SOLPS modelling of a snowflake configuration for the future upper divertor in ASDEX Upgrade

The power fluxes to the divertor target plates expected in a fusion reactor based on the tokamak design in single-null (SN) configuration might challenge the current material limits. Alternative divertor geometries, such as the snowflake (SF) configuration, are therefore currently discussed as a possible solution for the power exhaust problem.

Heat fluxes parallel to the magnetic field lines at the outer target (OT) in the single null (SN, blue) and snowflake (SF, reddish colors) configuration. For the SF the heat flux is split into two regions OT1 and OT2 and the peak value is reduced.

As reported in a previous highlight, the power flux can be significantly reduced in a snowflake configuration with respect to a single null configuration. For the first time, the SOLPS transport code has now been successfully applied for simulating a snowflake configuration. This code is able to simulate ‘detached’ plasma conditions, where the plasma pressure is reduced when approaching the divertor target plates, thus figuratively detaching the plasma. It was found that “detachment” is easier to achieve and that the power flux is reduced substantially in a snowflake compared to a single null configuration. In order to study this effect experimentally, ASDEX Upgrade is currently planning the details of a hardware modification of its upper divertor.

This work was recently published in "Plasma Physics and Controlled Fusion":

https://doi.org/10.1088/1361-6587/aac706

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