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(CD2/EX9/1) Plasma Control Issues for an Advanced Steady State Tokamak Reactor

   
D. Moreau 
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).

 

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