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

E. Lerche, D. Van Eester, Y. Kazakov, P. Jacquet, I. Monakhov, M. Goniche, L. Colas, F. Rimini, K. Crombé, R. Dumont, V. Kiptily, M. Santala

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

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<3×1019/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.

Original languageEnglish
Title of host publicationRadio Frequency Power in Plasmas
Subtitle of host publicationProceedings of the 21St Topical Conference
EditorsRobert I. Pinsker
PublisherAmerican Institute of Physics Inc.
ISBN (Electronic)9780735413368
DOIs
Publication statusPublished - 10 Dec 2015
Event21st Topical Conference on Radiofrequency Power in Plasmas - Lake Arrowhead, United States
Duration: 27 Apr 201529 Apr 2015

Publication series

NameAIP Conference Proceedings
Volume1689
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

Conference21st Topical Conference on Radiofrequency Power in Plasmas
Country/TerritoryUnited States
CityLake Arrowhead
Period27/04/1529/04/15

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