Compound sawtooth in EAST LHCD plasma：An experimental study

A compound sawtooth with an incomplete relaxation was observed in EAST's lower hybrid current drive (LHCD) plasma. The sub-crash phase of the compound sawtooth corresponds to a longer-lasting and slower-growing 1/1 mode. Based on the two-dimensional (2D) SXR tomography, the time-dependent 2D image of a compound sawtooth crash is obtained. The island produced during a resistive internal kink mode is observed in the all crash phases of the compound sawtooth. The destabilization of 1/1 long-lasting saturated 1/1 mode is related to the current driven by the LHCD near the q=1 surface.