGA laser facility, experiments on warm dense matter were performed by firing lasers at an ablator foil and driving a planar shock into cryogenically cooled liquid deuterium. XRTS in the collective scattering regime was implemented to probe the matter, measuring densities of n<sub>e</sub> ~ 4.3 x 10<sup>23</sup> cm<sup>-3</sup>, temperatures of T<sub>e</sub> ~ 12 eV and ionizations of Z ~ 1.0. Through an extension to XRTS theory for inhomogeneous systems, it was possible to extract an additional parameter, the length scale of the shock, whose value of ? ~ 1.33 nm was consistent with the predicted mean free path, and therefore the thickness of the shock. A unique triple Langmuir probe prototype was designed and tested at the Gregori group's lab at the University of Oxford. This probe was designed for a high temporal resolution of ~ 200 MHz for probing laser-produced shocks. The probes were used to measure the shock formed from ablating carbon rods in an argon gas fill. The probe yielded plasma parameters of n<sub>e</sub> ~ 1.0 x 10<sup>17</sup> cm<sup>-3</sup> , and T<sup>e</sup> ~ 1.5 eV, consistent with measurements from interferometry and emission spectroscopy.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:730153 |
| Date | January 2016 |
| Creators | Kozlowski, Pawel |
| Contributors | Gregori, Gianluca |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ora.ox.ac.uk/objects/uuid:a436a632-d5aa-4e1a-8711-3814d059053c |
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