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Author: Jacob R King
Requested Type: Poster
Submitted: 2018-02-27 17:30:03

Co-authors: SE Kruger, BA Grierson, RJ Groebner, S Taheri, U Shumlak

Contact Info:
Tech-X Corp
5621 Arapahoe Ave Ste A
Boulder, Colorado   80303
United States

Abstract Text:
Experimentally, it is established that tokamak flows can have a substantial effect on MHD stability. This is particularly true for the edge plasma where large flow shear is correlated with the occurrence of the Quiescent H-mode (QH- mode) state [1] as opposed to operation with edge localized modes (ELMs). Prior NIMROD [2] simulations of QH-mode [3] have used implicit sources that maintain the flow profiles in the absence of MHD perturbations. However, these implicit sources complicate the analysis of transport caused by the MHD perturbations and a more complete model is required. Understanding plasma flows is challenging because of the many physical effects that come into play: turbulence, particle orbit losses, neutrals, field errors, and sheath conditions are all important. As an initial step, we plan to study the forces and nonlinear flow evolution within the context of an extended-MHD simulation by using the NIMROD code. Our simulation will be initialized with reconstructed DIII-D state where the flow is measured by both main-ion and Carbon impurity
charge-exchange recombination spectroscopy. The initial forces and subsequent evolution of the flow given the model equations will determine the suitability of a given model. In this work we will begin by studying the evolution with MHD with Braginskii closures and the impact of neutral collisions, ionization, recombination and charge exchange. It is anticipated that future work will quantify the impact of including a drift-kinetic closure such that the force density from the neoclassical stress and ion-orbit loss are included. Other effects, such as that of high-k turbulence,
may be outside the capability of the NIMROD code and will required coupling to additional codes.