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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

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

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Author(s):
Martins, Caroline G. L. [1, 2] ; Roberto, M. [1] ; Caldas, I. L. [3]
Total Authors: 3
Affiliation:
[1] Inst Tecnol Aeronaut, Dept Fis, BR-12228900 Sao Jose Dos Campos, SP - Brazil
[2] Univ Texas Austin, Inst Fus Studies, Dept Phys, Austin, TX 78712 - USA
[3] Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo - Brazil
Total Affiliations: 3
Document type: Journal article
Source: Physics of Plasmas; v. 21, n. 8 AUG 2014.
Web of Science Citations: 2
Abstract

We analyze a Hamiltonian model with five wire loops that delineates magnetic surfaces of tokamaks with poloidal divertor. Non-axisymmetric magnetic perturbations are added by external coils, similar to the correction coils that have been installed or designed in present tokamaks. 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 stickiness evidences 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, the observed trapping still influences the field line transport. The results obtained for our numerical estimations indicate that the reported trapping may affect the transport in present tokamaks. (C) 2014 AIP Publishing LLC. (AU)

FAPESP's process: 13/03401-6 - Transport of magnetic field lines and particles in tokamaks and plasma modeling for deposition and etching
Grantee:Marisa Roberto
Support Opportunities: Regular Research Grants
FAPESP's process: 10/13162-0 - Magnetic Fields Topology in Tokamaks
Grantee:Caroline Gameiro Lopes Martins
Support Opportunities: Scholarships in Brazil - Doctorate