Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Role of Helium-Hydrogen ratio on energetic interchange mode behaviour
  and its effect on ion temperature and micro-turbulence in LHD   In the Large helical device, a change of energetic particle mode is observed
as He concentration is varied in ion-ITB type experiments, having constant
electron density and input heating power but with a clear increase of central
ion temperature in He rich discharges. This activity consists of bursty, but
damped energetic interchange modes (EICs, X Du et al., Phys. Rev. Lett. 114
p.155003 (2015)), whose occurrence rate is dramatically lower in the He-rich
discharges. Mechanisms are discussed for the changes in drive and damping of
the modes with He concentration. These EIC bursts consist of marked changes in
the radial electric field, which is derived from the phase velocity of
turbulence measured with the 2D phase contrast imaging (PCI) system. Similar
bursts are detected in edge fast ion diagnostics. Ion thermal transport by
gyro-Bohm scaling is recognised as a contribution to the change in ion
temperature, though fast ion losses by these EIC modes may also contribute to
the ion temperature dependence on He concentration, most particularly
controlling the height of an "edge-pedestal" in the $T_{i}$ profile. The
steady-state level of fast ions is shown to be larger in Helium rich discharges
on the basis of a compact neutral particle analyser (CNPA), and the fast-ion
component of the diamagnetic stored energy. These events also have an influence
on turbulence and transport. The large velocity shear induced produced during
these events transiently improves confinement and suppresses turbulence, and
has a larger net effect when bursts are more frequent in Hydrogen discharges.
This exactly offsets the increased gyro-Bohm related turbulence drive in
Hydrogen which results in the same time-averaged turbulence level in Hydrogen
as in Helium.

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The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
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The categories of this paper are: nlin