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Title: Total fluid pressure imbalance in the scrape-off layer of tokamak plasmas

Simulations using the fully kinetic neoclassical code XGCa (X-point included guiding-center axisymmetric) were undertaken to explore the impact of kinetic effects on scrape-off layer (SOL) physics in DIII-D H-mode plasmas. XGCa is a total-f, gyrokinetic code which self-consistently calculates the axisymmetric electrostatic potential and plasma dynamics, and includes modules for Monte Carlo neutral transport. Previously presented XGCa results showed several noteworthy features, including large variations of ion density and pressure along field lines in the SOL, experimentally relevant levels of SOL parallel ion flow (Mach number similar to 0.5), skewed ion distributions near the sheath entrance leading to subsonic flow there, and elevated sheath potentials (Churchill 2016 Nucl. Mater. Energy 1-6). In this paper, we explore in detail the question of pressure balance in the SOL, as it was observed in the simulation that there was a large deviation from a simple total pressure balance (the sum of ion and electron static pressure plus ion inertia). It will be shown that both the contributions from the ion viscosity (driven by ion temperature anisotropy) and neutral source terms can be substantial, and should be retained in the parallel momentum equation in the SOL, but still falls short of accounting for themore » observed fluid pressure imbalance in the XGCa simulation results.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ; ORCiD logo [1] ;  [3] ; ORCiD logo [1] ;  [1] ; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. General Atomics, San Diego, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; FC02-04ER54698; AC05-00OR22725; AC02-09CH11466
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 4; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Scrape-off layer; Pressure; Simulation; Viscosity; Diii-d; Flow; scrape-off layer; pressure; simulation; viscosity
OSTI Identifier:
1414947
Alternate Identifier(s):
OSTI ID: 1353396