Global simulation of ion temperature gradient instabilities in a field-reversed configuration

Physics of Plasmas ARTICLE
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Global simulation of ion temperature gradient instabilities in a field-reversed configuration
Cite as: Phys. Plasmas 26, 042506 (2019); doi: 10.1063/1.5087079 Submitted: 27 December 2018 . Accepted: 25 March 2019 . Published Online: 15 April 2019
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J. Bao, AFFILIATIONS
Z. Lin,
H. Y. Wang,
D. P. Fulton,
S. Dettrick,
and T. Tajima
C. K. Lau,
1University of California, Irvine, California 92697, USA
2Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics,
Chinese Academy of Sciences, Beijing 100190, China
3University of Chinese Academy of Sciences, Beijing 100049, China
4TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, California 92610, USA 5Fusion Simulation Center, Peking University, Beijing 100871, China
a)jianbao0626@gmail.com b)zhihongl@uci.edu
ABSTRACT
We investigate the global properties of drift waves in the beam driven field-reversed configuration (FRC), the C2-U device, in which the cen- tral FRC and its scrape-off layer (SOL) plasma are connected with the formation sections and divertors. The ion temperature gradient modes are globally connected and unstable across these regions, while they are linearly stable inside the FRC separatrix. The unstable global drift waves in the SOL show an axially varying structure that is less intense near the central FRC region and the mirror throat areas, while being more robust in the bad curvature formation exit areas.
Published under license by AIP Publishing. https://doi.org/10.1063/1.5087079
I. INTRODUCTION
A field-reversed configuration (FRC) is an elongated prolate com-
pact toroid (CT) with magnetic fields predominantly along the poloidal
direction, which consists of a core with closed field lines and a scrape-
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has many advantages: The average beta (the ratio between plasma
kinetic pressure and magnetic energy density) is close to unity, which
suggests a much cheaper fusion energy than the tokamak. The compact
shape and simple geometry of FRC also lead to construction conve-
nience and high magnetic efficiency. The SOL region extends to the
device ends and forms natural divertors, which are far away from the
core region and allow extraction of fusion energy without restriction.
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offlayer(SOL)withopenfieldlines. Asafusionreactorconcept,FRC
and electron-scale turbulence is observed.
Thus, it is important to
TAE Technologies, Inc. has launched a series of FRC experiments.
A significant energetic ion population generated from neutral beam
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microturbulence and the ion scale turbulent transport is suppressed. These experimental efforts lead to the sustainment of beam-driven hot FRC plasmas for more than 5 ms in C-2U experiments, which is in the confinement regime limited by turbulent transport.
Phys. Plasmas 26, 042506 (2019); doi: 10.1063/1.5087079 Published under license by AIP Publishing
For the particle-in-cell study of turbulence in
Meanwhile, the large orbit size effects of the energetic particle would not destabilize the
state-of-the-art fusion plasma simulation code: Gyrokinetic Toroidal Code (GTC). GTC has been successfully applied to simulate microtur-
26, 042506-1
injection (NBI) can suppress the macroinstability.
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In FRC, the open field line SOL region is connected to the closed
field line core region, and the turbulence in these two regions affects
each other. In recent C2-U experiment, it is found that ion-scale
turbulence fluctuation is suppressed in the core, while in the SOL, ion-
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understand the transport mechanism in FRC for the improvement of
plasma confinement. 1D and 2D magnetohydrodynamic (MHD)
codes have been built up to model the global FRC transport, which
requires turbulence simulation codes to provide the transport coeffi-
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First-principles particle-in-cell simulation is a powerful
cients.
tokamak plasmas.
tool to study the fusion plasmas combining with theory, which has
successful applications in understanding the anomalous transport in
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FRC, some pioneer works25–27 have been performed based on the
bulence, energetic particle transport, Alfven eigenmodes, and MHD instabilities31,32 in toroidal plasmas. An upgrade to the FRC geometry in the Boozer coordinates of GTC has been carried out by Fulton et al.,25,26 and local gyrokinetic particle simulation study by Lau