Speaker
Guillermo Suarez Lopez
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1072.pdf
ICRF antenna coupling in ASDEX Upgrade 3D plasmas
G. Suarez Lopez1,2 , R. Ochoukov1 , M. Willensdorfer1 , H. Zohm1,2 , D. Aguiam3 , V. Bobkov1 ,
M. Dunne1 , H. Faugel1 , H. Funfgelder1 , J.-M. Noterdaeme1,4 , E. Strumberger1 , W. Suttrop1 ,
∗ †
the ASDEX Upgrade Team , and the EUROfusion MST1 Team.
1 Max Planck Institute for Plasma physics, Garching b. Munchen, Germany
2 Ludwig-Maximilians-University of Munich, Munich, Germany.
3 Instituto de Plasmas e Fusao Nuclear, Universidade de Lisboa, Lisboa, Portugal
4 Applied Physics Department, University of Ghent, Ghent, Belgium
The excitation of the fast branch of the ion cyclotron (IC) plasma wave by an antenna is a
method for efficient energy transport to the plasma core used for ionic heating. The amount of
power coupled to the plasma by the antenna is a function of the radiation impedance, which
is characterized by the plasma parameters, such as plasma density, the magnetic field, and the
antenna strap phasing for multiport networks.
Antenna coupling has been extensively studied under the assumption of axisymmetry in the
plasma. Non-axisymmetric scenarios have become more relevant in view of the gas puff tech-
niques used for coupling improvement and the usage of magnetic perturbations (MPs) for edge
localized modes control. The application of MPs produces a plasma kink-peeling response that
amplifies the vacuum field perturbation and leads to significant non-axisymmetric field-aligned
displacements of the flux surfaces. These displacements create a 3D density profile in front of
the IC antenna.
Dedicated discharges in the ASDEX Upgrade tokamak have been performed to study the ef-
fect of MP-induced boundary displacements on IC coupling. Different phasings between the
upper and lower row of MP coils with n=2 toroidal periodicity were applied. The MP field is
rotated in order to diagnose the effect of the rotating 3D profiles on the antenna performance.
Strap loading resistance oscillations, coherent with the rotating density profile, of the order of
|∆RL | ≈ ±0.2 Ω have been recorded. Embedded reflectometry in one of the 3-strap antennas
is used to correlate the density distribution to the observed antenna behavior. NEMEC ideal
MHD modeling is performed, allowing a direct comparison of the measured loading resistance
oscillations with the computed plasma deformation in the confined region.
∗
For a complete list of authors, see A. Kallenbach et al, Nucl Fus 57 (2017) 102015
†
For a complete list of authors, see H. Meyer et al, Nucl Fus 57 (2017) 102014
