https://doi.org/10.1140/epjs/s11734-025-01833-3
Regular Article
External kink modes with scrape-off layer in diverted tokamaks
Institute for Fusion Theory and Simulation, Zhejiang University, 310027, Hangzhou, China
Received:
3
March
2025
Accepted:
24
July
2025
Published online:
1
August
2025
We investigate external kink modes in a diverted tokamak using the initial-value code CLTx and the free-boundary equilibrium solver CLT-EQ. We initially focus on the low-n 
peeling mode, analyzing its characteristics in the presence of the X-point and the scrape-off layer (SOL). The simulation results exhibit a certain degree of consistency with the ideal external kink theory in the limiter configuration. Furthermore, the presence of the X-point can trigger the 
peeling–tearing mode when considering a non-zero edge current profile with the Spitzer resistivity model. Simulation results exhibit a favorable agreement with the experimental observations of external kink modes as the current in a tokamak is ramped up, and 
decreases through rational values. Remarkably, our simulation results demonstrate that the presence of the scrape-off layer (SOL), characterized by high resistivity and low-density properties, effectively absorbs perturbations close to the separatrix. This observation raises the potential for stabilizing the unstable external mode.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
