Role ofE ×B Shear Flow in Transport Barrier Oscillations

Abstract

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 the first part of this work, a one dimensional model for such relaxation oscillations is investigated. This model has been derived from three dimensional turbulence simulations in the presence of a transport barrier generated by an imposed shear flow. A proper orthogonal decomposition of the spatio-temporal behavior in this model then leads to a reduced set of ordinary equations for the amplitudes of the relevant modes. These modes are found to be different from linear eigenmodes. The zero dimensional model reproduces barrier oscillations.