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Title	317: Study on sawteeth in the neutral beam (NB) heated plasmas
Name:	Jun-Gyo Bak jgbak@nfri.re.kr	Affiliation:	Korea National Fusion Research Center
Research Area:	Stability & Disruption Avoidance	Presentation time:	Not requested
Co-Author(s):	J.H. Kim, E.J. Strait, R.J. La Haye, B. Tobias, E. Hollmann, W. Heidbrink, G. McKee, C. Holcomb, R.J. Buttery, S.G. Lee, K.D. Lee, W.H. Ko, H.S. Kim, W.C. Kim, Y.S. Bae	ITPA Joint Experiment :	No
Description:	Long period sawteeth, due to fast ions, triggered the NTMs degrading plasma confinement and causing plasma disruption, so control of the sawtooth period is required for reducing the NTM occurrence due to sawteeth. In this experiment, the study on the sawteeth in the NB heated plasma will carried out for the sawteeth control by using NB. There are two items for the study. Item#1 : Investigation of sawteeth behavior in co/counter NB heating - Counter on-axis NB power for achieving minimum sawtooth period in L-mode / H-mode plasmas - Growth rate of n=1 internal kink mode vs. sawtooth period - Effect of fast ion on the period near q=1 surface - Core impurity accumulation as increasing the period - Coupling between internal kink mode and other MHDs by poloidal density asymmetry in high core-rotation due to co-NB heating - Dependence of counter on-axis NB power for achieving minimum sawtooth period on plasma parameters and plasma shape Item #2 : Investigation of Sawteeth behavior in off-axis co-NB heating - Reduction of sawtooth period due to off-axis co-NB heating - Effect of fast ion on the period near q=1 surface Some investigations from this experiment will be compared with KSTAR.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Item #1 : For fixed counter on-axis NB power (210 deg. beam line) of ~ 2 MW (or optimum power?), co on-axis NB powers (three beam line) are varied scanned from 0 to 10 MW (or max power) during L-mode and H mode discharge (Ip : 0.8 ~ 1.5 MA, BT: 1 ~ 2.5 T, ne : 2 ~ 6 x 1019 m-3, q95 : 3~4 ) Item #2 : For fixed co on-axis NB powers (two beam lines) of ~ 2 MW ( or optimum power ?), co off-axis NB power (150 deg. beam line, optimum tilt angle ?) is varied from 0 to 3 (max. power ?) during L-mode discharge. Note that the 210 deg. beam line is turn off in this experiment. ( Ip : 0.8 ~ 1.5 MA, BT: 1 ~ 2.5 T, ne : 2 ~ 6 x 1019 m-3, q95 : 3~4)
Background:	Experiments for studies on the sawteeth controls were done in MAST, JET, TEXTOR and AUG; 1) Asymmetric stabilization of sawteeth by NBI heating: sawtooth period became longer as co-NB power increases, and minimum value of the period was observed in the counter-NB regime. The minimum value was shorter than the period in Ohmically heated plasmas, 2) Destabilization of sawteeth by off-axis co-NB heating: The sawtooth period became shorter when heated with off-axis co-NB than with on-axis co-NB beams NB. The stabilization and destabilizations of sawteeth in the NBI heated plasmas are strongly related to the parameters such as toroidal flows due to NB heating, fast ion distribution near q=1 surface, ion diamagnetic drift frequency. We will carry out the investigation of sawteeth behaviors in the NB heated plasmas during L and H-mode discharges for the sawtooth control by the NB heating
Resource Requirements:	NBI ( counter-NB, off-axis NB ), ECH
Diagnostic Requirements:	ECE radiometer and SXR with low and high sampling rate, ECEI, magnetic diagnostics, CER, MSE, Diagnostics for impurity measurement (Ar at core), BES, Thomson scattering, density interferometer, reflectometer, Diagnostics for fast ion (distribution) detection, BES
Analysis Requirements:
Other Requirements: