Investigations of plasma response associated with Resonant Magnetic Perturbation fields using perturbation method in KSTAR H-mode plasmas

The plasma response associated with the Resonant Magnetic Perturbation (RMP) field was investigated using the small edge perturbations induced by a modulated Supersonic Molecular Beam Injection (SMBI) in KSTAR. The modulated SMBI provides a time-varying perturbation of the plasma density source in the region just inside the last closed flux surface (LCFS) and a modulated flow damping rate. Radial propagation of the toroidal rotation perturbation induced by SMBI from the q=3 surface to the q=2 surface was observed. Theoretical analysis using the General Perturbed Equilibrium Code (GPEC) of the RMP intensity profiles of the RMP field is consistent with the phase profile of the toroidal rotation perturbation.

Understanding core heavy impurity transport in a hybrid discharge on EAST

The behavior of heavy/high-Z impurity tungsten (W) in the core of hybrid (high normalized beta β_N plasmas) scenario on EAST with ITER-like divertor (ILD) is analyzed. W accumulation is often observed and seriously degrades the plasma performance (Xiang Gao et al 2017 Nucl. Fusion 57 056021). The dynamics of the W accumulation process of a hybrid discharge are examined considering the concurrent evolution of the background plasma parameters. It turns out that the toroidal rotation and density peaking of the bulk plasma are usually large in the central region, which is particularly prone to the W accumulation. A time slice during the W accumulation phase is modeled, accounting for both neoclassical and turbulent transport components of W, through NEO with poloidal asymmetry effects induced by toroidal rotation, and TGLF, respectively. This modeling reproduces the experimental observations of W accumulation and identifies the neoclassical inward convection/pinch velocity of W due to the large density peaking of the bulk plasma and toroidal rotation in the central region as one of the main reasons for the W accumulation. In addition, the NEO+TGLF+STRAHL modeling can not only predict the core W density profile but also closely reconstruct the radiated information mainly produced by W in the experiment.