NSTX/NSTX-U theory, modeling and analysis results
S.M. Kaye, (E. Schuster) et al. (Collaboration Paper)
Nuclear Fusion 59 (2019) 112007 (16pp)
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Abstract
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The mission of the spherical tokamak NSTX-U is to explore the physics
that drives core and pedestal transport and stability at high-β and
low collisionality, as part of the development of the spherical tokamak
(ST) concept towards a compact, low-cost ST-based pilot plant. NSTX-U
will ultimately operate at up to 2 MA and 1 T with up to 12 MW of neutral
beam injection power for 5 s. NSTX-U will operate in a regime where
electromagnetic instabilities are expected to dominate transport, and
beam-heated NSTX-U plasmas will explore a portion of energetic particle
parameter space that is relevant for both α-heated conventional and low
aspect ratio burning plasmas. NSTX-U will also develop the physics
understanding and control tools to ramp-up and sustain high performance
plasmas in a fully-noninductive fashion. NSTX-U began research operations
in 2016, but a failure of a divertor magnetic field coil after ten weeks
of operation resulted in the suspension of operations and initiation of
recovery activities. During this period, there has been considerable
work in the area of analysis, theory and modeling of data from both
NSTX and NSTX-U, with a goal of understanding the underlying physics
to develop predictive models that can be used for high-confidence
projections for both ST and higher aspect ratio regimes. These studies
have addressed issues in thermal plasma transport, macrostability,
energetic particlet-driven instabilities at ion-cyclotron frequencies
and below, and edge and divertor physics.
