Speaker
Spyridon-Iason Valvis
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.4005.pdf
RF beam scattering by cylindrical filaments
and interfacial density fluctuations (*)
S. I. Valvis1, A. Zisis2, A. Papadopoulos1, P. Papagiannis1, A. K. Ram3, K. Hizanidis1,
I. G. Tigelis2, E. Glytsis1
1
National Technical University of Athens, Athens, Greece
2
National and Kapodistrian University of Athens, Athens, Greece
3
Plasma Science and Fusion Center, MIT, Cambridge MA, USA
Radio Frequency (RF) waves are routinely used in tokamaks for heating, current drive, NTM
control, as well as for diagnostics purposes. Frequently, RF waves, aiming towards the plasma
core, propagate through a turbulent environment. The latter can exhibit strong coherent density
fluctuations as well as filamentary structures mainly (though, not perfectly) aligned along the
local magnetic field lines. The scattering process of RF waves by these structures is studied
both analytically and numerically. RF waves can be either single plane waves or spatially
confined beams. For that purpose, the filaments are considered to have cylindrical shape with
infinite length with the cylinder axis not aligned with the local magnetic field and the results are
compared to the ones from the study of the aligned case [1,2]. On the other hand, the interfacial
density fluctuations are considered periodic with spatial periods larger, smaller or of the same
order of the wavelength of the incident RF waves. The frequency range of the RF waves studied
is mainly in the Electron Cyclotron (EC) range of frequencies for ITER-like and Medium Size
Tokamak applications. Furthermore, the study covers a variety of density contrasts, filament
sizes and fluctuation strengths.
References
[1] A. K. Ram and K. Hizanidis, “Scattering of radio frequency waves by cylindrical density filaments in tokamak
plasmas”, Physics of Plasmas 23, 022504 (2016)
[2] Z. C. Ioannidis, A. K Ram, K. Hizanidis, I. G. Tigelis, “Computational studies on scattering of radio frequency
waves by density filaments in fusion plasmas”, Physics of Plasmas 24, 102115 (2017)
(*) This work was supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion
associated with the EUROfusion Consortium.
