Escape patterns of chaotic magnetic field lines in a tokamak with reversed magnetic shear and an ergodic limiter

Kroetz, Tiago; Roberto, Marisa; Silva, E. C. da; Caldas, Iberê L.; Viana, Ricardo L.

doi:10.1063/1.2988335

Cited by 36 publications

(29 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, transport barriers are regions in the tokamak plasma where the turbulent transport is significantly reduced. Such transport barriers are present when there are dimerized magnetic islands owing to non-monotonic plasma current profiles and reversed magnetic shear [60,70,71].…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Fractal structures in nonlinear plasma physics

Viana

Silva

Kroetz

et al. 2011

Phil. Trans. R. Soc. A.

Self Cite

View full text Add to dashboard Cite

Fractal structures appear in many situations related to the dynamics of conservative as well as dissipative dynamical systems, being a manifestation of chaotic behaviour. In open area-preserving discrete dynamical systems we can find fractal structures in the form of fractal boundaries, associated to escape basins, and even possessing the more general property of Wada. Such systems appear in certain applications in plasma physics, like the magnetic field line behaviour in tokamaks with ergodic limiters. The main purpose of this paper is to show how such fractal structures have observable consequences in terms of the transport properties in the plasma edge of tokamaks, some of which have been experimentally verified. We emphasize the role of the fractal structures in the understanding of mesoscale phenomena in plasmas, such as electromagnetic turbulence.

show abstract

Section: Discussionmentioning

confidence: 99%

“…These are defined as the sets of initial conditions which generate field lines escaping through a given exit [41,54,60]. This exit can be a material surface, such as a divertor plate, or simply a region we choose from any position along the tokamak region.…”

Section: Wada Basins and Magnetic Footprintsmentioning

confidence: 99%

Fractal structures in nonlinear plasma physics

Viana

Silva

Kroetz

et al. 2011

Phil. Trans. R. Soc. A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…One may find in the literature examples of FA that may present transport distinct from the normal diffusion, as exponential [3][4][5][6], ballistic [7,8] or even slower growths [9,10]. Also, interesting FA applications can be found in research areas such as plasma physics [11][12][13], astrophysics [14,15], atom-optics [16,17], and especially billiard dynamics [18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Transition from normal to ballistic diffusion in a one-dimensional impact system

et al. 2018

View full text Add to dashboard Cite

We characterize a transition from normal to ballistic diffusion in a bouncing ball dynamics. The system is composed of a particle, or an ensemble of noninteracting particles, experiencing elastic collisions with a heavy and periodically moving wall under the influence of a constant gravitational field. The dynamics lead to a mixed phase space where chaotic orbits have a free path to move along the velocity axis, presenting a normal diffusion behavior. Depending on the control parameter, one can observe the presence of featured resonances, known as accelerator modes, that lead to a ballistic growth of velocity. Through statistical and numerical analysis of the velocity of the particle, we are able to characterize a transition between the two regimes, where transport properties were used to characterize the scenario of the ballistic regime. Also, in an analysis of the probability of an orbit to reach an accelerator mode as a function of the velocity, we observe a competition between the normal and ballistic transport in the midrange velocity.

show abstract

“…By the same consideration, we define a limit range for the current in our perturbation coils for ITER tokamak, which is therefore, (represented by the black segment in figure 5(b)), following the manifolds that leave the X point. One can notice, in figures 5(b), magnetic islands immersed in the chaotic layer, which play an important role in the field lines escape [26].…”

Section: Figurementioning

confidence: 99%

Delineating the magnetic field line escape pattern and stickiness in a poloidally diverted tokamak

2014

Self Cite

View full text Add to dashboard Cite

We analyze a Hamiltonian model with five wire loops that delineates the magnetic surfaces of the tokamak ITER, including a similar safety factor profile and the X-point related to the presence of a poloidal divertor. Non-axisymmetric magnetic perturbations are added by external coils, similar to the correction coils installed at the tokamak DIII-D and those that will be installed at ITER. To show the influence of magnetic perturbations on the field line escape, we integrate numerically the field line differential equations and obtain the footprints and deposition patterns on the divertor plate.Moreover, we show that the homoclinic tangle describes the deposition patterns in the divertor plate, agreeing with results observed in sophisticated simulation codes. Additionally, we show that while chaotic lines escape to the divertor plates, some of them are trapped, for many toroidal turns, in complex structures around magnetic islands, embedded in the chaotic region, giving rise to the so called stickiness effect characteristic of chaotic Hamiltonian systems. Finally, we introduce a random collisional term to the field line mapping to investigate stickiness alterations due to particle collisions. Within this model, we conclude that, even reduced by collisions, stickiness still influences the field line transport.

show abstract

Escape patterns of chaotic magnetic field lines in a tokamak with reversed magnetic shear and an ergodic limiter

Cited by 36 publications

References 71 publications

Fractal structures in nonlinear plasma physics

Fractal structures in nonlinear plasma physics

Transition from normal to ballistic diffusion in a one-dimensional impact system

Delineating the magnetic field line escape pattern and stickiness in a poloidally diverted tokamak

Contact Info

Product

Resources

About