Transport control by coherent zonal flows in the core/edge transitional regime

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Computational Astrophysics

Background:

• Tokamak devices are crucial for magnetic confinement fusion energy research.
• Understanding plasma turbulence and energy transport is key to achieving sustained fusion reactions.
• Zonal flows are known to influence plasma turbulence but their precise role in energy flux modulation requires further investigation.

Purpose of the Study:

• To investigate the modulation of tokamak energy flux by zonal flows using 3D Braginskii turbulence simulations.
• To identify the primary drivers of zonal flows and their impact on anomalous transport.
• To explore the role of wave-kinetic effects and magnetic curvature in flow excitation and transport modulation.

Main Methods:

• Performed 3D Braginskii turbulence simulations.
• Analyzed the interaction between zonal flows and energy flux in the tokamak core/edge transition region.
• Investigated wave-kinetic effects and the influence of magnetic curvature on flow dynamics.

Main Results:

• Demonstrated strong modulation of energy flux by radially propagating zonal flows.
• Identified anomalous transport and the Stringer-Winsor term as primary drivers of zonal flows.
• Revealed that wave-kinetic effects are responsible for transport modulation and flow excitation.

Conclusions:

• Zonal flows significantly modulate tokamak energy flux through wave-kinetic effects.
• The Stringer-Winsor term and anomalous transport are key drivers of these flows.
• Plasma cross-section shaping can influence magnetic curvature, offering a potential method to control zonal flows and transport.