Comparison of plasma response models for RMP effects on the divertor and scrape-off layer in KSTAR

TL;DR

This study compares different plasma response models to understand their impact on RMP-induced divertor and scrape-off layer structures in KSTAR, highlighting significant differences and the importance of plasma conditions for accurate predictions.

Contribution

It evaluates four plasma response models' effects on magnetic footprints and heat loads, revealing model-dependent variations and conditions for better agreement with measurements.

Findings

Significant differences in magnetic footprints from different models.

Overestimation of heat load striations in simulations.

Better agreement with measurements under specific plasma conditions.

Abstract

Resonant magnetic perturbations (RMPs) are beneficial for control of edge localized modes (ELMs) in tokamaks. Nevertheless, a side effect is the appearance of a helical striations in the particle and heat loads onto divertor targets. The extent and field line connection of these striations is significantly altered by the plasma response to external perturbations. For an ELM suppressed H-mode plasma at KSTAR, magnetic footprints are computed by FLARE based on plasma response from GPEC, MARS-F, M3D-C1 and JOREK with substantial differences in the resulting footprints (from 2 cm to 14 cm). This is reflected in EMC3-EIRENE simulations of the resulting heat loads: it is found that either the peak value or the extent of the striations appear to be overestimated compared to IRTV measurements. Reasonable agreement can only be achieved for the smallest footprint for lower input power and lower cross-field transport, or for higher upstream density and radiative power losses.