A study authored by Florian Effenberg et al., published in Nuclear Fusion, presents a method of radiative power exhaust employing impurity seeding with neon (Ne) and nitrogen (N2) in the island divertor of the Wendelstein 7-X (W7-X) stellarator. This research offers insights into the process's efficacy in controlling heat loads on plasma-facing components of the 3D divertor.

The work is referenced under the citation F. Effenberg et al 2019 Nucl. Fusion 59 106020 (DOI: 10.1088/1741-4326/ab32c4) demonstrates that the introduction of Ne and N2 into one of the magnetic islands can lead to an appreciable increase in radiative power losses, thereby facilitating a significant reduction in the divertor heat fluxes.

The study reports an enhancement in edge radiation following Ne seeding and a plasma response correlated to the duration of N2 seeding. Additionally, the research indicates a dampening effect on counter-streaming scrape-off layer (SOL) flows, pointing to a convective heat flux decrease.

Further credibility to the findings is provided by the comparison of experimental results with EMC3-EIRENE simulations for both Ne and N2 seeding scenarios, showing congruence between the observed and predicted radiative cooling effects. The 3D modeling also reproduces qualitatively the effect of increased Ne seeding on the toroidal asymmetries in the 3D radiation distribution.

Although the process was accompanied by a reduction in plasma energy and density, these impacts were offset by implementing controlled fueling techniques, ensuring plasma stability. The findings of the paper suggest that impurity seeding is an effective strategy for managing the heat fluxes and plasma-material interactions in the complex 3D divertor geometry of stellarators, an essential factor for the development and longevity of fusion reactor plasma-facing components.

F. Effenberg et al 2019 Nucl. Fusion 59 106020 DOI 10.1088/1741-4326/ab32c4
Accepted manuscript