A new experimental approach has successfully mitigated transient heat loads on tokamak divertors by employing high-frequency sweeping of the plasma strike point. This technique, tested on the EAST tokamak, involves moving the plasma-wall interaction zone across the divertor surface at speeds up to 100 meters per second. The rapid motion effectively distributes the heat flux, preventing localized overheating and potential damage to divertor components, a critical challenge for sustained fusion operations.

Transient heat pulses, often referred to as Edge Localized Modes (ELMs), can deliver significant energy to divertor surfaces in tokamaks, posing a threat to the long-term integrity of fusion devices. Traditional methods for ELM control include injecting pellets or using resonant magnetic perturbations, but these can introduce complexities or have limited effectiveness. The fast sweeping method offers a potentially simpler and more robust solution by dynamically altering the plasma-material interaction footprint.

Traditional methods for ELM control include injecting pellets or using resonant magnetic perturbations, but these can introduce complexities or have limited effectiveness.

The EAST experiment utilized a divertor configuration with a sweep frequency of 25 Hz, achieving a strike point velocity of approximately 100 m/s. Measurements indicated a reduction in peak heat flux by a factor of 2.5 compared to static strike point conditions. This suppression of peak heat flux is crucial for maintaining the operational window for future fusion power plants, such as ITER, where sustained high-power plasma operation is envisioned.

Previous research on divertor heat load management has focused on optimizing magnetic field configurations and material properties. However, the dynamic control of the plasma footprint through fast sweeping represents a novel paradigm. The success of this method on EAST, a superconducting tokamak known for its long-pulse operation capabilities, suggests its applicability to a range of tokamak designs and operational regimes.

Further investigation is warranted to fully understand the underlying physics of heat pulse suppression under fast sweeping conditions and to optimize sweep parameters for different plasma scenarios. The development of advanced divertor concepts, including this fast sweeping technique, is a key area of research for enabling continuous and reliable operation of fusion power plants. The EAST team plans to explore higher sweep frequencies and their impact on plasma confinement and stability.