Speaker
Jong-Kyu Park
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I2.106.pdf
Phase Space Visualization and Validation of
3D Field Operating Windows for ELM Suppression in KSTAR
J.-K. Park1 , Y. M. Jeon2 , Y. In2 , J.-W. Ahn3 ,
N. C. Logan1 , Z. Wang1 , G. Y. Park2 , J. Kim2 , H. H. Lee2 , W. H. Ko2 , H. S. Kim2 ,
E. A. Feibush1 , R. Nazikian1 , J. E. Menard1 , and M. C. Zarnstroff1
1 Princeton Plasma Physics Laboratory, Princeton, NJ 08540, USA
2 National Fusion Research Institute, Daejeon 34133, South Korea
3 Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
A small degree of 3D relaxation is a key component of tokamaks in the path towards fu-
sion burning plasmas, as it provides the great means to control various instabilities such as
edge-localized-modes (ELMs). However, the number of choices available for a 3D magnetic
field is virtually unlimited and most of them will only destabilize or degrade plasmas by global
symmetry-breaking, presenting a major challenge to the concept of 3D tokamaks. Here, we
present a complete visualization of 3D field operating windows for ELM suppression in a toka-
mak, and its remarkable validation with a complex 3D coil system. The Korean superconducting
tokamak advanced research (KSTAR) facility is presently unique by its versatile 3 rows of in-
vessel coils, which enabled KSTAR to suppress the type-I ELM crashes using an n = 1 resonant
magnetic perturbation (RMP) without triggering core MHD instabilities [1] in high-β plasmas
and for a duration longer than ∼ 90τE [2]. This stable RMP window exists only within a small
fraction of the total phase space volume that the KSTAR 3D coils can access, as predicted
based on local 3D response metrics and validated by a special group of RMPs [3]. The phase
space visualization of RMP windows offered excellent opportunities to navigate all available
3D fields and optimize new RMPs, such as the ones only accessible by dynamic passages, the
off-midplane RMPs for the first time in KSTAR, and the potentially favorable RMPs for higher
toroidal shaping or wider q95 windows. The method and principle adopted in this study is also
being used to optimize 3D fields in DIII-D and ITER, and to develop innovative 3D coils feasi-
ble for a reactor where long-range ex-vessel RMP solutions are necessary.
References
[1] Y. M. Jeon, J.-K. Park et al., Physics Review Letters 109, 035004 (2012)
[2] Y. In, J.-K. Park et al., Nuclear Fusion 57, 116054 (2017)
[3] J.-K. Park, Y. M. Jeon et al., Nature Physics, Under Review (2018)
This work was supported by US DOE Contract DE-AC02-09CH11466, and also by the Ko-
rean Ministry of Science, ICT and Future Planning.
