Abstract Details
Abstracts
Author: Richard Reksoatmodjo
Requested Type: Poster
Submitted: 2019-02-22 10:56:22
Co-authors: S. Mordijck, J.W. Hughes, J. Lore, X. Bonnin
Contact Info:
College of William and Mary
2112 Reserve Way
Newport News, Virginia 23602
United States
Abstract Text:
The effect of edge plasma neutral opacity on pedestal density structure is evaluated in experiments on Alcator C-Mod, in H-mode regimes nearing ITER-like edge opacities. Two high power EDA H-mode discharges, one at high current and high density, and one at lower current and thus lower density and opacity, are selected as base cases for a numerical investigation into the role of fueling versus transport. Using the SOLPS-ITER code to vary radial transport coefficients, we match the experimental data and extract neutral density profiles. Assuming a purely diffusive transport model for the plasma, we find a minimal difference in the fitted diffusion coefficients between the high and low Ip discharges, but observe that SOLPS calculates the neutral density, na~1014 m-3, at the midplane separatrix for the high Ip discharge to be less than the low Ip discharge, where na~1015 m-3. As turbulent transport is higher on the low field side, we numerically increase the poloidal asymmetry of the transport coefficients using a ballooning-like model. Increasing the ballooning nature of the transport results in an increase in the poloidal asymmetry of the neutral density distribution, with an increase in neutral densities on the LFS and a reduction on the HFS. In order to compare the 2D SOLPS neutral density results to estimates based on experimental data, we fit an exponential function to the neutral density profiles, as an approximation to the neutral penetration depth. We find that the decay length derived from the first principle Monte Carlo simulations of the EIRENE model agrees well with a simplistic model based on experimental values of ne and Te at the separatrix [1]. Drawing from these comparisons of our simulations to experimental data, we discuss the relative role of transport versus fueling in determining the local electron density in the SOL and pedestal region.
[1] Mordijck, S. et. al. IAEA Conference Paper 2018
Work supported by US DoE under DE-SC0014264,DE-SC0007880
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