High-confinement mode is the ITER tokamak’s most efficient and promising operating state. However, periodic disturbances at the plasma edge, known as edge-localized modes, can occur in this state, which could damage the fusion device.
Energetic (suprathermal) particles provide momentum and energy in fusion plasmas, especially in future self-sustaining fusion reactions. They must be effectively confined to ensure the reaction’s stability.
An international team has studied the impact of these energetic ions on Edge-Localized Modes (ELMs) by combining experiments, modeling, and simulations. For the first time, the work offers significant insights into the interaction between energetic ions and ELMs.
According to findings, an intense energy and momentum exchange between ELMs and energetic ions is expected for ITER.
The team took measurements for the study at the ASDEX Upgrade tokamak at the Max Planck Institute for Plasma Physics in Germany. They then performed simulations using a hybrid code called MEGA, which models the interaction between ELMs and energetic particles.
A liquid metal evaporator could protect the inside of the tokamak from intense heat
By comparing experimental data with modeling results, the team gained new insights into the behavior of ELMs when energetic particles are present.
Their findings show that the energetic particle population significantly influences the structure of ELMs, and the interaction between ELMs and energetic particles involves a resonant energy exchange.
This interaction mechanism helps explain the similarities between the experimental signs of ELMs observed in magnetic diagnostics and fast-ion loss detectors. This research, combining experimental and computational efforts, was conducted within the framework of the European fusion consortium EUROfusion.
Main author Jesús José Domínguez-Palacios Durán said, “In our publication, we demonstrate that energetic ion kinetic effects can alter the spatio-temporal structure of the edge localized modes. The effect is analogous to a surfer riding the wave. The surfer leaves footprints on the wave when riding it. In a plasma, the energetic particle interacts with the MHD wave (the ELM) and can change its spatio-temporal pattern. Our results can have important implications for the optimization of ELM control techniques. For instance, we could use energetic particles as active actuators in the control of these MHD waves.”
Journal Reference:
- Dominguez-Palacios, J., Futatani, S., Garcia-Munoz, M. et al. Effect of energetic ions on edge-localized modes in tokamak plasmas. Nat. Phys. (2025). DOI: 10.1038/s41567-024-02715-6
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