This title appears in the Scientific Report :
2005
Please use the identifier:
http://dx.doi.org/10.1088/0741-3335/47/10/014 in citations.
On the properties of turbulence intermittency in the boundary of the TEXTOR tokamak
On the properties of turbulence intermittency in the boundary of the TEXTOR tokamak
Intermittent convective transport has been investigated in the edge and the scrape-off layer (SOL) of TEXTOR using Langmuir probe signals. The probability distribution function (PDF) of the density fluctuations and the turbulence-induced flux are all positively skewed, while a Gaussian shape is reco...
Saved in:
Personal Name(s): | Xu, Y. H. |
---|---|
Jachmich, S. / Weynants, R. R. / TEXTOR, Team | |
Contributing Institute: |
Institut für Plasmaphysik; IPP |
Published in: | Plasma physics and controlled fusion, 47 (2005) |
Imprint: |
Bristol
IOP Publ.
2005
|
DOI: |
10.1088/0741-3335/47/10/014 |
Document Type: |
Journal Article |
Research Program: |
Fusion |
Series Title: |
Plasma Physics and Controlled Fusion
47 |
Subject (ZB): | |
Publikationsportal JuSER |
Intermittent convective transport has been investigated in the edge and the scrape-off layer (SOL) of TEXTOR using Langmuir probe signals. The probability distribution function (PDF) of the density fluctuations and the turbulence-induced flux are all positively skewed, while a Gaussian shape is recorded for the negative fluctuations. The deviation of the signals from Gaussian statistics clearly increases from the plasma edge to the SOL. Conditional averaging reveals that in the SOL region the waveform of intermittent structures is asymmetric in time and the burst events move radially outwards with E-theta x B-T/B-2 velocities of similar to 450 m s(-1). It is found that the large burst fluctuations (>= 2.5 x rms) account for nearly 40% of the total transport in the SOL. Statistics of the waiting-time between successive bursts indicate that the PDF of the time interval follows a Poisson-distribution for small-duration events (selected by size <= 2.5 x rms) and changes into a power-law form for larger ones. Moreover, the intermittency density fluctuation data clearly show self-similar characters and long-range time correlations through the presence of (1) sandpile-like frequency spectra and existence of the f(-1) region; (2) a long tail in the autocorrelation function and (3) Hurst exponents H > 0.5 from R/S analysis, suggesting a Possible role of avalanche-like transport in the turbulence intermittency. |