Abstract
We present recent results on steady states of translational symmetric and axisymmetric ITER relevant plasmas with incompressible sheared flow in connection with a generalized Grad-Shafranov (GGS) equation and on their stability. On the basis of a vari- ety of ITER pertinent solutions of the GGS equation constructed it turns out that the flow affects noticeably the equilibrium quantities in qualitative agreement with the advanced confinement regimes phenomenology. Also, application of a sufficient condition for linear stability indicates that stabilization is mainly caused by the variation of the magnetic field in the direction perpendicular to the magnetic surfaces, related to the magnetic shear, depends on the plasma shaping and is sensitive to the up-down asymmetry. In certain cases the sheared flow has a weaker stabilizing effect enhanced by the equilibrium nonlinearity.
Highlights
It has been established in a number of fusion devices that sheared flows both zonal and mean play a role in the transitions to improved confinement regimes as the L-H transition and the Internal Transport Barriers (ITBs)
For flows parallel to the magnetic field we examine the linear stability of the equilibria constructed by means of the sufficient condition of [6]
The equilibrium characteristics have been examined by means of the pressure, safety factor (q), current density, toroidal velocity, poloidal Mach function and electric field (E) associated with the non parallel flow
Summary
It has been established in a number of fusion devices that sheared flows both zonal and mean (equilibrium) play a role in the transitions to improved confinement regimes as the L-H transition and the Internal Transport Barriers (ITBs). These flows can be driven externally in connection with electromagnetic power and neutral beam injection for plasma heating and current drive or can be created spontaneously (zonal flows). The stability of equilibria with parallel flows are examined on the basis of these solutions in Sec. 3 and Sec. 4 summarizes the main conclusions
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