Speaker
Dr
YoungMu Jeon
(National Fusion Research Institute)
Description
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)
Co-authors
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)
