Investigation of ion and electron heat transport of high-Te ECH heated discharges in the Large Helical Device
Authors: N.A. Pablant, S. Satake, M. Yokoyama,
D.A. Gates, M. Bitter, N. Bertelli,
L. Delgado-Aparicio, A.
Dinklage, M. Goto, K.W. Hill, S. Igamai, S. Kubo, S. Lazerson,
S.
Matsuoka, D.R. Mikkelsen, S. Morita, T. Oishi, R. Seki, T.
Shimozuma, C. Suzuki,
Y. Suzuki, H. Takahashi, H. Yamada, Y.
Yoshimura, and the LHD Experiment Group
Abstract: An analysis of the radial electric field
and heat transport, both for ions and electrons, is presented for
high-Te electron cyclotron heated
(ECH) discharges on the Large Helical Device (LHD). Transport
analysis is done using the TASK-3D
transport
suite1
utilizing experimentally measured profi les for
both ions and electrons. Ion temperature and poloidal rotation
profi les are measured using the recently installed x-ray imaging
crystal spectrometer diagnostic (XICS)2, while electron temperature
and density pro files are measured using Thomson scattering. The
analysis also includes calculated ECH power deposition profi les
as determined through the TRAVIS ray-tracing
code. This is the first time on LHD that this type of integrated
transport analysis with measured ion temperature pro files has
been performed without NBI injection, allowing the heat transport
properties of plasmas with only ECH heating to be more clearly
examined. For this study, a plasma discharge is chosen which
develops a high central electron temperature (Teo
= 9keV ) at moderately low densities (neo = 1.5 x 1019m-3).
The experimentally determined transport properties from TASK-3D are compared to neoclassical
predictions as calculated by the GSRAKE
and FORTEC-3D codes. Predictions of a
strong positive neoclassical ambipolar electric fi eld (Er) in the plasma core are compared to poloidal
rotation measurements from the XICS diagnostic. Both the new
diagnostic capabilities (XICS) and the integrated modeling help to
provide a better understanding of the interplay of transport and
the radial electric field in the formation of high temperature
electron heated stellarator/heliotron plasmas at low
collisionalities.
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Submitted to: Plasma Physics and Controlled Fusion
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Download PPPL-5138 (pdf 2.7 MB 12pp)
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