Kinetic Neoclassical Transport In The H-mode Pedestal
Authors: Devon Battaglia, et. al.
Abstract:
Multi-species kinetic neoclassical transport through the QH-mode pedestal and
scrape-off layer on DIII-D is calculated using XGC0, a 5D full-f particle-in-cell driftkinetic
solver with self-consistent neutral recycling and sheath potentials. Quantitative
agreement between the flux-driven simulation and the experimental electron density,
impurity density and orthogonal measurements of impurity temperature and flow profiles
is achieved by adding random-walk particle diffusion to the guiding-center drift motion.
The radial electric field (Er) that maintains ambipolar neoclassical transport across flux
surfaces and to the wall is computed self-consistently on closed and open magnetic field
lines, and is in excellent agreement with experiment. The Er inside the separatrix is the
unique solution that balances the outward flux of thermal tail deuterium ions against the
outward neoclassical electron flux and inward pinch of impurity and colder deuterium
ions. Particle transport in the pedestal is primarily due to anomalous transport, while the
ion heat and momentum transport is primarily due to the neoclassical transport. The full-f
treatment quantifies the non-Maxwellian energy distributions that describe a number of
experimental observations in low-collisionallity pedestals on DIII-D, including intrinsic
co-Ip parallel flows in the pedestal, ion temperature anisotropy and large impurity
temperatures in the scrape-off layer.
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Submitted to: Physics of Plasmas
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Download PPPL-4987 (pdf 4.03 MB 44 pp)
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