# Divertor Heat Load in ASDEX Upgrade L-Mode in Presence of External Magnetic Perturbation

## TL;DR

This study investigates how external magnetic perturbations affect the heat load distribution on the divertor in ASDEX Upgrade tokamak L-Mode discharges, revealing that the 2D heat flux pattern depends on plasma density and magnetic alignment.

## Contribution

It provides a quantitative analysis of the 2D heat flux pattern caused by magnetic perturbations and shows that the overall heat flux and transport parameters remain unchanged.

## Key findings

- 2D heat flux pattern depends on magnetic alignment and density.
- Increasing density broadens the divertor heat flux profile.
- Magnetic perturbations do not increase cross-field transport.

## Abstract

Power exhaust is one of the major challenges for a future fusion device. Applying a non-axisymmetric external magnetic perturbation is one technique that is studied in order to mitigate or suppress large edge localized modes which accompany the high confinement regime in tokamaks. The external magnetic perturbation brakes the axisymmetry of a tokamak and leads to a 2D heat flux pattern on the divertor target. The 2D heat flux pattern at the outer divertor target is studied on ASDEX Upgrade in stationary L-Mode discharges. The amplitude of the 2D characteristic of the heat flux depends on the alignment between the field lines at the edge and the vacuum response of the applied magnetic perturbation spectrum. The 2D characteristic reduces with increasing density. The increasing divertor broadening $S$ with increasing density is proposed as the main actuator. This is supported by a generic model using field line tracing and the vacuum field approach that is in quantitative agreement with the measured heat flux. The perturbed heat flux, averaged over a full toroidal rotation of the magnetic perturbation, is identical to the non-perturbed heat flux without magnetic perturbation. The transport qualifiers, power fall-off length $\lambda_q$ and divertor broadening $S$, are the same within the uncertainty compared to the unperturbed reference. No additional cross field transport is observed.