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Département de Recherches sur la Fusion Contrôlée,
Association Euratom-CEA, Centre d'Etudes de Cadarache,
13108 Saint Paul lez Durance Cedex, France
I. Voitsekhovitch
Equipe Turbulence Plasma, Laboratoire de Physique des
Interactions Ioniques et Moléculaires Université de Provence,
UMR 6633 CNRS, Centre Universitaire de St Jérôme, case 321 Avenue
Escadrille Normandie Niemen, 13397 Marseille Cedex 20, France
(Permanent address: RRC ``Kurchatov Institute'', Moscow, Russia)
Abstract. This paper deals with specific
control issues related to the advanced tokamak scenarios in which rather
accurate tailoring of the current density profile is a requirement in
connection with the steady state operation of a reactor in a high confinement
optimized shear mode. It is found that adequate current profile control can be
performed if real-time magnetic flux reconstruction is available through a set
of dedicated diagnostics and computers, with sufficient accuracy to deduce the
radial profile of the safety factor and of the internal plasma loop
voltage. It is also shown that the safety factor can be precisely controlled
in the outer half of the plasma through the surface loop voltage and the
off-axis current drive power, but that a compromise must be made between the
accuracy of the core safety factor control and the total duration of the
current and fuel density ramp-up phases, so that the demonstration of the
steady state reactor potential of the optimized/reversed shear concept in the
Next Step device will demand pulse lengths of the order of one thousand
seconds (or more for an ITER-size machine).
IAEA 2001
