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(IC/P-03) Towards an Experimental Investigation of Stochastic Magnetic Fields to Control Edge Transport Barriers in Next Step Tokamaks

A. Grosman¹⁾, J.M. Ané¹⁾, M. Bécoulet¹⁾, W.E. Evans²⁾, K.H. Finken³⁾, Ph. Ghendrih¹⁾, G. Huysmans¹⁾, A.W. Leonard²⁾, M. Lipa¹⁾, M.A. Mahdavi²⁾, P.R. Thomas^1)
 
1) Association EURATOM CEA sur la Fusion-DSM/DRFC, St Paul lez Durance, France
²⁾ General Atomics, San Diego, USA
³⁾ Association EURATOM-KFA, Jülich, Germany

Abstract.  While present plasma scenarios rely on self generated situations, active control with ergodic divertor (ED) coils provide means to operate the H mode in conditions that are compatible with the technical constraints. The stochastisation of field lines in the vicinity of the separatrix, will produce a localised enhancement of electron heat transport. This may provide an actuator on the edge temperature (and thus pressure) barriers. Thus, H-mode edge barriers might be controlled and type I Elms would be avoided. The paper will discuss this in view of the theoretical and experimental advances of the last years: Tore Supra experiments gave evidence of the fine tuning capability of the perturbation on a well defined magnetic configuration while JFT-2M experiments showed that the edge stochastisation of the X point configuration has widened the operating windows of the type III ELM regime. The possible implementations of such control in a medium size tokamak (DIII-D) and eventually on ITER will also be described. For more advanced reactors, the development of permanent magnets with very high coercive fields may prove valuable provided they might be installed just behind the blanket.

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