B Labit et al 2007 Plasma Phys. Control. Fusion 49 B281 doi:10.1088/0741-3335/49/12B/S26
B Labit1, A Diallo1, A Fasoli1, I Furno1, D Iraji1, S H Müller1,3, G Plyushchev1, M Podestà1,4, F M Poli1, P Ricci1, C Theiler1 and J Horaček2
Show affiliationsA unique parabolic relation is observed to link skewness and kurtosis of density fluctuation signals, measured over the whole cross-section of the simple toroidal device TORPEX for a broad range of experimental conditions. This relationship is also valid for density fluctuation signals measured in the scrape-off layer of the TCV tokamak. All the probability density functions (PDFs) of the measured signals, including those characterized by a negative skewness, are universally described by a special case of the beta distribution. In TORPEX, fluctuations in the drift-interchange frequency range are necessary and sufficient to assure that PDFs can be described by this specific beta distribution. For a more detailed plasma scenario, it is shown that electron temperature and plasma potential fluctuations have different statistical properties compared with the density.
52.25.Gj Fluctuation and chaos phenomena
52.55.Fa Tokamaks, spherical tokamaks
52.40.Hf Plasma-material interactions; boundary layer effects
Issue 12B (December 2007)
Received 6 July 2007, in final form 2 September 2007
Published 16 November 2007
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