Observation and Analysis of a High Frequency MHD Activity during Sawteeth in KSTAR Tokamak

During the second campaign of the KSTAR operation in 2009, off-axis ECRH/ECCD heating was applied to the high-field side of the q=1 surface during a set of four plasma discharges. In these experiments we have observed high frequency MHD activity which varies from 4 to 6 kHz in both temperature and magnetic fluctuation. Our analysis suggests this is the electron fishbone instability.