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

Experimental observations of the plasma shape effect on the RMP-ELM coupling for optimization of the KSTAR ELM-crash control

26 Oct 2018, 08:30
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Poster P7 Posters


Dr YoungMu Jeon (National Fusion Research Institute)


Reliable and robust resonant magnetic perturbation (RMP) on the edge-localized-mode (ELM) crash control is crucial for the success of ITER and beyond. In recent KSTAR experiments, a critical dependence of RMP-ELM coupling on the plasma shape was found to be as important as much as $\mathrm{q_{95}}$. In application of the low-n RMP fields, small variations in the lower triangularity by controlled $\mathrm{R_{X,lower}}$ (radial position of lower X-point) made significant changes on RMP coupling, suggesting a narrow window for the ELM-crash suppression. For the shape effects found in 2016, such $\mathrm{R_{X}}$ window for the RMP induced ELM-crash suppression was surprisingly narrow ($\mathrm{\delta_{lower}=0.74\pm0.04}$ and $\mathrm{R_{X,lower}=144\pm2cm}$), while the other shape parameters, such as $\mathrm{Z_{X}}$, seem to have weak effects. Also it was found that the same shape valid for the n=1 RMP was not effective for the n=2 RMP induced ELM-crash suppression. In 2017, further study revealed that such a strict condition of triangularity ($\mathrm{R_{X,lower}}$) can be relaxed by allowing for an additional small up-down asymmetry on the plasma shape. Applying this new optimized plasma shape led us to make substantial improvements on reliability and robustness of the RMP induced ELM-crash control. As a result, the n=1 RMP induced ELM-crash suppression were successfully demonstrated in a wide range of $\mathrm{q_{95}}$ even with a fixed RMP spectra, achieving a record-long sustainment of ELM suppression more than ~30 sec. Similarly, the n=2 RMP-induced ELM-crash suppression was achieved with the same shape (universality) at ITER-relevant low $\mathrm{q_{95}}$=3.3~3.5. Furthermore, we found a singular response to the shape change for the RMP-plasma coupling, with a support of ideal MHD modeling.
Country or International Organization Korea, Republic of
Paper Number EX/P7-15

Primary author

Dr YoungMu Jeon (National Fusion Research Institute)


Dr Gunyoung Park (National Fusion Research Institute) Prof. Hyeon K. Park (UNIST) Dr Hyunsun HAN (Nuclear Fusion Research Institute, Korea) Dr Jayhyun Kim (National Fusion Research Institute) Dr Jong-Kyu Park (Princeton Plasma Physics Laboratory) Dr Joon-Wook Ahn (Oak Ridge National Laboratory) Dr Kimin Kim (National Fusion Research Institute) Dr Si-Woo Yoon (National Fusion Research Institute) Dr Yeong-Kook Oh (National Fusion Research Institute) Prof. Yongkyoon In (Ulsan National Institute of Science and Technology)

Presentation Materials