The Woodruff School

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 also by other phenomena than diffusion, viscosity, and conduction, respectively. 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, viscous radial momentum fluxes that can be used to interpret viscosities, and conductive radial energy fluxes that can be used to interpret thermal conductivities.

The improved methodology is employed to interpret particle diffusion and heat conductivity coefficients in several DIII-D shots in different confinement regimes and compare with theoretical models.

The new 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 GTNEUT neutral particle transport code, is applied to several DIII-D shots to enable comparisons of various theoretical particle diffusion coefficient and thermal conductivity models with experiment. The new code corrects for non-diffusive radial particle flux contributions and non-conductive radial heat flux contributions (including IOL, convection, 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.

This code is used in this research to examine differences in these particle diffusion and heat conductivity coefficients among shots in different operating regimes when correcting for the various non-diffusive and non-conductive phenomena. The experimental results will be compared with various theoretical models for particle and energy transport, including neoclassical, paleoclassical, ITG, drift ballooning mode, TEM, and ETG. This research will also interpret a toroidal viscous drag and a pinch velocity using IOL-corrected radial particle fluxes.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Jonathan Roveto

TIME:	Wednesday, May 26, 2021, 2:00 p.m.

PLACE:	https://bluejeans.com/785234944, Online

TITLE:	Interpretation of Radial Particle Diffusion Coefficients, Thermal Conduction Coefficients and Toroidal Viscosity Coefficients

COMMITTEE:	Dr. Weston Stacey, Co-Chair (NRE) Dr. Steven Biegalski, Co-Chair (NRE) Dr. Dan Kotlyar (NRE) Dr. Theresa Wilks (Massachusettes Institute of Technology) Dr. Shaun Haskey (Princeton Plasma Physics Laboratory) Dr. Rich Groebner (General Atomics - DIII-D) Dr. Bojan Petrovic (NRE)

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 also by other phenomena than diffusion, viscosity, and conduction, respectively. 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, viscous radial momentum fluxes that can be used to interpret viscosities, and conductive radial energy fluxes that can be used to interpret thermal conductivities. The improved methodology is employed to interpret particle diffusion and heat conductivity coefficients in several DIII-D shots in different confinement regimes and compare with theoretical models. The new 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 GTNEUT neutral particle transport code, is applied to several DIII-D shots to enable comparisons of various theoretical particle diffusion coefficient and thermal conductivity models with experiment. The new code corrects for non-diffusive radial particle flux contributions and non-conductive radial heat flux contributions (including IOL, convection, 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. This code is used in this research to examine differences in these particle diffusion and heat conductivity coefficients among shots in different operating regimes when correcting for the various non-diffusive and non-conductive phenomena. The experimental results will be compared with various theoretical models for particle and energy transport, including neoclassical, paleoclassical, ITG, drift ballooning mode, TEM, and ETG. This research will also interpret a toroidal viscous drag and a pinch velocity using IOL-corrected radial particle fluxes.