Lower hybrid current drive (LHCD) plays a crucial role in non-inductive current profile control in tokamaks; however, the key parameters governing its characteristics are not yet fully understood. On the Experimental Advanced Superconducting Tokamak, we conducted parameter-scan experiments combined with numerical simulations to investigate the effects of plasma current (Ip) and line-averaged electron density (n¯e) on the current profile peakedness, quantified by internal inductance (li). This study advances beyond the potential power deposition model Zhai et al., Plasma Phys. Controlled Fusion 61, 045002 (2019)—which offers initial theoretical insights but has inherent limitations—by employing self-consistent equilibrium reconstructions coupled with ray-tracing and Fokker–Planck simulations. Results show a clear transition from peaked on-axis current profiles (high li) at low Ip and n¯e to broad off-axis profiles (low li) at high parameters, with Ip exhibiting a stronger influence. Simulations validate the measured li trends and reveal that safety factor modifications drive the deposition shifts. Additionally, the trapped-gyro-Landau-fluid (TGLF) analysis Staebler et al., Phys. Plasmas 14, 055909 (2007) links the current profile to confinement properties, highlighting the role of electron heating. This work provides experimental benchmarks for LHCD optimization in steady-state operations.
Qian et al. (Fri,) studied this question.
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