Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct Gyrokinetic Comparison of Pedestal Transport in JET with Carbon
  and ITER-Like Walls   This paper compares the gyrokinetic instabilities and transport in two
representative JET pedestals, one (pulse 78697) from the JET configuration with
a carbon wall (C) and another (pulse 92432) from after the installation of
JET's ITER-like Wall (ILW). The discharges were selected for a comparison of
JET-ILW and JET-C discharges with good confinement at high current (3 MA,
corresponding also to low $\rho_*$) and retain the distinguishing features of
JET-C and JET-ILW, notably, decreased pedestal top temperature for JET-ILW. A
comparison of the profiles and heating power reveals a stark qualitative
difference between the discharges: the JET-ILW pulse (92432) requires twice the
heating power, at a gas rate of $1.9 \times 10^{22}e/s$, to sustain roughly
half the temperature gradient of the JET-C pulse (78697), operated at zero gas
rate. This points to heat transport as a central component of the dynamics
limiting the JET-ILW pedestal and reinforces the following emerging JET-ILW
pedestal transport paradigm, which is proposed for further examination by both
theory and experiment. ILW conditions modify the density pedestal in ways that
decrease the normalized pedestal density gradient $a/L_n$, often via an outward
shift of the density pedestal. This is attributable to some combination of
direct metal wall effects and the need for increased fueling to mitigate
tungsten contamination. The modification to the density profile increases $\eta
= L_n/L_T$ , thereby producing more robust ion temperature gradient (ITG) and
electron temperature gradient driven instability. The decreased pedestal
gradients for JET-ILW (92432) also result in a strongly reduced $E \times B$
shear rate, further enhancing the ion scale turbulence. Collectively, these
effects limit the pedestal temperature and demand more heating power to achieve
good pedestal performance.

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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio