The role of toroidal plasma currents for the island divertor scrape-off layer in the stellarator
Wendelstein 7-X is investigated using reciprocating electric probes. Experiments show that small
amounts (of a few kA) of plasma current are sufficient to significantly affect the scrape-off layer
plasma conditions, whereas higher plasma currents above 10kA result in more drastic changes.
This behavior is linked to the effect of the plasma current on the rotational transform profile,
which can result in significant shifts of the edge magnetic islands. These shifts affect the
interaction of the islands with the divertor and can eventually result in a transition from a
diverted to a limited plasma configuration. The probe observations are complemented by further
edge diagnostics including plasma flow measurements, divertor Langmuir probes, divertor thermography and impurity spectroscopy.This work has been carried out within the framework of the
EUROfusion Consortium and has received funding from the
Euratom research and training programme 2014-2018 and
2019-2020 under grant agreement number 633053
