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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone

Effect of multiscale interaction between an m/n=2/1 mode and micro instabilities on transport of KSTAR plasmas*

27 Oct 2018, 11:05
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Oral EXS - Magnetic Confinement Experiments: Stability EX/11-SEE/3-PD Stability, Environmental, Post Deadline


Dr Minjun J. Choi (National Fusion Research Institute)


Tokamak plasmas often encounter non-axisymmetric magnetic topology due to unavoidable magnetohydrodynamic (MHD) instabilities and/or external magnetic perturbation. Transport with non-axisymmetric perturbed equilibrium can be very complicated due to various multiscale interactions between a large scale MHD instability and small scale micro instabilities. This paper reports experimental observations and analyses of two distinguishing multiscale interactions. First, a multiscale interaction between the stationary large m/n=2/1 magnetic island and turbulence through profile modification has been identified using simultaneous 2-D measurements of electron temperature (Te) as well as turbulence and their flow profiles. A significant increase of Te turbulence is only observed near the X-point, while it is not observed both in inside and outside of the magnetic island near the O-point possibly due to the strong flow shear. The increased turbulence and Te gradient lead to the violent minor disruption of the plasma. In addition, a small amplitude m/n=2/1 mode can generate a modified spectrum of micro instabilities. The Doppler shift analysis of the measured frequencies of the modes revealed the nonlinear mode coupling among the m/n=12/6 main mode, the m/n=10/5 and m/n=14/7 side lobes, and the m/n=2/1 mode. These coupled modes appear to degrade the tokamak plasma confinement significantly without the violent disruption event. *This work is supported by the KSTAR research project funded by Korea Ministry of Science and ICT
Paper Number EX/11-2
Country or International Organization Korea, Republic of

Primary author

Dr Minjun J. Choi (National Fusion Research Institute)


Prof. Gunsu YUN (Pohang University of Science and Technology) Prof. Hyeon K. Park (UNIST) Dr Jae-Min Kwon (National Fusion Research Institute) Dr Jayhyun Kim (National Fusion Research Institute) Dr K.D. Lee (National Fusion Research Institute) Dr Min Ho Woo (National Fusion Research Institute) Dr Sehoon Ko (National Fusion Research Institute) Prof. Taik Soo Hahm (Seoul National University) Dr Yongkyoon In (Ulsan National Institute of Science and Technology)

Presentation Materials