Mode Conversion Heating in JET Plasmas with Multiple
Mode Conversion Layers
D. Van Eester, E. Lerche, T. Johnson, T. Hellsten, J. Ongena, M.-L. Mayoral, D.
Frigione, C. Sozzi, G. Calabro, M.
Lennholm, P. Beaumont, T. Blackman, D. Brennan, A. Brett,
M. Cecconello, I. Coffey, A. Coyne, K. Crombe, A. Czarnecka, R. Felton,
M. Gatu Johnson, C. Giroud, G. Gorini, C. Hellesen, P. Jacquet, Y. Kazakov, V.
Kiptily, S. Knipe, A. Krasilnikov, Y. Lin, M. Maslov, I. Monakhov, C. Noble, M. Nocente,
L. Pangioni, I. Proverbio, M. Stamp, W. Studholme, M. Tardocchi, T.W. Versloot,
V. Vdovin, A. Whitehurst, E. Wooldridge, V. Zoita and JET EFDA contributors
Mode conversion heating has become one of the standard tools to do transport analysis and
is often used in rotation experiments. It relies on the mode conversion, at the Ion-Ion Hybrid
(IIH) resonance, of the Fast Wave (FW) launched by standard RF antennas, to shorter
wavelength waves that are efficiently damped on electrons. The interference effect described by Fuchs et
al. allows to significantly enhance the mode conversion and thereby the overall RF heating
efficiency when the machine and plasma parameters are chosen such that an integer number of
FW wavelengths can be folded in between the High Field Side (HFS) FW cutoff and the IIH
layer. This effect was already experimentally identified in
(3He)-D plasmas and was recently tested
in (3He)-H JET plasmas. In the latter case, commonly referred to as an 'inverted scenario', the
ion-ion hybrid layer is positioned between the antenna on the Low Field Side (LFS) and the
ion-cyclotron layer of the minority'3He ions while in standard e.g.
(3He)-D - scenarios the ion-cyclotron layer is in between the IIH layer and the LFS. As shown in the past, the
(3He)-H scenarios require much lower
3He concentrations, X[3He], to reach the mode-conversion
heating regime and their RF wave behavior critically depends on the plasma composition.
Preprint of Paper to be submitted for publication in Proceedings of the
37th EPS Conference on Plasma Physics, Dublin, Ireland.
(21st June 2010 - 25th June 2010)