Magnetic Field Line Stickiness in Tokamaks

POSTER

Abstract

We analyze a Hamiltonian model with five wire loops that delineate magnetic surfaces of tokamaks with poloidal divertors. Non-axisymmetric magnetic perturbations are added by external coils, similar to the correction coils that have been installed or designed in present tokamaks. We obtain the footprints and deposition patterns on the divertor plates, and, 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, giving rise to evidence of stickiness characteristic of chaotic Hamiltonian systems [Caroline G. L. Martins et al. IEEE Transactions on Plasma Science (accepted), 2014]. In order to identify sticky structures, we perform a finite time rotation number calculation [J. D. Szezech Jr. et al. Phys. Lett. A, 377, 452, 2013]. Finally, we introduce a random collisional term to the field line mapping to investigate the effect of particle collisions on stickiness. The results indicate that the reported trapping may affect the transport in present tokamaks [Caroline G. L. Martins et al. Physics of Plasmas (Submitted), 2014].

Authors

  • Caroline G.L. Martins

    University of Texas at Austin, Department of Physics, Institute for Fusion Studies, Austin - TX 78712, USA

  • Marisa Roberto

    Departamento de Fisica, Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, SP, 12228-900, Brazil

  • Ibere L. Caldas

    Universidade de Sao Paulo, Instituto de Fisica, Sao Paulo, SP, 05315-970, Brazil

  • Philip J. Morrison

    The University of Texas at Austin, Institute for Fusion Studies and Department of Physics, University of Texas at Austin, Austin, TX 78712, The University of Texas at Austin, Physics Department, Austin, TX 78712-1192 - USA, Institute for Fusion Studies and Department of Physics, The University of Texas at Austin, Institute for Fusion Studies, The University of Texas at Austin, University of Texas at Austin, Department of Physics, Institute for Fusion Studies, Austin - TX 78712, USA