|Title||Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||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. Felton, C. 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, JET-EFDA Contributors|
|Journal||Plasma Physics and Controlled Fusion|
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 harmonic 3 He ICRF heating—were recently investigated in JET. Although the same magnetic field and RF frequencies ( f ≈ 42 MHz and f ≈ 52 MHz, 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 in 4 He plasmas, modest heating efficiencies ( η = P absorbed / P launched < 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 the 3 He 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 the 3 He ions reached about 260 keV in the second harmonic 3 He heating experiments when 5 MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the 3 He 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 (with 4 He) were confirmed in the H majority case, the 3 He concentration was the main handle on the heating efficiency in the second harmonic 3 He heating scenario.
|Alternate Title||Plasma Phys. Control. Fusion|
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