Evidence of Partial Reconnection during Sawtooth Crash on EAST ELM-Free H-Mode LHCD Plasma

摘要

Double q = 1 surfaces during a sawtooth crash were identified in EAST ELM-free H-mode LHCD plasma. An off-axis-peaking and enhanced soft-X-ray (SXR) profile due to the presence of high-Z impurities accumulated in the plasma core region is observed after a sawtooth crash. The observed sawtooth oscillations with a,nonmonotonic q profile can be explained satisfactorily by the partial reconnection model. Considerable high-Z impurities near the plasma centre are a response to the formation of double q = 1 surfaces.