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N=2 ICRH of H majority plasmas in JET-ILW.

Authors :
Lerche, E.
Van Eester, D.
Kazakov, Y.
Jacquet, P.
Monakhov, I.
Goniche, M.
Colas, L.
Rimini, F.
Crombé, K.
Dumont, R.
Kiptily, V.
Santala, M.
Source :
AIP Conference Proceedings. 2015, Vol. 1689 Issue 1, p1-4. 4p. 4 Graphs.
Publication Year :
2015

Abstract

Heating single ion species plasmas with ICRF is a challenging task: Fundamental ion cyclotron heating (w = wci) suffers from the adverse polarization of the RF electric fields near the majority cyclotron resonance while second harmonic heating (w = 2wci) typically requires pre-heating of the plasma ions to become efficient. Recently, w = 2wci ICRF heating was tested in JET-ILW hydrogen plasmas in the absence of neutral beam injection (L-mode). Despite the lack of pre-heating, up to 6MW of ICRF power were coupled to the plasma leading to a transition to H-mode for PICRH>5MW in most discharges. Heating efficiencies between 0.65-0.85 were achieved as a combination of the low magnetic field adopted (enhanced finite Larmor radius effects) and the deliberate slow rise of the ICRF power, allowing time for a fast ion population to gradually build-up leading to a systematic increase of the wave absorptivity. Although fast ion tails are a common feature of harmonic ICRF heating, the N=2 majority heating features moderate tail energies (<500keV) except at very low plasma densities (ne0<3x1019/m³), where fast H tails in the MeV range developed and fast ion losses became significant, leading to enhanced plasma wall interaction. The main results of these experiments will be reported. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
0094243X
Volume :
1689
Issue :
1
Database :
Academic Search Index
Journal :
AIP Conference Proceedings
Publication Type :
Conference
Accession number :
111721180
Full Text :
https://doi.org/10.1063/1.4936486