Strike point splitting induced by the application of magnetic perturbations on MAST

TL;DR

This study observes that magnetic perturbations induce strike point splitting on MAST, with the effect strongly dependent on coil configuration, challenging existing plasma response models.

Contribution

It demonstrates the coil configuration dependence of strike point splitting and provides experimental evidence that challenges current models of plasma response to RMPs.

Findings

Splitting observed only in even coil configuration

Consistent with density pump-out effects

Challenges existing plasma response models

Abstract

Divertor strike point splitting induced by resonant magnetic perturbations (RMPs) has been observed on MAST for a variety of RMP configurations in a plasma scenario with Ip=750kA where those configurations all have similar resonant components. Complementary measurements have been obtained with divertor Langmuir probes and an infrared camera. Clear splitting consistently appears in this scenario only in the even configuration of the perturbation coils, similarly to the density pump-out. These results present a challenge for models of plasma response to RMPs.