Escape patterns of chaotic magnetic field lines in a tokamak with reversed magnetic shear and an ergodic limiter
- Instituto Tecnologico de Aeronautica, Centro Tecnico Aeroespacial, Departamento de Fisica, 12228-900, Sao Jose dos Campos, Sao Paulo (Brazil)
- Instituto de Fisica, Universidade de Sao Paulo, 05315-970, Sao Paulo, Sao Paulo (Brazil)
- Departamento de Fisica, Universidade Federal do Parana, 81531-990, Curitiba, Parana (Brazil)
The existence of a reversed magnetic shear in tokamaks improves the plasma confinement through the formation of internal transport barriers that reduce radial particle and heat transport. However, the transport poloidal profile is much influenced by the presence of chaotic magnetic field lines at the plasma edge caused by external perturbations. Contrary to many expectations, it has been observed that such a chaotic region does not uniformize heat and particle deposition on the inner tokamak wall. The deposition is characterized instead by structured patterns called magnetic footprints, here investigated for a nonmonotonic analytical plasma equilibrium perturbed by an ergodic limiter. The magnetic footprints appear due to the underlying mathematical skeleton of chaotic magnetic field lines determined by the manifold tangles. For the investigated edge safety factor ranges, these effects on the wall are associated with the field line stickiness and escape channels due to internal island chains near the flux surfaces. Comparisons between magnetic footprints and escape basins from different equilibrium and ergodic limiter characteristic parameters show that highly concentrated magnetic footprints can be avoided by properly choosing these parameters.
- OSTI ID:
- 21269046
- Journal Information:
- Physics of Plasmas, Vol. 15, Issue 9; Other Information: DOI: 10.1063/1.2988335; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of the resonant modes on the magnetic footprint patterns in a tokamak wall
Twist mapping for the dynamics of magnetic field lines in a tokamak ergodic divertor