Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

E. Lerche, D Van Eester, T.J. 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. FeltonC. Giroud, G. Gorini, C. Hellesen, P. Jacquet, V. Kiptily, S. Knipe, A. Krasilnikov, M. Maslov, I. Monakhov, C. Noble, M. Nocente, L. Pangioni, I. Proverbio, G. Sergienko, M. Stamp, W. Studholme, M. Tardocchi, V. Vdovin, T. Versloot, I. Voitsekhovitch, A. Whitehurst, E. Wooldridge, V. Zoita

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Abstract

Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas - fundamental H majority and second harmonic3He ICRF heating - were recently investigated in JET. Although the same magnetic field and RF frequencies (f42MHz and f52MHz, respectively) were used, the density and particularly the plasma temperature were lower than those expected in the initial phase of ITER. Unlike for the well-performing H minority heating scheme to be used in4He plasmas, modest heating efficiencies (η=Pabsorbed/Plaunched<40%) with dominant electron heating were found in both H plasma scenarios studied, and enhanced plasma-wall interaction manifested by high radiation losses and relatively large impurity content in the plasma was observed. This effect was stronger in the3He ICRF heating case than in the H majority heating experiments and it was verified that concentrations as high as 20% are necessary to observe significant ion heating in this case. The RF acceleration of the heated ions was modest in both cases, although a small fraction of the3He ions reached about 260keV in the second harmonic3He heating experiments when 5MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the3He heating experiments (where both the second and third harmonic ion cyclotron resonance layers of the D ions are inside the plasma) whilst it was practically absent in the majority hydrogen heating scenario. While hints of improved RF heating efficiency as a function of the plasma temperature and plasma dilution (with4He) were confirmed in the H majority case, the3He concentration was the main handle on the heating efficiency in the second harmonic3He heating scenario. © 2012 IOP Publishing Ltd.
Original languageEnglish
Article number074008
Pages (from-to)-
JournalPlasma Physics and Controlled Fusion
Volume54
Issue number7
DOIs
Publication statusPublished - Jul 2012
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

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