Low dimensional models for the nonlinear dynamics of transport barrier oscillations in tokamak edge plasmas
Transport barriers at the plasma edge are key elements of high confinement regimes in fusion devices. In typical configurations, such barriers are not stable but exhibit quasi-periodic relaxation oscillations. In this work, one-dimensional and zero-dimensional models for such oscillations are presented that give insight into the underlying mechanisms which are found to be intrinsically nonlinear. The models are systematically derived from three-dimensional turbulence simulations based on a fluid description of the plasma. In these simulations, a transport barrier is generated by an imposed E x B shear flow. This barrier exhibits quasiperiodic relaxation oscillations even if the E x B shear flow is frozen. The models presented here are therefore different from those based on turbulent shear flow generation. They allow to isolate and illustrate a different mechanism for barrier oscillations. Furthermore, these models reproduce regimes characterized by a decrease of the oscillation frequency with the E x B flow shear.
Bibliographic Reference: An article published in: Journal of Physics: Conference Series 7 (2005), pp. 227-232
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://dx.doi.org/10.1088/1742-6596/7/1/019
Record Number: 200719071 / Last updated on: 2007-04-11
Original language: en
Available languages: en