<p> The Lithium Tokamak Experiment (LTX) is a spherical tokamak designed to study the lowrecycling regime through the use of lithium-coated shells conformal to the last closed flux surface (LCFS). A lowered recycling rate is expected to flatten core <i>T</i><sub>e</sub> profiles, raise edge <i>T</i><sub>e</sub>, strongly affect <i>n</i><sub> e</sub> profiles, and enhance confinement.</p><p> To study these unique plasmas, a Thomson scattering diagnostic uses a ≤ 20 J, 30 ns FWHM pulsed ruby laser to measure <i>T</i><sub>e</sub> and <i>n</i><sub>e</sub> at 11 radial points on the horizontal midplane, spaced from the magnetic axis to the outer edge at a single temporal point for each discharge. Scattered light is imaged through a spectrometer onto an intensified CCD. The diagnostic is absolutely calibrated using a precision light source and Raman scattering. Measurements of <i>n</i><sub> e</sub> are compared with line integrated density measurements from a microwave interferometer. Adequate signal to noise is obtained with ne ≥ 2 ×10<sup> 18</sup> m<sup>–3</sup>.</p><p> Thomson profiles of plasmas following evaporation of lithium onto room-temperature plasmafacing components (PFCs) are used in conjunction with magnetic equilibria as input for TRANSP modeling runs. Neoclassical calculations are used to determine <i> T</i><sub>i</sub> profiles, which have levels that agree with passive charge exchange recombination spectroscopy (CHERS) measurements. TRANSP results for confinement times and stored energies agree with diamagnetic loop measurements. Results of χ<sub>e</sub> result in values as low as 7 m<sup>2</sup>/s near the core, which rise to around 100 m<sup>2</sup>/s near the edge. These are the first measurements of χe in LTX, or its predecessor, the Current Drive Experiment-Upgrade (CDX-U), with lithium PFCs.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3615076 |
| Date | 16 May 2014 |
| Creators | Jacobson, Craig Michael |
| Publisher | Princeton University |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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