Speaker
Mariia Usoltceva
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1019.pdf
Sheath modelling for IShTAR ICRF antenna
M. Usoltceva1,2,3,*, R. Ochoukov2, W. Tierens2, K. Crombé1,4, A. Kostic1,2, S. Heuraux3, E.
Faudot3, J-M. Noterdaeme1,2 and the IShTAR team
1
Department of Applied Physics, Gent University, 9000 Gent, Belgium
2
Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
3
Université de Lorraine, 54506 Vandœuvre-lès-Nancy, France
4
LPP-ERM-KMS, TEC partner, 1000 Brussels, Belgium
Plasma heating with Ion Cyclotron Range of Frequency (ICRF) waves is one of the crucial
systems of hot plasma devices. It is important to not only increase the effectivity of such a
system, but to avoid destructive effects on plasma and plasma facing components. Among
those effects it is known that in the proximity of the antenna limiters increased DC potentials
are formed, causing particle and heat loads to rise significantly during the ICRF system
operation. A study of the relevant sheath physics is performed on a dedicated linear device
IShTAR [1] in conditions similar to the tokamak SOL.
A combined experimental-numerical method is used to obtain the DC plasma potentials in
the SOL plasma near the limiters of the IShTAR ICRF antenna. The experimental part
consists of 3D magnetic field mapping in a broad region in front of the antenna. An array of
B-dot probes on a movable manipulator is used to measure components of the RF magnetic
field. The resulting experimental field map is compared to calculations performed in
COMSOL software to validate the accuracy of the model.
The COMSOL model includes precise geometrical representation of the experimental
device. The parallel electric field in the region in front of the antenna between the antenna
limiters, which is hard to be measured experimentally, is calculated in the COMSOL model.
The plasma is simulated as a material with numerically assigned cold dielectric tensor. Fast
and slow components of the wave are decoupled and studied separately.
SSWICH-SW [2] is used as a final step of the procedure to obtain the rectified potentials on
the limiters from the input parallel electric field from the COMSOL IShTAR model. A
density profile in the SOL region is measured in the argon plasma discharge on IShTAR. The
calculated DC potential can be compared to experimental measurements and can be studied
for different plasma parameters and ICRF antenna regimes.
[1] K. Crombé et al., 26th IAEA Fusion Energy Conference (2016)
[2] L. Colas et al., Phys. Plasmas 19, 092505 (2012)
