TRANSPORT STUDIES OF HIGH-Z ELEMENTS IN NEON EDGE RADIATION COOLED DISCHARGES IN TEXTOR-94

Citation
J. Rapp et al., TRANSPORT STUDIES OF HIGH-Z ELEMENTS IN NEON EDGE RADIATION COOLED DISCHARGES IN TEXTOR-94, Plasma physics and controlled fusion, 39(10), 1997, pp. 1615-1634
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Phsycs, Fluid & Plasmas
ISSN journal
0741-3335
Volume
39
Issue
10
Year of publication
1997
Pages
1615 - 1634
Database
ISI
SICI code
0741-3335(1997)39:10<1615:TSOHEI>2.0.ZU;2-T
Abstract
High-Z materials as tungsten are intended to be used in future fusion reactors due to their low sputtering rates and high melting points. In this context the important question is whether the use of high-Z mate rials is compatible with the concept of a cold radiative boundary. To investigate the local release and transport behaviour of the high-Z Im purities, Mo and W test limiters were used in auxiliary heated dischar ges under different radiation scenarios with neon seeding. In addition , laser blow-off of tungsten as well as xenon gas puffing were perform ed. In some particular discharge conditions impurity accumulation was observed in the plasma core, which in the case of ohmic discharges led to minor disruptions. The connection between the accumulation and the evolution of the current density profiles is discussed. A transport a nalysis is made, in order to compare the observations with the neoclas sical theory. it is shown that with neon the impurity-impurity driven fluxes enhance the high-Z concentration in the plasma core. However, i f the source of the high-Z elements is significantly reduced, by incre asing the plasma density, a development of an accumulation instability can be avoided.