Modelling of error field correction for H-mode scenario in CFEDR

Error field correction represents a critical challenge for the China Fusion Engineering Demo Reactor (CFEDR), where millimetric coil imperfections can trigger mode locking and plasma disruption. This study presents a detailed framework for designing error field correction coils (EFCC) for the CFEDR's inductive H-mode scenario. An equivalent surface current method is employed to model an intrinsic error field of <i>B_r</i>/<i>B_T</i>=1.46×10^-4 at the <i>q</i>=2/1 rational surface, and utilize the MARS-F code to compute the plasma response to both the error field and that produced by the correction coils. The optimization criterion targets full cancellation of the <i>m</i>/<i>n</i>=2/1 resonant radial field component including the plasma response, rather than merely correcting the vacuum field. Systematic parameter scans reveal that optimal EFCC current decreases nonlinearly with increasing poloidal coverage of EFCC as well as the plasma toroidal flow speed. The low intrinsic torque input of this scenario necessitates substantial correction currents (│<i>I</i>_EFCC^opt│=82.5 kAt) for effective error field suppression. Concomitant effects of the optimal correction are also investigated, including plasma response perturbations at secondary rational surfaces (<i>q</i>=3, 4) and toroidal torques produced by EFCC. The modeled torque distribution, with the dominant contribution from neoclassical toroidal viscosity, is favorably localized near the plasma edge region—supporting both mode locking avoidance and potential edge-localized mode suppression. These results establish quantitative design guidelines for EFCC system in CFEDR.