Tokamak equilibria with toroidal-current reversal in the plasma core consistent with experimental data

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Magnetohydrodynamics

Background:

• Tokamak devices are crucial for magnetic confinement fusion energy research.
• Understanding plasma behavior, including current profiles, is essential for achieving stable fusion reactions.
• Previous models often assumed nested magnetic field configurations, potentially overlooking complex scenarios.

Purpose of the Study:

• To compute tokamak equilibria with negative toroidal current in the plasma core.
• To validate these computed equilibria against experimental measurements from current-hole discharges.
• To investigate the implications of non-nested magnetic configurations on equilibrium reconstruction.

Main Methods:

• Utilized advanced computational methods to reconstruct tokamak equilibria.
• Incorporated experimental data, including plasma pressure profiles and motional Stark effect (MSE) measurements.
• Developed equilibrium reconstruction techniques capable of handling non-nested magnetic configurations and magnetic islands.

Main Results:

• Successfully computed tokamak equilibria featuring negative toroidal current in the plasma core.
• Achieved good agreement between computed and experimental plasma pressure profiles.
• Demonstrated an excellent fit to experimental motional Stark effect data, supporting the validity of the computed equilibria.
• Observed the unfolding of axisymmetric magnetic islands, characteristic of non-nested configurations.

Conclusions:

• Tokamak equilibria with central toroidal current reversal are computationally feasible and consistent with experimental data.
• The existence of non-nested magnetic configurations, including magnetic islands, should be considered in equilibrium reconstruction.
• Current reconstruction tools that cannot handle non-nested configurations may lead to premature exclusion of equilibria with central toroidal current reversal.