Fast ions in mode conversion heating (3He)-H plasmas in JET

• Published in: Plasma physics and controlled fusion Vol. 54; no. 7; pp. 74010 - 74028
• Main Authors: Kiptily, V G, Van Eester, D, Lerche, E, Hellsten, T, Ongena, J, Mayoral, M-L, Cecil, F E, Darrow, D, Gatu Johnson, M, Goloborod'ko, V, Gorini, G, Hellesen, C, Johnson, T, Lin, Y, Maslov, M, Nocente, M, Tardocchi, M, Voitsekhovitch, I
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.07.2012
• Subjects: Electric discharges; Experiments; Magnetic fields; Plasma heating; Plasmas
• ISSN: 0741-3335; 1361-6587; 1361-6587
• DOI: 10.1088/0741-3335/54/7/074010

Fast ions were analysed in experiments focusing on fundamental 3He minority and mode conversion (MC) in the ion cyclotron resonance range of frequencies (ICRF) in H plasmas and on second harmonic heating of 3He ions at 2.65 T mimicking D-T plasma heating in ITER at half its nominal toroidal magnetic field. Gamma-ray spectrometry, neutral particle analysers and fast-ion loss diagnostics provided information on the generation of fast-ion populations and on the distribution of ICRH power among the species in various heating scenarios and for a large range of 3He concentrations. In the scenario with the fundamental 3He minority and MC wave heating at BT(0) = 3.41 T and f 32 MHz, fast 3He ions accelerated by ICRH in the MeV energy range were detected in discharges with low 3He concentration. In the experiments with a 3He concentration scan it was found that at a 3He concentration of 2.2% the 3He ion losses disappeared while a population of energetic D ions gradually built up due to a redistribution of the ICRH power between species on reaching the first MC regime. Under those conditions the ICRF-heated D beam ions effectively absorbed the wave power at their Doppler shifted resonance, which was close to the plasma centre. In discharges with second harmonic heating of 3He ions at BT(0) = 2.65 T and f 52 MHz, the confined energetic 3He ions were found in the MeV energy range. There is some evidence that the D ions were also accelerated by ICRF. This paper also demonstrates that the synergy of the various fast ion diagnostics allows making a broad picture of the physics of the redistribution of the absorbed ICRH power in complicated heating scenarios of JET.