Research news from the division Plasma Edge and Wall
Power loads in snow flake divertors
Most of the high-power tokamaks worldwide investigate the single-null configuration (left figure), which is also foreseen for ITER. In such a configuration the targets and in particular the outer one are exposed to very high power fluxes that may limit the life-time of the corresponding plasma-facing components. In continuation to previous collaborations with the Swiss experiment TCV we further investigated as an alternative configuration the so called Snowflake (SF) divertor (right figure). It is characterized by a magnetic configuration, where two null points are localized close to each other. In a recently published article  the properties of the SF divertor in dependence of the radial distance of the null points were studied systematically by means of the transport code EMC3-EIRENE. It was found that the power load at the outer targets can be reduced significantly in a snowflake divertor as illustrated by the red diagrams in the figures.
These results fed into plans for the installation of further poloidal field coils in ASDEX Upgrade that would allow an experimental study of snowflake and other configurations in the upper divertor under high heating power conditions.
 T Lunt et al. 2016 Plasma Phys. and Control. Fusion 58 045027