Comparison of divertor heat flux splitting by 3D fields with field line tracing simulation in KSTAR

Abstract

We present the experimental and numerical analysis of divertor heat flux spitting by 3D magnetic fields in KSTAR. A dedicated experiment to measure the modification of the divertor heat flux profile in the n = 2 resonant and non-resonant field configurations has been conducted. The measured heat flux profiles were directly compared to the magnetic field line tracing (FLT) simulation using the POCA-FLT code, which fully considers vacuum and ideal plasma response models. Measurements indicate that the 3D fields induce strong splitting of heat flux on the divertor target due to the formation of stochastic field layers. Splitting characteristics largely depend on the applied 3D field structure and its alignment to the axisymmetric magnetic pitch. The modeling of the field line connection length shows good agreement with measurements, reproducing well the pattern of heat flux splitting. Simulations with the ideal plasma response better reproduce measured heat flux profiles by excitation of non-resonant field components in the non-resonant 0° phase and shielding of resonant field components in the resonant 90° phase.