Speaker
Audun Theodorsen
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1016.pdf
Intermittent fluctuations in the Alcator C-Mod
A. Theodorsen1 , O. E. Garcia1 , R. Kube1 , D. Brunner2 , B. LaBombard2 , J. L. Terry2
1 UiT - The Arctic University of Norway, Tromsoe, Norway
2 Plasma Science and Fusion Center, MIT, Cambridge, US
In the far scrape-off layer (SOL), radial motion of filamentary structures leads to excess trans-
port of particles and heat. Single point dwell probe measurements from the SOL of several
tokamaks [1, 2, 3] reveal order unity relative fluctuations with positively skewed histograms
with exponential tails towards high amplitudes. Conditional averaging of fluctuations reveal the
large-amplitude bursts to have two-sided exponential structures, with a sharp rise and trailing
wake. This is consistent with the power spectral density and autocorrelation function of the time
series.
Investigations of SOL fluctuations in the Alcator C-Mod using both the mirror Langmuir
probe (MLP) [4] and gas puff imaging (GPI) [5] conform well to these general results. However,
there are discrepancies: the MLP time series generally has lower fluctuation levels and larger
filament width than those taken with GPI. In this contribution, we investigate measurements
taken with a conventional Langmuir probe using both the well known techniques listed above
as well as a new deconvolution method for unambiguously revealing filament arrival times and
amplitudes [6].
With measurements from plasmas with different parameters as well as in both upper and
lower single null configurations, the Langmuir probe data set is well suited to address this
discrepancy and reveal universality in the behavior of SOL fluctuations.
References
[1] A. Theodorsen, O. E. Garcia, J. Horacek, R. Kube and R. A. Pitts, Plasma Physics and Controlled Fusion 58,
044006 (2016)
[2] R. Kube, A. Theodorsen, O. E. Garcia, B. LaBombard and J. L. Terry, Plasma Physics and Controlled Fusion
58, 054001 (2016)
[3] O. E. Garcia, R. Kube, A. Theodorsen, J.-G. Bak, S.-H. Hong, H.-S. Kim, the KSTAR Project Team and R.
A. Pitts, Nuclear Materials and Energy 12, 36-43 (2017)
[4] R. Kube, O. E. Garcia, A. Theodorsen, D. Brunner, A. Q. Kuang, B. LaBombard and J. L. Terry, ’Intermittent
electron density and temperature fluctuations and associated fluxes in the Alcator C-Mod scrape-off layer’,
submitted to Plasma Physics and Controlled Fusion
[5] O. E. Garcia, R. Kube, A. Theodorsen, B. LaBombard and J. L. Terry, ’Intermittent fluctuations in the Alcator
C-Mod scrape-off layer for ohmic and high confinement mode plasmas’, submitted to Physics of Plasmas
[6] A. Theodorsen, O. E. Garcia, R. Kube, B. LaBombard and J. L. Terry, ’Universality of Poisson-driven plasma
fluctuations in the Alcator C-Mod scrape-off layer’, submitted to Physical Review Letters
