Impact of core electron temperature on current profile broadening with radio-frequency wave heating and current drive in EAST

In recent EAST experiments, current profile broadening characterized by reduced internal inductance has been achieved by utilizing radio-frequency current drives (RFCD). In contrast to previous density scan experiments, which showed an outward shift of the current density profile of lower hybrid current drive (LHCD) in higher plasma density, the core electron temperature (T_e(0)) is found to affect the LHCD current profile as well. According to equilibrium reconstruction, a significant increase in on-axis safety factor (q₀) from 2.05 to 3.41 is observed by careful arrangement of RFCD. Simulations using ray-tracing code GENRAY and Fokker–Planck code CQL3D have been performed to thoroughly analyze the LHCD current profile, revealing the sensitivity of the LHCD current profile to T_e(0). The LHCD current density tends to accumulate in the plasma core with higher current drive efficiency benefiting from higher T_e(0). With a lower T_e(0), the LHCD current profile broadens due to off-axis deposition of power density. The sensitivity of the power deposition and current profile of LHCD to T_e(0) provides a promising way to effectively optimize current profile via control of the core electron temperature.