Stability analysis of the high poloidal bet scenario on DIII-Dtowards operation athigher plasma current

The high poloidal beta scenario with plasma current I^P 600 kA and large-radius internal transport barrier (ITB) on DIII-D is subject to n =1 MHD kink modes when the current profile becomes very broad at internal inductance values li 0.5-0.6. It is desirable to extend this scenario to higer plasma current ( 1 MA) for highernormalized fusionperformance. However, higher current at constant normalized beta, ?^N 3, would reducethe poloidal bet, ?^P, below the threshold for ITB sustainment, observed at ?^P 1.9. Thus, to avoid loss of the IT, ?N^?? must be increased together with I^P while avoiding the kink instability. MHD analysis is presented that explains possible paths to high ?^N stability limit for the kink mode in tis scenario.

Work supported by National Magnetic Confinement Fusion Program of Chin under 2015GB110001 and 2015GB102000 - National Natural Science Foundation of China under Grant No. 1147521 and by US DOE under DE-FC02-04ER54698.