SUBJECT: Ph.D. Dissertation Defense
   
BY: Jonathan Roveto
   
TIME: Wednesday, December 1, 2021, 2:00 p.m.
   
PLACE: https://bluejeans.com/420816296/5251, Virtual
   
TITLE: Interpretation of Thermal Conductivity and Toroidal Momentum Transport in DIII-D Taking Into Account IOL and Pinch Velocity
   
COMMITTEE: Dr. Weston Stacey, Co-Chair (NRE)
Dr. Steven Biegalski, Co-Chair (NRE)
Dr. Bojan Petrovic (NRE)
Dr. Dan Kotlyar (NRE)
Dr. Theresa Wilks (Massachusettes Institute of Technology)
Dr. Richard Groebner (General Atomics - DIII-D)
Dr. Shaun Haskey (Princeton Plasma Physics Lab)
 

SUMMARY

The objective of this PhD research is to improve the methodology used to interpret the diffusive radial particle flux and the conductive radial heat flux from the experimentally inferred total radial particle and energy fluxes, respectively, in order to more accurately infer experimental values for the heat conductivity and particle diffusion coefficients, respectively. The difficulty lies in the fact that the experimental radial particle, momentum, and energy fluxes are determined by phenomena other than simply diffusion, viscosity, and conduction, respectively, alone. The contributions of these ``other phenomena'' must be subtracted from the ``experimental'' radial fluxes to obtain diffusive radial particle fluxes that can be used to interpret particle diffusivities and conductive radial energy fluxes, which can be used to interpret thermal conductivities. The Georgia Tech GTEDGE2 transport interpretation code, with improved Ion Orbit Loss (IOL) models for neutral beam and thermalized ions in the edge plasma, and the GTNEUTPY neutral particle transport code, are applied to several DIII-D shots to enable comparisons of various theoretical particle diffusion coefficient and thermal conductivity models with experiment in multiple operating regimes (L-mode, H-mode, RMP, QH-mode, and SH-mode). The new code corrects for non-diffusive radial particle flux contributions and non-conductive radial heat flux contributions (including IOL, the convective outflow of plasma energy, viscous heating, transport of rotational energy, and work done by the flowing plasma against the pressure tensor) when determining the experimental radial particle and heat fluxes. We find that the effects of IOL on the interpretation of the radial ion heat flux are significant in the edge plasma. Furthermore, correcting for convective heating and work done by the plasma on the pressure tensor is seen to in general substantially reduce the inferred radial ion conductive heat flux. Importantly, we also find that viscous heating, which is driven by asymmetries in the toroidal and poloidal rotation velocities, can be as important of a heat transfer mechanism that must be corrected for when inferring transport coefficients. We find that, upon correcting for these non-conductive heat transport mechanisms, some combination of neoclassical and ITG transport may be able to explain ion heat transport in the edge plasma. We also show that the particle pinch is an important driver of transport in the edge plasma. We hope that future research will apply the IOL methodology found in the GTEDGE2 code while also correcting for the above-described non-conductive heat transport phenomena and taking measures to estimate rotational asymmetries to determine the viscous heating, which we believe is an important non-conductive heat transport mechanism.