Speaker
Attila Buzás
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1091.pdf
Statistical analysis of SOL fluctuations on COMPASS tokamak as
measured by the Li-BES diagnostic
A. Buzás1 , A. Bencze1 , J. Krbec2,3 , P. Hacek2,4 , J. Seidl2 , R. Panek2
1 Wigner Research Center for Physics, Budapest, Hungary
2 Institute of Plasma Physics of the CAS, Prague, Czech Republic
3 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in
Prague, Prague, Czech Republic
4 Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
In this paper the COMPASS Li-BES (Lithium Beam Emission Spectroscopy) system is intro-
duced to demonstrate its capabilities in Scrape-off Layer (SOL) density fluctuation studies. The
effect of atomic physics is examined by applying small perturbations (with different amplitudes
and radial locations) to artificial density profiles. From these synthetic perturbed density pro-
files, using a collisional-radiative model, Li-light profiles are calculated. It has been shown that
the beam attenuation has a significant effect on the observed perturbation amplitudes and local-
isation. Simple numerical simulations based on stochastic models of the SOL filaments (blobs)
[1] have been performed and the effect of atomic physics on the statistical properties of the
same filament events in the Li-light fluctuations such as amplitude distributions, waiting times,
conditionally averaged waveforms have been studied. The results are compared to experimental
data and theoretical expectations [2]. It is found that they are in good agreement with what is
seen on other tokamaks and what the models suggest. Moreover the interesting problem of the
so called ’hole’ emergence has also been addressed in the context of atomic physics effects.
Analysing the statistics of the measured Li-BES signals, it has been shown that the PDFs are
not in fact dominated by large an rare events but by the small and frequent. However the emerg-
ing statistics are qualitatively still in line with model predictions albeit with different model
parameters. These results can also be recreated by numerical simulations using the modified
parameter set.
References
[1] Garcia, O. E., Physical Review Letters 108, 6 (2012)
[2] Theodorsen, A. and Garcia, O. E. and Horacek, J. and Kube, R. and Pitts, R. A., Plasma Phys. Control. Fusion
58, 1 (2016)
