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

Heating single ion species plasmas with ICRF is a challenging task: Fundamental ion cyclotron heating (w = w{sub ci}) suffers from the adverse polarization of the RF electric fields near the majority cyclotron resonance while second harmonic heating (w = 2w{sub ci}) typically requires pre-heating of the plasma ions to become efficient. Recently, w = 2w{sub ci} 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 P{sub ICRH}>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 (n{sub e0}<3x10{sup 19}/m{sup 3}), where fast H tails in the MeV range developed and fast ion losses became significant, leading to enhanced plasma wallmore » interaction. The main results of these experiments will be reported.« less
Authors:
 [1] ;  [2] ; ; ;  [1] ; ; ; ; ;  [3] ; ; ;  [4] ;
  1. LPP-ERM-KMS, Association EUROFUSION-Belgian State, TEC partner, Brussels (Belgium)
  2. (United Kingdom)
  3. CCFE Fusion Association, Culham Science Centre, Abingdon (United Kingdom)
  4. IRFM, Association EUROFUSION-CEA, Saint-Paul-Lez-Durance (France)
Publication Date:
OSTI Identifier:
22496195
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1689; Journal Issue: 1; Conference: 21. topical conference on radio frequency power in plasmas, Lake Arrowhead, CA (United States), 27-29 Apr 2015; Other Information: (c) 2015 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTIVITY; BEAM INJECTION; ELECTRIC FIELDS; H-MODE PLASMA CONFINEMENT; HYDROGEN; ICR HEATING; ION CYCLOTRON-RESONANCE; IONS; JETS; LARMOR RADIUS; L-MODE PLASMA CONFINEMENT; MAGNETIC FIELDS; MEV RANGE; PLASMA DENSITY; POLARIZATION; RADIOWAVE RADIATION; WALL EFFECTS