Speaker
Oulfa Chellaï
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I4.406.pdf
Direct measurements of mm-wave beam scattering by field-aligned blobs
in magnetically-confined plasmas
O. Chellaï1 , S. Alberti1 , M. Baquero-Ruiz1 , I. Furno1 , T. Goodman1 , F. Manke1 , G. Plyushchev1 ,
L. Guidi2 , A. Koehn 2,3 , O. Maj2 , E. Poli2 , K. Hizanidis4 , L. Figini5 , D. Ricci5 and the TCV team1
1 Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
2 Max Planck Institute for Plasma Physics, Garching, Germany
3 Institute of Interfacial Process Engineering and Plasma Technology, Stuttgart, Germany
4 National Technical University of Athens, Greece
5 Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, Milan, Italy
In magnetically confined fusion devices, the use of EM radiations ranges from plasma di-
agnostics to plasma heating, current drive and core confinement preservation. For large toka-
maks such as ITER, numerical simulations and analytical studies suggest that, in the presence
of plasma edge turbulence, the path length of the beam will be long enough to significantly
broaden the EC-beam, which could lead to a loss of current drive efficiency and possibly pre-
vents tearing modes stabilization at the expected power levels [1, 2].
We report first direct measurements of millimeter wave (mmw) beam scattering by plasma
turbulence. The experiments are carried out in the basic plasma physics device TORPEX and
the Tokamak à Configuration Variable (TCV) . The two devices are equipped with an exten-
sive set of diagnostics, which provide an ideal environment to diagnose plasma turbulence and
associated structures, such as blobs. A mmw-beam is injected from the top of the device and
the power is measured at the bottom. We show that the measured plasma density fluctuations
are the cause of fluctuations of the transmitted mmw-power. Conditional sampling is used to
identify the effect of measured density structures. On TORPEX, electron density fluctuations
are measured using an in-situ array of Langmuir probes. A full-wave model based on COM-
SOL multiphysics is presented and compared to experiments [3]. Using the SOL turbulence
simulations from the GBS turbulence code, comparison between the scattering effect on the
mmw-beam using both COMSOL Multiphysics and the WKBeam code [2] are in progress in
TCV. The results of the two codes as well as comparison with the experiments are discussed.
References
[1] C. Tsironis et al. Phys. Plasmas, vol. 16, p. 112510, 2009.
[2] A. Snicker et al. Nucl. Fusion, vol. 58, p. 016002, 2018.
[3] O. Chellaï et al., “Millimeter-wave beam scattering by field-aligned blobs in simple magnetized toroidal plas-
mas,” Phys. Rev. Lett., vol. Accepted for publication, 2018.
