Aachen PK 2003 – wissenschaftliches Programm
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P: Plasmaphysik
P 10: Poster II
P 10.14: Poster
Dienstag, 18. März 2003, 17:30–19:15, Foyer
Impurity Transport Studies in the divertor operation of the W7-AS Stellarator — •Maciej Krychowiak, Maciej Krychowiak, Ralf König, Rainer Burhenn, Hartmut Ehmler, Rainer Fischer, Jens Knauer, Ekkehard Pasch, Andreas Werner, and Thomas Klinger — Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, EURATOM Assoziation, Wendelsteinstr. 1, D-17491 Greifswald
W7-AS is a low shear, 5-period modular stellarator (R = 2 m, aeff ∼ 14 cm for ιa ∼ 5/9), equipped with ten discrete divertor modules. The impurity behaviour in various divertor operating regimes has been investigated.
The effective ion charge, Zeff, was derived by means of bremsstrahlung measurements. For this purpose a two channel microspectrometer (PC card) covering the spectral range from 350-900 nm has been installed on the W7-AS. It allowed to spectrally resolve the plasma radiation integrated along a toroidal line of sight crossing the plasma centre, with a time resolution of up to 7 ms. Its spectral resolution was sufficient to differentiate between line radiation and spectral regions with pure bremsstrahlung. A Bayesian probability theory based experimental data analysis was applied. Additional information on the plasma impurity behaviour was gained from radial Zeff profiles derived by means of the Thomson scattering diagnostic. Laser blow-off experiments have shown that with the transition into a newly found High Density High Confinement (HDH) regime the impurity confinement time drops from several 100 ms to values comparable to the energy confinement time (few 10 ms).