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High density discharges with and without the ergodic divertor (ED) are compared. With increasing density the radiation maximum swings from the outside divertor modules to the inner wall. A strongly radiating cold plasma layer (ED-marfe) appears on the high field side. Different from the marfe in the limiter configuration, this ergodic divertor marfe has a poloidal extension of more than 120 and can be run in steady-state conditions. It shows a poloidal structure with temperature modulations which reflect the magnetic structure of the divertor configuration. The modifications of the plasma edge electron temperature and density profiles are used for the identification of three different divertor regions with characteristic transport properties. The importance of charge exchange (CX) processes due to a high neutral density in the radiating edge layer is shown. The neutral density within the ED-marfe and the ergodic region is estimated via CX-sensitive intensity ratios of carbon impurity ions. Densities of about 1.0 E18/m3 in the marfe and 1.0 E16 to 1.0 E17/m3 in the ergodic region are estimated.

Additional information

Authors: HESS W R ET AL., CEA, Département de Recherches sur la Fusion Contrôlée, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Report: EUR-CEA-FC-1536 EN (1994) 36 pp.
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
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