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Title: Temperature and density measurements of plasmas
Author: Kozlowski, Pawel
ISNI:       0000 0004 6494 7658
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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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 ne ~ 4.3 x 1023 cm-3, temperatures of Te ~ 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 ne ~ 1.0 x 1017 cm-3 , and Te ~ 1.5 eV, consistent with measurements from interferometry and emission spectroscopy.
Supervisor: Gregori, Gianluca Sponsor: European Research Council ; University of Rochester
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: plasma physics ; Physics ; Plasma ; Laboratory Astrophysics ; X-ray Thomson Scattering ; Langmuir Probes ; HEDP ; Lab Astro ; High Energy Density Physics ; XRTS ; Astrophysics