Speaker
Elisee Trier
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1023.pdf
Studying ELM filaments with Doppler reflectometry in ASDEX upgrade
E. Trier1,2 , P. Hennequin2 , M. Hoelzl1 , C. Lechte3 , M.Cavedon1 , G. Conway1 ,
T. Happel1 , B. Kurzan1 , F. Mink1,4 , F. Orain1,5 , J. Pinzon1,4 , B. Vanovac6 , E. Wolfrum1 ,
the ASDEX Upgrade Team and the EUROfusion MST1 Team∗
1 Max Planck Institute for Plasma Physics, D-85748 Garching, Germany
2 LPP, Ecole Polytechnique, CNRS, F-91128 Palaiseau Cedex, France
3 Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie IGVP,
Universität Stuttgart, 70569 Stuttgart, Germany
4 Physik-Department E28, Technische Universität München, 85747 Garching, Germany
5 CPHT, Ecole Polytechnique, CNRS, Université Paris-Saclay, 91128 Palaiseau, France
6 DIFFER - Dutch Institute for Fundamental Energy Research, Eindhoven, the Netherlands
During edge localized modes (ELMs), filament structures are expelled from the edge of H-
mode plasmas [1]. In the non-linear development of the underlying instabilities leading to the
formation and expulsion of filaments, shear flows have been shown to be an important ingredi-
ent, and are now included in the modeling tools. It is therefore essential to investigate experi-
mentally the dynamics of the filaments during an ELM crash, and to compare them to simula-
tions. In this respect, the Doppler reflectometers installed in ASDEX Upgrade probe the density
fluctuations in the pedestal region and can detect filaments and their movement during an ELM.
In this contribution, we report observations of an acceleration, followed by a reversal of the
filaments velocity during type-I ELMs. Assuming it is due to a poloidal motion, this would cor-
respond to an initial velocity increase in the electron diamagnetic direction, before a reversal in
the ion direction; but a possible influence coming from radially propagating structures is a priori
not excluded and needs to be considered. By changing the probing beam angle, and hence the
direction of the probed wavevector, it is possible to distinguish whether these velocity changes
are due to radial or poloidal motions. Possible changes in the measurement localization due to
filament-induced modifications of the density profile are also discussed. These measurements
are compared with the modelling of an ELM done with the non-linear MHD code JOREK [2, 3],
using full wave simulations [4] to simulate the Doppler reflectometry diagnostic.
References
[1] A. Kirk et al., Phys. Rev. Lett. 96, 185001 (2006)
[2] F. Orain et al., Phys. Plasmas 20, 102510 (2013)
[3] F. Mink et al., Nucl. Fusion 58, 026011 (2018)
[4] C. Lechte et al., Plasma Phys. Control. Fusion 59, 075006 (2017)
∗
See author list of "H. Meyer et al 2017 Nucl. Fusion 57 102014"
