Internal transport barrier formation in the Tore Supra tokamak

Abstract

The characteristics of the safety factor profile (q) have been studied for a database of discharges featuring internal transport barrier phenomena under different heating and current drive conditions in the Tore Supra tokamak. The presence of a recurrent link between the time of formation of an internal barrier and the central safety factor (q 0 ) crossing a low order rational surface is reported on and discussed for a database of ∼40 discharges. Other relevant features of the current profile (e.g. the minimal q value, the magnetic shear and the presence of magnetic islands in the plasma) have been investigated, yielding to little or no correlation with the time and location of the barrier.

Helical equilibria and magnetic structures in the reversed field pinch and analogies to the tokamak and stellarator

“…In tokamaks the ITB dynamics is dominated by the micro-turbulence stabilization effect associated with both the flow and the magnetic shear (Eriksson 2002, Connor et al 2004, Litaudon 2006, Tala and Garbet 2006. However, the magnetic shear alone can produce electron transport barriers (Buratti et al 1999, Sauter et al 2005, Turco et al 2009. Theoretical works (del-Castillo-Negrete et al 1996, Nasi andFirpo 2009) singled out the importance of flatness of the q profile close to the zero-shear point, in relation to the presence and width of a belt of KAM tori, producing an ITB.…”

Impurity dynamics in the presence of transport barriers in tokamaks

“…20 Steepening is found in the profiles of the ion temperature, the electron temperature, and the ion density. The barrier onset is sensitive to the value of q min ͑Ref.…”