Ch. Hill (I): Validation of the GENE-X gyrokinetic code on the edge and scrape-off layer of Wendelstein 7-X

• Christopher Hill

L. Hollendonner (P): Experiment and modelling of early-heating reversed-shear discharges

• Lea Hollendonner (IPP-Garching)

This topic is all about the distribution of plasma current. In the case when most of the current is located off-axis (contrary to the „normal“ case when the current is on-axis) the resulting profiles of the safety factor (q-profile, bending of field-lines) is non-monotonic and there is a region of negative shear (change of field-line bending from one flux surface to the next) which can lead to the formation of internal transport barriers (ITBs). The formation and sustainment of this kind of current distribution with a lot of plasma current off- axis is not straight-forward. To this end, the approach of early-heating is pursued. This approach slows down the current diffusion of inductive current into the core in the very early phase of a discharge. Examples of this scenario during the last campaign and next steps to improve the scenario in the next campaign are presented. Another constraint on the study of transport effects of negative shear is the measurement of the current distribution with very high precision. Thus, the second half of the talk is dedicated to explain the working principle and some of the challenges of the relevant diagnostic.

K.A. Siever (I): Radiation dynamics and stability in high radiated power fraction scenarios

• Kevin Andrea Siever (IPP Bereich Greifswald)