Abstract Details
Abstracts
Author: Eric C Howell
Requested Type: Poster
Submitted: 2019-02-20 16:56:16
Co-authors: J.R.King, S.E.Kruger, D.Orlov, R.A.Moyer, T.Evans
Contact Info:
Tech-X Corporation
5621 Arapahoe Ave, Ste A
Boulder, Co 80303
United States
Abstract Text:
NIMROD calculations are used to study the resonant magnetic perturbation (RMP) induced footprint structures in DIII-D. RMPs are routinely used for ELM control in tokamak experiments, and the ITER design includes a flexible set of RMP coils for this purpose. The application of the 3D RMP fields significantly alters the magnetic field structure near the divertor, splitting the separatrix in a homoclinic tangle of spiral lobes. Large asymmetric heat and particle fluxes can result where these lobes intersect the divertor (the magnetic footprint). Impurity radiation in the divertor acts to smooth out the heat flux reducing the asymmetry. Accurate modeling of the footprint is needed to predict and control the asymmetric fluxes to the divertor.
Due to the chaotic nature of the homoclinic tangle, the magnetic footprint structure is highly sensitive to the plasma response to the RMP. Previous modeling efforts using vacuum and ideal MHD responses qualitatively predict the footprint structure, but quantitatively underpredict the experimentally observed lobe splitting. Here we present NIMROD results using both linear and nonlinear resistive MHD to model the plasma response. These models allow field penetration to drive the formation of islands, and the experimentally measured equilibrium flow profiles are included to account for the plasma screening. Numerical results are compared with measurements of the footprint splitting inferred from striations in DIII-D divertor particle flux measurements.
This work is supported by the US DOE under DE-SC0018313, DE-FC02-04ER54698, DE-FG02-05ER54809, and DE-SC00180303
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