Abstract Details
Abstracts
Author: Walter Guttenfelder
Requested Type: Pre-Selected Invited
Submitted: 2019-02-21 14:16:31
Co-authors: R.J. Groebner, B.A. Grierson, J.M. Canik, E.A. Belli, J. Candy
Contact Info:
PPPL
PO Box 451
Princeton, NJ 08543
USA
Abstract Text:
The spectral multiscale gyrokinetic code CGYRO is used to calculate theoretical nonlinear turbulent transport in the edge region of DIII-D H-mode discharges. We focus on two discharges with different divertor geometries in an attempt to clarify the role of transport vs. sources in setting the pedestal density and temperature profiles. Linear simulations predict that ion-scale instabilities dominate at the top of the pedestal where strong rotation shear (specifically parallel velocity shear) enhances the growth rates. In contrast, in the steep gradient region, ExB shearing rates are much larger than growth rates of ion scale instabilities. The electron temperature profiles closely follow the electron-scale ETG instability threshold calculated by CGYRO. Nonlinear electron-scale simulations in the sharp gradient region predict that ETG turbulence can produce significant electron heat flux, comparable to the observed heat flux, while neoclassical transport calculated by NEO provides a significant contribution to the total electron particle flux. To begin developing a theory-based ETG pedestal transport model for the sharp gradient region, nonlinear simulation scans are performed to predict the sensitivity of both electron thermal and particle transport contributions to input gradients. A pedestal-ETG transport model is derived using an analytic fit to the simulation results that follows theoretical expectations. The pedestal-ETG model is used, in addition to neoclassical fluxes from NEO, to predict both ne and Te pedestal profiles using target fluxes determined from SOLPS-ITER interpretive analysis. This work supported by the U.S. Department of Energy under DE-AC02-09CH11466 (PPPL), DE-FC02-04ER54698 (DIII-D), DE-FG02-95ER54309 (GA Theory) and DE-AC02-05CH11231 (NERSC).
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