Plasma current modulation system and AC operation in the CT-6B tokamak

To perform alternating current (AC) operations in the CT-6B tokamak, a newly developed plasma current modulation system (PCMS) has been designed for the ohmic heating circuit. The modulation system is reliable, simple in technique, easy to operate, and has four operation modes to modulate CT-6B plasma current. Reproducible multicycle AC operation at a current of ~5 kA and a fast current ramped down and then up with a linear rate of 6 kA/ms AC discharge with trapezoidal waveform have been achieved using PCMS. Feedback control of the plasma current plateau, plasma current weak modulation, and the plasma transition from a low to high current for the studies of the anomalous transport and the plasma edge turbulence have also been demonstrated