Abstract Details
Abstracts
Author: Jacob R King
Requested Type: Poster
Submitted: 2019-02-21 09:36:43
Co-authors: E.C. Howell, S.E. Kruger, A.Y. Pankin (Tech-X Corp) B.A. Grierson, S.R. Haskey (Princeton Plasma Phys Lab) R.J. Groebner (General Atomics) S. Taheri, U. Shumlak (Univ of Washington) J.D. Callen (Univ of Wisconsin-Madison)
Contact Info:
Tech-X Corp
5621 Arapahoe Ave Ste A
Boulder, CO 80303
US
Abstract Text:
The dynamics of the tokamak H-mode edge pedestal are known to depend strongly on the flow and its associated shear. The flow profile is critical to determining accessibility to operation in regimes free from edge-localized modes (ELMs), such as those with resonant magnetic-field perturbations or quiescent H-mode. While MHD simulations of these regimes without ELMs is now routine, the physics that determines the edge pedestal flow structure is outside the scope of the MHD model. Without a fully coupled momentum-transport model, these simulations are limited to being interpretive in nature. Long term, a transport model must incorporate the dominant transport physics in the edge: neoclassical stresses which include ion-orbit loss, high-turbulent fluxes if needed, neutral fueling, and potentially impurity physics. Recent measurements in the DIII-D tokamak [1] show that the main-ion and fully ionized carbon rotation rates can differ substantially in the edge pedestal and indicate the importance of impurities in tokamak modeling with a carbon wall.
We present a set of extended-MHD equations, which are inherently quasi-neutral, that include auxiliary equations for impurity species that are suitable for simulation of low-frequency dynamics. Energy conservation of this system and modification of the MHD waves is discussed. A Von Neumann analysis of the time-discretized system is presented as extended from the mixed implicit/semi-implicit leapfrog time advance in the NIMROD code [2]. Finally, the system of equations, along with a set of fluid-neutral auxiliary equations, is applied to axisymmetric modelling of the DIII-D tokamak edge. Future work towards including the force density from the neoclassical stress and the associated ion-orbit loss is discussed.
[1] SR Haskey et al., Plasma Phys. Control. Fusion 60 (2018) 105001
[2] CR Sovinec et al., J. Comput. Phys. 195 (2004) 355
*Work supported by US DOE under DE-SC0018311, DE-SC0018313 and DE-FC02-04ER54698
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