Noble internal transport barriers and radial sub-diffusion of toroidal magnetic lines
Internal transport barriers (ITBs) observed in tokamaks are described by a purely magnetic approach. Magnetic line motion in toroidal geometry with broken magnetic surfaces is studied from a previously derived Hamiltonian map in situation of incomplete chaos. This appears to reproduce in a realistic way the main features of a tokamak, for a given safety factor profile and in terms of a single parameter L representing the amplitude of the magnetic perturbation. New results are given concerning the Shafranov shift as function of L. The phase space (Psi, Theta) of the �tokamap� describes the poloidal section of the line trajectories, where Psi is the toroidal flux labelling the surfaces. For small values of L, closed magnetic surfaces exist (KAM tori) and island chains begin to appear on rational surfaces for higher values of L, with chaotic zones around hyperbolic points, as expected. Island remnants persist in the chaotic domain for all relevant values of L at the main rational q-values.
Bibliographic Reference: An article published in: Annales de Physique, vol.28 n°6 (2003) p.1-101
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Record Number: 200417417 / Last updated on: 2004-02-24
Original language: en
Available languages: en