Speaker
Mr
Jun-Gyo BAK
(Republic of Korea)
Description
The ELM and pedestal structure are studied in Korea Superconducting Tokamak Advanced Research (KSTAR) ELMy H-mode plasmas. KSTAR H-mode plasmas have three distinctive types of ELMs ; large type-I ELMs with low ELM frequency (f_ELM = 10 - 50 Hz) and good confinement (H_98(y,2) = 0.9 - 1), intermediated, possibly type-III, ELMs with high ELM frequency (f_ELM = 50 - 250 Hz) at a reduced confinement (H_98(y,2) = 0.7 - 0.8), and a mixed, large and small, ELM regime with good confinement (H_98(y,2) ~ 1). The NBI power scan shows that ELM frequency is increased with increasing input power for large ELMs, which is a typical behavior of type-I ELMs. Type-I ELMs are appeared in a wide range of NBI power, 0.8 ≤ P_NBI ≤ 1.5MW, but in a limited density range (0.35 ≤ n_e/n_G ≤ 0.45). Intermediate ELMs are observed in a wider density range, 0.35 ≤ n_e/n_G ≤ 0.55, than for type-I ELMs and we suspect that these ELMs might be type-III considering that the confinement quality is degraded compared to type-I ELMs and the relatively lower n_e/n_G value compared to the type-II ELMs. Mixed ELMs often occur in late H-mode and the density range is also wider, 0.38 ≤ n_e/n_G ≤ 0.57, than that of type-I ELMs. Pedestal profiles of electron temperature (T_e) from the ECE measurement and toroidal velocity (V_t) from the charge exchange spectroscopy (CES) measurement show continuous build up on the low field side (LFS) during the inter-ELM period for type-I ELMy H-mode. However, the recovery of Ti pedestal from the CES after the ELM crash does not occur until it finally rises back up at the last stage of the inter-ELM period, i.e. > 80 % of the ELM cycle. The estimated electron pedestal collisionality, \mu_e^* =q_{95}R \epsilon^{-1.5} \lamda_{ee}^-1, is quite low, \mu_e^*~0.2-0.5, for the type-I ELMy H-mode. An ideal MHD stability analysis for ELMy H-mode plasmas is also carried out by the ELITE code in order to investigate unstable domains for the ELM occurrence, as well as its sensitivity to a range of estimated/measured profiles. In this work, the experimental investigations of the characteristics of the ELM and the pedestal structure during the ELM in the KSTAR H-mode plasmas will be reported, and the preliminary results from the ideal MHD analysis for ELMy H-mode plasmas will be presented.
Country or International Organization of Primary Author
Korea
Primary author
Mr
Jun-Gyo BAK
(Republic of Korea)
Co-authors
Dr
A.C. ENGLAND
(National Fusion Research Institute, Korea)
Dr
D.L. HILLIS
(Oak Ridge National Laboratory, USA)
Mr
H.H. LEE
(National Fusion Research Institute, Korea)
Dr
H.S. HAN
(National Fusion Research Institute, Korea)
Mr
H.S. KIM
(Seoul National University, Korea)
Dr
J. KIM
(National Fusion Research Institute, Korea)
Dr
J.G. KWAK
(National Fusion Research Institute, Korea)
Dr
J.W. AHN
(Oak Ridge National Laboratory,USA)
Mr
J.W. LEE
(Seoul National University, Korea)
Dr
K. IDA
(National Institute for Fusion Science , Japan)
Dr
K.D. LEE
(National Fusion Research Institute, Korea)
Dr
R. MAINGI
(Oak Ridge National Laboratory, USA)
Dr
S.A. SABBAGH
(Columbia University, USA)
Dr
S.H. HAHN
(National Fusion Research Institute, Korea)
Dr
S.I. PARK
(National Fusion Research Institute, Korea)
Dr
S.W. YOON
(National Fusion Research Institute, Korea)
Dr
W.C. KIM
(National Fusion Research Institute, Korea)
Dr
W.H. KO
(National Fusion Research Institute, Korea)
Dr
Y.K. OH
(National Fusion Research Institute, Korea)
Dr
Y.M. JEON
(National Fusion Research Institute, Korea)
Dr
Y.S. BAE
(National Fusion Research Institute, Korea)
Prof.
Y.S. NA
(Seoul National University, Korea)
Dr
Y.S. PARK
(Columbia University, USA)
Dr
Y.U. NAM
(National Fusion Research Institute, Korea)
