59th Annual Meeting of the APS Division of Plasma Physics
Volume 62, Number 12
Monday–Friday, October 23–27, 2017;
Milwaukee, Wisconsin
Session GI2: Pedestal and Low-Temperature Physics
9:30 AM–12:30 PM,
Tuesday, October 24, 2017
Room: 102ABC
Chair: Venkattraman Ayyaswamy, University of California, Merced
Abstract ID: BAPS.2017.DPP.GI2.3
Abstract: GI2.00003 : Tamed stability and transport using controlled non-axisymmetric fields in KSTAR*
10:30 AM–11:00 AM
Preview Abstract
Abstract
Author:
Yongkyoon In
(Natl Fusion Res Inst)
Meticulously orchestrated non-axisymmetric fields enabled KSTAR to explore
various paths to tame plasma stability and transport in a very rigorous
manner. Given an extremely low level of intrinsic non-axisymmetry, KSTAR has
now established high-precision 3-D field control capability that can not
only robustly suppress edge localized modes using resonant magnetic
perturbation (RMP), but also exclusively alter plasma rotation without
invoking particle and energy transport. In highly shaped plasmas
(triangularity of $\delta $ \textasciitilde 0.6), we have secured low-n RMP
ELM suppressions in a wide range of edge safety factors at
q$_{\mathrm{95\thinspace =\thinspace }}$3.4 -- 6.4. One of the best n$=$1
RMP ELM suppressions has been sustained for more than 30 secs (comparable to
wall saturation time), satisfying a low edge collisionality ($\nu $*
\textasciitilde 0.2), close to ITER-target. Beyond a typical 3-row RMP
configuration, we have newly succeeded in suppressing ELMs with n$=$1
off-midplane RMPs only, whose configuration is nearly orthogonal to
conventional helical RMP structure. Also, a-priori calculation of ideal
plasma response led us to identify an optimal window of ELM suppression
distinctively separated from mode-lockings. With RMP configuration fixed, a
gradual torque control between perpendicular and parallel components helped
us access the onset of ELM suppression, strongly supporting a theoretical
hypothesis of $\omega_{\mathrm{\bot Ñ,e}}$ \textasciitilde 0 as necessary
condition for ELM-suppression, consistent with direct measurement by ECEI.
Among non-resonant fields that are quite sensitive to a variation of
q$_{\mathrm{95\thinspace }}$in NTV physics, a `most-quiescent' configuration
has been identified to fully decouple plasma rotation from particle and
energy transport. In support of ITER, KSTAR has conducted a series of
experiments regarding RMP misalignment impact and its compatibility with
detached plasmas. Preliminary experimental analysis suggests that divertor
heat flux might not be sufficiently diffused by misalignment alone, once
RMP-driven ELM suppression takes place.
*Korean Ministry of Science, ICT and Future Planning
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DPP.GI2.3