TSC and TRANSP Simulations on Current Ramp-up Studies in NSTX-U

Reactor design studies show that some solenoid-free plasma startup capability is needed for a tokamak to operate at sufficiently low aspect ratios. Non-solenoidal startup is being studied on the Pegasus-III experiment at the Univ. of Wisconsin and the QUEST ST in Japan. In support of these non-solenoidal plasma startup studies, some experiments on NSTX-U would examine the solenoid flux saving for various current ramp-up scenarios. These studies would help identify the initial plasma target parameters that need to be generated by the solenoid-free plasma startup system. The objective is to minimize the size of a single swing solenoid that, with the assistance of the initial solenoid-free plasma startup system generated target, permits the plasma current in a reactor to be ramped up to the sustained operation levels. In support of these studies, TSC and TRANSP simulations are being conducted to study the current ramp-up phase on NSTX-U and reduce the solenoid flux consumption.