Filamentation in the RTP tokamak plasma

TitleFilamentation in the RTP tokamak plasma
Publication TypeJournal Article
Year of Publication2001
AuthorsM.NA Beurskens, N.JL Cardozo, E.R Arends, C.J Barth, H.J van der Meiden
JournalPlasma Physics and Controlled Fusion
Date PublishedJan
ISBN Number0741-3335

Experimental data are presented showing filamentation of the Rijnhuizen tokamak project (RTP) plasma. These filaments are only resolved by the high-resolution double pulse Thomson scattering diagnostic, and appear as multiple peaks in the T-e profile with a typical width of 5-10 mm and an amplitude as high as 1 keV in a 2 keV ambient plasma. This paper shows the occurrence of filaments under various plasma conditions. It shows that filaments are statistically significant plasma physical phenomena. A parameter study shows a weak dependence of their amplitude on q(a), whereas a strong inverse dependence on plasma density has been found. It takes filaments several milliseconds to develop after the switch-on of electron cyclotron heating; they are wiped out by a sawtooth crash and take only a few hundred microseconds to reappear after such a crash. They mainly occur in the centre of additionally heated plasmas by means of electron cyclotron heating, but have also been observed in transiently heated plasmas and off-axis in non-centrally heated plasmas. Finally, two interpretations of filament topology are tested by means of three experiments. It turns out that the interpretation of filaments as independent closed tube-like structures seems to best fit the RTP data.



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