Quasi-Symmetric Magnetic Perturbation for Robust Tokamak Operation

Effective non-axisymmetric field control is vital for advanced tokamak operation, particularly for error field correction and ELM suppression. Among the various 3D field strategies, while RMP is widely used for ELM control, quasi-symmetric magnetic perturbation (QSMP) is optimized for EFC by minimizing magnetic field strength variations along field lines, enabling non-axisymmetric field application without significant confinement degradation. This study presents detailed kinetic and transport profiles in KSTAR under various 3D fields. Comprehensive TRANSP analysis provides detailed temporal and spatial profiles of plasma parameters, torque, and transport coefficients, highlighting QSMP’s minimal negative impact on plasma profiles compared to conventional RMP, which induces density pump-out and rotation damping. Notably, during the transition from QSMP to RMP by phase variation, plasma temperature, density, and rotation progressively decreased, correlating with the increased resonant field strength and integrated torque, as confirmed by kinetic profile analysis and GPEC/M3D-C1 calculations. These results indicate that QSMP offers a robust path for safe and flexible 3D field applications, serving as a foundation for transport optimization and ELM suppression, and highlight its unique advantage in preserving performance even during critical operational phases such as ramp-up and L-H transition.