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Grad-Shafranov equilibria with negative core toroidal current in Tokamak plasmas
Paulo Rodrigues1, João P S Bizarro
1Centro de Fusão Nuclear, Associação Euratom--IST, Instituto Superior Técnico, 1049-001 Lisboa, Portugal. par@cfn.ist.utl.pt
Physical Review Letters
|August 11, 2005
Summary
Numerical Grad-Shafranov (GS) equilibria computations reveal that tailored plasma profiles can create islands, sustaining negative-current cores. Reversed GS equilibria are generally non-nested, except in unstable degenerate cases.
Area of Science:
- Plasma Physics
- Computational Magnetohydrodynamics (MHD)
Background:
- Achieving stable plasma confinement is crucial for fusion energy.
- Understanding plasma equilibrium and stability, particularly with reversed current profiles, is essential.
Purpose of the Study:
- To compute numerical Grad-Shafranov (GS) equilibria without pre-defined profile models.
- To investigate the formation of plasma islands and their role in sustaining negative-current cores.
- To analyze the topological properties of reversed GS equilibria.
Main Methods:
- Numerical computation of Grad-Shafranov equilibria.
- Flexible profile tailoring for pressure and current density.
- Topological analysis of equilibrium configurations.
Main Results:
- Successful computation of GS equilibria with negative core current density.
- Demonstrated island formation on the low-field side, even in elongated plasmas.
- Proved that reversed GS equilibria are generally non-nested, barring degenerate cases.
Conclusions:
- Flexible profile modeling enables the sustainment of negative-current plasma cores.
- Plasma island formation is a key mechanism for core stability.
- The non-nested nature of reversed GS equilibria highlights their structural instability in most configurations.