Date of Award
Doctor of Philosophy
David Donovan, Lawrence Heilbronn, Ezekial Unterberg, Peter Stangeby
Experiments with outer strike point injection of isotopically enriched methane (13CD4) in DIII-D L-mode discharges have demonstrated the ability to infer near scrape-off-layer (SOL) impurity density profiles based on: far-SOL collector probe (CP) measurements; a stable isotopic mixing model; and SOL impurity transport modelling. This work enables one of the first in-depth investigations on the source and transport of SOL impurities which could hinder performance of future fusion devices. Modelling by DIVIMP and 3DLIM of 13C SOL evolution is consistent with diagnostic observations and indicates that the buildup of injected impurities on plasma-facing surfaces must be considered while inferring representative impurity distributions. Namely, 13C deposits on the inner and outer targets are shown to contribute 50% at a minimum of the enriched 13C deposition on CPs and to cause poloidal shifting of the impurity density peaks in the near-SOL. This analysis elucidates the importance of source location, connection length, poloidal diffusion, and radial convective velocity of impurities to accurately model and interpret SOL impurity behavior.
Duran, Jonah David, "DETERMINATION OF NEAR-SOL CARBON IMPURITY CONTENT DUE TO DIVERTOR TARGET LEAKAGE USING CARBON-13 TRACERS VIA METHANE INJECTION ON THE DIII-D TOKAMAK. " PhD diss., University of Tennessee, 2022.